Role of Electrically Evoked Auditory Brainstem Response in Cochlear Implantation of Children With Inner Ear Malformations

Role of Electrically Evoked Auditory Brainstem Response (EABR) in Cochlear Implantation for Children with Inner Ear Malformations

Ana H. Kim, MD, P. R. Kileny, PhD H. A. Arts, MD, H. K El-Kashlan, MD S. A. Telian, MD, T. A. Zwolan, PhD

Objective: To evaluate the utility of preoperative promontory EABR testing in children with inner ear malformations prior to cochlear implantation based on postoperative audiometric performance. Study Design: Retrospective analysis. Setting: Tertiary academic cochlear implant center. Patients: Forty-three children ages 12 months to 13 years with congenital inner ear malformations. They were categorized into Group A for cochlear and/or vestibular malformations and Group B for those with internal auditory malformation suggestive of eighth nerve aplasia. Interventions: Needle electrode was placed onto the promontory transtympanically to provide the EABR stimulus. Response threshold, wave morphology, and latency were recorded. Subjects with positive EABR received multichannel cochlear implants. Main Outcome Measures: Postoperative performance was measured using the open-set Glendonald Auditory Speech Perception test for words and sentences and the closed-set Minimal Pairs and Early Speech Perception tests. Results: Thirty-nine children showed positive EABR responses. Mean EABR threshold for Group A (31 patients) was 548 microamps (µA) and 457 µA for Group B (8 patients). There were no significant differences in latency or amplitude of wave V between the two groups. Most children in Group A demonstrated good performance on open-set testing by 30-36 months post-activation. Although Group B also showed acoustic benefit, their overall performance was inferior to Group A. Children with multiple inner ear anomalies, CHARGE association, and autism demonstrated poorer performance. Conclusions: Preoperative EABR is useful in determining cochlear implant candidacy in children with radiographic evidence suggestive of cochlear nerve aplasia. Cochlear implantation in these patients can result in meaningful aural rehabilitation.

Measurements of Human Middle- and Inner-Ear Mechanics with Dehiscence of the Superior Semicircular Canal

Wade Chien, MD, Michael E. Ravicz, MS

John J. Rosowski, PhD, Saumil N. Merchant, MD

Specific Aims: 1) To develop a cadaveric temporal-bone preparation to study the mechanism of hearing loss resulting from superior semicircular canal dehiscence (SCD), and 2) To assess the potential utility of clinical measurements of umbo velocity in the diagnosis of SCD. Background: Superior semicircular canal dehiscence syndrome is a clinical condition encompassing a variety of vestibular and auditory symptoms, including an air-bone gap at low frequencies. It has been hypothesized that the dehiscence acts as a “third window” into the inner ear that shunts acoustical energy away from the cochlea at low frequencies, causing a hearing loss. Methods: In our temporal-bone preparations (N=8), stapes, umbo, and round-window velocities were measured in response to air-conducted sound using laser-Doppler vibrometry with the superior semicircular canal intact, after creation of a dehiscence in the superior canal, and with the dehiscence patched. Clinical measurements of umbo velocity in live SCD ears (N=21) were compared with similar data from our cadaveric temporal-bone preparations. Results: An SCD caused a significant reduction in sound-induced round-window velocity at low frequencies, small but significant increases in sound-induced stapes and umbo velocities, and a measurable fluid velocity inside the dehiscence. The increase in sound-induced umbo velocity in temporal bones was also found to be similar to that measured in the 21 live ears with SCD. Conclusion: Findings from the cadaveric temporal-bone preparation were consistent with the “third-window” hypothesis. In addition, measurement of umbo velocity in live ears is helpful in distinguishing SCD from other otologic pathologies with similar presentations (e.g. otosclerosis). Acknowledgments: Funded by NIDCD (NIH grant # DC04798 to SNM), Anne and Monte Wallace, and the Silverstein Young Investigator Award (to WC).

Audiologic Findings in Patients with Superior Semicircular Canal Dehiscence Syndrome Before and After Middle Fossa Craniotomy with Canal Repair

Charles J. Limb, MD, John P. Carey, MD

Sharmila Srireddy, MS, MA Lloyd B. Minor, MD

Objective: To characterize pre- and post-operative audiologic findings in patients with superior semicircular canal dehiscence syndrome Study Design: Retrospective case review Setting: Tertiary referral center Patients: Patients with documented superior semicircular canal dehiscence syndrome (according to history, vestibular testing, and high-resolution computed tomography imaging) that underwent surgical repair of their dehiscence. Intervention: Middle fossa craniotomy for superior semicircular canal plugging and/or resurfacing. Main Outcome Measures: Audiologic testing both before and following surgery with pure-tone threshold measurements of air and bone conduction. Results: Twenty-nine subjects underwent surgical repair of superior semicircular canal dehiscence. Overall, there were no statistically significant differences by ANOVA in hearing before or after surgery, in either air conduction or bone conduction thresholds. Reduction of air-bone gaps was achieved in four patients. Three patients with previous stapes surgery had worse hearing both before and after middle fossa surgery compared to those without previous surgery. Two patients that had undergone previous middle fossa surgery with incomplete resolution of symptoms developed sensorineural hearing loss after revision surgery. Prior middle-ear exploration and tympanostomy tube placement did not appear to affect audiologic outcomes. Surgical hearing results did not differ according to method of canal repair (plugging vs. resurfacing). Conclusions: Middle fossa repair of superior semicircular canal dehiscence is not associated with hearing loss.

Habituation and Attention Deficits in Tinnitus Patients

John L. Dornhoffer, MD, Christopher J. Danner, MD Mark S. Mennemeier, PhD, Edgar Garcia-Rill, PhD

Donna Blake,MAP

Objective: Investigate the etiology of tinnitus by testing various levels of the neuraxis for arousal and attention. Study Design: Prospective study. Setting: Tertiary referral center. Patients: Individuals with tinnitus of at least 6 months duration and healthy controls. Subjects with significant neurological disease, acoustic neuromas or glomus tumors, active Meniere’s disease, profound hearing loss (>90 dB at 4000Hz), or who were taking psychotropic medicines (antidepressants, anticonvulsants, sleep aids, etc.) were excluded. We enrolled 29 tinnitus patients (15 males, 14 females) and 38 controls (20 males, 18 females). Intervention(s): Patients were tested for tonic arousal and habituation at the brainstem-thalamus level by measuring the P50 potential, a scalp-recorded, auditory-evoked response, using pairs of click stimuli. The Psychomotor Vigilance Task, a reaction time (RT) test, was used to assess attentional vigilance. Main Outcome Measure(s): Deficits in arousal and attention were correlated with perceived tinnitus severity. Results: Controls and tinnitus patients showed no difference in arousal or habituation, as measured by the P50 potential and the ability to suppress a second, closely paired stimulus, respectively. However, RT assessments showed that patients with tinnitus have difficulty remaining vigilant over time relative to controls (p=0.02). There were no significant correlations between sleep disturbance or tinnitus severity and RT testing. Conclusions: Patients with tinnitus have normal levels of tonic arousal, and their habituation deficit does not occur at the level of the brainstem. The vigilance detriment we observed in patients with tinnitus may be linked to their tinnitus etiology and not to any associated co-morbidities, such as sleep disturbance or diminished quality of life.

