Surgical Anatomy of the Labyrinthine and Subarcuate Arteries and Clinical Implications

Objective: To study the surgical anatomy of the labyrinthine artery (LA) and the subarcuate artery (SA), their anatomic relationships, and clinical implications, as injury of the LA can result in hearing loss.

Methods: Ten formalin-fixed, latex-colored specimens were studied (20 sides). After retrosigmoid craniotomy and neurovascular dissection under microscopic magnification, 4-mm 0° and 30° endoscopic lenses were used to improve visualization. Results were statistically analyzed.

Results: The LA was a constant artery that followed the vestibulocochlear nerve into the internal auditory canal. The SA was an inconstant artery that ended in the dura mater around the subarcuate fossa in 35% of cases. The LA originated from the anterior inferior cerebellar artery in 89.3% of specimens and from the basilar artery in 10.7% of specimens. The SA branched off from the anterior inferior cerebellar artery when present. The origin of the LA was inferomedial to the vestibulocochlear nerve in most cases (71.4%), whereas the SA was usually lateral (70%). The distal portion of the LA was inferomedial to the vestibulocochlear nerve in 71.4% of cases. The distal portion of the SA was superolateral to the nerve in all cases (P < 0.00001).

Conclusions: Knowledge of the different trajectory and anatomic relationship of the LA and the SA with the vestibulocochlear nerve is of paramount importance to differentiate them during surgery. The LA is usually inferomedial to the vestibulocochlear nerve at its distal and proximal aspects, whereas the SA usually originates lateral and ends superolateral to the nerve.