Intracranial Endoscopy

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eurosurg Focus 6 (4):Article 1, 1999

ntracranial endoscopy

enry W. S. Schroeder, M.D., and Michael R. Gaab, M.D., Ph.D.

epartment of Neurosurgery, Ernst Moritz Arndt University, Greifswald, Germany

he authors' intention is to reduce the invasiveness of intracranial procedures while avoiding

aumatization of brain tissue, to decrease the risk of neurological and mental deficits. Intracranial

doscopy is a minimally invasive technique that provides rapid access to the target via small burr hoithout the need for brain retraction. Craniotomy as well as microsurgical brain splitting and dissecti

n often be avoided. Furthermore, because obstructed cerebrospinal fluid pathways can be

hysiologically restored, the need for shunt placement is eliminated. The ventricular system and

barachnoid spaces provide ideal conditions for the use of an endoscope. Therefore, a variety of

sorders, such as hydrocephalus, small intraventricular lesions, and arachnoid and parenchymal cyst

n be effectively treated using endoscopic techniques. With the aid of special instruments, laser fibe

d bipolar diathermy, even highly vascularized lesions such as cavernomas may be treated. Moreovuring standard microsurgical procedures, the endoscopic view may provide valuable additional

formation ("looking around a corner") about the individual anatomy that is not visible with the

icroscope. In transsphenoidal pituitary surgery, transseptal dissection can be avoided if an endonas

proach is taken. In the depth of the intrasellar space, the extent of tumor removal can be more

curately controlled, especially in larger tumors with para- and suprasellar growth.

he combined use of endoscopes and computerized neuronavigation systems increases the accuracy

e approach and provides real-time control of the endoscope tip position and approach trajectory. In

ture, the indications for neuroendoscopy will certainly expand with improved technical equipment.

ey Words * neuroendoscopy * neuronavigation * aqueductoplasty * third ventriculostomy *

achnoid cyst * hydrocephalus * intraventricular tumor * pituitary surgery

lthough the first intracranial endoscopic procedures were performed at the beginning of this

ntury,[21,22,29,90] endoscopic techniques have never achieved widespread popularity among

urosurgeons. The main reasons were poor miniaturization of endoscopes, insufficient instruments,

umination, and attendant problems with hemostasis and infections. However, because of the ongoi

finement of endoscopes and instruments, as well as development of bright cold light sources and m

deo cameras, endoscopes have been increasingly used in brain surgery since the late 1980s.[116] T

e of neuroendoscopy in combination with frame-based or, recently, frameless stereotaxy (compute

uronavigation) increases the safety and precision of the endoscopic approach. Nevertheless,


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uroendoscopy is still in its infancy. In this paper, we will continue the discussion of neuroendoscop

dications as well as its advantages and disadvantages; the debate is ongoing as new endoscopes and

struments are presented with increasing frequency.

DESCRIPTION OF EQUIPMENT

or intracranial neuroendoscopy, a sophisticated and complex neuroendoscopic system that includes

rious rigid, semiflexible, and flexible scopes, and bright cold light sources is needed, as well as a

gh-resolution video camera system, effective instruments, and irrigation devices. Combination with

uiding system is helpful, and sometimes even mandatory. We use the universal Gaab neuroendosco

stem developed by the senior author.[35]

he endoscopes are introduced via an operating sheath (6.5-mm Gaab I; 4.0-mm Gaab II miniature

stem) that is initially inserted with the aid of a trocar, which permits the intraoperative exchange of

fferent scopes without reinserting scopes through brain tissue, thus eliminating unnecessary injury

e surrounding healthy brain. Rigid rod-lens scopes (Karl Storz GmbH and Co., Tuttlingen, German

e preferable because of their superb optical quality and wide-angle view, as well as ease of guidanc

d orientation. These endoscopes provide an excellent overview of the intraventricular anatomy.

lthough minor hemorrhages may blur the view, the surgeon will remain oriented, which is extremelfficult with the poor optics of a fiberscope. Rigid scopes with four different angles of view areailable (0, 30, 70, and 120). The 0 and 30 scopes are used for inspection and manipulation; the 7

d 120 scopes are used for inspection only ("looking around a corner"). Because the operating

doscope (wide-angle straight-forward scope with angled eyepiece) has no separate working channe

lows the whole inner diameter (about 6 mm) of the endoscopic sheath to be used, which permits

fective tissue removal and implant insertion of devices such as stents. The miniature endoscope

.2-mm outer diameter) has been developed for use in pediatric patients. This semirigid minifiber

doscope (10,000 fibers/mm2) incorporates an instrument channel as well as two separate channels

rigation in- and outflow. When manipulations "around a corner" are to be performed, steerable

berscopes containing an instrument channel of 1.2 mm (outer diameter 2.5 mm and 3.5 mm) are useowever, for most endoscopic procedures we prefer the rigid rod-lens scopes because of their superi

ptical properties.

