Original Article
Infundibular Recess Angle Reduction After Endoscopic Third Ventriculostomy: Does It Reflect Clinical Success? Waleed A. Azab1, Radovan M. Mijalcic1,3, Ehab A. Abdelnabi2, Tufail A. Khan1, Mohammad H. Mohammad1, Mohammed S. Shaat1
BACKGROUND: Although the ventricular size is significantly reduced after endoscopic third ventriculostomy (ETV) in most successfully treated patients, ventricular size reduction is not always seen after a successful ETV. Practical and reliable radiologic parameters are still needed to assess the clinical success of an ETV.
infundibular recess angle measurement is easy to perform and may prove helpful in cases with no clear-cut clinical evidence of success of ETV.
METHODS: We retrieved the clinical and radiologic data of patients who underwent an ETV. Patients with the following criteria were included: (1) preoperative magnetic resonance imaging studies available, (2) postoperative magnetic resonance imaging studies done within the first 2 postoperative weeks, and (3) the infundibular recess clearly visible on preoperative and postoperative sagittal magnetic resonance imaging. Preoperative and postoperative measurements of the angle of the infundibular recess of the third ventricle were performed on midsagittal T1-weighted, T2-weighted, fast imaging employing steadystate acquisition, or constructive interference in steady state images.
INTRODUCTION
-
-
RESULTS: The extent of reduction of the infundibular recess angle predicted the clinical outcome of ETV during the early postoperative period with a high degree of accuracy. The average reduction was about 48% in successful procedures versus only 15% in failed procedures.
-
CONCLUSIONS: The degree of reduction of the angle of the infundibular recess of the third ventricle correlated with the amount of third ventricular decompression after ETV. Most importantly, such a reduction was noted to occur during the early postoperative period when radiologic changes are less pronounced. Assessment of change in
S
ince endoscopic third ventriculostomy (ETV) has become a popular procedure, a multitude of radiologic modalities and morphometric indexes have been used to demonstrate reduction of the size of the ventricular system after a successful procedure (16, 21, 25, 28). However, debate still exists over the extent of reduction that should be expected when weighed against clinical findings (23). Moreover, such a reduction is not always associated with clinical success and is inadequately sensitive as a sole parameter for determining success or failure of ETV (7). We observed that after a successful ETV, the change of the angle of the infundibular recess of the third ventricle was more pronounced and detected earlier than changes of the lateral and third ventricular global dimensions. To investigate whether this observation is of practical significance, we conducted a retrospective comparative evaluation of the infundibular recess angle measurements before ETV and early after the procedure in a cohort of our patients with successful and failed procedures. To the best of our knowledge, no previous study has quantitatively evaluated this morphometric parameter in patients undergoing ETV.
-
Key words Endoscopic third ventriculostomy - Infundibular recess - Radiologic - Third ventricle -
Abbreviations and Acronyms CSF: Cerebrospinal fluid ETV: Endoscopic third ventriculostomy MRI: Magnetic resonance imaging
MATERIALS AND METHODS From a prospective database of neuroendoscopic procedures maintained by our group, we retrieved clinical and radiologic data of patients who underwent an ETV. We included cases that met the following criteria: (1) preoperative magnetic resonance
From the Departments of 1Neurosurgery and 2Radiology, Ibn Sina Hospital, Kuwait City, Kuwait; and 3Clinical Centre of Serbia, University Medical School, Clinic for Neurosurgery, Belgrade, Serbia To whom correspondence should be addressed: Waleed A. Azab, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 84, 2:549-554. http://dx.doi.org/10.1016/j.wneu.2015.04.007 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY 84 [2]: 549-554, AUGUST 2015
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ORIGINAL ARTICLE WALEED A. AZAB ET AL.
INFUNDIBULAR RECESS ANGLE AFTER ETV
Figure 1. Method of measurement of the infundibular recess angle. Note the larger preoperative angle (q) and its 0 change after surgery (q ).
imaging (MRI) studies available, (2) postoperative MRI studies done within the first 2 postoperative weeks, and (3) the infundibular recess clearly visible on preoperative and postoperative sagittal MRI.
Figure 2. Measurement of the infundibular recess angle. Midsagittal T1-weighted images obtained before endoscopic third ventriculostomy before (A) and after (B) measuring the infundibular recess angle. Midsagittal T1-weighted images of the same case obtained after endoscopic third ventriculostomy before (C) and after (D) measuring the
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Preoperative and postoperative measurements of the angle of the infundibular recess of the third ventricle (Figures 1 and 2) were performed on midsagittal T1-weighted, T2-weighted, fast imaging employing steady-state acquisition, or constructive interference in
infundibular recess angle. Preoperative axial T2 fluid attenuated inversion recovery image (E). Postoperative axial T2 fluid attenuated inversion recovery image (F). Note the signal change within the third ventricle denoting cerebrospinal fluid flow after endoscopic third ventriculostomy. Postoperative axial (G) and sagittal (H) T2-weighted images.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.007
ORIGINAL ARTICLE WALEED A. AZAB ET AL.
