Septal vein symmetry: implications for endoscopic septum pellucidotomy.

BACKGROUND

Endosopic septum pellucidotomy is used for treating patients with unilateral and specific types of bilateral hydrocephalus. The ideal location for septostomy is controversial; however, an avascular region is preferred.

OBJECTIVE

As the septal veins (SVs) are viewed only from one side, we studied the symmetry of the SVs in an attempt to define a safe area for septostomy.

METHODS

Sixteen cadaver brains were dissected. The septum pellucidum was exposed bilaterally and divided into 3 regions. SVs of both sides were evaluated according to number, size, distribution, and location relative to common markers on both sides.

RESULTS

Each side included 1 to 7 large veins (mean ± standard deviation, 2.3 ± 1.4), 0 to 3 small veins (2.05 ± 1.73), and a total of 2 to 7 veins (4.35 ± 1.53). Of the large veins, 88% were located in the anterior septal region (anterior to the foramen of Monro). Among the 10 brains that were extensively dissected, 90% had asymmetric SVs (either in the number of large veins or in the existence of any veins) in at least 1 of the septal regions, and 50% of brains had asymmetric SVs in the anterior region.

CONCLUSION

Distribution of the SVs is asymmetric in most cases. We recommend septostomy be performed at the anterior area of the middle septal region, at the level of the foramen of Monro, mid-height between the corpus callosum and fornix. Careful evaluation of preoperative images and thorough coagulation at the septostomy site are essential to avoid injury to a contralateral large SV.