endoscopic third ventriculostomy in the management of obstructive hydrocephalus: an outcome analysis

INCE the development of valve-regulated shunts in the1950s,53 shunt surgery has widely been used to treathydrocephalus. Nevertheless, high failure rates and

numerous complications have been reported.47,56,57,65 Withthe introduction of neuroendoscopic methods, ETV has be-come the preferred treatment for obstructive hydrocephalusbecause the approach is minimally invasive and offers thesurgeon brilliant visual control of the maneuver.6,26,29,31,40,58,71

In the present study, we retrospectively analyzed the indica-tions for ETV, the surgical technique itself, and outcomes ina consecutive group of 58 patients who underwent ETV forobstructive hydrocephalus.

J Neurosurg 100:626–633, 2004

626

Endoscopic third ventriculostomy in the management ofobstructive hydrocephalus: an outcome analysis

HAILONG FENG, M.D., PH.D, GUANGFU HUANG, M.D., XIAOLING LIAO, M.D., KAI FU, M.D.,HAIBIN TAN, M.D., HONG PU, M.D., YONG CHENG, M.D., WEIDONG LIU, M.D.,AND DONGDONG ZHAO, M.D.

Departments of Neurosurgery and Radiology, Sichuan Provincial People’s Hospital, Sichuan Province,People’s Republic of China

Object. The purpose of this paper is to elucidate the safety and efficacy of, and indications and outcome prognosis forendoscopic third ventriculostomy (ETV) in 58 patients with obstructive hydrocephalus.

Methods. Between September 1999 and April 2003, 58 ETVs were performed in 58 patients with obstructive hydroceph-alus (36 male and 22 female patients) at the authors’ institution. The ages of the patients ranged from 5 to 67 years (meanage 35 years) and the follow-up period ranged from 3 to 41 months (mean duration of follow up 24 months). Patients weredivided into four subgroups based on the cause of the obstructive hydrocephalus: 21 with intracranial tumors; 11 with in-tracranial cysts; 18 with aqueductal stenosis; and eight with intracranial hemorrhage or infection. Both univariate and multi-variate statistical analyses were performed to assess the prognostic relevance of the cause of the obstructive hydrocephalus,early postoperative clinical appearance, and neuroimaging findings in predicting the result of the ETV.

The survival rate was 87% at the end of the 1st year and 84% at the end of the 2nd year post-ETV. One month after ETVan overall clinical improvement was observed in 45 (77.6%) of 58 patients. If we also consider the successful revision ofETV in two patients, a success rate of 78.3% (47 of 60 patients) was reached. The ETV was successful in 17 (81%) of 21patients with intracranial tumors, nine (82%) of 11 with cystic lesions, 16 (88.9%) of 18 with aqueductal stenosis, and three(38%) of eight with intracranial hemorrhage or infection. A Kaplan–Meier analysis illustrates that the percentage of func-tioning ETVs stabilizes between 75 and 80% 1 year after the operation. In a comparison of results 1 year after ETV, theauthors found that the aqueductal stenosis subgroup had the highest proportion of functioning ETV (89%). The proportionsof the tumor and cyst subgroups were 84 and 82%, respectively, whereas the proportion was only 50% in the ventriculitis/intracranial hemorrhage subgroup (strata log-rank test: �2 = 7.93, p = 0.0475).

In the present study, ETV failed in eight patients (13.8%) and the time to failure after the procedure was a mean of 3.4months (median 2 months, range 0–8 months). The logistic regression analysis confirmed an early postoperative improve-ment (within 2 weeks after ETV, significance [Sig] of log likelihood ratio [LLR] � 0.0001) and a patent stoma on cinephase–contrast magnetic resonance (MR) images (Sig of LLR = 0.0002) were significant prognostic factors for a successfulETV. The results demonstrated the multivariate model (B = � 53.7309, standard error = 325.1732, Wald = 0.0273, Sig =0.8688) could predict a correct result in terms of success or failure from ETV surgery in 89.66% of observed cases. ThePearson chi-square test demonstrated that little reliance could be placed on the finding of a reduced size of the lateral ven-tricle (�2 = 5.305, p = 0.07) on neuroimaging studies within 2 weeks after ETV, but it became a significant predictive fac-tor at 3 months (�2 = 8.992, p = 0.011) and 6 months (�2 = 10.586, p = 0.005) post-ETV. Major complications occurred inseven patients (12.1%), including intraoperative venous bleeding in three, arterial bleeding in one, and occlusion of the sto-ma in three patients. The overall mortality rate was 10.3% (six patients). One of these patients died of pulmonary infectionand another of ventriculitis. Four additional patients died of progression of malignant tumor during the follow-up period.