arious mechanical instruments of different sizes are available, such as scissors, biopsy and grasping

rceps, hooks, and puncture needles. Both the operating endoscope and the miniature scope allow

anipulations to be performed with rigid instruments in a straight line, which provides a good tactile

edback from the tissue and makes easy guidance of the tools possible. Bipolar as well as monopola

athermy probes and a laser guide are used for hemostasis and dissection. We prefer a 1.064-m

d:YAG laser. Balloon catheters are used to enlarge ventriculostomies or other fenestrations.

or irrigation, we use the Malis irrigator for which the flow is easily controlled using a foot switch.

actated Ringer's solution at 36 to 37C is preferable to saline, because postoperative increases in bo

mperature, often observed after abundant irrigation with saline, are rarely encountered. It is very

mportant to make sure that the outflow channel is open to prevent dangerous increases in intracrania

essure (ICP).

enon light sources provide the best illumination, because the color temperature of xenon light

sembles that of sunlight (6000 K). The light is transmitted via fiberglass or fluid cables from the liguntain to the endoscope.


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igital 1- or 3-chip mini video cameras are attached to the endoscope via a sterile optical bridge.

ecause the camera and bridge are draped with a sterile covering, the sterile intraoperative exchange

doscopes is allowed using the same camera without sterilizing the sensitive electronics.

igh-resolution video monitor screens display the endoscopic picture. Each endoscopic procedure is

ped with a S-VHS recorder. Analog video recordings can be processed using a digital processing u

Digivideo, Karl Storz GmbH and Co.) to enhance contrast as required. Finally, the documentationuipment includes a video printer and digital still recorder. For some endoscopic procedures, the

multaneous use of two endoscopes is beneficial. The images from both scopes can be displayed on deo monitor with the aid of a digital picture-in-picture device (Twinvideo, Karl Storz GmbH and C

this way, the surgeon obtains information provided by both scopes while looking at only one scree

GENERAL OPERATIVE TECHNIQUE

fter induction of general anesthesia, the patient is typically placed in the supine position with the

ghtly anteflexed head placed in a horseshoe-shaped headrest or pin fixation. If computerized

uronavigation is used, the dynamic reference frame is mounted on the Mayfield clamp and the cam

r adjusted. After image registration, the operating field is prepared and draped. Antibiotics are not

utinely used.

he optimum position of the entry point is commonly determined by evaluating preoperativemputerized tomography (CT) scans or magnetic resonance (MR) images.[36] However, if the

ntricles are small or the target is located in the posterior part of the third ventricle, it is very helpfu

e a guiding system to find the ideal access route, thus avoiding infliction of unnecessary brain trau

hen treating some cystic lesions, such as parenchymal cysts or loculated hydrocephalus, it is

andatory to use navigational guidance because there are often no anatomical landmarks, and one ca

sily get lost in the cavity. Frame-based stereotaxy,[4,32,44,9699,143] ultrasound-guided stereotax

d recently, frameless computer-based stereotaxy[28,81,82] have been used in combination with

uroendoscopy to increase the accuracy of the approach. In cooperation with Carl Zeiss and Karl StmbH & Co., we have developed a universal guiding system for endoscopic purposes.[119] With th

an infrared-based computerized navigation system, the Surgical Tool Navigator, the endoscopic sh

n be inserted precisely into the ventricles even if they are very narrow. This technique also allows

curate planning of the approach before starting with surgery (for example, the straight approachrough the foramen of Monro to the aqueduct without injuring the fornix). Frameless neuronavigatio

ables free-hand movement of the endoscope with real-time control of the endoscope tip position an

e approach trajectory. The accuracy is between 2 mm and 3 mm, which has proved to be sufficient

doscopic purposes. After reaching the target area with navigational guidance, minor position

rrections can be made under direct endoscopic view.

general, the entry point is located contralateral to the dominant hemisphere. However, if the

ntricular system is asymmetrical, the approach should be performed via the larger foramen of Monfter a 3-cm straight scalp incision, a 10-mm burr hole is made. Once the dura has been opened, the

perating sheath with trocar is inserted free hand or under navigational guidance into the lateral ventr

d fixed with two Leyla retractor arms. The trocar is then replaced by the rigid diagnostic scope. Af

entification of the main landmarks--choroid plexus, fornix, and veins--the target area is approached

are must be taken to avoid damaging the fornix and subependymal veins while introducting the she

to the foramen of Monro. After completion of the procedure, the diagnostic scope is used to inspec


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rget area to ensure that there is no active bleeding. Then the operating sheath and the endoscope are

multaneously withdrawn to visualize any bleeding in the cortical puncture channel. We pack the bu

ole with a gelatine sponge and tightly suture the galea to prevent subgaleal cerebrospinal fluid (CSF

cumulation and fistula formation. The skin is closed using running atraumatic suture.

