Variant intraneural vein-trigeminal nerve relationships: an observation during microvascular decompression surgery...

Trigeminal neuralgia is often caused by compression, demyelination, and injury of the trigeminal nerve root entry zone by an adjacent artery and/or vein. Previously described variations of the nerve-vessel relationship note external nerve compression. We offer a detailed classification of intraneural vessels that travel through the trigeminal nerve and safe, effective surgical management.

We report 3 microvascular decompression operations for medically refractory trigeminal neuralgia during which the surgeon encountered a vein crossing through the trigeminal nerve. Two types of intraneural veins are described: type 1, in which the vein travels between the motor and sensory branches of the trigeminal nerve (1 patient), and type 2, in which the vein bisects the sensory branch (portio major) (2 patients).

We recommend sacrificing the intraneural vein between the motor and sensory branches if the vein is small (most likely type 1). If the intraneural vein is large and bisects the sensory branch (most likely type 2), vein mobilization can be achieved, but often requires extensive dissection through the nerve. Because this maneuver may lead to trigeminal nerve injury and result in uncomfortable neuropathy and numbness (including corneal hypoesthesia), we recommend against mobilization of the vein through the nerve, suggesting instead, consideration of a selective trigeminal nerve rhizotomy.

Because aggressive dissection of intraneural vessels can lead to higher than normal complication rates, preoperative knowledge of vein-trigeminal nerve variants is crucial for intraoperative success.