Conclusions. The results indicate that ETV is a most effective treatment in cases of obstructive hydrocephalus that iscaused by aqueductal stenosis and space-occupying lesions. For patients with infections or intraventricular bleeding, ETVhas considerable effects in selected cases with confirmed CSF dynamic studies. Early clinical and cine phase–contrast MRimaging findings after the operation play an important role in predicting patient outcomes after ETV. The predictive valueof an alteration in ventricle size, especially during the early stage following ETV, is unsatisfactory. Seventy-five percent ofETV failures occur within 6 months after surgery. A repeated ventriculostomy should be considered to be a sufficient treat-ment option in cases in which stoma dysfunction is suspected.

KEY WORDS • endoscopic third ventriculostomy • hydrocephalus • complication •outcome

S

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Abbreviations used in this paper: CSF = cerebrospinal fluid;CT = computerized tomography; ETV = endovascular third ventric-ulostomy; ICP = intracranial pressure; IVH = intraventricular hem-orrhage; LL = log likelihood; LLR = LL ratio; MR = magnetic reso-nance; SE = standard error; Sig = significance.

Clinical Material and Methods

Patient Population

Fifty-eight ETVs were performed in 58 patients (36 maleand 22 female patients) for the treatment of obstructive hy-drocephalus at our institution between September 1999 andApril 2003. The mean age of the patients was 35 years(range 5–67 years). Symptoms of obstructive hydroceph-alus included headaches (42 patients), nausea (38 patients),vomiting (33 patients), seizures (three patients), blurred vi-sion (25 patients), memory disturbances (41 patients), gaitdisturbances (16 patients), urinary incontinence (three pa-tients), and reduction of physical power (seven patients).Patient selection was based on findings of CT and MR im-aging studies, which indicated the presence of obstructivehydrocephalus with the obstruction located in the posteri-or aspect of or distal to the third ventricle. In selected cas-es, cine phase–contrast MR imaging was performed beforeor after surgery. Patients who experienced meningitis, ven-triculitis, and intraventricular or subarachnoid hemorrhagewho met the aforespecified criteria were also included.It was determined that the obstructive hydrocephalus wascaused by space-occupying lesions in 32 patients (including21 with intracranial tumors and 11 with intracranial cysts),aqueductal stenosis in 18 patients, and intracranial hemor-rhage or infection in eight patients. The follow-up periodlasted between 3 and 41 months (mean duration of followup 24 months).

Outcome of ETV was evaluated according to patients’follow-up data or patients’ status before they were lost tofollow up. The treatment was recorded as a success or fail-ure (the latter includes no change and a deterioration in thecondition). Success of the ETV was defined as partial orcomplete relief of symptoms; unchanged outcome was de-fined as neither significant relief from nor progression ofsymptoms; and deterioration was defined as progression ofsymptoms. Any patient who died as a direct result of theETV procedure or had to undergo a shunt implantation op-eration after the ETV procedure was described as havingtreatment failure. Considering the potential predictive roleof the early clinical appearance after ETV, we defined it asclinical presentation in the first 2 weeks after ETV and clas-sified it with the same criteria as those used for the ETVoutcome evaluation. Repeated CT or MR images (the initialstudy was completed within 2 weeks after ETV) were ob-tained in each patient to evaluate the results of surgery andduring the follow-up period, including 29 patients in whomcine phase–contrast MR images were obtained to verify thepatency of the stoma.

Endoscopic Maneuver

Endoscopic third ventriculostomy was performed usingthe freehand method in all 58 cases while the patient wasin a state of general anesthesia. In each case we used a rig-id endoscope (Clarus Medical, Minneapolis, MN) with aworking length of approximately 21.6 cm and an outer di-ameter of 4.5 mm, which was equipped with three channelsfor instruments, suction, and irrigation, and a 2.3-mm optic.Observation and flexible endoscopes were applied in somecases for confirmation of anatomical orientation and for tu-mor biopsy. Before surgery, the relationship between thefloor of the third ventricle and the tip of basilar artery was

carefully evaluated on sagittal MR images to reduce injuryto the basilar artery and its branch.