Treatment of Tinnitus with Gabapentin: Results of a Pilot Study

David L. Witsell, MD, Christopher Lansford, MD Sandra S. Stinnett, DrPH, Debara L. Tucci, MD

This clinical trial was designed to investigate the possible effectiveness of gabapentin (Neurontin ®) in the treatment of chronic tinnitus in human subjects. The study design is a randomized, double blind placebo controlled single site trial conducted in an academic medical center. Inclusion criteria included patients between ages 18 and 70 with a complaint of non-pulsatile, subjective tinnitus, bilateral or unilateral, greater than 3 months in duration. Subjects received either a placebo, low dose Neurontin ® (300 mg po qhs) or high dose Neurontin ® (300 mg po tid). The primary outcome measure is the Tinnitus Handicap Inventory; secondary measures include the Profile of Mood States rating scale, Tinnitus Severity Index, and the Short-form 36. The null hypothesis addressed in this study is that the drug would not result in significant alleviation of the symptom of tinnitus. Seventy-six patients completed the trial; of these 52 received the drug. No significant differences were found between the two groups after 5 weeks of treatment with gabapentin. Acknowledgments: We acknowledge the support of Pfizer for provision of study drug, placebo and a small stipend for salary for a study coordinator.

Importance of Post-Implantation Experience on Performance in Children with Bilateral Cochlear Implants

B. Robert Peters, MD, Ruth Litovsky, PhD Aaron Parkinson, MA, Jennifer Lake, MS

Objectives: Clinical trials in which children received bilateral cochlear implants in sequential surgeries were conducted to determine the extent to which bilateral implantation offers benefits on a number of measures. The present investigation was particularly focused on measuring the effects of age at implantation and experience after activation of the second implant on performance. Study Design: Thirty children, ages 3 to 13 years, were recipients of two cochlear implants, received in sequential surgeries, a minimum of 6-months apart. Pre- and postoperative age appropriate speech perception testing, sound localization testing, speech detection measures, and patient/parent questionnaires were performed preoperatively and postactivation at 3, 6, 9, 12, and 24 months in both the unilateral and bilateral conditions. Results: Results for speech perception in quiet show that children implanted sequentially acquire open-set speech perception relatively quickly (within 6 months). However, children under the age of 8 years do so more rapidly, consistent with the notion of a more “plastic” auditory system. Speech intelligibility for spondees in noise was significantly better under bilateral conditions than with either ear alone. Sound localization abilities improved significantly during the first two years following the onset of bilateral hearing. Children who showed best performance at 3-months postactivation of the second CI had acquired deafness post-lingually, suggesting the important role of auditory experience in establishing binaural circuits. Conclusion: Sequential bilateral cochlear implantation in children has the potential to improve speech perception abilities in quiet and in noise as well as localization abilities. The improvement unfolds over time and continues to grow during the 12 to 24 months following activation of the second implant.

The Relationship Between Communication Approach and Spoken Language Comprehension in Young Cochlear Implant Recipients

Krista S. Heavner, MS, Brandi L. Griffin, MA

Hussam K. El-Kashlan, MD, Teresa A. Zwolan, PhD

Objective: Few empirical studies have evaluated the communication and academic outcomes of the Auditory-Verbal approach for rehabilitating children with a cochlear implant. This study evaluated the effect that use of Auditory-Verbal, Oral, and Total Communication approaches had on performance of children who received recent cochlear implant technology at a young age. Study Design: Restrospective analysis using repeated measures analysis of variance of speech recognition and speech comprehension scores for children who utilized three different types of post-operative communication methodologies: Auditory-Verbal, Oral, and Total Communication. Setting: Tertiary academic cochlear implant center Subjects: 156 children who received their cochlear implant prior to the age of five years. Children with cochlear anomalies and known cognitive disabilities were excluded from the study. Intervention: All children received a cochlear implant. Main Outcome Measures: Speech recognition and speech comprehension scores obtained 12, 24, and 36 months post-activation with a cochlear implant. Results: Although all three groups showed significant improvements over time in all areas, children in the A-V group demonstrated more rapid improvements than children in the Oral and Total Communication groups (significant group by time interaction). Additionally, significant group effects were noted for all measures, and mean scores obtained by the A-V children were consistently higher than the mean scores obtained by children in the Oral and Total Communication groups. The results of this study can be used to assist with clinical recommendations regarding the preferred communication methodology to use with a child who has a cochlear implant.

Internal Auditory Canal Morphology in Children with Cochlear Nerve Deficiency

Oliver F. Adunka, MD, Patricia A. Roush, AuD Holly F.B. Teagle, AuD, Carolyn J. Brown, MS Carlton J. Zdanski, MD, Craig A. Buchman, MD

Objective: To describe the internal auditory canal (IAC) and inner ear morphological characteristics of children with cochlear nerve (CN) deficiency. Study Design: Retrospective case series. Setting: Academic tertiary care referral center Methods: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution magnetic resonance imaging (MRI). A review of the medical records, audiological testing results, and imaging studies was undertaken. Images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs and inner ears. Audiometric thresholds were evaluated in all subjects. Results: Among the 14 cases, 5 had known syndromes. Five children had bilateral deficient CNs while the remaining 9 subjects were affected unilaterally. Thus, 19 ears had CN deficiency (16 absent CN; 3 small CN). Eleven (58%) ears with deficient CNs had normal IACs, while the remaining 8 (42%) ears had small IACs (? 3mm). Of particular interest, 2 ears in this selected group of patients were identified as having small IACs but present CNs. Of the ears with CN deficiency, 1 (5%) had an isolated cochlear labyrinthine malformation, 5 (26%) had a vestibular labyrinthine malformations, 5 (26%) had combined cochleo-vestibular malformations, while the remaining 8 (42%) ears had normal labyrinthine morphology. Of the children with complete behavioral audiometry, profound hearing loss was confirmed in all ears affected by an absent CN. One child with a small CN had a progressive hearing loss in the affected ear. Conclusions: The findings of this study suggest that CN deficiency is not an uncommon cause of congenital hearing loss. That the majority of ears with CN deficiency had normal IAC morphology and 2 ears with small IACs had CNs present, indicates that IAC morphology is an unreliable surrogate marker of cochlear nerve integrity. Based on these findings, we believe high resolution MRI, rather than CT imaging, should be performed in all cases of pediatric hearing loss, especially in those cases where profound hearing loss has been documented.

Music Perception with a Cochlear Implant: The Effectiveness of Frequency Alignment to Electrode Placement

Bernard Fraysse, MD, O. Sterkers,MD

M. Mondain,MD, J.P. Bebear, MD B. Frachet, MD, D. Pressnitzer, PhD

J. Bestel, PhD

This European multi-centric clinical study aims at determining the effect of frequency alignment (FA) for music perception in adults implanted with the HiResTM90k cochlear implant. The FA setting uses a Greenwood-like model to derive the filter bank cut-off frequencies according to the individual electrode placement inside the cochlea, evaluated on the post-operative x-ray. Subjects wear a HiResTM90k implant and have an interest in music, confirmed through a high score to a Gfeller-like questionnaire on listening habits prior to hearing loss. For each subject the study lasts six months. Twenty subjects were randomly separated in two groups: subjects belonging to group A start with the default filter setting for the first three months and then are given the FA option for the following three months. Subjects in group B receive the two options in the opposite order. Music perception is evaluated at: one month, three months, four months, and six months after initial device activation. The test battery includes pitch, melody, and timbre comparisons; for each test, the result is a measure of a “just noticeable difference” as a given parameter is varied. We observe that subjects perform reasonably well on the pitch comparison task, and that the custom setting FA allowed some subjects to improve pitch discrimination abilities. Despite those improvements, the subjects show no significant improvement for the melody identification task. Concerning the timbre tests, subjects perform around normal-hearing people. Attack perception appears to be independent on FA, whereas FA allowed some subjects to improve on brightness discrimination.

