Endoscopic Approach

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NEUROSURGICAL OPERATIVE ATLAS, VOL. 3

ENDOSCOPIC NEUROSURGERY

ALAN R. COHEN, M.D.

© 1993 The American Association of Neurological Surgeons

INTRODUCTIONOn the basis of a remarkable series of technological inno-vations in the field of endoscopy, neurosurgeons are nowequipped to perform a variety of major intracranial pro-cedures with minimal invasiveness. Some would considera �minimally invasive� neurosurgical procedure to be anoxymoron, because neurosurgical procedures, by their verynature, are generally associated with maximal degrees ofinvasiveness. However, endoscopic surgical techniquesnow make it possible to perform certain highly invasiveintracranial procedures through small exposures with mini-mal trauma to neural structures. One can appreciate thepower of endoscopy by considering the numerous ad-vances made possible by such instruments as the ar-throscope, bronchoscope, cystoscope, and laparoscope.Endoscopic technology has so changed the face of gen-eral surgery that �laparoscopic cholecystectomy� has be-come a household term. Almost every body cavity con-taining air or fluid can be accessed currently by some formof endoscope.

The same basic endoscopic technology which hascontributed to the development of so many other medicaland surgical subspecialties is now feasible for use in neu-rosurgery. The cerebral ventricles, located deep within thesubstance of the brain and filled with clear fluid, are ide-ally suited for endoscopic navigation. Recent improve-ments in optics and miniaturization now make it practicalto apply endoscopic techniques to perform several thera-peutic intraventricular neurosurgical procedures. Thiscommunication discusses the neurosurgical applicationsof endoscopy, focusing on endoscopic dissections whichcan be carried out within the cerebral ventricles.

EVOLUTION OF NEUROENDOSCOPYEndoscopic neurosurgery began at the turn of the centuryas an effort to diagnose and treat hydrocephalus. The firstrecorded endoscopic neurosurgical procedure was in 1910when L�Espinasse, a urologist in Chicago, used a cysto-scope to fulgurate the choroid plexus in two hydrocepha-

lic infants. Dandy coined the term �ventriculoscope� in1922 and used the instrument for the same purpose. BothL�Espinasse and Dandy reported discouraging results, andventriculoscopy was all but abandoned because of theprimitive nature of the instruments, the high surgical mor-tality and morbidity rates, the development of better indi-rect means of imaging the intracranial contents, and ulti-mately, the introduction of simple and effective valvedshunts for the treatment of hydrocephalus.

As experience with ventricular shunts increased,however, it became apparent that although shunts wereoften effective, the problems associated with them werenot necessarily simple. Ventricular shunts can be extremelytroublesome devices, and shunt surgery is associated witha higher rate of complications than any other commonlyperformed neurosurgical procedure. The currentresurrection of interest in neuroendoscopy was fueledinitially by efforts to simplify or eliminate ventricular shuntsystems. Recent technical breakthroughs in optical designhave made possible the development of endoscopicsurgical procedures for dealing with various deep-seatedventricular tumors. I have found the endoscope helpfulfor treating such conditions as simple noncommunicatinghydrocephalus due to aqueductal stenosis and complexcompartmentalized hydrocephalus including loculatedventricular cysts and trapped ventricles, for retrieval ofadherent ventricular catheters, and for biopsy or removalof ventricular tumors.

OPERATIVE TECHNIQUEEndoscopic ventricular surgery is usually performed withthe patient under general anesthesia. In cooperative adultpatients or those whose medical condition precludes gen-eral anesthesia, the surgery may be carried out using localanesthesia. A dose of oxacillin is administered intrave-nously prior to incision and is continued every 6 hours for1 day. Anticonvulsants are not generally used. I keep asterile craniotomy tray unopened on a back table in theevent of an emergency, but I have not yet had to open this.

