Ocular neuromyotonia, a rare but important cause of episodic diplopia, is thought to be neurogenic in origin. Prior skull-based radiation therapy, typically for neoplasm (eg, meningioma), is the most common historical feature. Months to years postradiation, patients experience episodic diplopia lasting typically 30–60 seconds. Ocular neuromyotonia may affect any of the ocular motor nerves or their divisions. Diplopia is often triggered by activation of the affected nerve in eccentric gaze with resultant sustained muscle contraction producing ocular misalignment (eg, CN VI neuromyotonia produces sustained lateral rectus muscle spasm of the involved eye and attendant exotropia). If unrecognized, such patients often undergo extensive and largely unnecessary workup in the search for a recurrent neoplasm. The disorder generally responds well to medical therapy. Carbamazepine and its derivatives constitute first-line treatment.
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Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.