INFUNDIBULAR RECESS ANGLE AFTER ETV
Table 1. Demographics, Causes of Hydrocephalus, Clinical Outcomes of Endoscopic Third Ventriculostomy, and Preoperative and Postoperative Infundibular Recess Angle Measurements Infundibular Recess Angle ( ) Patient Number
Age (years)/ Sex
1
9/M
Third ventricle choroid plexus cyst
2
42/M
Aqueduct stenosis— metastatic
3
13/F
Primary aqueduct stenosis
4
1.5/M
5
Diagnosis
Timing of Postoperative MRI (days) 6
ETV Outcome Successful
Before ETV
After Percentage Reduction ETV (%) P Value
28
15
46.4
12
48
33
31.2
10
138
43
69
Posthemorrhagic hydrocephalus
2
65
34
47.7
42/F
Thalamic glioma
6
99
66
33.3
6
9/F
Posttraumatic hydrocephalus
13
70
46
34.3
7
37/M
Aqueduct stenosis— posttuberculous
10
86
47
45.3
8
17/M
Posterior fossa astrocytoma
8
12
21
42
9
52/M
CP angle schwannoma
10
76
51
32.9
10
51/F
Tectal plate cavernoma
11
120
56
53.3
11
14/F
Primary aqueduct stenosis
7
106
25
76.4
12
22/M
Quadrigeminal cistern arachnoid cyst
9
34
14
58.9
13
17/F
Primary aqueduct stenosis
4
100
56
44
14
12/F
Cerebellar astrocytoma
3
62
30
51.6
15
8/M
Pineal germinoma
6
95
25
73.7
16
39/F
CP angle meningioma
8
80
43
46.2
17
11/F
Postmeningitic aqueduct stenosis
7
71
41
42.3
18
33/M
Posterior fossa astrocytoma
6
63
39
38.1
19
19/M
Primary aqueduct stenosis
7
32
18
43.8
20
63/M
Pineal region metastasis
7
51
37
27.5
21
6/M
Primary aqueduct stenosis
13
62
24
61.3
22
27/F
Primary aqueduct stenosis
3
87
54
38
23
36/F
Posthemorrhagic hydrocephalus
6
67
46
31.3
24
35/M
CP angle schwannoma
4
38
32
15.8
25
11/F
Pineal cyst
4
52
41
21.2
26
10/M
Primary aqueduct stenosis
9
65
50
23.1
27
45/F
Cerebellar AVM
2
64
59
7.8
28
42/F
Posttraumatic hydrocephalus
6
87
74
15
29
30/M
Meningeal carcinomatosis
11
70
63
10
Failed
0.000007
0.16
MRI, magnetic resonance imaging; ETV, endoscopic third ventriculostomy; M, male; F, female; CP, cerebellopontine; AVM, arteriovenous malformation.
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steady state images. The angle function of the MRI console monitor was used for measurements. Measurements were performed by a neuroradiologist (E.A) and 2 neurosurgeons (W.A and R.M). In cases of discrepancy, the neuroradiologist’s measurements were used. Statistical evaluations were calculated using Microsoft Office Excel 2007 software (Microsoft Corp., Redmond, Washington, USA). Student t test was used to determine statistical significance (P < 0.001) of differences between measurements. RESULTS Application of the inclusion criteria retrieved 29 patients (14 males and 15 females) with a mean age of 25.9 years (range, 1.5e63 years). ETV was successful in 23 patients and unsuccessful in 6 patients. The mean preoperative infundibular recess angle was 71.8 in successful procedures versus 62.7 in unsuccessful procedures. The mean postoperative infundibular recess angle was 37.6 in successful procedures and 53.2 in unsuccessful procedures. The mean postoperative reduction in infundibular recess angle in successful procedures was 34.2 (47.6%) versus 9.5 (15.2%) in unsuccessful procedures. The degree of reduction was highly statistically significant in successful ETVs (P ¼ 0.000007) and nonsignificant in failed ETVs (P ¼ 0.16). Postprocedure MRI was performed a mean 7.5 days after successful ETVs and a mean 6 days after failed ETVs. Table 1 summarizes the demographics, causes of hydrocephalus, clinical outcomes of ETV, preoperative and postoperative infundibular recess angle measurements, and the number of days elapsing between ETV and postoperative MRI. Table 2 shows the change of the infundibular recess measurements in successful and unsuccessful ETVs. Figures 3 and 4 demonstrate the infundibular recess angle in successful and failed procedures, respectively. DISCUSSION
Figure 3. Bar graph demonstrating the degrees of infundibular angle reduction in successful cases.
ventricular size reduction is not always seen after a successful ETV (1). Subtle but clinically significant changes in ventricular size are difficult to estimate visually (3). Despite this difficulty, detailed measurements of configuration and diameters of the ventricles (20, 26) as well as volumetric studies (24) disclose significant reductions in most successfully treated patients. Using volumetric measurements, Schwartz et al. (27) showed decreases in ventricular volumes of 5%e80% within the first 3 weeks after successful ETV. Volumetric studies in combination
The current neurosurgical literature shows a consensus among most investigators that a gradual decrease of ventricular size usually occurs over a period of 3e6 months in most patients successfully treated with an ETV. The reduction of the ventricular size subsequently tapers off without reaching baseline (25, 28). Pindrik et al. demonstrated that third ventricular width decreased by an average of 0.32 cm after a successful ETV and increased by an average of 0.35 cm when the procedure failed (21). However,
Table 2. Change in Infundibular Recess Measurements in Successful and Unsuccessful Endoscopic Third Ventriculostomy Cases Successful ETV (n [ 23)
Unsuccessful ETV (n [ 6)
Mean preoperative angle
71.8
62.7
Mean postoperative angle
37.6
53.2
Mean angle reduction (%)
34.2 (47.6%)
9.5 (15.2%)
Infundibular Recess Angle ( )
P value
0.000012
ETV, endoscopic third ventriculostomy.