INDICATIONS FOR NEUROENDOSCOPY

prerequisite for safe endoscopic procedures is clear visualization of the anatomy. Preformed caviti

led with crystal-clear CSF, such as the ventricular system, subarachnoid space, and some cystic

sions, provide optimum conditions for the application of endoscopes. Therefore, hydrocephalus,

traventricular lesions, and space-occupying arachnoid or parenchymal cysts are ideal indications foe of an endoscopic approach. Due to the further improvement of endoscopic hemostasis (that is, th

velopment of bipolar coagulation probes and suitable laser devices), even highly vascularized tum

n be resected. Furthermore, neuroendoscopes can also be used together with the operating microsc

obtain more detailed information for the dissection.

anagement of Hydrocephalus

ydrocephalus represents the classic indication for a neuroendoscopic approach. As early as 1910,

espinasse performed fulguration of the choroid plexus in two infants.[22] In 1923, Mixter[90]rformed the first endoscopic third ventriculostomy. Currently, hydrocephalus remains the most

equent intracranial disease treated endoscopically.

ndoscopic third ventriculostomy has become a well-established procedure for the treatment of

oncommunicating hydrocephalus (Fig. 1).[6264,71,129] In our experience, third ventriculostomy h

en successful in controlling obstructive hydrocephalus caused by tumors, aqueductal stenoses,morrhages, and infarctions. Although the procedure is commonly considered to be safe and

raightforward, severe and, rarely, fatal complications may occur.[48,87,123] The correct placement

e fenestration in the floor of the third ventricle is of utmost importance to avoid vascular and neura

mage. The perforation of the floor should be made halfway between the infundibular recess andammillary bodies in the midline, just behind the dorsum sellae. In this way, hypothalamic injury,

ulomotor palsy, and vascular injury are unlikely to occur. Careful inspection of a CT scan or sagitt

R image to assess the individual relation of the basilar artery and the floor of the third ventricle is

visable.


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Fig. 1. Imaging studies demonstrating noncommunicating hydrocephalus caused by

aqueductal stenosis. AD: Intraoperative neuroendoscopic views; EH: magnetic resonance

images. A: Photograph demonstrating enlarged foramen of Monro with fornix (F), septalvein (S), and atrophic choroid plexus (C). The aqueduct can be seen behind interthalamic

adhesion (A). B: Photograph revealing that the aqueduct is occluded by gliotic tissue above

posterior commissure (P). C: Photograph demonstrating third ventriculostomy performed

between clivus (C) and mammillary bodies (M). D: View obtained through ventriculostomy

into prepontine cistern with basilar artery (B). E: Axial T1-weighted image revealingenlarged lateral ventricles with flattening of gyri. F: Sagittal T2-weighted image

demonstrating aqueductal stenosis with dilated proximal aqueduct and markedly enlargedthird ventricle (note suprapineal recess compressing cerebellum and floor of third ventricle

that bulges into interpeduncular cistern). G: Axial T1-weighted image obtained 20 months

postsurgery revealing decrease in ventricular size and normal cortical relief. H: Sagittal

T2-weighted image obtained 20 months postsurgery revealing decrease in size of third

ventricle and vigorous CSF flowvoid sign through patent ventriculostomy.

ifferent techniques have been recommended for performing third ventriculostomy, including blunt

rforation with a leukotome[45,67] or the scope itself,[64,129,132] inflation of balloon catheter,[94

agulation with monopolar diathermy,[71,109] and laser fiber.[131] We prefer the blunt perforation

iginally proposed by Frerebeau, et al.,[33] in which a No. 3 French Fogarty catheter or closed biop

rceps is used along with subsequent enlargement of the opening by inflating the balloon of the cath

ometimes the floor is very tough and its blunt perforation causes considerable tension to the floor an

jacent hypothalamus. Furthermore, there is a risk that the catheter may slip away and perforate the

oor too far laterally or posteriorly, which increases the risk of vascular or nerve complications. In th

ses, we use a bipolar diathermy rod to achieve the initial perforation, which is then enlarged by

flating the balloon of the Fogarty catheter.