The patient was placed supine with the head supported bya horseshoe frame. A coronal burr hole was placed approxi-mately 3 cm lateral from the midline and just anterior to thecoronal suture. For patients undergoing endoscopic biopsyfor a tumor in the posterior portion of the third ventricle, theburr hole was modified on the basis of MR imaging find-ings (usually 3–5 cm anterior to the coronal suture). Afterincision of the dura mater, the endoscope was advanced in-to the lateral ventricle through the peel-away sheath. Afteridentification of the foramen of Monro, the operating sheathand endoscope were passed into the third ventricle. Afterclose inspection of the floor of the third ventricle, the tubercinereum was identified as the site of perforation. Blunt for-ceps and a Fogarty balloon catheter were used in most casesfor perforation and widening of the stoma whose diameterwas usually larger than 5 mm. Bipolar coagulation was onlyused in cases in which there was a tough or floating floor.The endoscope was advanced through the stoma to the cli-vus and the prepontine cistern for confirmation of a freecommunication between the third ventricle and the sub-arachnoid space. The Liliequist membrane acts as a barrierbetween them in some cases; thus it was essential to com-bine a Liliequist membranostomy with all the aforemen-tioned procedures to reduce the incidence of failure. After afinal inspection, the operating sheath was withdrawn withthe endoscope inside so that we could look for active bleed-ing at the foramen of Monro and in the puncture channel.External ventricular drains were not routinely inserted. Theburr hole was packed with a gelatin sponge and the galeawas tightly sutured to prevent a subgaleal CSF accumula-tion and fistula. The skin was closed using a running atrau-matic suture.

Statistical Analysis

Statistical analyses (Kaplan–Meier Survival analysis, lo-gistic regression, and the Pearson chi-square test) were con-ducted using statistical software (SPSS, Inc.; Chicago, IL).

Results

Fifty-eight ETVs were performed in 58 patients. Therewere 36 male and 22 female patients among whom 87%survived the 1st year and 84% the 2nd year after ETV (Fig.1). One month after ETV an overall clinical improvementwas observed in 45 (77.6%) of 58 patients. If we considersuccessful revision of ETV, which was performed in twopatients, the success rate reached 78.3% (47 of 60 patients).A Kaplan–Meier analysis illustrated that the proportion offunctioning ETVs became stable at rates of 75 to 80% afterthe 1st postoperative year (Fig. 2). Initially the procedurefailed in eight patients (13.8%). Cases of treatment failureincluded two cases of aqueductal stenosis, one of third ven-tricular ependymoma, two of giant suprasellar arachnoidcyst, and three of ventriculitis or intracranial hemorrhage.In these eight patients, five failures (62.5%) occurred with-in 3 months, six (75%) within 6 months, and all within9 months after surgery. Time to failure after ETV for thewhole group was a mean of 3.4 months (median 2 months,range 0–8 months). Two patients underwent second suc-cessful ETVs because membranes of Liliequist or occlusion


Endoscopic third ventriculostomy for obstructive hydrocephalus

627

of the fenestration were identified on postoperative MR im-ages. Thus overall there were six failures (10.3%) in 58 pa-tients. Five patients had previously received shunts; amongthese there were three successes. Fifty-three patients hadnot received previous treatment; of these there were fivefailures.

The proportion of functioning ETVs between separatedgroups was analyzed using a Kaplan–Meier curve (Fig. 3;log-rank test: �2 = 4.6, p = 0.0319). In a comparison of theresults 1 year after ETV, the aqueductal stenosis subgrouphad the highest rate of functioning ETVs (89%). In the tu-mor and cystic subgroups the rates of functioning ETVswere 84 and 82%, respectively. This rate was only 50%in the ventriculitis/intracranial hemorrhage subgroup (stra-ta log-rank test: �2 = 7.93, p = 0.0475). In the largest sub-

