Lack of functional patency of the lamina terminalis after fenestration following clipping of anterior circulation aneurysms.

OBJECT

Fenestration of the lamina terminalis (FLT) during aneurysm surgery for subarachnoid hemorrhage can, in theory, improve CSF circulation from the lateral and third ventricles to the cortical subarachnoid space, which may, in turn, decrease the incidence of hydrocephalus and vasospasm. However, the actual effects of FLT on CSF circulation have been difficult to determine, due to confounding factors. In addition, it is unclear whether the lamina terminalis remains functionally patent when the brain resumes its normal position. The goal of this study was to assess the functional patency of the fenestrated lamina terminalis in patients who underwent surgery for ruptured aneurysms.

METHODS

This prospective study included 15 patients who underwent surgical clipping of ruptured anterior circulation aneurysms, with FLT performed during surgery. On postoperative Day 1, the external ventricular drain of each patient was closed, and 1 ml of Omnipaque 300, an iodine based contrast agent, was injected intraventricularly, accompanied by cranial maneuvering designed to position the contrast agent adjacent to the lamina terminalis. Three to 5 minutes after cranial maneuvering, the flow of contrast agent into the basal cisterns was assessed with CT imaging. Flow was verified by an increase in Hounsfield units in a prespecified "region of interest" within the basal cisterns on the CT scan. This procedure was performed using a standardized protocol designed in consultation with the Department of Radiology and approved by the institutional review board. One patient who underwent endoscopic third ventriculostomy was recruited as a positive control to validate the technique, and 1 patient who underwent aneurysm clipping but not FLT was recruited as a negative control.

RESULTS

Seventeen patients consented to study participation. In the 15 patients who underwent aneurysm clipping and FLT, and the negative control patient who underwent aneurysm clipping but not FLT, the contrast agent followed the normal ventricular pathway from the lateral ventricles into the fourth ventricle, and did not appear in the basal cisterns. In the positive control patient, the contrast agent robustly and immediately filled the basal cisterns.

CONCLUSIONS

Fenestration of the lamina terminalis did not result in functional patency of the lamina terminalis when performed as part of surgical clipping for ruptured aneurysms.