Abstract

To the Editor: We read the article by Hopf et al. (5) and the letter by Buxton et al. (2), and we have reviewed the literature on the cerebrospinal fluid (CSF) pathway and the anatomy of the Liliequist membrane, to elucidate the possi- ble causes of failure of third ventriculostomy. It is important to understand the pathway of CSF circulation in the brain for validating the usefulness of Liliequist membranotomy in third ventriculostomy or aneurysm surgery. The cause of congenital or acquired hydrocephalus is multifactorial, i.e., there is a combination of pathogenetic factors, such as fourth ventricular outlet or aqueductal stenosis, in addition to defective CSF circulation in the subarachnoid spaces. Hence, in CSF diversion procedures from the ventricles to the subarachnoid space, it is essential to establish the free flow of CSF to the cerebral convexity. The usual pathway of CSF from the fourth ventricle is to the cisterna magna through the foramen of Magendie and to the cerebellopontine angle cistern through the foramen of Luschka. CSF from the cisterna magna flows either cranially or caudally to the spinal subarachnoid space. The caudally directed CSF usually follows the posterior spinal subarachnoid space and flows through the anterior spinal subarachnoid space to the premedullary cistern. The cranially directed CSF follows the subarachnoid space of the cerebellar hemisphere to the basal cisterns. CSF arriving in the basal cisterns (premedullary, prepontine, and cerebellopontine) follows a course through the interpeduncular and prechiasmatic cisterns, the sylvian fissures, and the callosal cisterns, to the lateral and frontal cerebral hemisphere subarachnoid space. A dorsomedial flow from the basal cisterns directs the fluid through the ambient cisterns and the cisterna venae magna cerebri to the medial and posterior cerebral hemisphere subarachnoid space. The CSF is absorbed through the arachnoid villi associated with the superior longitudinal sinus and other dural sinuses (8). In summary, the predominant component of CSF flow is through the ventral surface of the brain (4). The nonfenestrated Liliequist membrane acts as a barrier between the CSF flow from the infratentorial cisterns to the supratentorial cisterns. The fenestrated arachnoidal membranes spreading out from the Liliequist membrane permit CSF flow through them. These fenestrated membranes are blocked in infective processes and subarachnoid hemorrhage. Understanding this concept of CSF flow is the basis of all CSF diversion procedures from the ventricles to the subarachnoid space (e.g., third ventriculostomy, Torkildsen procedure, opening of the lamina terminalis in aneurysm surgery). It is not only important to establish a pathway from the ventricle to the subarachnoid space, but it is also essential to ease CSF flow from the infratentorial cisterns to the supratentorial cisterns. As the Liliequist membrane acts as a barrier between them, it is essential to combine Liliequist membranotomy with all of the aforementioned procedures, to reduce the incidence of failures (2, 3). The Liliequist membrane may be opened accidentally or may require a deliberate attempt to open it, depending on the anatomic attachment of the membrane. All authors agree that the site of the lower attachment of the Liliequist membrane is the dorsum sellae; however, they differ on the site of attachment of the superior attachment (Table 1). Liliequist (6), Yaşargil (9), and Brasil and Schneider (1) have reported attachment to the premammillary area, in contrast to the studies of Hopf et al. (5) and Matsuno et al. (7), which reported retromammillary attachment. In patients with premammillary attachment of the Liliequist membrane, third ventriculostomy leads to communication with the prepontine cistern; thus, it is essential to attempt to open the Liliequist membrane. In patients with retromammillary attachment, it is not necessary to open the Liliequist membrane, as the third ventricle has been opened to the interpeduncular cistern. Table 1: Literature Review of Descriptions of the Liliequist MembraneManas Panigrahi Federico C. Vinas Murali Guthikonda

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call