Stereotactic Gamma Knife Raiodusrgery For Vestibular Schwannoma Ming-Hsi Sun Hung-Chuan PanChiung-Chyi Shen Neurosurgery Taichung Veterans General Hospital.

Stereotactic Gamma Knife Raiodusrgery For

Vestibular Schwannoma

Ming-Hsi Sun Hung-Chuan Pan Chiung-Chyi Shen

NeurosurgeryTaichung Veterans General Hospital

Neuroscience combined conference

1968 - The first prototype of Leksell Gamma Knife® was installed in Stockholm, Sweden.

The delivery of a single, high dose of irradiation to a small and critically located intracranial volume through the intact skull

Protective shielding

Spherical collimator helmet

Leksell Stereotactic System®

Isocenter/Target in the brain

Automatic Positioning System™

201 sources of radiation

Bony wall of

Internal acoustic canal

Superior vestibular nerve Facial nerve

Cochlear nerve

Vestibular tumor arising from Inferior vestibular nerve

50% isodose line

Depiction of the internal auditory canal and its content in the sagittal plane

Inferior vestibular nerve

Selectivity in radiosurgery

Selectivity - describes how well a desired biological effect is achieved in a target volume without complications.

target biological effect

=

Conformity of dose to target

The two pictures show the necessity for multiple isocenters in order to minimize dose delivered to normal tissue.

target target

Selectivity & ConformityConformity describes only how well the prescription dose is fitted to the target volume, whereas selectivity also takes irradiation to normal tissue into account.

Conformal

Conformal and selective

Gamma Knife® surgery

95-3

92-9

93-3

Indications for Gamma Knife® surgery

Vascular disorders (15%)

Benign tumors (35%)

Malignant tumors (42%)

Functional disorders (7%)

Ocular disorders (1%)

Vascular DisordersAVMAneurysmCavernous AngiomasOther Vascular

Benign TumorsVestibular SchwannomaTrigeminal SchwannomaOther SchwannomaBenign Glial Tumors (Grade I+II)MeningiomaPituitary Adenoma (Secreting)Pituitary Adenoma (Non-secreting)Pineal Region TumorHemangioblastomaHemangiopericytomaCraniopharyngiomaChordomaGlomus TumorOther Benign Tumors

Malignant TumorsMalignant Glial Tumor (Grade III+IV)Metastatic TumorChondrosarcomaNPH CarcinomaOther Malignant Tumors

Functional DisordersTrigeminal NeuralgiaParkinson's DiseaseIntractable PainEpilepsyOCDOther Functional

Ocular DisordersUveal MelanomaGlaucomaOther Ocular Disorder

Source: Leksell Gamma Knife Society, June 2004

Neurilemmomas

Vestibular n. 12*Trigeminal n. 3Faical n. 1Hypoglossal n. 2

Total 18

July 2003 --- April 2006 follow up > 12 months in VGHTC

* Two cases of Neurofibromatosis type II

Treatment Plan : Dose –volume

Mean Margin

Dose Gy

Mean Max.

Dose GyIsodose %

at margin

Ave. Tx volume

CC

Neurilemmoma

12 24.9 50% 5.35

(11-13) (22-30) (40-50%) (0.17-20.00)

2004-02-24

2004-08-10

2005-02-03

58 y/o MGamma knife on 2004-2-2412 Gy at 50% /4.4 CC

Radiographic follow-up

Tumor volume decrease Stable Enlarge Failure

Control rate

Acoustic

Neurilemmoma

(12)

4 6 1 1* 91.6%

5 cases in hearing function (audiometry : 1 improvement, 1 worsening , 3 stable )Facial nerve function preservation :all

*One large acoustic neuroma underwent surgical resection 6 months after GKS due to persistent dizziness and imbalance

2004-8-12 2005-2-242004-3-8

62 y/o F 11 Gy at 40% /19.7CC

62 y/o F

2004-10-20 2005-04-04

Surgical resection 2005-04-30

12 Gy , 40% isodose ; 20 CC

Microsurgery

•Retrosigmoid ( Suboccipital ) Approach •Transslabyrinthine Approach

•Middle Cranial Fossa Approach

Functional Outcome of Microsurgery

Facial function Overall 80% H-B grade I-II

Size < 1.5 cm >90% ; >4 cm 40-50%

Hearing impairment Overall 30-80% preservation

8-57% retrosigmoid approach

32-68% middle fossa approach

Tinnitus Post-op immediate new symptom 30-50%

Worse 6-20%; No change: most cases; improve 25-60%

Complications CSF leakage : 2-20% ; 2.9-18% retrosigmoid approach

Death 0.5%

ICH: 1-2%

Subcutaneous hematoma 3%

Cerebellar , brainstem edema 1.2%

Hemiparesis 1.2%

Meningitis 1.2%

Cranialnerve paresis 1-2%

Recurrent rate 5-10%

Study No. Patients % of local control Facial nerve morbidity Loss of hearing

Lunsford LD,2005 829 97% 1% 21%

Regis J,2004 1000 97% 1.3% 2.2%

Landy HJ,2004 34 97% 0% 0%

Rowe JG,2003 234 92% 1% 25%

Iwai Y,2003 51 96% 0% 41%

Unger F,2002 100 96% 2% 45%

Litvack ZN,2003 134 97% 0% 38%

Petit JH,2001 45 96% 0% 12%

Bertallanfy A,2001 32 91% 12.5% 21%

Prasad D,2000 153 92% 2% 35%

Liscak R,1998 122 96% 1.9% 17%

Kwon Y,1998 63 95% 5% 35%

Noren G, 1998 669 95% 2% 30%

Radiosurgery

Treatment of choice

Source: Neurosurgery 1998; 43/3 (475-481). Pollock B.E., Lunsford L.D., Norén G.

“Vestibular Schwannoma Management in the Next Century: A Radiosurgical Perspective”

Num

ber

of

Case

s

Gamma Knife® Surgery

Microsurgery

Tumor diameter > 3 cmSymptomatic brainstem compression

Management Algorithm for Acoustic Tumors

Tumor Size,Brainstem Compression

Intracanalicular tumor Tumor diameter < 3 cmNo or mild brainstem compression

Age,Health Review of Treatments, GoalsPatient’s choice

> 75 yr < 75 yr

Observation

Tumor growth Tumor growth

Radiosurgery

Residual or Recurrent tumor

Observation

MicrosurgeryMicrosurgery

Microsurgery

Microsurgery

Residual tumor Complete resection

Radiosurgery

Radiosurgery Radiosurgery

Tumor growth

Radiosurgery Practice Guideline By L. Dade Lunsford; Ajay Niranjan

IRSAIRSA