group of patients, 21 (36.2%) had tumors in or adjacent tothe third ventricle, which caused obstructive hydrocephalus.By performing endoscopic biopsy or craniotomy, patho-logical diagnoses were confirmed for two ependymomas,two medulloblastoma, eight pineocytomas, three thalamicastrocytomas, and four hemangioblastomas. In these cas-es of tumor ETV was successful in 17 (81%) of 21 patients.Eleven patients had cystic lesions (four suprasellar cysts,three third ventricular arachnoid cysts, and four fourth ven-tricular cysts); successful ETVs were completed in nine(82%) of these patients. Sixteen (88.9%) of the 18 patientswith aqueductal stenosis improved after ETV. The improve-ment was most striking and rapid in the 11 patients who hadsymptoms of acute increased ICP, including severe head-aches and vomiting. The conditions of two other patientsdeteriorated after ETV. These two patients both belong toour early phase of ETV procedures. One patient was re-moved from the study because of severe intraventricular ve-nous bleeding and the other one because of early occlusionof the stoma. Both of these patients underwent shunt place-ment surgery, which was successful. Five patients with IVHreceived ETV. Only two patients improved and becameshunt free after the operation. Two other patients receivedshunts 1 month later and a third died 2 months after surgeryof a severe pulmonary infection. Only one of three patientswith ventriculitis benefited from ETV and became shuntfree after surgery. In the other two patients the condition re-mained unchanged and shunts were required.

Neuroimaging evaluation within 2 weeks after ETVdemonstrated an improvement in the conditions of 29 pa-tients (50%), including 10 patients in whom ventricle sizeremained unchanged, but a definite CSF flow void was ob-served on MR images and there were no imaging signs ofICP. All 10 patients experienced clinical improvement. Cor-relations between ETV outcome and the postoperative sizeof the lateral ventricle, a patent stoma on cine phase–con-trast MR images, and an early postoperative clinical re-

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628 J. Neurosurg. / Volume 100 / April, 2004

FIG. 2. Kaplan–Meier plot illustrating functioning ETVs as aproportion of the whole group (58 patients). The success rate for the1st year was 80%. The rate stabilized at 75% after 2 years.

FIG. 1. Kaplan–Meier plot demonstrating survival after ETV in58 patients. For 1 year, 2 years, and 3 years, the rates of survivalwere 87, 84, and 84%, respectively.

FIG. 3. Kaplan–Meier plot showing functioning ETVs as propor-tions of the subgroups (aqueductal stenosis, cyst, tumor, and ventric-ulitis/intracranial hemorrhage [VI] subgroups). Log rank test: �2 =4.6, p = 0.0319. Strata log-rank test for the ventriculitis/intracranialhemorrhage subgroup: �2 = 7.93, p = 0.0475.

sponse was documented in 58 patients. Although the Pear-son chi-square test demonstrated that little reliance could beplaced on a reduced size of the lateral ventricle (�2 = 5.305,p = 0.07) on neuroimages within 2 weeks after ETV as asign of success, because this ventricle remained unchangedin 35 patients and enlarged in 10 patients 2 weeks aftersurgery (Table 1), ventricle size became a significant pre-dictive factor 3 months (�2 = 8.992, p = 0.011) and 6 months(�2 = 10.586, p = 0.005) after ETV.

In our study, the early clinical response (within 2 weeksafter surgery) and the patent stoma on cine phase–con-trast MR images provided a high correlation with overallETV success (Tables 2 and 3). The logistic regression anal-ysis confirmed that the early postoperative improvement(B = 11.3453, SE = 65.037, Wald = 0.0304, Sig = 0.8615,LL = �30.032, �2 LLR = 47.019, Sig of LLR � 0.0001)and a patent stoma on cine phase–contrast MR images (B =20.3881, SE = 130.0631, Wald = 0.0246, Sig = 0.8754,LL = �13.354, � 2 LLR = 13.662, Sig of LLR = 0.0002)were significant prognostic factors for a successful ETV.Our results demonstrated that the multivariate model(B = �53.7309, SE = 325.1732, Wald = 0.0273, Sig =0.8688) could be used to predict a correct result in termsof the success or failure of ETV surgery in 89.66% of ob-served cases (�2 LL = 13.045, goodness of fit = 12). If thepredicted probability was less than 0.25, the chance for suc-cess was 93.75%; if the predicted probability was greaterthan 0.75, the chance for success was 0%.