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Figure 4. Bar graph demonstrating the degrees of infundibular angle reduction in failed cases.
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ORIGINAL ARTICLE WALEED A. AZAB ET AL.
with MRI flow studies were suggested to be most valuable in controversial cases (12). Conversely, changes in ventricular size per se cannot fully predict outcome. Some investigators reported that after ETV some patients with larger ventricles were successfully treated, whereas some with smaller ventricles were not. The investigators concluded that the actual size of the lateral ventricles had little bearing on success (2). Kulkarni et al. (17) used the frontal and occipital horn ratio to determine the postoperative ventricular size in 29 children who underwent ETV. The ventricular size was reduced in clinically successful cases and in cases that were deemed failures; however, the reduction was significantly greater among the clinically successful cases (16% vs. 7% mean reduction in ventricular size). Resolution of symptoms in association with decreased ventricular size is thought to correlate best with outcome after the procedure (10, 15). The significance of flow studies was noted by investigators who demonstrated the cerebrospinal fluid (CSF) flow void in the anterior inferior third ventricle was even more constant than reduction in ventricular size (30). Although cine phase-contrast MRI was established as the gold standard method for the preoperative and postoperative evaluation of CSF dynamics (6, 8), this modality has been reported to be not completely reliable in differentiating successful from failed ETVs (4). CSF flow demonstrable on imaging has frequently been reported to be useful in determining success or failure (18, 19, 22, 30). However, the absence of a flow void does not rule out a functioning stoma, and a patent fenestration of the third ventricular floor does not indicate a restored physiologic CSF flow (9). In one study by Kulkarni et al. (17), a flow void was present in 94% of successful ETVs and absent in 75% of failed ETVs. In contrast, other investigators (2, 29) reported clinical failure in 50%e73% of patients who had CSF flow voids on MRI. Practical and reliable radiologic parameters to assess the clinical success of ETV are still needed. In this study, we demonstrated that the extent of reduction of the infundibular recess angle predicted the clinical outcome of ETV during the early postoperative period with a high degree of accuracy. The average reduction was about 48% in successful procedures versus only 15% in failed procedures. These percentages may offer a useful clue as to whether an ETV is functioning in patients who do not show a definite clinical improvement. The early postoperative detection of such a reduction is relevant in a time frame during which the decision to observe or reoperate may prove difficult. In our patients, the lowest reduction of the infundibular recess angle in successful procedures was 27.5% (patient 20), whereas the highest reduction in failed procedures was 23.1% (patient 26). We suggest a cutoff value of 25% reduction of the infundibular recess angle above which the procedure can be considered successful. Using a third ventricular morphometric parameter to evaluate the ventricular size response to ETV seems to be more practical and sensitive than using parameters that involve the lateral ventricles. Changes in third ventricular volume after ETV were found to be more pronounced than changes of the lateral ventricles (21). We believe this finding can be explained by the fact that the floor and the lamina terminalis of the third ventricle are mainly formed by thin sheets of tissue that are bordered
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extraventricularly by cisternal CSF and not by compact neural tissues. Such an anatomic arrangement renders the floor and the lamina terminalis of the third ventricle more displaceable and sensitive to the third ventricle pressure alteration early after an ETV. In support of this hypothesis, third ventricular wall motion, especially the lamina terminalis, seen by true fast imaging with steady-state precision cardiac-gated MRI was found to be a very sensitive method of determining third ventricular decompression (7, 11). In patients with hydrocephalus, the extent of preoperative downward bulging of the floor of the third ventricle has been postulated to reflect the pressure gradient between the third ventricle and the basal cisterns (13, 14). The dramatic reduction of the infundibular recess angle noted in our successful procedures can be explained by elimination of the pressure gradient after a successful ETV leading to flattening of the third ventricular floor. Taking into consideration that the inferior limb of the infundibular recess represents the anterior anatomic continuation of the third ventricular floor, restoration of the third ventricular floor position to a higher level leads to a reduced angle of the infundibular recess. Seen through the aforementioned anatomic scope, our findings are in concordance with