Abducens Neuromyotonia as the Presenting Sign of an Intracranial Tumor

Abstract

In this case series and review of the literature, we describe 2 cases of abducens neuromyotonia (ANM) as the presenting sign of an intracranial tumor (meningioma). Review of the literature suggests that the pathophysiology of ocular neuromyotonia is incompletely understood. Most patients with ANM have a history of radiation therapy. The diagnosis of ANM is made on the basis of clinical findings and can be supported by electrophysiological studies. A complete neurologic examination is mandatory for patients with ANM. Treatment consists of eliminating the underlying cause; carbamazepine is effective in alleviating the symptoms of ANM. Neuroimaging should be performed if patients with ANM lack the typical history of radiation therapy, as ANM may be the presenting sign of an intracranial mass.

Abducens ocular neuromyotonia as a delayed complication of oropharyngeal carcinoma treated with radiation

“…There are 20 reported cases of abducens neuromyotonia in the English language literature (Table ). The vast majority of these patients received RT for tumors located in the sella, nasopharynx, or posterior fossa (most frequently the cerebellum) . Our case is unusual in that ONM followed RT of the oropharynx, an association not previously reported likely because of the more remote anatomic location of the cancer relative to the course of the sixth nerve.…”

Novel Case of Ocular Neuromyotonia Associated with Thyroid-Related Orbitopathy and Literature Review

“…Interestingly, the cranial nerve involved in ONM was not always the same nerve affected by the concurrent palsy or paresis. 22 Multiple cases have also documented oculomotor nerve aberrant regeneration in the presence of oculomotor nerve paresis and oculomotor nerve neuromyotonia. 1,4,8,14,23 Electronic eye movement recordings, electromyography, videotaping, cover testing, biopsy, and clinical observation have been used to analyze ocular motor spasms in ONM.…”

Ocular neuromyotonia: differential diagnosis and treatment

“…9 Sporadic case reports followed, including a series of 6 cases by Shults et al in 1986. 4,5,8,12 ONM has been reported following radiation to the skull base, 6,7,13,14 in thyroid eye disease, 8,9 as the presenting sign in intracranial tumor, 15 and after alcohol ingestion, 4 but many are idiopathic. 16 It is thought to be caused by ephaptic neural transmission.…”

“…4,17 In ONM there is a sustained tonic contraction lasting the duration of the episode lasting from seconds to 3-4 min. 15 In SOM, multiple contractions are brief and phasic, each lasting less than a second. 21 In both conditions, the episodes are repeated at intervals during the day.…”