Reduction of shunt dependency rates following aneurysmal subarachnoid hemorrhage by tandem fenestration of the lamina terminalis and membrane of Liliequist during microsurgical aneurysm repair

Restricted access


Shunt-dependent hydrocephalus is an important cause of morbidity following aneurysmal subarachnoid hemorrhage (aSAH) in excess of 20% of cases. Hydrocephalus leads to prolonged hospital and ICU stays, well as to repeated surgical interventions, readmissions, and complications associated with ventriculoperitoneal (VP) shunts, including shunt failure and infection. Whether variations in surgical technique at the time of aneurysm treatment may modify rates of shunt dependency remains a matter of debate. Here, the authors report on their experience with tandem fenestration of the lamina terminalis (LT) and membrane of Liliequist (MoL) at the time of open microsurgical repair of the ruptured aneurysm.


The authors conducted a retrospective review of 663 consecutive patients with aSAH treated from 2005 to 2015 by open microsurgery via a pterional or orbitozygomatic craniotomy by the senior author (M.T.L.). Data collected from review of the electronic medical record included age, Hunt and Hess grade, Fisher grade, need for an external ventricular drain, and opening pressure. Patients were stratified into those undergoing no fenestration and those undergoing tandem fenestration of the LT and MoL at the time of surgical repair. Outcome variables, including VP shunt placement and timing of shunt placement, were recorded and statistically analyzed.


In total, shunt-dependent hydrocephalus was observed in 15.8% of patients undergoing open surgical repair following aSAH. Tandem microsurgical fenestration of the LT and MoL was associated with a statistically significant reduction in shunt dependency (17.9% vs 3.2%, p < 0.01). This effect was confirmed with multivariate analysis of collected variables (multivariate OR 0.09, 95% CI 0.03–0.30). Number-needed-to-treat analysis demonstrated that tandem fenestration was required in approximately 6.8 patients to prevent a single VP shunt placement. A statistically significant prolongation in days to VP shunt surgery was also observed in patients treated with tandem fenestration (26.6 ± 19.4 days vs 54.0 ± 36.5 days, p < 0.05).


Tandem fenestration of the LT and MoL at the time of open microsurgical clipping and/or bypass to secure ruptured anterior and posterior circulation aneurysms is associated with reductions in shunt-dependent hydrocephalus following aSAH. Future prospective randomized multicenter studies are needed to confirm this result.

ABBREVIATIONS aSAH = aneurysmal subarachnoid hemorrhage; EVD = external ventricular drain; LT = lamina terminalis; MoL = membrane of Liliequist; VP = ventriculoperitoneal.

Article Information

Correspondence Michael T. Lawton, Department of Neurological Surgery, Barrow Neurological Institute, 2901 N 3rd Ave., Phoenix, AZ 85013. email:

INCLUDE WHEN CITING Published online December 15, 2017; DOI: 10.3171/2017.5.JNS163271.

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.



  • View in gallery

    Illustration depicting microsurgical technique for tandem fenestration of the LT and MoL to promote circulation of CSF following aSAH. A and B: The patient is positioned supine with head rotated to the contralateral side and extended to bring the malar prominence to the highest point of the operative field. A pterional or orbitozygomatic craniotomy is performed in standard fashion, and subarachnoid dissection is begun. C: After the sylvian fissure is split, the carotid and LT cisterns are widely opened, and the LT is widely fenestrated to release CSF and relax the brain. Subarachnoid dissection is then continued along the posterior communicating artery (PCoA) and anterior choroidal artery in the carotid-oculomotor triangle. The MoL is then widely fenestrated medial to the oculomotor (III) nerve, and CSF is released from the interpeduncular cistern. D: Tandem fenestration of the LT and MoL allows communication between the infratentorial (green) and supratentorial (blue) compartments and unobstructed circulation of CSF to the absorptive arachnoid granulations over the convexity. Tandem fenestration promotes the clearance of subarachnoid blood products and prevents the development of hydrocephalus. A1 = first segment of anterior cerebral artery; ICA = internal carotid artery; II = optic nerve; M1 = first segment of middle cerebral artery; STA = superficial temporal artery. Copyright University of California, San Francisco. Published with permission.



Cited By



All Time Past Year Past 30 Days
Abstract Views 280 280 22
Full Text Views 532 532 19
PDF Downloads 462 462 9
EPUB Downloads 0 0 0


Google Scholar