Cochlear Implants in Elderly Patients

Teresa A. Zwolan, PhD, Steven A. Telian, MD

Objective: To report on the demographic characteristics and long term post-operative speech recognition performance of patients who received a cochlear implant after the age of 65, and to compare their results to those obtained by younger adults. Special clinical considerations for working with elderly patients were reviewed. Study Design: Retrospective analysis of speech recognition scores using repeated measures analysis of variance. Setting: Tertiary academic cochlear implant center. Patients: Results from 107 post-lingually deafened adults who received their cochlear implant after the age of 65 were compared to results obtained by 291 post-lingually deafened adults who received their devices prior to the age of 65. Of the 107 elderly patients, 37 received their implant after the age of 75. Intervention: All patients received a cochlear implant. Main Outcome Measures: Scores obtained at various post-implant intervals on HINT sentences, CID sentences, NU-6 Monosyllabic Words and/or CNC Monosyllabic Word tests when using hearing alone. Results: When averaged across all devices, patients who received their implant after the age of 65 obtained a mean sentence recognition score of 57% correct one year post-implant. Patients implanted after the age of 75 obtained a mean sentence score of 55% while patients implanted prior to the age of 65 averaged 60% correct on sentence tests. Scores obtained with more recent technology were superior to those obtained with earlier devices. Special medical and audiological considerations for providing cochlear implants to elderly patients will be discussed.

Dexamethasone Protects Against Progressive Loss of Hearing After Cochlear Implant Electrode Insertion Trauma in the Guinea Pig

Adrien A. Eshraghi MD, MSc, Jiao He MD

Thomas J. Balkany MD; Thomas R. Van De Water, PhD

Hypothesis: The progressive decrease of hearing post cochlear implant electrode insertion trauma (EIT) can be prevented by local delivery of Dexamethasone (DXM) to the inner ear. Background: Hearing loss (HL) that develops following cochlear implant EIT occurs in two stages in the guinea pig. An initial sudden loss followed by a progressive loss over the next 7 days. Direct infusion of DXM into the scala tympani of guinea pig provides a partial protection against both ototoxin and noise induced HL. Methods and Measures: Hearing acuity (DPOAEs ands ABRs) of guinea pigs was measured before cochlear implant EIT, immediately after and over the following seven days for experimental (EIT; and EIT + DXM) and control (controlateral untreated cochlea, DXM without EIT) groups of animals. Results: There were progressive increases in ABR thresholds over 7 days following EIT. DPOAE amplitudes in the EIT cochleae showed progressive decreases. Control cochleae had no significant changes in either DPOAE amplitudes or ABR thresholds. At 7 days post-EIT, the EIT+DXM animals did not have increases in ABR thresholds and their DPOAE amplitudes did not decrease. The one month follow up of these animals found that the hearing preservation by DXM is stable over this period of time post trauma. Conclusions: These results of direct infusion of Dexamethasone in an animal model of cochlear implant EIT suggest a novel therapeutic strategy for preventing the progressive loss of hearing that result from the consequences of EIT during the process of cochlear implantation. Acknowledgments: Supported by a Grant from MedEL Corporation

Conservation of Hearing with the Nucleus Advance Soft Tip Electrode

Sarah S. Connell, MD, Stacy Payne, MA; Thomas J Balkany, MD; Annelle V Hodges, PhD; Fred Telischi, MD; Simon Angeli, MD

Adrien Eshraghi, MD; Ross Germani,MD

Objective: This study was designed to test the hypothesis that partial hearing conservation is attainable after cochlear implantation with a long perimodiolar electrode. Surgical strategies for hearing conservation with the Nucleus Freedom cochlear implant are described. Study Design: Prospective, single subject repeated measures design. Setting: Academic tertiary care center. Patients: 37 patients with measurable residual hearing who received the Nucleus Freedom device with minimum 3 month follow-up. Interventions: Cochlear implantation using Nucleus Contour Advance electrode in the Freedom device. Main Outcome Measures: Standardized testing of pure tone thresholds and speech recognition. Methods: Audiometric testing was performed on 37 patients who received a Nucleus Freedom cochlear implant. Pre- and post-implant pure tone thresholds and speech recognition were measured to determine the incidence and degree of conserved hearing. Results: Some degree of hearing was conserved in 94% of patients. Forty-four percent of subjects experienced no significant change in threshold response after implantation. Speech recognition was lost in all but one subject. Conclusion: These data support the hypothesis that partial conservation of auditory function is possible with a long scala tympani electrode. However, this residual hearing is not considered functional; acoustic speech recognition was conserved in only one subject. Keywords: Hearing Preservation, cochlear implant, hearing in noise, advance off stylet technique, atraumatic electrode insertion

Evaluation of the Short Hybrid Electrode in Human Temporal Bones

J. Thomas Roland, Jr., MD Hypothesis: The current hybrid electrode can be inserted without trauma to the temporal bone and, after insertion, assumes a position within the scala tympani near the outer cochlear wall. Background: Conservation of residual hearing after cochlear implant electrode insertion requires a special insertion technique and an atraumatic short electrode. This allows electro-acoustical stimulation in ears with significant residual hearing. Methods: Human cadaveric temporal bones were implanted with soft surgical technique under fluoroscopic observation. Dehydrated and resin impregnated bones are dissected. Real time electrode insertion behavior and electrode position were evaluated. The bones are examined for evidence of insertion related trauma. Results: No trauma was observed in the implanted temporal bones and the electrode insertion dynamics evaluation revealed smooth scala tympani insertions. Conclusion: Atraumatic insertion of the 10mm hybrid electrode can be accomplished using an appropriate cochleostomy and insertion technique.

Standard Cochlear Implantation of Adults with Residual Low-Frequency Hearing: Implications for Combined Electro-Acoustic Stimulation

Michael A. Novak, MD, Jennifer M. Black, MA

Dawn B. Koch, PhD

Objective: This study compared pre- and post-operative cochlear implant performance in subjects with steeply sloping high-frequency hearing losses who were implanted with standard long cochlear implant electrodes (1) to determine the effect of etiology, and (2) to compare outcomes to studies exploring the use of combined electrical and acoustic stimulation. Study Design: Retrospective case review. Setting: Tertiary referral center. Subjects: Nine adults with steeply sloping high-frequency congenital (n = 2) or acquired (n = 7) bilateral sensorineural hearing loss. All audiograms fit the criteria for trials of a short electrode aimed at preserving low-frequency acoustic hearing. Intervention: Subjects were implanted with commercial long electrodes in the poorer ear. Outcome Measures: Pre- versus postoperative audiograms, word and sentence recognition in quiet and noise. Results: Patients with progressive acquired hearing losses experienced significantly improved speech understanding in quiet and in noise with the cochlear implant, especially when combined with hearing aid use. Patients with congenital hearing losses experienced little or no improvement in the implanted ear when tested alone, but achieved some benefit when combined with a hearing aid in the non-implanted ear. Conclusions: Patients with acquired steeply sloping high-frequency hearing losses obtain significant benefit from cochlear implantation with standard long electrodes. In progressive losses, full insertion of a long electrode would be preferable to a short electrode because acoustic hearing may diminish over time. In contrast, patients with congenital losses may not benefit from long electrodes, and may be better served by implanting a short electrode, thereby allowing use of low-frequency acoustic stimulation.