the results of Fouroughi et al. (7), who reported flattening of the third ventricular floor to occur after ETV in 33 of 36 successfully treated patients. These authors also described a change from a preoperative epsilon-shaped to a postoperative W-shaped morphology of the third ventricle floor, lamina terminalis, and supraoptic and infundibular recesses. They pointed out that such a change denotes a transition from a compressed third ventricle into a decompressed third ventricle. Qualitatively, this morphology was found in 80% of successfully treated patients and was seen in only 1 failed case. In contrast to the work of Fouroughi et al. (7), we quantitatively measured the infundibular recess angle before and after ETV. Furthermore, Dlouhy et al. (5) found that preoperative bowing of the anterior third ventricular floor (between the optic chiasm and the posterior aspect of the infundibulum) was significant and predictive of ETV success. A differential movement between the anterior and posterior third ventricular floor may further explain why we have encountered such a high percentage of correlation between infundibular recess reduction and success of ETV in our study. The significant degree of reduction of the infundibular recess angle noted in all our successfully treated patients may not occur with the same magnitude in patients with low cerebral compliance. Additionally, we are aware that the retrospective nature and the relatively small number of cases are limitations of our study. Further prospective studies incorporating a larger number of patients of younger pediatric age as well as postinfectious and posthemorrhagic etiologies of hydrocephalus are required to validate our results and make more solid conclusions. CONCLUSIONS In this study, a single third ventricular morphometric parameter was used to determine radiologic change after ETV. The degree of reduction of the angle of the infundibular recess of the third ventricle correlated with the amount of third ventricular decompression after ETV. Most importantly, such a reduction was noted
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to occur during the early postoperative period when radiologic changes are less pronounced. Assessment of change in third ventricular infundibular recess measurement is easy to perform
REFERENCES 1. Bargalló N, Olondo L, Garcia AI, Capurro S, Caral L, Rumia J: Functional analysis of third ventriculostomy patency by quantification of CSF stroke volume by using cine phase-contrast MR imaging. AJNR Am J Neuroradiol 26:2514-2521, 2005. 2. Buxton N, Macarthur D, Mallucci C, Punt J, Vloeberghs M: Neuroendoscopic third ventriculostomy in patients less than 1 year old. Pediatr Neurosurg 29:73-76, 1998. 3. Clatterbuck RE, Sipos EP: The efficient calculation of neurosurgically relevant volumes from computed tomographic scans using Cavalieri’s DirectEstimator. Neurosurgery 40:339-342, 1997. 4. Di X, Ragab M, Luciano MG: Cine phase-contrast MR images failed to predict clinical outcome following ETV. Can J Neurol Sci 36:643-647, 2009. 5. Dlouhy BJ, Capuano AW, Madhavan K, Torner JC, Greenlee JD: Preoperative third ventricular bowing as a predictor of endoscopic third ventriculostomy success. J Neurosurg Pediatr 9:182-190, 2012. 6. Foroutan M, Mafee MF, Dujovny M: Third ventriculostomy, phase-contrast cine MRI and endoscopic techniques. Neurol Res 20:443-448, 1998. 7. Foroughi M, Wong A, Steinbok P, Singhal A, Sargent MA, Cochrane DD: Third ventricular shape: a predictor of endoscopic third ventriculostomy success in pediatric patients. J Neurosurg Pediatr 7:389-396, 2011. 8. Fukuhara T, Vorster SJ, Ruggieri P, Luciano MG: Third ventriculostomy patency: comparison of findings at cine phase-contrast MR imaging and at direct exploration. AJNR Am J Neuroradiol 20: 1560-1566, 1999. 9. Gangemi M, Donati P, Maiuri F, Longatti P, Godano U, Mascari C: Endoscopic third ventriculostomy for hydrocephalus. Minim Invasive Neurosurg 42:128-132, 1999. 10. Goumnerova L, Frim D: Treatment of hydrocephalus with third ventriculocisternostomy: outcome and CSF flow patterns. Pediatr Neurosurg 27:149-152, 1997. 11. Hodel J, Decq P, Rahmouni A, Bastuji-Garin S, Maraval A, Combes C, Jarraya B, Le Guérinel C, Gaston A: Brain ventricular wall movement assessed by a gated cine MR true FISP sequence in
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and may prove helpful in cases with no clear-cut clinical evidence of success of ETV. Large-scale prospective studies are required to validate these results further.
patients treated with endoscopic third ventriculostomy. Eur Radiol 19:2789-2797, 2009.
communicating hydrocephalus. Minim Invasive Neurosurg 39:17-20, 1996.
12. Hopf NJ, Grunert P, Fries G, Resch K, Perneczky A: Endoscopic third ventriculostomy: outcome analysis of 100 consecutive procedures. Neurosurgery 44:795-804, 1999.
23. Romeo A, Naftel RP, Griessenauer CJ, Reed GT, Martin R, Shannon CN, Grabb PA, Tubbs RS, Wellons JC 3rd: Long-term change in ventricular size following endoscopic third ventriculostomy for hydrocephalus due to tectal plate gliomas. J Neurosurg Pediatr 11:20-25, 2013.
