Ocular neuromyotonia: differential diagnosis and treatment

Abstract

Ocular neuromyotonia (ONM) is a rare but distinctive clinical entity characterized by involuntary episodic contraction of one or more muscles supplied by the ocular motor nerves. A retrospective review was conducted on all patients with ONM seen by the neuroophthalmology service in the past 20 years. Ten patients were identified with ONM; six affecting vertical muscles (superior oblique; inferior rectus; superior rectus) and four affecting lateral rectus muscles. Case 1 has been reported previously. Most episodes occurred every 10-40 min, lasted a few seconds to several minutes, and were repeated throughout the day. Only two patients had previously undergone cranial radiation. Two had thyroid eye disease. One patient presented with superior oblique myokymia and subsequently developed ONM. Membrane stabilizing medications were prescribed in 7 of the 10 patients with varied success. ONM episodes ceased after extraocular muscle surgery in one patient with thyroid eye disease.

Ocular Neuromyotonia Associated with Chronic Inflammatory Demyelinating Polyneuropathy

“…4,5 Because of our newly associated findings, both ocular neuromyotonia and CIDP should prompt a complete neurological history and examination of the patient, even in the presence of a normal brain MRI and MRA.…”

“…1 Most patients with ONM have a history of cranial irradiation or local intracranial pathology. [1][2][3][4][5] We report a patient whose ocular neuromyotonia arose in the setting of a subacute demyelinating polyneuropathy consistent with chronic inflammatory demyelinating polyneuropathy (CIDP) with cranial nerve involvement.…”

Ocular Neuromyotonia Noted after Recent Botulinum Toxin Injection for Sixth Nerve Palsy Following Resection of a Posterior Fossa Skull Base Meningioma

“…1 Hence, membrane-stabilising agents such as carbamazepine and gabapentin have been utilised for treatment. 4 Currently, sparse literature exists describing the relationship to prior cranial nerve palsies affecting ocular motility or the potential association with botulinum toxin. We present a patient with ONM that developed after botulinum toxin was utilised in the treatment of a sixth nerve palsy that occurred immediately after neurosurgery for resection of a recurrent meningioma with a history of prior radiation therapy.…”

Teaching Neuro Images : Ocular neuromyotonia

“…Axonal "cross-talk" causes irritability and abnormal firing independent of the synapse. 1 Without thin, heavily T2-weighted constructive interference in steady state or FIESTA (fast imaging employing steady-state acquisition) sequences, neurovascular contact can be missed. 2 ONM has also been associated with radiation therapy, thyroid eye disease, mass lesions, or superior oblique myokymia.…”

“…2 ONM has also been associated with radiation therapy, thyroid eye disease, mass lesions, or superior oblique myokymia. 1 If diplopia manifests or worsens after prolonged eccentric gaze, ONM should be considered.…”