Cochlear Implant Integrity Following Electrocautery and Coblation Adenoidectomy

Patrick J. Antonelli, MD, Roxana Baratelli, MD

Background: Conventional electrosurgical adenoidectomy has been deemed contraindicated in subjects with cochlear implants, because of risk to the implant and the underlying neural tissues. No published studies have evaluated the safety of electrosurgical adenoidectomy techniques. The goal of this study was to compare the impact of monopolar electrocautery and Coblation™ radiofrequency bipolar energy on cochlear implant integrity. Methods: Twelve fresh, cadaveric pigs received unilateral cochlear implants then 15 – 30 minutes of continuous monopolar electrocautery or Coblation treatment to the nasopharynx. Implants were tested for device integrity before and after treatment. Results: Cochlear implant integrity was retained in all implants treated with either electrocautery or Coblation. Conclusions: Although the safety of electrosurgical adenoidectomy following cochlear implantation remains unproven, these observations suggest that judicious use of conventional monopolar electrocautery and Coblation radiofrequency bipolar energy in adenoidectomy do not convey a serious risk to cochlear implant integrity. Acknowledgments: Supported in part by Cochlear Americas, Med-El Medical Electronics, and Arthrocare Corporation.

Vibration-induced Nystagmus in Superior Semicircular Canal Dehiscence

Judith A. White MD, PhD, Gordon B. Hughes MD Paul M. Ruggieri MD

Objective: To describe newly characterized nystagmus induced by skull vibration in a case series of eight patients with superior semicircular canal dehiscence. Study Design: Consecutive case series. Setting: Tertiary vestibular center. Patients: 8 consecutive patients seen in the last 24 months with CT confirmed superior semicircular canal dehiscence syndrome. Intervention: Vertex, bilateral mastoid and bilateral suboccipital skull vibration was performed using 100Hz. vibration for 10-15 seconds on patients in the seated position. Main Outcome Measure: Nystagmus was monitored by infrared video oculography with digital recording. Results: All patients demonstrated distinct torsional/vertical vibration-induced nystagmus. Maximal recorded slow phase velocity was 20 d/s, induced with sub-occipital vibration on the side of the dehiscence. Conclusion: Torsional/vertical nystagmus induced with vertex and suboccipital skull vibration in the seated position appears to be a sensitive test for the presence of superior semicircular canal dehiscence.

The Gaze Stabilization Test (GST): A New Test for Detection of Vestibular Dysfunction

Joel A Goebel, MD, Nilubon Sangasilp, MD

Belinda Sinks, MA, CCC-A, Jaime Carmody, MS, CCC-A

Objective: Evaluate the sensitivity and specificity of the Gaze Stabilization Test (GST) for detection of unilateral vestibular dysfunction Study Design: Prospective controlled clinical trial Setting: Tertiary academic referral laboratory Patients: Fourteen patients (mean age 63.8 yrs, range 43-77 yrs) with history of vertigo and >50% caloric asymmetry; Fourteen control subjects (mean age 45.8 yrs, range 23-78 yrs) Intervention(s): Diagnostic test protocol with computerized system of target presentation and head velocity monitoring Main outcome measure(s): Comparison of peak head velocity with ipsilesional and contralesional head movement allowing gaze stability of randomly presented transient (75 msec) targets three optotypes above static acuity in patients and normal subjects during self-generated headshake movements Results: GST demonstrated 93% specificity, 64% sensitivity and reliability index of .91 for detection of unilateral dysfunction with ipsilesional movement. Peak head velocity in normal subjects averaged 147 deg/s while ipsilesional velocities dropped to an average of 84 deg/s. Surprisingly, peak velocities were also significantly reduced to an average of 112 deg/s with contralesional movements. Conclusions: GST is a reliable specific test of gaze stability which has diagnostic and rehabilitative applications in patients with vestibular dysfunction. Reduced contralesional velocities may help explain oscillopsia in unilateral dysfunction patients. Acknowledgments: We acknowledge technical support from NeuroCom Intl,Inc for software and hardware assistance in development of this test. Data presented in part at the 2005 ARO Midwinter Meeting and published in abstract form only.

Anterior Canal Benign Paroxysmal Positional Vertigo: An Under-appreciated Entity

Lance E. Jackson, MD, Barry Morgan, BS Jeffrey C. Fletcher, Jr., Wesley W.O. Krueger, MD

Objective: Evaluate the frequency and characteristics of benign paroxysmal positional vertigo (BPPV) arising from involvement of the anterior semicircular canal (AC) as compared to the posterior canal (PC) and horizontal canal (HC). Study Design: Prospective review of BPPV patients. Setting: Tertiary referral center. Patients: 260 patients evaluated for vertigo were identified as suffering from BPPV. Interventions: Standard vestibular assessment including electro- or videonystagmography (ENG/VNG) was completed on all patients. Based upon ENG/VNG findings, the BPPV origin was attributed to AC, PC, or HC involvement secondary to canalithiasis versus cupulolithiasis. Treatment was performed with canalith repositioning maneuvers (CRMs) appropriate for type of canal involvement. Results: For the 260 patients, the canal of origin was AC in 21.2%, PC in 66.9%, and HC in 11.9%. Cupulolithiasis was observed in 27.3% of the AC, 6.3% of the PC, and 41.9% of the HC patients. Head trauma was confirmed in the history preceding the onset of vertigo in 36.4% of the AC, versus 9.2% of the PC and 9.7% of the HC patients (p ≤ 0.001). The number of CRMs completed to treat the BPPV did not differ between canals involved (1.32 for AC, 1.49 for PC, and 1.34 for HC). Conclusions: The direction of subtle vertical-beating nystagmus underlying the torsional component is critical in differentiating AC versus PC origin; ENG/VNG aids in accurate assessment of the vertical component for diagnosis of canal involvement. AC involvement may be more prevalent than previously appreciated, particularly if the examiner does not appreciate the vertical component of the nystagmus or the diagnosis is made without the assistance of ENG/VNG. Head trauma is significantly more frequently present in AC versus other forms of BPPV, and patients with a history of head trauma should be examined closely for AC involvement. CRM is as successful for treatment of AC BPPV as for other types of BPPV.