13. Kehler U, Gliemroth J: Extraventricular intracisternal obstructive hydrocephalus—a hypothesis to explain successful 3rd ventriculostomy in communicating hydrocephalus. Pediatr Neurosurg 38:98-101, 2003. 14. Kehler U, Regelsberger J, Gliemroth J, Westphal M: Outcome prediction of third ventriculostomy: a proposed hydrocephalus grading system. Minim Invasive Neurosurg 49:238-243, 2006. 15. Kida H, Nishikawa N, Ohta M, Miyao S, Takimoto H: A case of suspected pulmonary air embolism in endoscopic neurosurgery [abstract]. Masui 50:419-421, 2001. 16. Kulkarni AV, Drake JM, Armstrong DC, Dirks PB: Measurement of ventricular size: reliability of the frontal and occipital horn ratio compared to subjective assessment. Pediatr Neurosurg 31:65-70, 1999. 17. Kulkarni AV, Drake JM, Armstrong DC, Dirks PB: Imaging correlates of successful endoscopic third ventriculostomy. J Neurosurg 92:915-919, 2000. 18. Lev S, Bhadelia RA, Estin D, Heilman CB, Wolpert SM: Functional analysis of third ventriculostomy patency with phase-contrast MRI velocity measurements. Neuroradiology 39: 175-179, 1997. 19. Maeder P, Gudinchet F, Meuli R, Fankhauser H: Dynamic MRI of cerebrospinal fluid flow in endoscopic percutaneous ventriculostomy. Br J Neurosurg 12:18-22, 1998. 20. Oka K, Kin Y, Go Y, Ueno Y, Hirakawa K, Tomanaga M, Inoue T, Yoshioka S: Neuroendoscopic approach to tectal tumors: a consecutive series. J Neurosurg 91:964-970, 1999.
24. Sainte-Rose C: Third ventriculostomy. In: Manwaring KH, Crone KR, eds. Neuroendoscopy. New York: Mary Ann Liebert; 1992:47-62. 25. Santamarta D, Martin-Vallejo J, Díaz-Alvarez A, Maillo A: Changes in ventricular size after endoscopic third ventriculostomy. Acta Neurochir (Wien) 150:119-127, 2008. 26. Schwartz TH, Yoon SS, Cutruzzola FW, Goodman RR: Third ventriculostomy—postoperative ventricular size and outcome. Minim Invasive Neurosurg 39:122-129, 1996. 27. Schwartz TH, Ho B, Prestigiacomo CJ, Bruce JN, Feldstein NA, Goodman RR: Ventricular volume following third ventriculostomy. J Neurosurg 91: 20-25, 1999. 28. St. George E, Natarajan K, Sgouros S: Changes in ventricular volume in hydrocephalic children following successful endoscopic third ventriculostomy. Childs Nerv Syst 20:834-838, 2004. 29. Tisell M, Almstrom O, Stephensen H, Tullberg M, Wikkelso C: How effective is endoscopic third ventriculostomy in treating adult hydrocephalus caused by primary aqueductal stenosis? Neurosurgery 46:104-111, 2000. 30. Wilcock DJ, Jaspan T, Worthington BS, Punt J: Neuroendoscopic third ventriculostomy: evaluation with magnetic resonance imaging. Clin Radiol 52:50-54, 1997. Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Received 27 February 2015; accepted 6 April 2015
21. Pindrik J, Jallo GI, Ahn ES: Changes in third ventricular size in pediatric patients undergoing endoscopic third ventriculostomy. Childs Nerv Syst 29:2027-2034, 2013. 22. Rieger A, Rainov NG, Sanchin L, Schopp G, Burkert W: Ultrasound-guided endoscopic fenestration of the third ventricular floor for non-
Citation: World Neurosurg. (2015) 84, 2:549-554. http://dx.doi.org/10.1016/j.wneu.2015.04.007 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.007
Infundibular Recess Angle Reduction After Endoscopic Third Ventriculostomy: Does It Reflect Clinical Success? Waleed A. Azab1, Radovan M. Mijalcic1,3, Ehab A. Abdelnabi2, Tufail A. Khan1, Mohammad H. Mohammad1, Mohammed S. Shaat1
BACKGROUND: Although the ventricular size is significantly reduced after endoscopic third ventriculostomy (ETV) in most successfully treated patients, ventricular size reduction is not always seen after a successful ETV. Practical and reliable radiologic parameters are still needed to assess the clinical success of an ETV.
infundibular recess angle measurement is easy to perform and may prove helpful in cases with no clear-cut clinical evidence of success of ETV.
METHODS: We retrieved the clinical and radiologic data of patients who underwent an ETV. Patients with the following criteria were included: (1) preoperative magnetic resonance imaging studies available, (2) postoperative magnetic resonance imaging studies done within the first 2 postoperative weeks, and (3) the infundibular recess clearly visible on preoperative and postoperative sagittal magnetic resonance imaging. Preoperative and postoperative measurements of the angle of the infundibular recess of the third ventricle were performed on midsagittal T1-weighted, T2-weighted, fast imaging employing steadystate acquisition, or constructive interference in steady state images.
INTRODUCTION
-
-
RESULTS: The extent of reduction of the infundibular recess angle predicted the clinical outcome of ETV during the early postoperative period with a high degree of accuracy. The average reduction was about 48% in successful procedures versus only 15% in failed procedures.