Major complications occurred in seven patients (12.1%).Complications included intraoperative venous bleeding inthree patients. In one of these patients thalamic infarctiondeveloped but improved successfully. Arterial bleedingfrom a small perforating vessel occurred in one patient; itwas treated successfully by extensive irrigation and shuntplacement 3 weeks later. Three patients experienced oc-clusion of the stoma after ETV. In one this occurred in theearly stage and in the other two after a delay (maximal time13 months after ETV). Other minor complications includ-ed transient fever and vomiting in six patients. No infec-tion was related to intervention with ETV in this group. The

overall mortality rate was 10.3% (six patients). One patientdied of pulmonary infection and another of ventriculitis.An additional four patients died of progression of malignanttumor during the follow-up period. No death was directlycaused by the ETV.

Discussion

Endoscopy has changed neurosurgical treatment in manyways.14,15,37,55,63,77 Obstructive hydrocephalus represents themost important indication for endoscopic intervention. En-dovascular third ventriculostomy has been considered to bean effective and safe treatment for occlusive hydrocepha-lus by many authors,5,7,22,32,68,70 but indications, surgical tech-niques, and outcomes related to different pathological find-ings are still under intensive investigation.

Consideration of the Endoscopic Technique

Although flexible fiberscopes have been used forETV,34,54,72 they offer a considerably inferior image qualityand there is difficulty with their orientation, guidance, andfixation. In our series, except in the first few cases, mostETVs were performed using rigid endoscopes for freehandprocedures. We applied a stereotactic technique in threeETV operations, but failed to observe any benefits to theprocedure. Instead it was time consuming and provided in-adequate accuracy for the stoma perforation. When ETVand a biopsy needed to be performed simultaneously, weroutinely adjusted the burr hole site for the convenient useof a rigid endoscope according to preoperative MR imagingstudies. If necessary, a “mother-and-daughter” method canbe used to perform biopsy and ETV.8 A variety of methodshave been described for perforation of the floor of the thirdventricle, including manipulation of the endoscope itself,19,74

blunt probes or catheters,9,23 monopolar coagulation,40,60 la-



629

TABLE 1Serial evaluation of ventricle size on post-ETV

MR images and CT scans*

Size of Ventricle Successful ETV† Failed ETV†

2 wks postopsmaller 11 2unchanged 29 6larger 5 5

3 mos postopsmaller 23 2unchanged 18 2larger 4 4

6 mos postopsmaller 31 2unchanged 10 2larger 2 3

* Alteration in the size of the ventricle was evaluated according to thefrontal and occipital horn ratio, a reliable and valid measure of ventricularsize (see Matsuno, et al.).

† Pearson chi-square test: �2 = 5.305, p = 0.07 for 2 weeks; �2 = 8.992,p = 0.011 for 3 months; �2 = 10.586, p = 0.005 for 6 months.

TABLE 2Early clinical response in 58 patients with obstructive

hydrocephalus after ETV*

Clinical ResponseW/In 2 Wks Postop Successful ETV Failed ETV

improved 32 2unchanged 7 5deteriorated 6 6

* Pearson chi-square test: �2 = 13.152, p = 0.01 (asymptotic significance[two sided]).

† Failed ETV includes unchanged and deteriorated conditions.

TABLE 3Patency of the stoma on cine phase–contrast MR

images obtained after ETV in 29 patientswith obstructive hydrocephalus*

Cine Phase–Contrast MRI Successful ETV Failed ETV

positive 12 4negative 5 8

* Pearson chi-square test: �2 = 3.948, p = 0.047 (asymptotic significance[two sided]).

ser energy,48,72 and, recently reported, reverse ETV via thecistern magna.36 We usually use blunt probes for perfora-tion. In most cases of obstructive hydrocephalus, the flooris translucent. Therefore, visualization of the basilar tip ispossible and perforation can be safely performed.