Autonomic Nervous System Function in Chronic Dizziness

Jeffery P. Staab, MD, MS, Michael J. Ruckenstein, MD, MS

Objective: Clinical studies have indicated that autonomic nervous system (ANS) dysfunction (dysautonomia) may cause chronic dizziness. Physiologic investigations have identified links between vestibular and autonomic nuclei in the brainstem. This study examined autonomic responses in patients with chronic, unexplained dizziness. Design: Laboratory investigation of ANS activity in 19 patients with idiopathic chronic dizziness. Methods: Subjects completed comprehensive neurotologic and psychiatric evaluations to exclude those with identifiable causes of dizziness or histories of syncope. They then underwent a series of autonomic challenges, including 45 minutes of head upright tilt (HUT) on a tilt table, 20 minutes of 5% carbon dioxide inhalation while supine followed by HUT, and 2 minutes of voluntary hyperventilation while supine followed by HUT. Heart rate, blood pressure, respiratory rate, end tidal carbon dioxide concentration, and peripheral arterial oxygen saturation were measured continuously and subjects rated dizziness, autonomic symptoms, and anxiety throughout these maneuvers. Results: Ten subjects experienced sustained elevations in heart rate (>20 beats/minute) plus reproduction of their symptoms of dizziness during HUT. Seven of these had decreases in systolic or diastolic blood pressure of >20%, including 5 who’s HUT was aborted by bradycardia and hypotension. Six developed involuntary hyperventilation (>20% decrease in end tidal CO2) prior to the onset of hypotension. CO2 inhalation and voluntary hyperventilation while supine did not provoke abnormal autonomic responses or dizziness. Conclusions: Dysautonomia may be an under-recognized cause of chronic dizziness in patients with normal vestibular function. Abnormalities in cardiorespiratory responses to upright posture appear to cause their symptoms.

Quality of life Assessment of Meniere’s Disease Patients Following Surgical Labyrinthectomy

Rodney C. Diaz, MD, Wayne T. Shaia, MD

Michael J. LaRouere, MD, Dennis I. Bojrab, MD John J. Zappia, MD, Eric W. Sargent, MD

Objective: To examine the impact of surgical labyrinthectomy on quality of life of Meniere’s Disease patients. Study Design: Cross-sectional survey. Setting: Otology subspecialty referral center. Patients: All patients with Meniere’s Disease who underwent surgical labyrinthectomy between December 1998 and December 2004 were selected. Fifty-three patients satisfied inclusion criteria. Completed questionnaires were obtained from 40 patients. Intervention(s): The Meniere’s Disease Outcomes Questionnaire was used to assess the quality of life of patients before and after surgical labyrinthectomy. The questionnaire spans the physical, emotional, and social well-being domains of quality of life. Main outcome measure(s): The change in total quality of life score was used to assess the overall impact of surgical labyrinthectomy on subjective patient outcome. Individual quality of life domains were also assessed. Results: Thirty-nine of 40 respondents (97.5%) had improvement in total score following surgery. Average pre- and post-operative scores were 34±14 and 66±16, respectively (p<0.001). All pre- versus post-operative question pairs showed significant improvement (p<0.001) except questions pertaining to memory, which showed no change, and hearing loss, which showed decrease in score but no statistical significance. Conclusions: This study comprises the first directed assessment of quality of life outcomes in Meniere’s Disease patients following surgical labyrinthectomy. Despite the major disadvantage of permanent hearing loss, patients consistently reported significant improvement in all domains of quality of life and do not report a significant loss of quality of life in terms of their hearing loss. Surgical labyrinthectomy remains a viable and highly effective management option for Meniere’s Disease patients.

Treating Migraine Associated Vertigo with Topiramate

Terry D. Fife, MD, Judith A. White, MD, PhD

Introduction: Topiramate is an anticonvulsant with effectiveness as a migraine prophylactic medication. This study reviews the clinical features and responses of 41 patients treated with topiramate for migraine associated vertigo. Study Design: Retrospective chart review, 2003-2005. Setting: Tertiary neuro-otology clinics Patients: Patients with migraine associated vertigo had: (1) Episodic vestibular symptoms for at least 2 months, (2) a current or previous history of migraine according to 1988 International Headache Society criteria, (3) a history of at least one of the following on two separate occasions or at least once during a vertigo attack: migraine headache, photophobia, phonophobia, visual or other auras, (4) no other cause identified by appropriate investigations. Intervention: Therapeutic trial of daily oral topiramate (25-100 mg daily). Main Outcome Measure: 50% decrease in self-reported symptom severity and/or frequency. Results: 32 patients were female, 9 male. Vertigo occurred coincident with headache but more often independently. 31/41 (76%) had at least 50% improvement in symptoms. Side effects were mentioned in 39% (16/41), and caused 22% (9/16) to discontinue medication. These included paresthesias, dysgeusia, weight loss, and cognitive slowing. Treatment ranged from 1-41 months (median 8 months). Conclusions: Migraine associated vertigo is characterized by varying illusions of motion and motion sensitivity, often with nausea. The duration of vertigo is highly variable and often occurs independent of headache. In this cohort of patients from two institutions, topiramate was an effective medication with at least 50% improvement in 76%. Side effects, mainly paresthesias and cognitive slowing, caused 22% to discontinue medication.

Transcranial Corticobulbar Tract Stimulation and F-Wave Recordings for the Monitoring of Facial Nerve Function During Surgery for Acoustic Neuroma

Joseph G. Feghali, MD, Adauri Bueno de Camargo, MD

Vedran Deletis, MD, PhD, Chandranath Sen, MD

Objective: to study the usefulness of distant (non-direct) stimulation of the facial nerve for the monitoring of facial function during surgery for acoustic neuroma Study Design: retrospective case review Setting: tertiary referral center Patients: 20 consecutive patients who underwent surgery for acoustic neuroma. Intervention(s): Patients undergoing surgical procedures for the removal of acoustic neuroma had their facial nerves monitored using well-established electromyographic monitoring and two additional techniques of distant stimulation of the facial nerve. With the first technique, scalp electrodes are used to achieve transcranial stimulation the corticobulbar tract (TCBT). This stimulation elicits compound action potentials that are recorded from the distal facial muscles. With the second technique distal facial nerve branches are stimulated. This distal stimulation results in an antidromic stimulation of the facial nerve cell bodies. The stimulation of the cell bodies, in turn, results in a delayed contraction of the facial muscles (F-wave) that is recorded distally. Main Outcome Measure(s): 1. ability to achieve TCBT stimulation and F-wave recordings. 2. Postoperative facial nerve function. Results: Our early results indicate that TCBT stimulation of the facial nerve is highly dependable. It can be achieved and recorded in 95% of patients. It is predictive of postoperative facial nerve function in a similarly high number of cases. F-wave responses were more difficult to record (approximately 60% of patients). However, this percentage appears to be improving with experience. Conclusions: Distant –non-direct– stimulation and monitoring of the facial nerve is a useful adjunct to established methods of facial nerve monitoring during surgery for acoustic neuroma. It allows the stimulation of the facial nerve even when the nerve is not exposed. Distant stimulation is also helpful when the surgeon is not sure of the location or integrity of the facial nerve especially during large tumor removal. The paper will review the feasibility, sensitivity and specificity of non-direct facial nerve stimulation. It will also detail the theory, technique, advantages and potential pitfalls of TCBT stimulation and F-wave recordings during surgery for acoustic neuroma

A Novel Method in Predicting Immediate Post-Operative Facial Nerve Function Post Acoustic Neuroma Excision