-
CONCLUSIONS: The degree of reduction of the angle of the infundibular recess of the third ventricle correlated with the amount of third ventricular decompression after ETV. Most importantly, such a reduction was noted to occur during the early postoperative period when radiologic changes are less pronounced. Assessment of change in
S
ince endoscopic third ventriculostomy (ETV) has become a popular procedure, a multitude of radiologic modalities and morphometric indexes have been used to demonstrate reduction of the size of the ventricular system after a successful procedure (16, 21, 25, 28). However, debate still exists over the extent of reduction that should be expected when weighed against clinical findings (23). Moreover, such a reduction is not always associated with clinical success and is inadequately sensitive as a sole parameter for determining success or failure of ETV (7). We observed that after a successful ETV, the change of the angle of the infundibular recess of the third ventricle was more pronounced and detected earlier than changes of the lateral and third ventricular global dimensions. To investigate whether this observation is of practical significance, we conducted a retrospective comparative evaluation of the infundibular recess angle measurements before ETV and early after the procedure in a cohort of our patients with successful and failed procedures. To the best of our knowledge, no previous study has quantitatively evaluated this morphometric parameter in patients undergoing ETV.
-
Key words Endoscopic third ventriculostomy - Infundibular recess - Radiologic - Third ventricle -
Abbreviations and Acronyms CSF: Cerebrospinal fluid ETV: Endoscopic third ventriculostomy MRI: Magnetic resonance imaging
MATERIALS AND METHODS From a prospective database of neuroendoscopic procedures maintained by our group, we retrieved clinical and radiologic data of patients who underwent an ETV. We included cases that met the following criteria: (1) preoperative magnetic resonance
From the Departments of 1Neurosurgery and 2Radiology, Ibn Sina Hospital, Kuwait City, Kuwait; and 3Clinical Centre of Serbia, University Medical School, Clinic for Neurosurgery, Belgrade, Serbia To whom correspondence should be addressed: Waleed A. Azab, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2015) 84, 2:549-554. http://dx.doi.org/10.1016/j.wneu.2015.04.007 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY 84 [2]: 549-554, AUGUST 2015
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INFUNDIBULAR RECESS ANGLE AFTER ETV
Figure 1. Method of measurement of the infundibular recess angle. Note the larger preoperative angle (q) and its 0 change after surgery (q ).
imaging (MRI) studies available, (2) postoperative MRI studies done within the first 2 postoperative weeks, and (3) the infundibular recess clearly visible on preoperative and postoperative sagittal MRI.
Figure 2. Measurement of the infundibular recess angle. Midsagittal T1-weighted images obtained before endoscopic third ventriculostomy before (A) and after (B) measuring the infundibular recess angle. Midsagittal T1-weighted images of the same case obtained after endoscopic third ventriculostomy before (C) and after (D) measuring the
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Preoperative and postoperative measurements of the angle of the infundibular recess of the third ventricle (Figures 1 and 2) were performed on midsagittal T1-weighted, T2-weighted, fast imaging employing steady-state acquisition, or constructive interference in
infundibular recess angle. Preoperative axial T2 fluid attenuated inversion recovery image (E). Postoperative axial T2 fluid attenuated inversion recovery image (F). Note the signal change within the third ventricle denoting cerebrospinal fluid flow after endoscopic third ventriculostomy. Postoperative axial (G) and sagittal (H) T2-weighted images.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2015.04.007
ORIGINAL ARTICLE WALEED A. AZAB ET AL.
INFUNDIBULAR RECESS ANGLE AFTER ETV
Table 1. Demographics, Causes of Hydrocephalus, Clinical Outcomes of Endoscopic Third Ventriculostomy, and Preoperative and Postoperative Infundibular Recess Angle Measurements Infundibular Recess Angle ( ) Patient Number
Age (years)/ Sex
1
9/M
Third ventricle choroid plexus cyst
2
42/M
Aqueduct stenosis— metastatic
3
13/F
Primary aqueduct stenosis
4
1.5/M
5
Diagnosis
Timing of Postoperative MRI (days) 6
ETV Outcome Successful
Before ETV
After Percentage Reduction ETV (%) P Value
28
15
46.4
12
48
33
31.2
10
138
43
69
Posthemorrhagic hydrocephalus
2
65
34
47.7
42/F
Thalamic glioma
6
99
66
33.3
6
9/F
Posttraumatic hydrocephalus
13
70
46
34.3
7
37/M
Aqueduct stenosis— posttuberculous
10
86
47
45.3
8
17/M
Posterior fossa astrocytoma
8
12
21
42
9
52/M
CP angle schwannoma
10
76
51
32.9
10
51/F
Tectal plate cavernoma
11
120
56
53.3
11
14/F
Primary aqueduct stenosis
7
106
25
76.4
12
22/M
Quadrigeminal cistern arachnoid cyst
9
34
14
58.9
13
17/F
Primary aqueduct stenosis
4
100
56
44
14
12/F
Cerebellar astrocytoma
3
62
30
51.6
15
8/M
Pineal germinoma
6
95
25
73.7
16
39/F
CP angle meningioma
8
80
43
46.2
17
11/F
Postmeningitic aqueduct stenosis
7
71
41
42.3
18
33/M
Posterior fossa astrocytoma
6
63
39
38.1
19
19/M
Primary aqueduct stenosis
7
32
18
43.8
20
63/M
Pineal region metastasis
7
51
37
27.5
21
6/M
Primary aqueduct stenosis
13
62
24
61.3
22
27/F
Primary aqueduct stenosis
3
87
54
38
23
36/F
Posthemorrhagic hydrocephalus
6
67
46
31.3
24
35/M
CP angle schwannoma
4
38
32
15.8
25
11/F
Pineal cyst
4
52
41
21.2
26
10/M
Primary aqueduct stenosis
9
65
50
23.1
27
45/F
Cerebellar AVM
2
64
59
7.8
28
42/F
Posttraumatic hydrocephalus
6
87
74
15
29
30/M
Meningeal carcinomatosis
11
70
63
10
Failed
0.000007
0.16
MRI, magnetic resonance imaging; ETV, endoscopic third ventriculostomy; M, male; F, female; CP, cerebellopontine; AVM, arteriovenous malformation.
