Putting Ocular Neuromyotonia in Context

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

BACKGROUND

Ocular neuromyotonia (ONM) is a disorder characterized by periodic involuntary extraocular muscle contraction that occurs almost exclusively in the setting of prior radiation to the sella or skull base. We present the first case of abducens neuromyotonia associated with oropharyngeal carcinoma.

METHODS AND RESULTS

We report a case of a 63-year-old patient with abducens ONM occurring 16 years after radiation treatment for oropharyngeal squamous cell carcinoma. A literature review was performed using Medline and PubMed databases to search for all documented cases of abducens neuromyotonia. Our review found 20 cases of abducens neuromyotonia but none after radiotherapy (RT) to the oropharynx.

CONCLUSION

Abducens ONM can occur because of disease at anatomic locations remote from the course of the sixth cranial nerve, most likely because of the irradiated area exceeding the intended field. Our case also supports the fact that RT can significantly precede symptom onset. © 2016 Wiley Periodicals, Inc. Head Neck 38: E2428-E2431, 2016.

Stereotactic radiosurgery XX: ocular neuromyotonia in association with gamma knife radiosurgery

We report three patients who developed symptoms and signs of ocular neuromyotonia (ONM) 3–6 months after receiving gamma knife radiosurgery (GKS) for functioning pituitary tumours. All three patients were complex, requiring multi-modality therapy and all had received prior external irradiation to the sellar region. Although direct causality cannot be attributed, the timing of the development of the symptoms would suggest that the GKS played a contributory role in the development of this rare problem, which we suggest clinicians should be aware of as a potential complication.

Acquired oculomotor nerve paresis with cyclic spasms in a young woman, a rare subtype of neuromyotonia

BACKGROUND

To report an unusual case of cyclic oculomotor nerve paresis and spasms, which developed 5 years following brain radiotherapy for cerebellar medulloblastoma.

METHODS

Observational case report.

RESULTS

The cyclic oculomotor nerve paresis and spasms resolved in our patient when treated with carbamazepine. However, because of severe photophobia and tearing, carbamazepine had to be discontinued leading to reappearance of the eye movement disorder.

CONCLUSION

Cyclic oculomotor nerve paresis and spasms appear to be a delayed effect of radiotherapy and respond to carbamazepine therapy. It may be a rare form of ocular neuromyotonia.

Oculomotor neuromyotonia with lid ptosis on abduction

Ocular neuromyotonia is an episodic involuntary contraction of one or more of the extraocular muscles resulting from spontaneous neural discharges of the oculomotor nerve. It is characterized by symptomatic diplopia for the duration of the contraction and occurs either spontaneously or after a sustained eccentric gaze. Although the mechanism of ocular neuromyotonia is not fully understood, primary or secondary aberrant regeneration and consequent ephaptic transmission generally are held to be involved. We report the case of a patient with right oculomotor neuromyotonia accompanied by lid ptosis on abduction of the left eye who was successfully treated with oral carbamazepine.

Ocular neuromyotonia in a 15-year-old girl after radiation therapy

A 15-year-old girl, previously treated with radiation, chemotherapy, and surgery for a posterior fossa medulloblastoma and parasellar metastasis at age 8, presented with a 10-month history of episodic horizontal diplopia. She was diagnosed with ocular neuromyotonia and successfully treated with oral carbamazepine. Given the strong association between peripheral neuromyotonia and the presence of autoimmune antivoltage-gated potassium channels, the patient's blood was tested and found negative for these autoantibodies. This is the first time this has been verified in a person with ocular neuromyotonia.

Abducens neuromyotonia due to internal carotid artery aneurysm

Ocular neuromyotonia refers to paroxysmal involuntary contraction of one or more ocular muscles resulting in paroxysmal diplopia and strabismus. A 73-year-old woman reported spells of horizontal diplopia that usually developed after leftward gaze and mostly lasted less than one minute. Between the episodes, the extraocular movements were normal without aberrant regeneration. The diplopic paroxysms could be triggered by leftward gaze for several seconds. During the episode, the left eye was exotropic with mild adduction limitation. Brain imaging revealed an aneurysm in the left internal carotid artery. The episodes resolved with carbamazepine. Aneurysm of the internal carotid artery is a rare cause of abducens neuromyotonia. A compressive lesion may give rise to ocular neuromyotonia even in the absence of prior irradiation.