Paresis of the Oculomotor Nerve due to Neurovascular Conflict with Superior Cerebellar Artery.

Background:  Neurovascular conflict between the oculomotor nerve and a posterior circulation cerebral artery is a relatively frequent radiologic finding; however, it manifests minimally clinically (by slower photoreaction on the ipsilateral side). Sustained paresis of the oculomotor nerve that arose directly due to neurovascular conflict between the superior cerebral artery (SCA) and the oculomotor nerve, and resolved after microvascular decompression, is extremely rare and has not yet been published.

Methods:  A 34-year-old female patient presented with an advancing ptosis and downward gaze on one side. Differential diagnostics ruled out all other causes of the oculomotor paresis. Magnetic resonance imaging showed significant compression of the oculomotor nerve by an aberrant SCA on the ipsilateral side. Neurovascular decompression performed microsurgically resulted in near complete resolution of the symptoms.

Results:  This case report aims to present a case of a rare clinical condition caused by a generally common anatomical variation. This variation proved to be the only cause of the patient's symptoms, which resolved after microsurgical restoration of the neuroanatomy.

Conclusions:  Oculomotor nerve paresis caused directly by neurovascular conflict is an extremely rare diagnosis. Microvascular decompression should be considered in these cases, if other causes have been excluded.