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INFUNDIBULAR RECESS ANGLE AFTER ETV
steady state images. The angle function of the MRI console monitor was used for measurements. Measurements were performed by a neuroradiologist (E.A) and 2 neurosurgeons (W.A and R.M). In cases of discrepancy, the neuroradiologist’s measurements were used. Statistical evaluations were calculated using Microsoft Office Excel 2007 software (Microsoft Corp., Redmond, Washington, USA). Student t test was used to determine statistical significance (P < 0.001) of differences between measurements. RESULTS Application of the inclusion criteria retrieved 29 patients (14 males and 15 females) with a mean age of 25.9 years (range, 1.5e63 years). ETV was successful in 23 patients and unsuccessful in 6 patients. The mean preoperative infundibular recess angle was 71.8 in successful procedures versus 62.7 in unsuccessful procedures. The mean postoperative infundibular recess angle was 37.6 in successful procedures and 53.2 in unsuccessful procedures. The mean postoperative reduction in infundibular recess angle in successful procedures was 34.2 (47.6%) versus 9.5 (15.2%) in unsuccessful procedures. The degree of reduction was highly statistically significant in successful ETVs (P ¼ 0.000007) and nonsignificant in failed ETVs (P ¼ 0.16). Postprocedure MRI was performed a mean 7.5 days after successful ETVs and a mean 6 days after failed ETVs. Table 1 summarizes the demographics, causes of hydrocephalus, clinical outcomes of ETV, preoperative and postoperative infundibular recess angle measurements, and the number of days elapsing between ETV and postoperative MRI. Table 2 shows the change of the infundibular recess measurements in successful and unsuccessful ETVs. Figures 3 and 4 demonstrate the infundibular recess angle in successful and failed procedures, respectively. DISCUSSION
Figure 3. Bar graph demonstrating the degrees of infundibular angle reduction in successful cases.
ventricular size reduction is not always seen after a successful ETV (1). Subtle but clinically significant changes in ventricular size are difficult to estimate visually (3). Despite this difficulty, detailed measurements of configuration and diameters of the ventricles (20, 26) as well as volumetric studies (24) disclose significant reductions in most successfully treated patients. Using volumetric measurements, Schwartz et al. (27) showed decreases in ventricular volumes of 5%e80% within the first 3 weeks after successful ETV. Volumetric studies in combination
The current neurosurgical literature shows a consensus among most investigators that a gradual decrease of ventricular size usually occurs over a period of 3e6 months in most patients successfully treated with an ETV. The reduction of the ventricular size subsequently tapers off without reaching baseline (25, 28). Pindrik et al. demonstrated that third ventricular width decreased by an average of 0.32 cm after a successful ETV and increased by an average of 0.35 cm when the procedure failed (21). However,
Table 2. Change in Infundibular Recess Measurements in Successful and Unsuccessful Endoscopic Third Ventriculostomy Cases Successful ETV (n [ 23)
Unsuccessful ETV (n [ 6)
Mean preoperative angle
71.8
62.7
Mean postoperative angle
37.6
53.2
Mean angle reduction (%)
34.2 (47.6%)
9.5 (15.2%)
Infundibular Recess Angle ( )
P value
0.000012
ETV, endoscopic third ventriculostomy.
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Figure 4. Bar graph demonstrating the degrees of infundibular angle reduction in failed cases.