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successful third ventriculostomy does not necessarily reduce the ventricles to normal size. Often th

ntricles remain dilated, in spite of complete clinical recovery.[75,129] In two large series in which

doscopy was performed in over 100 patients, the success rate was reported to be between 70% and

% in patients older than 2 years of age and between 45% and 50% in the patients under the age of

ars.[61,129] However, with proper patient selection, the success rate may be increased.[67]

nfortunately, to date there is no reliable test available to predict the success of the procedure. There

e use endoscopic techniques first to avoid placing a shunt (indication "ex juvantibus").

ven in long-term shunt-dependent patients in whom shunts have malfunctioned, third ventriculostom

ay be effective and should be attempted.[65,140] If the endoscopic attempt fails, a shunt may be

inserted with clear indication.

ndoscopic techniques are also useful in the accurate placement of ventricular catheters or in shunt

vision procedures.[74,133,141] Under direct view, the catheter is placed in the ideal position away

om the choroid plexus to decrease the risk of shunt obstruction. During a shunt revision procedure,

tained ventricular catheter can be freed from surrounding choroid attachments or scarring by using

polar diathermy or laser devices. Another valuable indication for an endoscopic approach is loculat

ydrocephalus.[77] Intraventricular septations are widely fenestrated and embedded ventricular cathe

moved. After converting the multiloculated compartment into a single loculation, shunt systems ca

mplified, which results in a lower complication and shunt-revision rate.

ith aqueductal stenosis, endoscopic aqueductoplasty offers an alternative treatment option to third

ntriculostomy. Initially, the aqueduct is inspected using the aid of rigid rod-lens scopes and steerab

berscopes. If the aqueduct is occluded by a thin membrane, this membrane is simply perforated. In

ort stenoses, the aqueduct is restored by gently inflating the balloon of a Fogarty catheter. A stent m

inserted into the aqueduct to prevent later occlusion by scarring. Reopening of the aqueduct in lon

enoses carries a high risk of midbrain injury with neurological sequelae, such as dysconjugate eye

ovement, Parinaud's syndrome, oculomotor palsy, or trochlear palsy. In these cases, it is safer to

rform a third ventriculostomy. Another potential use of aqueductoplasty and aqueductal stent

acement is in patients with trapped fourth ventricle.[130] Endoscopic aqueductoplasty in which ste

e not placed seems to be effective in short stenoses. However, longer follow-up periods are necessa

evaluate the long-term aqueductal patency after aqueductoplasty.

ndoscopic choroid plexus coagulation has been sporadically recommended for the treatment of

mmunicating hydrocephalus.[105,114,115] However, what explains the high failure rate is the fact

ere is a considerable amount of extrachoroidal ventricular fluid formation.[88,89] Recently choroid

exus coagulation has been proposed for use in selected milder forms of communicating

ydrocephalus.[104] Nevertheless, the efficacy of this procedure and clear indication criteria remain determined.

nsuring the independence of the shunt should be the primary aim in the management of obstructive

ydrocephalus. Moreover, even after long-term shunt dependence, endoscopic internal shunting shou

considered to eliminate the need for a shunt. If the endoscopic attempt fails, a shunt can be inserte

subsequent procedure.

traventricular Tumors

mall, poorly vascularized tumors of the lateral or third ventricle that cause enlargement of the ventr


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y occluding CSF pathways are ideal indications for an endoscopic approach. The ventricular dilatio

ovides sufficient space for maneuvering the endoscope and manipulating the instruments. However

traventricular lesions are also accurately approached via small ventricles by using computerized

uronavigation.

major limiting factor in endoscopic tumor resections is the tumor size. Most neuroendoscopes

rrently available have a working channel of 2.4 mm at best. It is clear that the use of the devices to

move even small tumors is a time-consuming procedure. The benefits of the minimally invasive

chnique--less brain retraction and small burr-hole approach--are then outweighed by the duration operation. Therefore, our operating endoscope has no separate working channel. The whole inner

ameter (> 6 mm) of the operative sheath through which the endoscope is introduced is available for

moval of large tumor pieces. The size limitation of a tumor to obtain effective endoscopic removal

fficult to determine. If the tumor is too large, however, endoscopic piecemeal resection may becom

me consuming and ineffective. Therefore, a solid tumor should not exceed 2 cm in diameter. In

dition, the consistency and vasculature of the tumor must be considered. Resection of a soft tumor

sier and faster than the removal of a firm lesion. If the tumor is cystic or contains major cystic parten larger lesions can be resected endoscopically (Fig. 2). Highly vascularized lesions such as

vernomas and hemangiomas can also be safely removed with the aid of a Nd:YAG laser and bipola

athermy. In the case of larger tumors (with accompanying hydrocephalus) not amenable to endoscosection, a third ventriculostomy or aqueductal stent placement to restore CSF flow is indicated. If t

mor occupies the entire third ventricle and risks obstructing the foramen of Monro and aqueduct, th

ent should be inserted through the entire third ventricle and aqueduct connecting lateral, third, and

urth ventricles. Unilateral occlusion of the foramen of Monro may be treated by septostomy of the

ptum pellucidum. Sometimes both stent placement and septostomy are necessary to restore CSF flo

biopsy sample can be obtained of any tumor visible at the ventricular surface.


