The criteria for identifying patients in whom endoscopic third ventriculostomy (ETV) provides control of hydrocephalus remain in evolution. In particular, it is not clear when ETV would be effective if intraventricular obstruction is not found preoperatively. The authors postulated that 1) displacement of the third ventricle floor inferiorly into the interpeduncular cistern and displacement of the lamina terminalis anteriorly into the lamina terminalis cistern could predict clinical success of ETV, and 2) improvement in these displacements would correlate with the success of ETV.
Magnetic resonance imaging in 38 consecutive patients treated between 2004 and 2010 was reviewed to assess displacement of the lamina terminalis and third ventricular floor prior to and following ETV. Displacements of the floor and lamina terminalis were judged qualitatively and quantitatively, using a newly created index, the Third Ventricular Morphology Index (TVMI). The association between the aforementioned morphological features and clinical success of ETV was analyzed.
Ninety-six percent of patients in whom the authors preoperatively observed displacement of the lamina terminalis and the third ventricular floor were successfully treated with ETV. Displacements of the third ventricular floor and lamina terminalis, as judged qualitatively, correlated with the clinical success of ETV. The TVMI correlated with the qualitative assessments of displacement. Postoperative decrease in the TVMI occurred in the majority of successfully treated patients. Changes in third ventricular morphology preceded changes in other measures of third and lateral ventricular volume following ETV.
Assessment of third ventricular floor and lamina terminalis morphology is useful in predicting clinical success of ETV and in the follow-up in treated patients. The TVMI provided a quantitative assessment of the third ventricular morphology, which may be useful in equivocal cases and in research studies.
Abbreviations used in this paper: ETV = endoscopic third ventriculostomy; FOHR; frontal and occipital horn ratio; TVI = Third Ventricle Index; TVMI = Third Ventricular Morphology Index; VP = ventriculoperitoneal.
Address correspondence to: D. Douglas Cochrane, M.D., F.R.C.S.C., Division of Neurosurgery, Department of Surgery, University of British Columbia, Division of Neurosurgery, Department of Pediatric Surgery, British Columbia Children's Hospital, 4480 Oak Street, Vancouver, British Columbia, Canada V6H 3V4. email: firstname.lastname@example.org.
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