Vasculature and neurovascular relationships of the trigeminal nerve root.

Background: Specific microanatomical characteristics of the trigeminal nerve root (TNR) blood supply and close neurovascular relationships with surrounding vessels as well as their possible clinical significance were the main reasons for this study.

Method: The vasculature of 25 adult and four fetal TNRs were microdissected and examined under the stereoscopic microscope, after injecting their arteries with India ink.

Results: The trigeminal vessels, which varied between two and five in number, arose from two or three of the following arteries: the superolateral pontine (92%), anterior inferior cerebellar (AICA) (88%), inferolateral pontine (72%), and superior cerebellar (SCA) (12%). The trigeminal vascular twigs had a mean diameter of 0.215 mm. A single vessel may supply either the motor portion of the nerve root or the sensory portion or both. The trigeminal vasculature formed the proximal and distal rings. The proximal ring was located at the trigeminal root entry zone. Its central branches extended along the TNR to the principal sensory and motor trigeminal nuclei while its peripheral longitudinal twigs followed the TNR fascicles. The incomplete distal arterial ring embraced the middle portion of the TNR before the level of its entrance into the arachnoid sleeve. The most frequent contact of the TNR was noticed with the SCA (20%), the petrosal or Dandy's vein (24%), and the AICA (12%).

Conclusions: The observed characteristics of the TNR vasculature could be the anatomical basis for decompressive neurovascular surgery.