The patient is positioned supine with the brow up andthe head elevated 20 to 30°, supported by a dough-

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COHEN : ENDOSCOPIC NEUROSURGERY

nut cushion. A small amount of hair is shaved and theright frontal scalp is cleansed with povidone-iodine soapand solution, walled off with towels, and covered with aniodoform-soaked adhesive drape. If it is anticipated thatthe patient will require insertion of a ventricular shunt ordrain, the preparation and draping are modified appropri-ately.

The operation is performed through a right coronalburr hole unless the location of the pathological processdictates otherwise. The scalp is infiltrated with a solutionof 0.25% lidocaine containing a 1:400,000 dilution ofepinephrine. A small curvilinear incision Is made in theright frontal scalp in the micipupillary line just anterior tothe coronal suture and a burr hole is placed at this site.The dura is incised with a No. 11 blade; the arachnoid andpia are coagulated with a bipolar cautery and are incised.Alternatively, the dura, arachnoid, and pia are opened andsealed simultaneously with a monopolar coagulator ap-plied to a bayonet forceps or a Penfield No. 4 dissector(Fig. 1).

The endoscope is inserted into the frontal horn of theright lateral ventricle. Usually, the ventricle is cannulatedfirst with a No. 13 Fr peel-away Swan-Ganz introducercatheter, and cerebrospinal fluid is collected for routinestudies including cell count, chemistries, culture and sen-

sitivity, and, when appropriate, cytology. The endoscopeis then inserted into the lateral ventricle through thepeel-away catheter. Sometimes the endoscope can be in-serted directly into the ventricle without a peel-away cath-eter, as is the case with some rigid endoscopes which havetheir own introducer sheath and obturator. Once the ven-tricle has been cannulated, normal anatomic structures areidentified. The choroid plexus and the septal andthalamostriate veins guide the operator to the foramen ofMonro. The foramen of Monro provides a constant ana-tomic landmark. When working within the third ventriclethe operator becomes oriented by identifying several strik-ing landmarks along the third ventricular floor, includingthe aqueduct of Sylvius posteriorly and the mammillarybodies and infundibular and optic recesses anteriorly. Froma coronal approach the anterior third ventricle is usuallyseen clearly. A large massa intermedia may obstruct visu-alization of the posterior third ventricle.

After the designated endoscopic dissection has beencompleted (see �Ventriculoscopic Procedures�), the en-doscope is removed from the peel-away catheter. If a ven-tricular drain or shunt is to be used, it can be insertedthrough the peel-away catheter to a preselected site, a tech-nique described by Manwaring. The peel-away catheteris then peeled away (Fig. 2). The scalp is closed in layers.


Figure 1. Through a standard coronal burr hole the dura, arachnoid,and pia. are opened and sealed using monopolar coagulation. The fron-tal horn of the right lateral ventricle is then cannulated with a 13 FrSwan-Ganz peel-away introducer catheter and the endoscope is insertedinto the ventricle through the introducer catheter.

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Figure 2. A technique is illustrated for inserting a ventricular catheter.Following the endoscopic dissection, a site for the ventricular catheteris chosen under direct vision, and the endoscope is removed from the

peel-away sheath. The ventricular catheter along with its stylet is in-serted through the peel-away sheath, and the peal-away sheath is thenpeeled away.

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INSTRUMENTATIONThere are two general types of endoscopes which canbe used to perform intraventricular dissections. One isa rigid lens telescope and the other is a flexiblefiberoptic endoscope. I have found both instrumentsto be useful. The rigid system provides superior opticsand superior working channel capabilities, whereas theflexible system, which can be steered, provides bettermaneuverability.

The rigid endoscope which I use is a modified pe-

diatric cystoscope. It consists of an 11 Fr sheath whichis 20 cm long and contains three small working chan-nels. The image is transmitted by a Hopkins telescopewhich fits into the central channel of the endoscope�ssheath (Fig. 3). This telescope, developed in 1960 byHarold H. Hopkins, a British physicist working at theUniversity of Reading, uses, an ingenious solid rod lenssystem. The solid rod lens system was a major opticalimprovement over the conventional endoscopes usedpreviously. The conventional endoscope system was


Figure 3. Rigid ventricular endoscope. The instrument is a modifiedpediatric cystoscope with multiple working channels. The operator may

look directly through the lens, but usually the image is projected via amicrochip camera to a television screen.