Dilation of the stoma is completed using a balloon cath-eter (No. 4 French), which can be passed freely by the endo-scope and can increase the size of the perforation up to 6mm. Floating tissue on the margin of the stoma needs to becoagulated carefully in a low-energy manner to avoid thedelayed closure of the stoma. In cases in which there is atough and nontranslucent floor, blunt perforation may be in-adequate and carry the risk of distortion of surrounding vi-tal tissue. In this situation, we prefer to create a perforationby using probes with sharp tips. Other methods include ul-trasonic or navigational guidance.59,63,67 The perforating sitedepends on findings on preoperative MR images. Specialattention should be directed toward the prepontine cistern.The nonfenestrated Liliequist membrane acts as a barrierbetween CSF flow from the infratentorial cisterns to the su-pratentorial cisterns;4 this membrane may be opened acci-dentally or may require a deliberate attempt to open it, de-pending on its anatomical attachment. The site of inferiorattachment of the Liliequist membrane is the dorsum sel-lae; however, the site of the superior attachment may vary(premammillary or retromammillary attachment).4,26,42,46,76

In patients in whom there is premammillary attachment ofthe Liliequist membrane, it is essential to include Liliequistmembranostomy to reduce the incidence of treatment fail-ures. In patients in whom there is a retromammillary attach-ment, it is not necessary to open the Liliequist membranebecause the third ventricle has been opened to the interpe-duncular cistern. Considering the potential harmful effect oflow ICP on ETV, postoperative drainage was not routinelyapplied in this series except in cases in which there was se-vere IVH or ventriculitis.

Patient Selection and Outcome Evaluation

The goal of ETV and, to date, the best objectively quan-tifiable measure of a successful outcome, is shunt indepen-dence. Authors of recent reports on ETV trials have claimedsuccess rates greater than 75% (50–94%) for carefully se-lected patients.1,5,11,19,24,31,32,35,61,68 In the present series of 58ETVs, overall shunt independence after ETV was achievedin 45 (77.6%) of 58 patients. If we consider the successfulrevision of ETV in two patients, the success rate reached78.3% (47 of 60 patients). According to the results of theKaplan–Meier analysis, the rate of functioning ETVs stabi-lized at 75 to 80% after the 1st postoperative year. Com-pared with this achievement, we are still struggling withshunt implantation surgery and many unsolved problemsthat lead to a 50% failure rate within 2 years and a 2:1 riskof shunt revision after the initial shunt insertion.12

Endovascular third ventriculostomy is commonly used totreat cases of noncommunicating hydrocephalus in whichthere are patent subarachnoid spaces and adequate CSF ab-sorption. Our studies have demonstrated that patients withaqueductal stenosis, cystic abnormalities, and tumors ob-structing outflow from the third or fourth ventricle are goodcandidates for ETV. High rates of shunt independency (�80%) were achieved in these patients. The success rateswere 88.9% for patients with aqueductal stenosis, 81% forthose with cystic abnormalities, and 82% for those with tu-

mors in selected series. Regarding the cause of obstructivehydrocephalus, a recent study revealed significantly pooroutcomes in patients with progressive tumorous lesions,compared with patients with benign space-occupying le-sions.26 Nevertheless, we did not find a significant differ-ence in the proportion of functioning ETVs in patients withmalignant tumors and those with benign space-occupyinglesions (data not shown). We believe that the major reasonsfor this result may be due to the small patient populationand the limited duration of follow up.

Given that ETV has proved to be an effective and safemaneuver for occlusive hydrocephalus, the duration offunctioning ETV in patients with malignant neoplasms isdependent on their length of survival. In our study, ste-reotactic radiosurgery or chemotherapy, which was used inpatients with malignant tumors to prolong their lives, hadeffects on evaluation of functioning ETV when comparedwith that in patients with benign space-occupying lesions.Patients with a reduced CSF resorption capacity, whichmay be seen after IVH, meningitis, or myelomenigocele,were usually thought to have a low success rate if they un-derwent ETV.13,28,35

According to the Kaplan–Meier analysis, the proportionof functioning ETVs in the ventriculitis/intracranial hem-orrhage subgroup was significantly lower than that in theaqueductal stenosis, tumor, and cystic subgroups. A sig-nificant difference between subgroups with regard to the1-year proportion of shunt independence was also shown.In contrast to this assumption, recent studies on ETV per-formed in patients with meningitis, shunt infections, andIVH demonstrated considerable success rates (� 60%).26,66