Vincent Yu-Wen Lin, MD, David Houlden, PhD

Allison Bethune, BSc, Meghan Nolan, BSc Farhad Pirouzmand, MD, David Rowed, MD

Julian Nedzelski, MD, Joseph Chen, MD

Objective: To determine whether percentages calculated by dividing the amplitude of post-excision direct facial nerve stimulus responses (0.1 mA at pontomedullary junction) with the amplitude of distal ipsilateral transcutaneous (stylomastoid region) supramaximal stimulus responses has predictive value for determining normal or near normal (House-Brackmann 1 or 2) immediate post-operative facial nerve function. Study Design: Prospective intraoperative recordings of three muscle groups: (a) frontalis, (b) obicularis oculi, and (c) obicularis oris. Post-excision direct facial nerve stimulation at the pontomedullary junction and trancutaneous supramaximal facial nerve stimulation at the ipsilateral stylomastoid region and their associated response amplitudes were recorded. Setting: Tertiary referral centre. Patients and Interventions: Patients who underwent acoustic neuroma surgery from January 2004 to September 2005 with intraoperative facial nerve monitoring and an intact facial nerve after tumor excision were included. Recordings were available for 24 patients. Main Outcome Measure: Patients were graded post-operatively using the House-Brackmann Facial Grading System. Results: The percentage of the response amplitude of proximal direct facial nerve stimulation when compared to transcutaneous stylomastoid stimulation were significantly (p < 0.05) higher in all three muscle groups in patients who had normal or near normal immediate post-operative facial nerve function. When the average percentage of the three muscle groups was greater than 10%, the sensitivity of predicting a normal or near normal immediate post-operative facial nerve outcome was 86%. Conclusions: The percentage of the response amplitude of direct facial nerve stimulation at the pontomedullary junction when compared to the response amplitude of ipsilateral transcutaneous stimulation at the stylomastoid foramen is a good predictor of normal to near normal immediate post-operative facial nerve function.

Intraoperative Monitoring of Hearing During Cerebellopontine Angle Tumor Surgery Using Transtympanic Electrocochleography

Krszyztof Morawski, MD, PhD, Kazimierz Niemczyk, MD, PhD

Jorge Bohorquez, PhD, Andrzej Marchel, MD, PhD Rafael Delgado, PhD, Ozcan Ozdamar, PhD

Fred Telischi, MEE, MD Objective: To investigate and compare the utility of transtympanic electrocochleography (ECOG) and auditory brainstem responses (ABR) to monitor auditory function during cerebellopontine tumor (CPAT) surgery. Study Design: Retrospective analysis of a series of intraoperative monitored data. Setting: Tertiery referral center. Interventions: Diagnostic evoked auditory potential measurements. Main Outcome Measures: Intraoperative ECOG and ABR data with data of the corresponding surgical manipulations. Methods: Twenty-one patients with CPATs were operated using either middle fossa or suboccipital approaches. Auditory function was monitored using both cochlear promontory needle electrode ECOG and traditional ABR simultaneously. Click stimuli were used in every case and tone bursts were added in five cases. Results of these evoked-potential recordings were compared to pre- and post-operative behavioral audiograms. Results: Near real-time ECOG measures were obtained every six seconds with sufficient signal to noise ratio to allow identification of changes within 2-3 data points (12-18sec). Amplitude and latency measures were analyzed simultaneously, providing confirmatory information. Corresponding ABR measures required multiple averages to refresh data and, thus, the time to identify changes was between 30-90 sec. Correlation between surgical maneuvers and changes in ECOG were studied. Alterations in ECOG at the conclusion of the tumor dissection corresponded to post-operative auditory function testing. Conclusions: A near real-time method to monitor cochlear auditory function was described and tested during human CPAT surgery. The ECOG appeared to be very sensitive to certain types of aversive surgical manipulations and was helpful to reverse the negative effects by alerting the surgeon almost immediately after the event. Transtympanic ECOG appears to be a valuable component of the testing battery to monitor the integrity of the auditory system intraoperatively. Acknowledgments: KBN Poland Grant #4B05DO5617

Single Photon Emission Computed Tomography (SPECT) Scanning for Otosclerosis

Timothy B. Molony, MD, Anne E. B. Long, MD

Objective: The diagnosis of vestibular and cochlear otosclerosis remains challenging. Imaging studies, including high resolution computerized tomography as well as routine temporal bone imaging, fail to detect this condition until the advanced stages. The need for a more sensitive detection study would enhance the clinician’s ability to diagnose and manage this condition. Recent reports have indicated that single photon emission computerized tomography (SPECT) scans with temporal bone markers may be a sensitive indicator for otosclerosis. The purpose of this study is to review imaging for otosclerosis and to present a case series of patients suspected of having otosclerosis who have undergone SPECT scans. Study Design: Literature review and retrospective case series. Setting: Tertiary care referral center. Patients: Patients who underwent SPECT scanning for suspected cochlear or vestibular otosclerosis. Intervention: SPECT scan with 99m Tc-medronate infusion with temporal bone markers. Main Outcome Measures: Uptake index on SPECT scan equal to or greater than 1.35. Results: Six of the 19 patients studied had SPECT uptake indices consistent with otosclerosis of the otic capsule. Conclusions: SPECT scanning may provide a useful diagnostic tool for patients with suspected cochlear and vestibular otosclerosis. It may also be a tool by which medical therapy for otosclerosis can be monitored.

The Scala Media Technique of Adenoviral Gene Transfer into the Mouse Organ of Corti

Etai Funk, MD, Gentiana Wenzel, MD, Anping Xia, MD, PhD

Philip Ng, PhD, Frederick A Pereira, PhD, John S. Oghalai, MD

Introduction: Cochlear gene therapy is a potential technique of treating sensorineural hearing loss. The most successful technique used to date has been injection of an adenoviral vector into scala media. While the ideal species to work with would be transgenic mice that model human hearing loss, most studies to date have been done in guinea pigs because their larger cochlea is substantially easier to access. Purpose: We demonstrate our technique for gene transduction within the mouse organ of Corti. Methods: A post-auricular incision was made and the tympanic bulla was opened. The scala media was identified using the stapedial artery and round window as landmarks. Using a Skeeter drill, the bone overlying the spiral ligament of the second turn was removed. Our adenoviral vector was injected into scala media using a micropipette. The wound was closed and the mouse awakened. After 4 days, the cochleae were harvested and fixed. Results: Examination of the harvested cochleae under the dissecting microscope verified that all injections were performed into scala media. The organ of Corti was microdissected and whole-mount specimens were prepared. Confocal microscopy was used to identify cells containing green fluorescent protein, the protein product of a gene conveyed within our adenoviral vector. In all five mice, we found substantial transduction of outer hair cells and supporting cells.

Prevalence of Geniculate Ganglion Dehicence in Normal and Congenitally Thin Temporal Bones

Brandon Isaacson, MD, Jeffrey T. Vrabec, MD

Objective: To determine the prevelence of a dehiscent geniculate ganglion on routine temporal bone computed tomography. Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: A consecutive series of 130 adult temporal bone computed tomography exams were reviewed. Imaging studies with inadequate or reconstructed coronal views or a pathologic process involving the geniculate ganglion were excluded. Additional selected CT scans from patients with superior canal dehiscence syndrome were compared. Main Outcome Measure(s): Radiographic dehiscence of the geniculate ganglion defined as at least two consecutive coronal CT images (1 mm spacing) showing absence of bone overlying the geniculate ganglion. Results: The prevalence of a dehiscent geniculate ganglion was 13% in a consecutive series of temporal bone CT scans. The prevalence is increased in patients with radiographic or clinical superior canal dehiscence as compared to normals (21% vs. 11%). Conclusions: The presence of radiographic geniculate ganglion dehiscence is common. This finding has particular importance when the middle cranial fossa approach is contemplated to repair superior canal dehiscence syndrome. Our findings imply the facial nerve is more at risk for injury in individuals with a congenitally thin tegmen.