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initially developed in Vienna by Nitze in 1887, and con-sisted of a train of biconvex lenses spaced out in anair-containing metal tube, a system which was opticallyinefficient. The Hopkins solid rod lens system has per-mitted the construction of a significantly smaller diam-eter instrument which has the advantages of a wider view-ing angle, improved light transmission, improved imageresolution, and reduced chromatic aberration.

I prefer a 0° straightforward telescope for viewing anda 30° forward-oblique Storz telescope for working. The ad-vantage of the 30° forward-oblique telescope is that it pro-vides the operator better visualization of instruments as theyemerge from the adjacent working channels. Instrumentsmust be inserted deeper to be seen through the 0° telescope,and may strike the ventricular wall prior to being visualized.This is particularly important at the foramen of Monro wherean instrument may puncture a venous structure or the fornixbefore it comes into the operator�s field of vision. The op-erative field can be viewed by looking directly through theendoscope, but more often it is projected via a microchipcamera to a television screen and videocassette recorder,enabling the operator and operating team to view the proce-dure while maintaining sterility. Illumination is provided bya fiberoptic cable connected to a xenon light source. Theendoscope system can either be held by hand or supportedby a Greenberg retractor system with a rack and pinion handlefor controlled adjustments. Other endoscopes are availablefor use in conjunction with stereotactic equipment.

The flexible Codman and Shurtleff endoscopewhich I use has a 4 mm diameter imaging catheter whichincludes a 1 mm (3 Fr) diameter working channel. It is38 cm long with a distal viewing tip that can be steeredvia a thumb control device. The same microchip cam-era can be adapted to both the rigid and flexibleendoscopes. A Greenberg retractor is used to supportthe base of the endoscope (Fig. 4). The coherentfiberoptic bundle system which serves as the basis forthe flexible endoscope was also developed by HaroldHopkins. Coherent fibers are a prerequisite for imagetransmission. Noncoherent fibers can transmit light butno image. Hopkins� innovation was to wrap a smallquartz fiber many times around a drum and then make asingle cut across all the fibers, thereby leaving themidentical in length and location at each end. By ensur-ing that each fiber at one end was identical in positionto its cut counterpart at the other end, Hopkins wasable to create a coherent fiberoptic bundle which couldtransmit not only light but a clear image as well. Theflexible nature of these fibers allows them to be steered.

Whether a rigid or flexible endoscope is chosen forworking within the cerebral ventricles, it is important to pro-

vide adequate irrigation. Because the diameter of the instru-ment is quite small, only a small area of the ventricle can beseen at any given time, and even minor venous bleeding canobscure the endoscopic view. Irrigation serves to keep theendoscopic window clean. I use a slow constant infusion oflactated Ringer�s solution provided by a pressurized bag con-nected in a closed system to one of the working channels inthe endoscope. It is imperative that there be a safety valvemechanism for the irrigation fluid to escape. Otherwise pro-gressive ventricular distension could result, leading to a dan-gerous elevation of intracranial pressure. The irrigation fluidusually escapes in the space between the endoscope and thepeel-away catheter. Fluid can also be vented by openinganother working channel.