Given the relative safety of ETV and the potential chancefor freedom from shunts, we performed ETV in patients inwhom there was bleeding into the ventricles or ventriculitisduring the early phase of the study. Unfortunately, only twoof five patients with IVH and one of three patients with ven-triculitis derived benefit from ETV and became shunt freeafter surgery. One possible explanation for this result is thata combination of obstruction and impaired CSF resorptioncoexisted in these patients. The adaptation of subarachnoidspace to altered CSF dynamics after ETV failed to compen-sate the preexisting malfunction of CSF resorption.21,25,30,31,62

Reliable and applicable clinical tests that can be used topredict whether ETV will be beneficial for selected patientsare still pending. According to recent studies, tests of CSFdynamics and ventricle wall function will offer a resolutionto these questions.43,51,70,73 Many studies have demonstrateda trend toward a more successful outcome of ventriculosto-my in patients with existing shunt systems.3,44,45 In our study,three of five patients who had previously received shuntsbecame shunt free after ETV.

According to recent studies, the failure rate of ETVranged from 6 to 50%.1,5,11,16,19,24,31,32,35,50,61,68 In the presentstudy, the procedure failed in eight patients (13.8%). Timeto failure after ETV for the whole group was a mean of 3.4months (median 2 months, range 0–8 months). Almost twothirds of failures occurred within 3 months, three fourths offailures occurred within 6 months, and all developed with-in 9 months after surgery. The cases of treatment failure in-cluded two patients with aqueductal stenosis, one with thirdventricular ependymoma, two with giant suprasellar arach-noid cysts, and three with ventriculitis or IVH. The majorcause of failure of ETV is obstruction of the stoma, which

H. Feng, et al.


occurs between 2 weeks and 6 years according to the lit-erature.38 We consider that the risk for obstruction of thestoma seems to be higher if the flow through the stoma isreduced or if there is a high concentration of protein and fi-brinogen. This may be the case in patients with partiallyfunctional shunts, in those patients with extracranial drain-age before ETV, and in those with intraventricular tumors,IVH, or ventriculitis.

In our series, five patients experienced partial or com-plete closure of the stoma. Two patients presented with low-pressure hydrocephalus caused by overdrainage and contin-ued to require a shunt after ETV. In the other three patientsthe problem may have been caused by conglutination of thestoma due to a high concentration of protein in one patientwith an intraventricular tumor and two with ventriculitis.Revision of the ETV is indicated in patients in whom thereare anatomical blocks such as a Liliequist membrane or oc-clusion of the fenestration.50 During our early experiencewith ETV the rate of surgical complication was obvious-ly higher than that associated with insertion of a shunt, in-dicating that there was a steep learning curve. Seven pa-tients (12.1%) experienced ETV-related complications inthis study. There were no cases of permanent morbidityand none of the six deaths was a direct result of the ETV.The major complication we encountered was intraoperativebleeding. Fortunately, in most cases, intensive irrigation ledto termination of the bleeding. Other complications includ-ed infarction of the thalamus, fever, and transient dysfunc-tion of the hypothalamus.

Neuroimaging Study and Outcome Prediction

Endovascular third ventriculostomy is considered supe-rior to shunt implantation in patients with obstructive hy-drocephalus to resolve intracranial hypertension and restoreCSF dynamics to nearly normal. Nevertheless, the adjust-ment of CSF dynamics is somewhat time consuming whenone observes the delay between the ETV operation and thedecrease in ventricular size.7,17,64 Therefore, the challengefor neurosurgeons is to predict patient outcomes by usingreliable predictors. During the early phase of our ETV pro-cedures, we used ventriculography to evaluate the dynamicsof CSF after ETV. Serial-enhanced contrast MR or CT im-ages showed a clear patency of the stoma,33 but several dayswere needed to elucidate the observation, thus increasingthe economic burden on the patient. More recently, we haveassessed the patency of ETV by performing cine phase–contrast MR imaging at our center. Cine phase–contrast MRimaging has been increasingly used during the last decadeto evaluate cranial and spinal flow.10,16,18 With the increas-ing frequency of neuroendoscopic procedures, cine MR im-aging has been recommended to evaluate the patency ofthird ventriculostomy.20,27,55,75 A recent study showed thatCSF flow studies might detect obstruction before symptomrecurrence or clinical deterioration.18,20,41 According to ourlogistic regression model, the finding of a patent stoma oncine MR images within 2 weeks after ETV was demon-strated to be a powerful prognostic factor for a successfulETV. We documented that 12 (75%) of 16 patients in whoma positive flow void was observed on postoperative cineMR images had a successful ETV, whereas we also noticedthat four patients in whom a positive flow void was imagedexperienced treatment failure.