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Fig. 2. Imaging studies demonstrating craniopharyngioma. AD: Intraoperative

neuroendoscopic views; E and F: computerized tomography scans. A: Photographdemonstrating foramen of Monro with fornix (F), choroid plexus (C), thalamostriate vein

(TV), and tumor (T) within the third ventricle. B: Photograph depicting the capsule resection

by using forceps. C: Photograph showing the outflow of greenish content after opening. D:

Photograph showing the stent placed in aqueduct. E: Axial scan revealing a hypodense

cystic tumor within the third ventricle and accompanying hydrocephalus. F: Postoperative

axial scan demonstrating the complete evacuation of the tumor, aqueductal stent in place,

and resolution of hydrocephalus.

lthough stereotactic biopsy sampling is the classic option to clarify the tissue diagnosis of lesions in

rious locations, "blind" stereotactic puncture of tumors in the vicinity of the foramen of Monro hasotential danger of injuring the fornix and causing the ependymal veins to hemorrhage.[76] Stereotac

opsy sampling of pineal lesions risks damaging the great vein and the internal veins. Endoscopic

opsy sampling offers distinct advantages when compared with pure stereotactic MR- or CT-guided

opsy sampling. The lesions can be visualized. The individual anatomy including the capsule's

sculature is inspected and vessels at risk can be cauterized. Anatomical changes in coordinates, suc

ter cyst aspiration, can be recognized, and much more tissue can be obtained under direct view.

eeding can be avoided or detected early, and hemostasis is achieved under visual control. Especialr lesions located in the pineal region, we consider the endoscopic approach to be superior to


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ereotactic biopsy sampling. Despite recent reports on large series of stereotactically obtained biopsy

mples of pineal lesions,[70,108] in which this technique was described as safe and reliable, we are

ncerned about the "blind" sampling of tissue in this area. We prefer neuroendoscopic exploration a

btaining a biopsy sample under direct visualization.[40] By using the same approach, accompanying

SF pathway obstruction can easily be relieved by placing a stent in the aqueduct or by performing aird ventriculostomy. Thus, endoscopy offers histological verification and permanent reconstitution

ocked CSF pathways. After obtaining an accurate histological diagnosis, the decision is made for

bsequent microsurgical intervention, radiotherapy, chemotherapy, and/or radiosurgery.

fter the scope has been guided to the tumor, the surgeon inspects the tumor to become familiar with

lationship to the surrounding structures. Before tumor dissection, capsule vessels are cauterized wi

e aid of a bipolar diathermy probe or an Nd:YAG laser in noncontact mode. Tissue specimens are t

btained for histological examination. Depending on the tumor size, removal usually starts withtracapsular debulking or dissection in the plane between tumor and normal brain tissue. During this

ssection, feeding arteries must be identified early and coagulated before bleeding obscures the clea

ew. Use of the Nd:YAG laser has proven suitable for the removal of well-vascularized tumors.[121

isel laser fiber is initially used in noncontact mode for vessel coagulation and tumor shrinking. Tum

ssection is then accomplished with the same or a conical fiber in contact mode for cutting. The

ser-assisted resection requires vigorous irrigation to avoid thermal damage to the adjacent brainsue.[42]

ecause each endoscopic tumor resection is accompanied by some bleeding, all procedures arerformed under continuous irrigation with Ringer's solution at 36C to maintain a clear view.[37] T

rigation is controlled with a Malis irrigator. To focus the irrigation on the hemorrhage source, a sep

rigation tube is precisely placed. For forced rinsing, a 20-ml syringe is used manually. The hemosta

small hemorrhages represents no problem, because these usually cease spontaneously after a few

inutes of irrigation. In rare cases, irrigation periods of more than 10 minutes become necessary to s

arger venous bleeding and to make visibility clear again. To prevent a dangerous increase in ICP, c

ust be taken to maintain a sufficient outflow of irrigation fluid. Larger vessels at risk of being torn

uring tumor resection should be cauterized using the bipolar diathermy probe. In well-vascularized

mors, the CSF can be aspirated and the procedure performed in a dry field. With this "dry-field"

chnique, bleeding vessels are more easily identified and hemostasis is quickly achieved, because

oody CSF no longer obscures vision.

he preliminary results of endoscopically managed intraventricular tumors are promising.[38] There

doscopic techniques should be considered for the treatment of selected intraventricular lesions.

owever, all preparations should be made for immediate microsurgical intervention should

mplications arise or the endoscopic procedure be deemed ineffective.