Endoscopic Intervention of Intra-labyrinthine Lesions using Micro-endoscopes and Report of a Case

Michael H Fritsch, MD

Objective: To correlate endoscopic access points to intra-labyrinthine structures, as revealed by temporal bone (TB) labs and clinical patient experience. A clinical case using endoscopic intra-labyrinthine surgery is reviewed and compared with current conventional treatment protocols. Study Design: A retrospective clinical case review is compared to lab study findings. Setting: University Medical Center; IRB approval. Intervention: Lab research and therapeutic clinical case treatment. Main Outcome Measures: Documented preservation of auditory and vestibular function in the operated ear. Results: Complete removal of a patient’s intra-cochlear schwannoma without disruption of vestibular function as predicted by lab study findings. Conclusion: TB lab and prior clinical case studies predict successful endoscopic access points for the intra-labyrinthine structures. Using these access points and endoscopic entry with micro-endoscopic (0.75 to 1.3mm diameter) technology, specific intra-labyrinthine lesions can possibly be approached using soft surgery interventional techniques and endoscopes. A case of an intra-labyrinthine schwannoma was approached in this way. The tumor, which spanned the second cochlear turn was removed in toto while vestibular function was completely preserved. The patient had no uni-labyrinth type symptoms post-operatively. Conventional approaches for this intra-cochlear lesion would likely have sacrificed vestibular function. Further inner ear pathologies have been prototype operated on in the labs with positive clinical correlations for future intra-labyrinthine organ preservation surgery.

Accuracy of a Novel, Dental-Affixed, Non-Invasive Fiducial System

for Use During Image-Guided, Middle Cranial Fossa Surgery In-Vitro

Bryan M. Davis, MD, Frank M. Warren, MD Ramya Ballachandran, MS, David M. Kaylie, MD David S. Haynes, MD, J. Michael Fitzpatrick, PhD

Robert F. Labadie, MD, PhD Hypothesis: A novel, dental-affixed, non-invasive fiducial system for use during image guided surgery (IGS) in the middle cranial fossa (MCF) will achieve sub-millimetric accuracy. Background: The anatomy of the MCF is highly variable with inconsistent landmarks - an ideal setting for IGS. Using a previously validated, non-invasive, dental-affixed, fiducial marker system, we evaluated the accuracy of IGS during cadaveric MCF surgery. Methods: Two studies were performed. The first utilized bone-implanted targets to rigorously document target registration error (accuracy) of the IGS system within the confines of the MCF. In three skulls, targets were affixed bilaterally to bone in close proximity to the foramen spinosum, internal auditory canals, and superior semicircular canals. Skulls then underwent CT scanning and locations of the targets in the CT scan were compared to corresponding locations found using the IGS system. Building on this, a second study was undertaken using IGS to define anatomic landmarks in the MCF of cadaveric heads (n=2) and comparing these landmarks to actual location after drilling to expose the landmarks. Results: In the first part of the study, target recognition error was found to be 0.75 +/- 0.26 mm (n = 18 targets). In the second part of the study, anatomic landmarks were found to be within 1mm of actual location (n=12, distance from IGS predicted to actual after drilling = 0.833 +/- 0.39). Conclusion: Using a non-invasive, dental-affixed fiducial system, IGS resulted in submillimetric identification of targets and anatomic landmarks within the MCF.

Spontaneous Middle Fossa Encephalocele and Cerebrospinal Fluid Leakage: Diagnosis and Management

Samuel P. Gubbels, MD, Nathan R. Selden, MD, PhD Johnny B. Delashaw, MD, Sean O. McMenomey, MD

Objective: To evaluate the clinical presentation, operative findings and surgical outcomes of patients with spontaneous middle fossa encephalocele (SMFE) and cerebrospinal fluid (CSF) leakage repaired using a middle fossa craniotomy (MFC) approach. Study Design: Retrospective. Setting: Tertiary referral center. Patients: Fifteen consecutive patients with 16 SMFE repaired using a MFC approach between January 1999 and July 2005. Interventions: Patients were evaluated clinically and radiologically with computed tomography or magnetic resonance imaging. Encephaloceles were approached via MFC and the skull base repaired using layered autogenous tissue and alloplastic materials including hydroxyapatite cement. Patients were followed clinically after discharge. Main Outcome Measures: Postoperative complications including CSF leak and the need for surgical revision were evaluated. Patient factors, diagnostic testing and operative findings were reviewed. Results: The diagnosis was made using clinical and radiological evaluation in the majority of patients. Beta2-transferrin testing was infrequently employed in the diagnostic workup. Multiple defects of the floor of the middle fossa were found in 50% of patients intraoperatively. Fifteen SMFE in fourteen patients were successfully repaired via MFC alone. One patient required revision with a combined transmastoid/MFC approach due to recurrent CSF leakage. Hydroxyapatite cement was used for repair of the skull base in nine patients without complication. Conclusions: MFC can be used to repair SMFE with CSF leakage with a high level of success and minimal complications. Hydroxyapatite cement is a safe and useful adjunct to aid in reconstruction of the skull base defects in cases of SMFE.

Facial Paralysis Associated with Glomus Jugulare Tumors

John P. Leonetti, MD, Douglas A. Anderson, MD Sam J. Marzo, MD, Thomas C. Origitano, MD, PhD

Rafael Quinonez, MD

Objective: To review the intraoperative findings and facial nerve management in nine patients who presented with facial paralysis associated with glomus jugulare tumors. Study Design: A retrospective analysis of patient medical records. Setting: Tertiary care, academic medical center. Patients: All patients who presented with facial paralysis and a glomus jugulare tumor who underwent surgical resection of their tumors at our institution. Intervention: A post-auricular, infratemporal fossa appraoch for tumor removal and greater auricular interposition neural repair. Main Outcome Measure: Intraoperative facial nerve findings and long-term facial recovery. Results: One hundred two patients underwent a post-auricular infratemporal approach for resection of glomus jugulare tumor from July 1988 through July 2005. Nine of these patients presented with ipsilateral facial paralysis. The medial surface of the vertical segment was invaded by tumor in all 9 cases. Facial recovery at two years was House-Brackmann Grade II in one patient, Grade III in seven patients and Grade IV in one individual. Facial recovery did not significantly change after two years (mean follow-up of 7.4 years). Discussion: Facial nerve invasion of the vertical segment occurred in nine of 101 patients (9%) in our series. Facial nerve resection with interposition grafting resulted in HB Grade II or III in eight of nine patients (89%). Facial nerve dissection and preservation was not possible when pre-operative facial paralysis was evident. Acknowledgments: The authors would like to thank Erin Sebastian for her work on the preparation and critique of this abstract.