Magnetic resonance imaging, which can be used to detectthe presence of a flow void signal through the third ven-tricular floor, has been reported to have a significantly highincidence of false-positive findings.2 We figured the rea-son for a false-positive finding was mainly a result of a de-layed occlusion of the stoma. Five (38.5%) of 13 patients inwhom postoperative cine MR images demonstrated no al-leviation of the condition improved after ETV. We believethat this was due to external drainage or partial shunting,which produce a no-flow image even when there is an openorifice. Most studies have demonstrated a gradual decreasein ventricle size over months to years postoperatively, co-inciding with a clinical improvement.7,54,70 We proved thatthe size of the ventricle is not a good predictor for neuro-surgeons to use in the evaluation of the outcome within 3months after surgery. In the early postoperative period, adecrease in the size of the ventricle is often minimal andnot visible before 3 and 4 weeks.2 Nevertheless, the op-posite opinion has been raised in a recent report in whichthe authors stated, “postoperative ventricular size reflectsoutcome.”69 The size of the ventricle was used as the mostimportant factor in determining failure and requirement forshunting.39,69 In our study, five of 10 patients with an in-creased ventricle size after ETV achieved satisfactory re-sults. The reason may have been because of the adaptationprocess of CSF absorption capacity; in three of these fivepatients a hemorrhage or ventriculitis was documented.

In patients who have arachnoid granulations with a de-creased level of absorbability, which often occurs in thesepatients, we believe that a large pressure gradient may de-velop due to the increasing ICP and that this may overcomethe partial blockage caused by the arachnoid granulations.49

A recent study showed that symptoms improved within 1week after ETV in patients with shunt-dependent noncom-municating hydrocephalus.52 We demonstrated that the ear-ly clinical response played a important role for prediction ofoutcome in patients who have undergone surgery for ETV.In clinically improved cases, the success predictive valuewas as high as 94.1% (32 of 34), which corresponds to ratesreported in the literature.6,26 Some authors considered clin-ical outcome to be the most important guide to success orfailure. Using a reduction in the size of the ventricle as asole indicator of success in this procedure is questionablebecause clinically successful cases can have no change inventricle size. Neuroimaging outcomes alone may be mis-leading and reliance on them should be avoided.7

Conclusions

In conclusion, our results indicate that ETV is most effec-tive in patients with obstructive hydrocephalus caused byaqueductal stenosis and space-occupying lesions. For pa-tients with IVH or infections, ETV has a considerable ef-fect on selected cases with confirmed CSF dynamic studies.Blunt perforation of the floor of the third ventricle is thepreferred method of the procedure. Postoperative shuntplacement and excess drainage should not been advocat-ed to avoid closure of the stoma. Early clinical results andpostoperative findings on cine phase–contrast MR imagesplay a important role in predicting outcomes of ETV. Thepredictive value of an alteration in the size of the ventricle,especially during the early stage after ETV, is unsatisfacto-ry. Most ETV failures occur 6 months after the operation.



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Repeated ventriculostomy should be considered as a suf-ficient treatment option in cases of suspected stoma dys-function. If performed correctly, ETV is a safe, simple, andeffective treatment option with an acceptable level of com-plications.

Acknowledgments

We are grateful to Su Qin and Li Xiayu (West China Universityof Medical Science) for performing the statistical analysis, and to K.Kiya, M.D., and H. Satoh, M.D. (Department of Neurosurgery, Hiro-shima Prefectural Hospital) for their technical assistance.

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Manuscript received June 19, 2003.Accepted in final form December 17, 2003.Address reprint requests to: Hailong Feng, M.D., Ph.D, De-

partment of Neurosurgery, Sichuan Provincial People’s Hospital,Chengdu 610072, Sichuan province, People’s Republic of China.email address: [email protected].



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