olloid Cysts

anscallosaltransventricular,[2,55] transcorticaltransventricular,[2,79,86,92]

anscallosalinterfornicial,[5] transcorticaltransventricular stereotactic approaches,[1,13] and

ereotactic aspiration[12,27,47,68] have been recommended for the treatment of colloid cysts. Shunt

ould not be considered as a treatment option because of its attendant high rate of complications.[17

icrosurgical procedures the complete removal of the cyst is the rule.[30] However, potential risks a

ell known. Complications associated with the transcallosal approach include venous infarction,


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rombosis of the sagittal sinus, disconnection syndromes, fornicial injury, and infarcts to the thalam

d basal ganglia.[80] The transcortical approach has been reported to be associated with a higher ra

izures.[79,86] Because of its simplicity and low risk, CT-guided stereotactic aspiration of colloid c

s been advocated.[12,27] However, in hyperdense cysts, in which solid content is indicated,

ereotactic aspiration has often failed.[68] An endoscopic or microsurgical procedure then iscessary.[69] In addition, performing "blind" stereotactic aspiration carries the risk of injuring the

rnix and causing bleeding from ependymal veins.[76] Most importantly, a high recurrence rate (up

0%) following aspiration of colloid cysts has been reported after long-term follow-up study.[85] Fa

the procedure has been detected within the first 2 months and after more than 8 years. Some patiencame comatose due to tentorial herniation. These findings underline the fact that simple aspiration

ot sufficient. The key seems to be achieving a wide opening of the cyst and complete or near-compl

section of the capsule. Because sudden death caused by colloid cysts has been reported,[1,110,113]

en asymptomatic cysts with signs of CSF pathway obstruction should be treated surgically.

our experience, any cyst contains at least partially solid components. Hence, simple stereotacticall

uided aspiration will not result in complete evacuation of the cyst. However, by using the endoscop

chnique a total evacuation and at least near-total resection of the membrane can be achieved.

ostoperative external ventricular drainage is not necessary. The aim of surgery in treating colloid cy

restoration of the foramina of Monro, resolution of hydrocephalus, and prevention of recurrentockade of the foramina. This can be achieved by using microsurgical and endoscopic techniques.

lthough currently, low morbidity and mortality rates following microsurgical removal of colloid cy

ve been achieved by experienced surgeons, the endoscopic minimally invasive burr-hole approach

ss traumatic to the brain and is equally as effective. Recently, Mathiesen, et al.,[84] have reported a

ries in which the microsurgical removal of 24 colloid cysts (22 transcallosal and two transcortical)

rformed by experienced neurosurgeons. Nevertheless, transient memory deficit caused by fornicialaction was noted in 26%. Two colloid cysts that were surgically treated by less experienced surgeon

en resulted in death or permanent memory loss. The authors stressed that piecemeal removal, as w

rformed in our endoscopic technique, rather than in toto removal is the key to avoid fornicial injuryd consequent memory impairment.

olloid cysts are the intraventricular lesions most often treated

doscopically.[14,19,20,24,26,76,106,143] The endoscopic approach combines the minimal

vasiveness of stereotactic aspiration with the effectiveness of microsurgery. By using an endoscopeSF pathways that are still obstructed after cyst removal can be restored, which is not possible when

ing simple stereotactic techniques.[134] Therefore we consider the endoscopic removal of colloid c

e therapy of choice.[117] However, the question remains whether small remnants of the membrane

hich may be left in place, cause cyst recurrence. Only long-term evaluations can answer this questio

rachnoid Cysts

he CSF-like content of congenital arachnoid cysts provides excellent conditions for the application

endoscope. Arachnoid cysts are predominantly located in the sylvian fissure.[18,51,139] However

sts in any other location, such as the anterior[7] and posterior cranial fossa,[31,58,78] quadrigemin

stern,[49,100,127] interhemispheric fissure,[51] suprasellar region,[56,103] or intraventricular

ace,[72,83,138] are suitable for an endoscopic approach.

any operative procedures have been recommended for the treatment of arachnoid cysts, including


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icrosurgical cyst excision[25,72,93,112] or fenestration,[7,58] stereotactic aspiration,[57,101] cyst

nestration with arachnoidplasty,[125] cystocisternostomies,[11] ventriculocystostomies,[103,107]

stosubdural shunting,[136] cystoperitoneal shunting,[6,18,51] and endoscopic fenestration.[16,23,

owever, the best treatment option remains to be determined. Major complications associated with

icrosurgical cyst fenestration/resection and shunting procedures reported in the literature includeeningitis, hemiparesis, oculomotor palsy, subdural hematomas, new grand mal seizures, and even d

llowing the former[3,18,78,137] and shunt malfunction and infection following the latter.[3,6,51,7

hunt placement is obviously safer, but it is associated with a higher incidence of additional surgical