An assortment of microinstruments can be intro-duced through small working channels in the endo-scope. These include flexible scissors, grasping for-ceps (Fig. 5), biopsy forceps, and suction and irrigationcatheters. I perform endoscopic dissections currentlyby passing a small laser fiber through one of the work-ing channels (Fig. 6). I use a fiberoptic neo-dymium-doped:yttrium-aluminum-gamet (Nd:YAG) la-ser which has a diameter of 600 µ. The Nd:YAG is asolid state laser which emits invisible light in the nearinfrared sector of the electromagnetic spectrum at awavelength of 1.064 µ. Because this emitted light isinvisible, the laser is aimed using a visible heliumneonpilot beam. The Nd:YAG laser is well-suited for endo-scopic use within the cerebral ventricles. Unlike thecarbon dioxide (CO2) laser, whose wavelength is 10times longer, the energy delivered by Nd:YAG is trans-missable through fluid and is absorbed preferentiallyby pigmented tissues. A sculpted fiber tip can be usedin both contact and free beam modes. The Nd:YAGlaser is very effective for cutting and coagulating; it isless effective than CO2 for vaporizing tissue, but tis-sue can be vaporized at higher power settings. Poorlypigmented tissue, such as the septum pellucidum, re-quires higher power settings for fenestration. Otherlasers can be used effectively to perform endoscopicventricular procedures. The potassium-titanyl-phosphate (KTP) laser has a wavelength of 0.532 µ, halfthat of the Nd:YAG laser, and emits green light in the vis-ible spectrum. It is a useful dissecting tool and producesless of a thermal injury than the Nd:YAG laser.

In the absence of a laser, ventricular dissectionscan be performed satisfactorily using radiofrequency(RF) current. This method of dissection replaces pho-tons with electrons. An insulated Bugbee wire (�theventricular torch�) can be passed through a workingchannel to deliver monopolar current from an RF gen-

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Figure 4. Flexible ventricular endoscope. There is a flexiblefiberoptic imaging catheter which can be steered via a thumb con-

trol. The base of the endoscope can be supported by a Greenbergretractor.

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Figure 5. Flexible grasping forceps.

Figure 6. Endoscopic ventricular surgery. A fiberoptic laser introduced through a working channel in the endoscope is visible on the television screen.



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erator for cutting and coagulating. Radiofrequency cur-rent can also be delivered using a �saline torch� whichessentially emits a jet of electrified saline from a smallTeflon catheter passed through a working channel.

VENTRICULOSCOPIC PROCEDURES

Endoscopic Third VentriculostomyEndoscopic third ventriculostomy can be used to treatcertain cases of noncommunicating hydrocephalus due toaqueductal stenosis, thereby eliminating the need for aventricular shunt. The procedure creates a fenestration inthe third ventricular floor, allowing cerebrospinal fluid(CSF) to escape into the basal cistems proximal to the siteof obstruction further downstream at the aqueduct. Forthird ventriculostomy to be successful, two conditions mustbe met. First, there has to be a significant obstruction tothe flow of CSF between the ventricles and the subarach-noid space, and second, there must be preservation of com-munication between the subarachnoid space and venoussystem so that CSF absorption can proceed once the ob-struction is bypassed.

In my experience, the best candidates for endoscopicthird ventriculostomy are those with acquired aqueductalstenosis, because they are more likely to have a function-ing communication between the subarachnoid space andvenous system. Infants with hydrocephalus and aqueductalstenosis respond variably to endoscopic third ventricu-lostomy; they may or may not have a communicating hy-drocephalus as well. Currently there is no simple diag-nostic study available to predict which patients withaqueductal stenosis will benefit from endoscopic thirdventriculostomy.

I study all patients with magnetic resonance imaging(MRI) scans pre- and postoperatively (Fig. 7). MRI pro-vides a clear demonstration of the aqueductal anatomy aswell as the location of the basilar artery. Gadolinium canbe administered to exclude an enhancing neoplasm.Two-dimensional phase contrast cine MRI, a noninvasivetechnique which is gated to the cardiac cycle, is useful forlooking at CSF flow. This study helps to confirm the di-agnosis of aqueductal stenosis preoperatively, and candocument patency of the third ventriculostomy postop-eratively. When there is diagnostic uncertainty, iohexolventriculography with computed tomography (CT) can beperformed.

