Trochlear Nerve Decompression by Endoscopic Suboccipital Supracerebellar Infratentorial Approach: A Technical Note: 2-Dimensional Operative Video.

Background And Importance: Superior oblique myokymia (SOM) is a rare, acquired aberration of the innervation of the superior oblique, resulting in episodic monocular contraction of the superior oblique muscle characterized by intermittent rotatory eye movement causing diplopia and oscillopsia. Several treatment modalities have been described to treat SOM, including medication and surgical interventions. There is a paucity of reports describing microvascular decompression (MVD) of the trochlear nerve near the root entry zone for the treatment of a neurovascular conflict. The authors describe a case report of a patient who presented with SOM by a supracerebellar infratentorial approach using microscopic and endoscopic visualization.

Clinical Presentation: A 40-year-old woman presented with an 8-month history of rhythmic contractions of her right orbit with worsening double vision and occasional balance issues. Neuro-ophthalmological evaluation which revealed a right-sided SOM. MRI evaluation demonstrated a potential vascular compression by the superior cerebellar artery near the origin of the trochlear nerve. She underwent MVD by a supracerebellar infratentorial approach using microscopic and endoscopic visualization. The patient experienced resolution of her SOM in the immediate postoperative period and a Trochlear nerve palsy that resolved within 6 months.

Conclusion: The endoscopic supracerebellar infratentorial approach for MVD of the trochlear nerve is a safe and efficacious approach that provides superior visualization of the trochlear nerve at its origin and in the setting of SOM. This approach shows outcomes comparable with those used in previously described cases.