ocedures and the disadvantage of life-long shunt dependence.[73,93] By using endoscopic technique complications associated with microsurgery are rare, and similar or even better results are achiev

urgical intervention is indicated in symptomatic space-occupying arachnoid cysts (Fig. 3). If MR

maging demonstrates no mass effect, or the relation of symptoms and arachnoid cyst is debatable, thCP should be monitored for increased ICP and/or pathological pressure waves. The surgical indicati

r asymptomatic arachnoid cysts is controversial.[6] In spite of the high vulnerability of arachnoid c

patients who have sustained minor head trauma, we consider surgery for asymptomatic arachnoid

sts in adults to be unjustified. In contrast, surgery should be performed in children who harbor

ymptomatic cysts that exert a mass effect,[6,95] although spontaneous regression of arachnoid cyst

s been sporadically reported.[135] Because cyst expansion may jeopardize normal development annction of the adjacent brain in children, this potentially harmful effect outweighs the risk of the

perative procedure.[18,51]

Fig. 3. Axial CT scans revealing a space-occupying arachnoid cyst in the sylvian fissure

(left) and, 6 months after cystocisternostomy, a decrease in cyst size as well as resolution of

midline shift and ventricular compression (right).

he entry point is selected according to the best trajectory determined from assessing MR imaging or

ith the aid of a computerized neuronavigation system that is especially helpful in cystic cavities lac

ell-known landmarks and when small hemorrhages obscure a clear view. It is of the utmost importa

cauterize the fragile arachnoidal blood vessels in the entry zone of the operating sheath to avoid


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eeding after movements of the endoscope. Outflow of CSF should be minimized to prevent collaps

e cyst and accumulation of CSF between the outer cyst membrane and the dura mater, which may

sult in subdural hematoma.[3] Additionally, care should be taken not to detach the outer cyst

embrane from the dura mater when inserting the operating sheath, which would also result in cyst

llapse. Depending on cyst location, cystocisternostomies, ventriculocystostomies, andntriculocystocisternostomies are performed. Each operation is performed under continuous irrigati

ith Ringer's solution at 36C. If significant bleeding occurs and even under intensive irrigation clea

sibility cannot be maintained, the endoscopic procedure must be abandoned, and the operation mus

ntinued microsurgically. Before removing the scope, the cyst is vigorously irrigated to remove anyots that may promote arachnoid fibrosis and closure of the fenestration.

suprasellar arachnoid cysts, a slit valvelike structure formed by arachnoid membranes around the

silar and vertebral arteries has been observed endoscopically.[16,111,118] The valves open and clonchronously with arterial pulsations. These cysts are obviously filled by CSF pulsations of vascula

igin, which pump the CSF into the cyst. Due to the one-way configuration of the valve, the CSF ca

cape from the cyst. Interestingly, in none of the arachnoid cysts in other locations have we found a

lvelike structure.

euroendoscopy is a safe and effective treatment option for arachnoid cysts and should be seriouslynsidered as the initial therapy. Should the endoscopic procedure fail, microsurgical fenestration or

unting can be subsequently performed without causing additional risk to the patient. By performing

uroendoscopy, the surgical trauma can be reduced to a minimum and craniotomies as well as shunpendence can be avoided.

tuitary Surgery

he microsurgical transseptal transsphenoidal approach to pituitary tumors has been established as th

andard technique for decades.[50] Guiot, et al.,[46] were the first to use an endoscope in

anssphenoidal pituitary surgery. Endoscopes were mainly used as an adjunct to the operatingicroscope in the transseptal approach.[41,124,142] However, transseptal dissection is not without

ported potential complications such as breathing problems, septum perforations and deviations, and

umbness of the maxillary dentation after sublabial incision. Inspired by the endoscopic sinus surger

rformed by otolaryngologists, an endoscopic endonasal approach to the pituitary gland has been

veloped.[52,59,60,126] To obtain sufficient working space for endoscope and instruments within o

ostril, it is necessary to outfracture or resect the middle turbinate and displace the nasal septum. Wit

doscopic sheath-aided access under the control of combined neuronavigation and lateral fluorosco

hich we are currently developing, this can be avoided.[39] Various endoscopes and instruments are

troduced via the sheath into the operating field without damaging the nasal mucosa. However, one

sadvantage is the restricted ability to maneuver the instruments, a problem that will be overcome we development of specially designed instruments.

he endonasal endoscopic approach to pitiutary or clival lesions offers simple and rapid access to the

rget, reduces the postoperative discomfort of the patients, and shortens the hospital stay. Nasal pack

not required, or, if it is, only for a short time. Endoscopes provide an excellent panoramic view in

pth of the sphenoid sinus and sella. The ability to inspect supra- and parasellar tumor extensions, n

sible when using the operating microscope, increases the completeness of tumor removal.