The endoscope is introduced into the right lateralventricle and the foramen of Monro is identified. The en-doscope is guided through the foramen of Monro into thethird ventricle, and the third ventricular floor is inspected.The basilar artery apex can usually be identified through

the translucent floor where it terminates just beneath themammillary bodies. A site for fenestration is chosen in theattenuated tuber cinereum. The fenestration is created inthe midline just anterior to the marnmillary bodies, butbehind the infundibular and optic recesses (Fig. 8). ANd:YAG fiberoptic laser inserted through a working chan-nel is used to make the fenestration (Fig. 9). Initially, multi-ple small holes are made in the third ventricular floor in acircular fashion. The small holes are connected to cre-ate one large hole measuring about 5 mm in diameter,and the entire endoscope is passed through the

Figure 7. A magnetic resonance imaging scan of the brain demonstrat-ing hydrocephalus secondary to stenosis of the caudal aqueduct ofSylvius (open arrow). The third ventricular floor is so attenuated it canbarely be seen (closed arrow). (Reproduced with permission from CohenAR: Endoscopic laser third ventriculostomy. N Engl J Med 328:552,1993.)

Figure 8. Endoscopic view of the third ventricular floor. A site forfenestration (x) is chosen in the midline anterior to the mammillarybodies (m).


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Figure 9. Endoscopic laser third ventriculostomy. A rigid endoscopehas been inserted through the foramen of Monro into the third ven-tricle. An Nd:YAG laser fiber (LA) is used to fenestrate the floor of

the third ventricle anterior to the basilar artery (B). VS = ventricu-lar system. (Reproduced with permission from Cohen AR: Endo-scopic laser third ventriculostomy. N Engl J Med 328:552, 1993.)

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hole. Confirmation of a satisfactory fenestration is madeby direct endoscopic visualization of the basilar artery inthe interpeduncular cistern (Fig. 10). The endoscope iswithdrawn back into the third ventricle and the edges ofthe fenestration can be seen flapping up and down as CSFmoves between the third ventricle and the basal cisterns.The edges of the fenestration are coagulated further withthe laser to widen the hole.

Treatment of Complex HydrocephalusEndoscopic fenestration techniques can be used to sim-plify the management of hydrocephalus associated withloculated collections of CSF. Such CSF collections in-clude suprasellar arachnoid cysts, parenchymal or intra-ventricular cysts associated with germinal matrix hemor-rhage or infection, trapped lateral ventricles secondary toobstruction at the foramen of Monro, and some cases oftrapped third and fourth ventricles. Preoperative radio-graphic workup includes either CT or MRI. Wheneverpossible, pre- and postoperative iohexol CT ventriculo-grams are performed.

Patients with suprasellar arachnoid cysts may presentwith hydrocephalus, visual loss, and endocrine dysfunc-tion. Symptomatic suprasellar arachnoid cysts can betreated by ventriculocystostomy. The endoscope is insertedinto the right lateral ventricle and the right foramen ofMonro is identified. The suprasellar arachnoid cyst is seenfilling the foramen with a bluish tinge to its wall. The cystwall, which can often be quite thick, is dissected with the

Nd:YAG laser. Grasping forceps are used to remove asmuch of the wall as possible. The key to success is thecreation of a wide fenestration; smaller fenestrations mayscar over and close. After the cyst has been opened, theendoscope can be passed through the foramen of Monro,often revealing a spectacular view of the anatomy of thebasal cisterns, including the entire length of the basilarartery, the brain stem and the cranial nerves as well as thepituitary gland and stalk. I usually shunt these patients aswell, using the peel-away catheter as a guide for the ven-tricular catheter once the endoscope has been removed.Some surgeons have managed this condition with cyst fen-estration alone, eliminating the need for a ventricular shunt.

Loculated ventricular cysts are dealt with in the samefashion. Rather than use multiple proximal shunt cathetersto decompress loculated cavities, windows in the cyst wallscan be created with an endoscope and laser. Using thistechnique, complex shunt systems can be simplified and asingle shunt used to drain multiple compartments. In gen-eral, it is best to identify normal anatomy first and worktoward abnormal anatomy. Therefore, whenever possibleI try to enter the ventricle first and work toward the cyst.If the cyst is entered first, the surgeon can sometimes findit difficult to get oriented because the normal ventricularanatomy may not be visualized through the cyst walls.Sometimes there are so many intraventricular septa thatno recognizable anatomy can be seen. When this occursin infants, intraoperative transfontanel ultrasonography canbe helpful in orienting the operator.

