Extra-axial endoscopic third ventriculostomy: preliminary experience with a technique to circumvent conventional endoscopic third ventriculostomy complications.

OBJECTIVE:Endoscopic third ventriculostomy (ETV) is mostly safe but may have serious complications. Most of the complications are inherent to the procedure's intra-axial nature. This study aimed to explore an alternative route to overcome inherent issues with conventional ETV. The authors performed supraorbital, subfrontal extra-axial ETV (EAETV) via the lamina terminalis. METHODS:This prospective study began in October 2021 and included patients with obstructive triventricular hydrocephalus with a Glasgow Coma Scale score of 8 or more and a minimum follow-up of 3 months. Patients with multiloculated hydrocephalus and those younger than 1 year of age were excluded. The preoperative parameters etiology, symptoms, Evans' Index, frontal occipital horn ratio (FOHR), and third ventricle index were recorded. The surgical procedure is described. Postoperative evaluation included clinical (modified Rankin Scale [mRS]) and radiological assessment with CT and cine phase-contrast MRI. Preoperative and postoperative parameters were compared statistically. RESULTS:Ten patients were included in this study. Six patients had acute hydrocephalus, and 4 had chronic hydrocephalus. After EAETV, all patients showed clinical improvement. An mRS score of 0 or 1 was achieved in 9 patients, but the mRS score remained at 4 in a patient with tectal tuberculoma. There was a significant reduction in Evans' Index, FOHR, and third ventricle index after EAETV (p < 0.05). The mean percent reduction in Evans' Index was 20.80% ± 13.89%, the mean percent reduction in FOHR was 20.79% ± 12.98%, and the mean percent reduction in the third ventricle index was 37.45% ± 14.74%. CSF flow voids were seen in all cases. The results of CSF flow quantification parameters were as follows: mean peak velocity 3.82 ± 0.93 cm/sec, mean average velocity 0.10 ± 0.05 cm/sec, mean average flow rate 46.60 ± 28.58 μL/sec, mean forward volume 39.90 ± 23.29 μL, mean reverse volume 34.10 ± 15.98 μL, mean overall flow amplitude 74.00 ± 27.61 μL, and mean stroke volume 37.00 ± 13.80 μL. One patient developed a minor frontal lobe contusion. The frontal air sinus was breached in 5 patients, but none had CSF rhinorrhea. Transient supraorbital hypesthesia was seen in 3 patients. No patient had electrolyte disturbance or change in thirst or fluid intake habits. CONCLUSIONS:EAETV is a feasible, safe, and effective surgical alternative to conventional ETV.