ndoscope-Assisted Microsurgery


13/22

nother field of application for neuroendoscopes in neurosurgery is endoscope-assisted microsurger

her words, the supplementary use of endoscopes during microsurgical procedures.[34,43,102] This

chnique is very useful for inspecting areas not visible in the field of the microscope (that is, "lookin

ound a corner"). In vestibular schwannoma surgery, the endoscope is used to confirm completenesmor removal in the internal auditory canal.[128] However, endoscopes cannot only be used for

sualization but also for microsurgical dissection. The surgeon can manipulate microsurgical

struments under endoscopic control by looking at the monitor screen. This is especially advantageo

surgery for deeply located lesions in which visualization obtained through the microscope is hindey structures in front of the lesion. The lack of stereoscopic vision can be compensated for by a surge

ith some experience in this technique. Retraction of brain tissue can be significantly reduced. Final

e optical quality in the depth of the brain is far superior compared with that obtained through a

icroscope. Another valuable indication for endoscope-assisted microsurgery is in aneurysm surgery

neurysms can be inspected before clip placement to identify the neck and adjacent vessels.

urthermore, the placement of the clip can easily be controlled without manipulating the aneurysm. I

is way, incidental occlusion of vessels or incomplete clipping of the aneurysm can be avoided.

ther Indications

ndoscopes have been used for the treatment of intracerebral and epidural, as well as acute and chron

bdural hematomas.[8,10,54,66] Although most chronic subdural hematomas respond to simple

urr-hole evacuation and temporary drainage, this treatment may fail in loculated hematomas. A valueatment option in these cases is the use of endoscopic membrane fenestration to create a single

culation that can be drained successfully. However, this procedure should be reserved for patients w

matomas in whom simple burr-hole drainage was insufficient. In our opinion, endoscopic evacuati

epidural hematomas via burr holes is rarely justified in cases of small hemorrhages when patients

good clinical condition. In most cases, especially with patients in a critical state, an immediate

aniotomy and decompressive procedure are required, which should not be delayed by using

me-consuming endoscopic techniques. Furthermore, hemostasis of sometimes profuse arterial bleedmore effectively achieved using bipolar forceps. Finally, circular tacking of the dura up to the edge

e craniotomy is essential to prevent reaccumulation of the hematoma. In treating intracerebral

matomas, we found endoscopic evacuation not to be superior to standard microsurgical removal. T

icrosurgical procedure was more effective, quick, and the visualization was better with the microsc

ndoscopically, we perform clot removals and third ventriculostomies to restore obstructed CSFthways in patients with intraventricular hemorrhages that cause hydrocephalus.

ereotacticendoscopic evacuation of brain abscesses has been reported.[53] The extent of abscess

piration can be controlled under direct vision. However, the results seem to be the same when

mpared with standard stereotactic puncture and drainage.

nother indication for an endoscopic approach is intraparenchymal cysts, which may occur in variou

cations of the brain.[15,122] Fenestration of the cyst wall that creates a communication with the

ntricles or subarachnoid space is the procedure of choice.

ndoscopic techniques can be considered for the removal of intraventricular cysticercosis cysts.[91]

ecause sudden cyst migration is well known, immediate preoperative MR imaging should be

rformed.


14/22

ources of Equipment

he Gaab neuroendoscope system is manufactured by Karl Storz Gmbh & Co., and by Codman and

hurtleff, Inc. (Randolph, MA). Both the Nd:YAG laser and the Surgical Tool Navigator were obtain

om Carl Zeiss (Oberkochen, Germany). Codman and Shurtleff, Inc. produces the Malis irrigator.

CONCLUSIONS

he introduction of the operating microscope in the 1960s permitted atraumatic microsurgical dissec

the depth of the brain via small craniotomies. With the use of neuroendoscopic techniques, surgicavasiveness can be further reduced and identical or even better results can be achieved. Craniotomie

d shunt placement can often be avoided. However, neuroendoscopy is still in its infancy. Like

icrosurgery, it has a steep learning curve. With proper patient selection and improvement of the

chnical equipment, the results will certainly improve. However, neuroendoscopy is not a technique

. It is one of the tools of the neurosurgeon, such as stereotaxy, the operating microscope, or

uronavigation, available to perform a sophisticated surgery and should be utilized together with oth

chniques as necessary. There is no doubt that with further development of specially designed

uroendoscopes and instruments, as well as the increasing skill of the surgeons, endoscopic techniq

ill be used more commonly and the indications will expand.

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ccepted in final form March 4, 1999.

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eurosurgery, Sauerbruchstrasse, D17487 Greifswald, Germany. email:[email protected].

Intracranial Endoscopy

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