The ventricular endoscope can also be used to un-block a trapped ventricle. If there is unilateral enlarge-ment of a lateral ventricle due to an obstruction at theforamen of Monro, the endoscope and laser can be usedto create a fenestration in the septum pellucidum. Theseptostomy should be positioned strategically to avoidinjury to the fornices or corpus callosum. In some casesthe endoscope can be used to open a third or fourth ven-tricle which has become isolated by adhesions.

Removal of Adherent CathetersOften, proximal shunt malfunctions develop because theventricular catheter has become occluded by choroidplexus. Sometimes these catheters become stuck in thechoroid plexus, and dislodging them can lead to ventricu-lar hemorrhage. I have been able to remove most adher-ent ventricular catheters by passing a stylet through thecatheter and coagulating it with a monopolar current. Thismaneuver usually frees the catheter from the choroidplexus and allows it to be removed easily.

Recalcitrant catheters can be dissected free under di-rect vision using the ventriculoscope. The scope is

Figure 10. Endoscopic view of the basilar artery (B) and its pontineperforating branches following third ventriculostomy. fl = laser-createdhole in the third ventricular floor. (Modified from Cohen AR: Endo-scopic laser third ventriculostomy. N Engl J Med 328:552, 1993.)

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passed into the lateral ventricle through a second burr holeand the shunt catheter is identified. The adherent choroidplexus is coagulated gently using either a laser fiber orRF torch, and the freed catheter can then be pulled out. Ifa fragment of catheter has broken off within the ventricle,it can be snared with a grasping forceps. The shunt cath-eter is too large to be withdrawn through the endoscopes�sworking channel, so the endoscope, forceps, and shuntcatheter are removed as a single unit. A new ventricularcatheter can be inserted through the peel-away catheter,and the peel-away catheter removed.

When necessary, a wandering distal catheter can beretrieved from the peritoneum using a similar technique.This procedure is easier than removing a ventricular cath-eter, because the peritonea] cavity can be filled with car-bon dioxide, and the shunt removed using standardlaparoscopic techniques. It should be stressed that not alladherent catheters need to be removed.

Ventricular TumorsVentricular tumors can be biopsied endoscopically underdirect vision, and cystic tumors drained. When necessary,the septum pellucidum can be fenestrated at the samesitting, and a ventricular shunt inserted. Some ventriculartumors can be vaporized and removed totally through anendoscope.

Ventriculoscopic surgery is particularly suited fordealing with colloid cysts of the third ventricle. Thesebenign lesions can produce symptomatic obstructionof the foramina of Monro. Standard surgical treatmenthas consisted of craniotomy and either transcallosalor transcortical-transventricular removal of the mass.Stereotactic cyst aspiration has been proposed and usedeffectively as a less invasive alternative to craniotomy.Problems associated with stereotactic cyst aspirationinclude: 1) difficulty penetrating the thick cyst wall,2) difficulty aspirating the viscous colloid material, and3) the possibility of neural or vascular injury due to aninability to visualize the operation. Endoscopic tech-niques eliminate the problems enumerated above andallow the operator to deal with colloid cysts with mini-mal invasiveness.

Two burr holes are placed in the midpupillary linenear the coronal suture and the lateral ventricle is cannu-lated with a peel-away catheter through each burr hole.The endoscope is passed through one of the peel-awaycatheters and the cyst wall is dissected using the Nd :YAG laser fiber. The cyst wall is opened widely and thethick cyst contents emptied under direct vision using alarge-bore sucker passed through the second catheter (Fig.11). After the cyst has been emptied, the remaining cap-

sule is coagulated, and if possible, either vaporized orremoved with grasping forceps. A septostomy can be cre-ated at the same sitting. The ventricle is irrigated copi-ously with lactated Ringer�s solution, a ventricular drainis inserted through one of the peel-away catheters andthe peelaway catheters are removed. The ventricular drainis used for 48 hours postoperatively. Dexamethasone isadministered pertoperatively and is continued for 5 days.