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ORIGINAL ARTICLE WALEED A. AZAB ET AL.
with MRI flow studies were suggested to be most valuable in controversial cases (12). Conversely, changes in ventricular size per se cannot fully predict outcome. Some investigators reported that after ETV some patients with larger ventricles were successfully treated, whereas some with smaller ventricles were not. The investigators concluded that the actual size of the lateral ventricles had little bearing on success (2). Kulkarni et al. (17) used the frontal and occipital horn ratio to determine the postoperative ventricular size in 29 children who underwent ETV. The ventricular size was reduced in clinically successful cases and in cases that were deemed failures; however, the reduction was significantly greater among the clinically successful cases (16% vs. 7% mean reduction in ventricular size). Resolution of symptoms in association with decreased ventricular size is thought to correlate best with outcome after the procedure (10, 15). The significance of flow studies was noted by investigators who demonstrated the cerebrospinal fluid (CSF) flow void in the anterior inferior third ventricle was even more constant than reduction in ventricular size (30). Although cine phase-contrast MRI was established as the gold standard method for the preoperative and postoperative evaluation of CSF dynamics (6, 8), this modality has been reported to be not completely reliable in differentiating successful from failed ETVs (4). CSF flow demonstrable on imaging has frequently been reported to be useful in determining success or failure (18, 19, 22, 30). However, the absence of a flow void does not rule out a functioning stoma, and a patent fenestration of the third ventricular floor does not indicate a restored physiologic CSF flow (9). In one study by Kulkarni et al. (17), a flow void was present in 94% of successful ETVs and absent in 75% of failed ETVs. In contrast, other investigators (2, 29) reported clinical failure in 50%e73% of patients who had CSF flow voids on MRI. Practical and reliable radiologic parameters to assess the clinical success of ETV are still needed. In this study, we demonstrated that the extent of reduction of the infundibular recess angle predicted the clinical outcome of ETV during the early postoperative period with a high degree of accuracy. The average reduction was about 48% in successful procedures versus only 15% in failed procedures. These percentages may offer a useful clue as to whether an ETV is functioning in patients who do not show a definite clinical improvement. The early postoperative detection of such a reduction is relevant in a time frame during which the decision to observe or reoperate may prove difficult. In our patients, the lowest reduction of the infundibular recess angle in successful procedures was 27.5% (patient 20), whereas the highest reduction in failed procedures was 23.1% (patient 26). We suggest a cutoff value of 25% reduction of the infundibular recess angle above which the procedure can be considered successful. Using a third ventricular morphometric parameter to evaluate the ventricular size response to ETV seems to be more practical and sensitive than using parameters that involve the lateral ventricles. Changes in third ventricular volume after ETV were found to be more pronounced than changes of the lateral ventricles (21). We believe this finding can be explained by the fact that the floor and the lamina terminalis of the third ventricle are mainly formed by thin sheets of tissue that are bordered
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extraventricularly by cisternal CSF and not by compact neural tissues. Such an anatomic arrangement renders the floor and the lamina terminalis of the third ventricle more displaceable and sensitive to the third ventricle pressure alteration early after an ETV. In support of this hypothesis, third ventricular wall motion, especially the lamina terminalis, seen by true fast imaging with steady-state precision cardiac-gated MRI was found to be a very sensitive method of determining third ventricular decompression (7, 11). In patients with hydrocephalus, the extent of preoperative downward bulging of the floor of the third ventricle has been postulated to reflect the pressure gradient between the third ventricle and the basal cisterns (13, 14). The dramatic reduction of the infundibular recess angle noted in our successful procedures can be explained by elimination of the pressure gradient after a successful ETV leading to flattening of the third ventricular floor. Taking into consideration that the inferior limb of the infundibular recess represents the anterior anatomic continuation of the third ventricular floor, restoration of the third ventricular floor position to a higher level leads to a reduced angle of the infundibular recess. Seen through the aforementioned anatomic scope, our findings are in concordance with the results of Fouroughi et al. (7), who reported flattening of the third ventricular floor to occur after ETV in 33 of 36 successfully treated patients. These authors also described a change from a preoperative epsilon-shaped to a postoperative W-shaped morphology of the third ventricle floor, lamina terminalis, and supraoptic and infundibular recesses. They pointed out that such a change denotes a transition from a compressed third ventricle into a decompressed third ventricle. Qualitatively, this morphology was found in 80% of successfully treated patients and was seen in only 1 failed case. In contrast to the work of Fouroughi et al. (7), we quantitatively measured the infundibular recess angle before and after ETV. Furthermore, Dlouhy et al. (5) found that preoperative bowing of the anterior third ventricular floor (between the optic chiasm and the posterior aspect of the infundibulum) was significant and predictive of ETV success. A differential movement between the anterior and posterior third ventricular floor may further explain why we have encountered such a high percentage of correlation between infundibular recess reduction and success of ETV in our study. The significant degree of reduction of the infundibular recess angle noted in all our successfully treated patients may not occur with the same magnitude in patients with low cerebral compliance. Additionally, we are aware that the retrospective nature and the relatively small number of cases are limitations of our study. Further prospective studies incorporating a larger number of patients of younger pediatric age as well as postinfectious and posthemorrhagic etiologies of hydrocephalus are required to validate our results and make more solid conclusions. CONCLUSIONS In this study, a single third ventricular morphometric parameter was used to determine radiologic change after ETV. The degree of reduction of the angle of the infundibular recess of the third ventricle correlated with the amount of third ventricular decompression after ETV. Most importantly, such a reduction was noted
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to occur during the early postoperative period when radiologic changes are less pronounced. Assessment of change in third ventricular infundibular recess measurement is easy to perform
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Citation: World Neurosurg. (2015) 84, 2:549-554. http://dx.doi.org/10.1016/j.wneu.2015.04.007 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2015 Elsevier Inc. All rights reserved.
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