Anterior third ventricular height and infundibulochiasmatic angle: two novel measurements to predict clinical success of endoscopic third ventriculostomy in the early postoperative period

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OBJECTIVE

The authors sought to develop a set of parameters that reliably predict the clinical success of endoscopic third ventriculostomy (ETV) when assessed before and after the operation, and to establish a plan for MRI follow-up after this procedure.

METHODS

This retrospective study involved 77 patients who had undergone 78 ETV procedures for obstructive hydrocephalus between 2010 and 2015. Constructive interference in steady-state (CISS) MRI evaluations before and after ETV were reviewed, and 4 parameters were measured. Two well-known standard parameters, fronto-occipital horn ratio (FOHR) and third ventricular index (TVI), and 2 newly defined parameters, infundibulochiasmatic (IC) angle and anterior third ventricular height (TVH), were measured in this study. Associations between preoperative measurements of and postoperative changes in the 4 variables and the clinical success of ETV were analyzed.

RESULTS

Of the 78 ETV procedures, 70 (89.7%) were successful and 8 (10.3%) failed. On the preoperative MR images, the mean IC angle and anterior TVH were significantly larger in the successful procedures. On the 24-hour postoperative MR images of the successful procedures, the mean IC angle declined significantly from 114.2° to 94.6° (p < 0.05) and the mean anterior TVH declined significantly from 15 to 11.2 mm (p < 0.05). The mean percentage reduction of the IC angle was 17.1%, and that of the anterior TVH was 25.5% (both p < 0.05). On the 1-month MR images of the successful procedures, the mean IC angle declined significantly from 94.6° to 84.2° (p < 0.05) and the mean anterior TVH declined significantly from 11.2 to 9.3 mm (p < 0.05). The mean percentage reductions in IC angle (11%) and anterior TVH (16.9%) remained significant at this time point but were smaller than those observed at 24 hours. The 6-month and 1-year postoperative MR images of the successful group showed no significant changes in mean IC angle or mean anterior TVH. Regarding the unsuccessful procedures, there were no significant changes observed in IC angle or anterior TVH at any of the time points studied. Reduction of IC angle and reduction of anterior TVH on 24-hour postoperative MR images were significantly associated with successful ETV. However, no clinically significant association was found between FOHR, TVI, and ETV success.

CONCLUSIONS

Assessing the IC angle and anterior TVH on preoperative and 24-hour postoperative MR images is useful for predicting the clinical success of ETV. These 2 measurements could also be valuable as radiological follow-up parameters.

ABBREVIATIONS CISS = constructive interference in steady-state; ETV = endoscopic third ventriculostomy; FOHR = fronto-occipital horn ratio; IC = infundibulochiasmatic; TVH = third ventricular height; TVI = third ventricle index.

Article Information

Correspondence Mehmet Sabri Gürbüz: İstanbul Medeniyet University, İstanbul, Turkey. mehmetsabrigurbuz@gmail.com.

INCLUDE WHEN CITING Published online May 10, 2019; DOI: 10.3171/2019.1.JNS181330.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Sagittal CISS MR images show how anterior TVH and IC angle were calculated: preoperative TVH (13.2 mm) (A), postoperative TVH (8.56 mm) (B), preoperative IC angle (130°) (C), and postoperative IC angle (93°) (D). Anterior TVH: The distance between the most displaced point of the lamina terminalis and the most displaced point of the tuber cinereum. IC angle: The angle between the anterior wall of the infundibular recess and the inferior border of the optic chiasm.

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    Preoperative, postoperative, and subsequent follow-up sagittal CISS MR images of 3 successful cases. Each row exhibits one case that shows significant reduction of IC angle and anterior TVH after endoscopic third ventriculostomy. Note that the most significant changes are apparent on the 24-hour (h) postoperative images. Case 1 anterior IVH: preoperative 19.81 mm; postoperative 24 hours 14.47 mm, 1 month (m) 10.67 mm, 6 months 10.477 mm, 12 months 10.49 mm; Case 2 IC angle: preoperative 136°; postoperative 24 hours 118°, 1 month 112°, 6 months 112°, 12 months 112°.

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    Preoperative, postoperative, and subsequent follow-up sagittal CISS MR images of 3 failed cases. Each row exhibits one case that shows no significant change in IC angle or anterior IVH after the operation. Case 1 anterior IVH: preoperative 9.11 mm; postoperative 24 hours 9.09 mm, 1 month 8.98 mm, 6 months 8.95 mm, 12 months 8.95 mm; Case 2 IC angle: preoperative 98°; postoperative 24 hours 98°, 1 month 97°, 6 months 97°, 12 months 97°.

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    Preoperative, 24-hour postoperative, and 1-month postoperative sagittal CISS MR images of 2 cases revealing the situations in which measuring the IC angle becomes somewhat difficult. A: Highly rounded anterior third ventricle that makes it somewhat difficult to measure the IC angle. B: Optic chiasm and infundibulum are pushed anteriorly with a high degree of displacement toward the sella, creating an IC angle of > 180°.

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