Endoscopic surgery is an effective method for deal-ing with colloid cysts of the third ventricle (Fig. 12). Thethick cyst wall can be dissected atraumatically under di-rect vision using the Nd: YAG laser. The reason for thesecond burr hole is to permit the introduction of alarge-bore sucker for aspiration of the viscous colloidmaterial. More recently I have been able to do the entireprocedure through a single burr hole using a rigid endo-scope and evacuating the colloid material with a largecatheter passed through one of the working channels.

COMPLICATIONSEndoscopic ventricular surgery is a powerful techniquewhich can be performed with minimal trauma, but whencomplications occur they are every bit as serious as thoseassociated with open exposures, if not more so because ofthe very limited size of the operative corridor.

Sometimes it can be difficult for the surgeon to be-come oriented. One reason for this is the unique eye-handcoordination involved in carrying out an operation whilewatching a television screen. Another reason is that theendoscopic picture, clear as it is, only reveals a small por-tion of the ventricular anatomy at any one time. Depthperception is lost and the operator must usethree-dimensional anatomic knowledge to help navigate.Furthermore, the region of interest is often eccentric ornonorthogonal when viewed through an angled lens scopeor a steerable fiber scope. I strongly recommend obtain-ing hands-on experience with either cadaver dissectionsor practical courses and workshops.

The major risk of therapeutic neuroendoscopy isbleeding. Great care must be taken to prevent bleeding;even minor amounts of blood can obscure the surgeon�sview, and significant bleeding mandates that the proce-dure be aborted. Most venous bleeding, although trouble-some, is usually self-limited and clears with irrigation.Sometimes the bleeding source can be identified throughthe endoscope and coagulated with the laser. Significantarterial bleeding cannot usually be controlled through theendoscope and may require an emergent craniotomy if itdoes not abate with ventricular irrigation and drainage.Endoscopic third ventriculostomy carries an inherent riskof injury to the basilar artery, which is situated just

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Figure 11. Endoscopic removal of a colloid cyst of the thirdventricle. A Nd:YAG laser is used to dissect the cyst wall, and theviscous cyst contents are aspirated using a large suction catheterintroduced through a second burr hole. Using a slightly larger

diameter endoscope, one can introduce the large suction catheterthrough a working channel and thereby perform the entire proce-dure through a single burr hole.


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Figure 12. A, a preoperative CT scan showing hydrocephalus second-ary to obstruction of the foramina of Monro by an isodense colloid cyst

of the anterior third ventricle. B, a postoperative CT scan followingendoscopic removal of the colloid cyst.

beneath the mammillary bodies, adjacent to the site ofventricular fenestration. Therefore, I do not recommendperforming endoscopic third ventriculostomy unless thethird ventricle is enlarged and the third ventricular flooris translucent. The size of the third ventricle and the posi-tion of the basilar artery should be checked on a preop-erative MRI scan.

Not all ventricular tumors are best managed endo-scopically. Highly vascular lesions may be handled op-timally via an open procedure. The long-term endoscopicresults for colloid cysts are not available, and those cystssimply drained may recur if the cyst wall has not beeneliminated. When colloid cysts are evacuated endoscopi-

cally, the ventricles must be irrigated copiously to pre-vent chemical ventriculitis from exposure to the highlyirritating colloid material. Any time a surgeon works nearthe foramina of Monro, great care must be taken to avoidinjuring the fornices.

CONCLUSIONSEndoscopic ventricular surgery has a role in the man-agement of hydrocephalus and certain ventricular neo-plasms. Shunt systems can be simplified in some casesand eliminated in others. Certain ventricular neoplasmscan be biopsied or dissected under direct vision with mini-mal invasiveness.


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