The Lateral Mesencephalic Vein: Surgical Anatomy and Its Role in the Drainage of Tentorial Dural Arteriovenous Fistulae

Background: The lateral mesencephalic vein (LMV) represents an important connection between the infratentorial and supratentorial compartments. It joins the basal vein of Rosenthal and the petrosal system. In our experience with management of tentorial dural arteriovenous fistulas (DAVFs) we have often noted involvement of the lateral mesencephalic vein (LMV) in the venous drainage of these fistulas. Methods: We reviewed the clinical and angiographic findings of 26 patients with tentorial DAVFs to study the incidence and pattern of drainage through the LMV. In addition, we reviewed the pertinent literature on the anatomy of the LMV. Results: The LMV was involved in the venous drainage of 31% (8/26) of patients with tentorial DAVFs. The direction of venous drainage through the LMV is more commonly from the infratentorial to the supratentorial compartment. There were no specific clinical symptoms/signs associated with tentorial DAVFs involving the LMV compared with those without LMV involvement. When involved in DAVF drainage, the LMV could be invariably identified on noninvasive imaging studies. We present illustrative clinical/angiographic cases and provide a detailed review of the pertinent clinical anatomy of this important but often neglected intracranial vein. Conclusions: The LMV is a constant venous anastomosis between the supratentorial and infratentorial compartments. Detailed knowledge of the most common variations of the LMV surgical and radiological anatomy has important clinical implications. The vein is an important anatomic landmark during surgery of midbrain lesions. It is often involved in the tentorial DAVF drainage, and it is critical in understanding some "unexpected" venous complications during surgery for posterior fossa lesions.