The Pre-auricular, Subtemporal Approach for Transcranial Petrous Apex Tumors

John P. Leonetti, MD, Douglas A. Anderson, MD

Sam J. Marzo, MD, Thomas C. Origitano, MD, PhD Rita Schuman, MD

Objective: To review our series of 51 patients with transcranial petrous apex tumors who were surgically managed through a pre-auricular, subtemporal approach. Study Design: A retrospective analysis of patient medical records. Setting: Tertiary care, academic medical center. Patients: All patients with transcranial petrous apex tumors who were surgically treated between July 1988 and July 2005 with a pre-auricular, subtemporal approach. Intervention: The pre-auricular, subtemporal approach with preservation of hearing was utilized in all 51 cases. Main Outcome Measures: The degree of tumor resection and long-term results. Results: Total tumor resection was achieved in 45 patients and tumor was left in the cavernous sinus in six cases. MRI surveillance revealed no recurrent tumor in 43 patients, stable residual disease in five cases, and regrowth of tumor in three individuals. (Mean follow-up of 8.8 years.) Discussion: The post-auricular infratemporal fossa approach allows adequate exposure to the petrous apex, but with the expense of conductive hearing deficit. The pre-auricular, abtemporal approach allows wide access for transcranial petrous apex tumors with preservation of hearing. Tumor control using this approach was achieved in 48 or 51, or 94%, of the patients in this series.

Management of Endolymphatic Sac Tumors at a Tertiary Neurotology Center

Rodney C. Diaz, MD, Esmael Amjad, MD Wayne T. Shaia, MD, Eric W. Sargent, MD

Michael J. LaRouere, MD

Objective: To report the behavior, diagnosis, management, and treatment outcomes of endolymphatic sac tumors in patients treated at a tertiary neurotology referral center. Study Design: Retrospective review. Setting: Otology/Neurotology subspecialty referral center. Patients: All patients diagnosed with endolymphatic sac tumors who were treated within our practice between 1994 and 2005 were included in the study. Intervention(s): All patients were treated with primary surgical excision of tumor. In addition, three patients were treated with adjuvant radiotherapy. Main Outcome Measure(s): Primary outcome measure is survival following resection of tumor. Secondary outcome measure is disease-free survival following definitive resection. Post-operative complications are assessed. Results: Seven cases of endolymphatic sac tumors were identified during this period. All cases were treated with primary surgical resection, and three were treated with additional adjuvant radiotherapy. Follow-up ranged from 4 to 129 months. Survival and disease-free survival were both 7/7 (100%). Two of 7 patients developed persistent facial nerve paresis post-operatively. Conclusions: Endolymphatic sac tumors are uncommon malignancies of the temporal bone. We report the incidence of these tumors in a high volume neuro-otological practice. Implications on adjuvant management in patients diagnosed with von Hippel-Lindau syndrome is discussed. Although malignant and locally invasive, endolymphatic sac tumors can be treated with excellent long term survival when aggressively managed surgically.

Non-Vestibular Cranial Nerve Schwannomas in Neurofibromatosis 2

William H. Slattery III, MD, Joni K. Doherty, MD, PhD Laurel M. Fisher, PhD

Objective: To describe the incidence, location, and treatment of non-vestibular cranial nerve schwannomas in Neurofibromatosis 2 (NF2) patients. Hypothesis: Patients with cranial meningiomas will tend to have more cranial schwannomas than those without cranial meningiomas. Study Design: Prospective international longitudinal study. Setting: Tertiary NF2 specialty referral center. Patients: 77 NF2 patients, all with bilateral vestibular schwannomas, had post-contrast dedicated thin slice cranial MRI were evaluated up to 4 time points. There were 25 (47%) females, average age at diagnosis of NF2 was 24 (SD=17). Main Outcome Measures: Number, location, and volume of non-vestibular cranial nerve schwannomas and change in schwannoma size over time. Results: Nearly one out of three patients (24 patients) had bilateral vestibular schwannomas (VS) only. Fifty-three patients had other cranial tumors: 23 (30%) had no meningiomas and at least one non-VS cranial nerve schwannomas, 17 (22%) had meningiomas and no cranial nerve schwannomas, and 13 (17%) had both meningiomas and non-VS cranial nerve schwannomas. Average size of the lower cranial schwannomas was 0.5 cm3. Change in tumor size over time is described and associations with NF2 disease characteristics is reviewed. Conclusion: Lower cranial neuropathy is associated with mortality in NF2. These neuropathies are associated with swallowing difficulty, aspiration, and other sequela. The importance of monitoring and timing of treatment will be discussed in light of the natural history of these tumors.

Management of Acoustic Neuromas in Patients 65 Years of Age and Older

Pamela C. Roehm, MD, PhD, Bruce J. Gantz, MD

Objective: To determine an optimal management protocol for patients age 65 years or older at the time of acoustic neuroma diagnosis. Study Design: Retrospective case review. Setting: Tertiary care hospital. Patients: 217 patients with ICD-9 code 225.1 >65 years at time of diagnosis. Intervention: Patients with smaller tumors were followed with serial MRIs. If significant growth occurred, they were treated with surgery. Surgery was performed at intial diagnosis to patients with larger tumors or in selected patients for hearing preservation. Stereotactic radiotherapy was performed for poor surgical candidates and for patient choice. Outcome Measures: Measurement of acoustic neuroma growth and tabulation of complications. Results: 104 patients were managed by observation, 80 with surgery, and 3 with radiation therapy, with an average follow-up of 35.9 months. For patients in the observation group, average tumor growth was 0.17 cm over mean follow-up time of 46.93 months. 30 patients required crossover to surgery or radiotherapy due to tumor growth (average growth 0.55 cm/18.3 months versus 0.02 cm/50.4 months for those remaining in the observation group). One of the patients in the observation group experienced a complication (0.85%). Conclusions: Management of acoustic neuromas in elderly patients can be based on size and "biological age" criteria. Surgical treatment can be reserved for the few patients who have significant tumor growth.

CPA Melanoma: Diagnosis and Management

Derald E. Brackmann, MD, Joni K. Doherty, MD, PhD

Objective: Melanoma rarely invades the CPA and can evade accurate diagnosis, which may alter management decisions. Diagnosis may be facilitated by careful history, MRI findings, and CSF analysis. Study Design: Retrospective case review Setting: Tertiary referral center Patients: Ten CPA lesions in seven patients who presented with CPA syndrome, and who had a pathologic diagnosis consistent with malignant melanoma. Three were bilateral and 4 unilateral. Six of seven patients had a history of melanoma. Intervention(s): T1-weighted, T2-weighted pre- and post-contrast gadolinium-enhanced magnetic resonance imaging (MRI) with fat suppression and FLAIR sequence images were obtained. Lumbar puncture (LP) with CSF centrifugation and cytological analysis performed in one case. Translabyrinthine craniotomy was performed for tumor extirpation in six patients. Main outcome measure(s): Symptoms at presentation, MRI findings, presence of malignant cells in CSF, tumor progression, intraoperative findings, response to treatment, time interval from initial diagnosis of melanoma, and survival Results: Six of seven patients had history and MRI findings suggestive of malignancy in the IAC and/or CPA. Diagnosis was confirmed by CSF analysis in one patient. In six patients, diagnosis was confirmed at surgery. Conclusions: CPA melanoma portends a grim prognosis, can occur up to 17 years after initial melanoma diagnosis/treatment, and can be detected with appropriate MRI sequences, especially FLAIR images. In disseminated cases, diagnosis can be confirmed with LP demonstrating malignant cells. Management includes tumor resection when melanoma appears to be solitary and malignant cells are not present in CSF. Intrathecal chemotherapy and radiation are recommended for dissemination.