Primary Aberrant Regeneration and Neuromyotonia of the Third Cranial Nerve

A Puzzling Ocular Motility Disorder: Apparent Up-Gaze Fatigability in a Patient With Oculomotor Nerve Compression

We report the case of a woman who developed right third nerve dysfunction with synkinesis and ocular neuromyotonia secondary to a compressive arterial aneurysm. Surprisingly, our examination showed a downward drift of the right eye in sustained up-gaze resulting in transient hypotropia, suggesting either fatigability of the superior rectus or contraction of the inferior rectus. We believe this ocular motility pattern is secondary to a co-contraction of the inferior rectus in up-gaze caused by synkinesis (explaining the downward drift), followed by failure of the inferior rectus to relax upon return to primary position caused by ocular neuromyotonia (explaining the hypotropia).

Strabismus Surgery in Patients With Ocular Neuromyotonia: Potential Unmasking of the Condition and Effective Management Tool

BACKGROUND

Ocular neuromyotonia (ONM) is a rare motility disorder in which paroxysms of tonic extraocular muscle contraction from abnormal ocular motor nerve firing result in episodic diplopia and strabismus. Medical therapy with membrane-stabilizing agents has varied success. A surgical approach to treatment has not yet been described. We report the outcomes of strabismus surgery in patients with ONM.

METHODS

We describe 3 patients with sixth nerve paresis and ONM of the affected lateral rectus muscle who underwent strabismus surgery. All patients had a history of radiation therapy for intracranial tumors. Ophthalmologic and orthoptic examinations were performed with appropriate medical and neuroradiologic evaluation. Preoperative and postoperative data are presented and analyzed.

RESULTS

Two patients were noted to have ONM after their first strabismus surgery for a sixth nerve palsy. Patients 1 and 2 had 3 surgeries, whereas Patient 3 had 1 operation. Extraocular muscles operated on included the medial rectus and lateral rectus. Preoperative primary gaze baseline esotropia ranged from 35 to 75 prism diopters (Δ). All patients achieved improvement in ocular alignment and motility. Postoperative primary gaze deviations ranged from orthotropia to 20Δ of esotropia. Abduction deficits were unchanged or improved. The follow-up period ranged from 15 months to 2 years.

CONCLUSIONS

Patients with ONM of a paretic rectus muscle can achieve binocular fusion with strabismus surgery. ONM may manifest postoperatively in patients with a sixth nerve palsy and a contractured medial rectus who, preoperatively, were not noted to have ONM.

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.

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.

[A case of Tolosa-Hunt syndrome presenting ocular neuromyotonia]

A 27-year-old woman noticed diplopia when gazing left and paresthesia of the left face and headache of the left side for 8 months. Abduction and supraduction of the left eye were moderately restricted. Hypoesthesia of the face innervated by the ophthalmic branch of the left trigeminal nerve was detected. Visual disturbance due to optic neuropathy developed 5 months later. MRI with gadolinium revealed a mass lesion extending from the left cavernous sinus to the orbital apex. Ocular neuromyotonia and corresponding diplopia were induced by sustained right gaze. Such episodes occurred almost every day on awaking in the morning. Prednisolone (60 mg/day) was given and the headache and visual disturbance ameliorated in two days. The diplopia disappeared in 4 days. The patient remains free from these symptoms after 6 months. This is the first report of ocular neuromyotonia associated with Tolosa-Hunt syndrome.

Ocular neuromyotonia treated by microvascular decompression: usefulness of preoperative 3D imaging

Ocular neuromyotonia is a rare ocular motility disorder characterized by involuntary contraction of extraocular muscles resulting in paroxysmal diplopia. Although ocular neuromyotonia is reported as a rare complication after radiation therapy, there are a few cases of ocular neuromyotonia in the absence of irradiation. In the reported cases the possibility of vascular compression has been suggested on radiological imaging. The authors report a case of ocular neuromyotonia treated by microvascular decompression of the third cranial nerve, supporting the hypothesis that neurovascular compression may play a role in its pathogenesis. The usefulness of preoperative 3D imaging for microvascular decompression is also discussed.

Novel case of ocular neuromyotonia associated with thyroid-related orbitopathy and literature review

PURPOSE

To present a novel case of pupillary involvement in ocular neuromyotonia (ONM), a rare ocular syndrome that causes intermittent diplopia because of an abnormal delay in extraocular muscle relaxation and to conduct a literature review.

METHODS

A case report is presented to demonstrate clinical characteristics and treatment of ONM. In addition, a literature review is conducted by searching Medline and Embase databases. Data are collected from all known published cases listed in these databases to collate patient demographic data, presumed etiology or associated pathologies, and treatment strategies.

RESULTS

The presented case demonstrates successful carbamazepine treatment of thyroid-related orbitopathy-associated ONM involving cranial nerve III. A review of the literature elicits 66 published cases of ONM, three of which were deemed to be associated with thyroid-related orbitopathy. The most common cause of reported ONM is suprasellar pathology, comprising approximately 60% of documented cases. Most published ONM cases (n = 41) were treated with carbamazepine, demonstrating a success rate of 87.8%. Of the published cases, cranial nerve III was involved 56% of the time, cranial nerve VI was affected in 39% of cases, and only 9% of ONM cases involved cranial nerve IV.

CONCLUSIONS

Ocular neuromyotonia is a rare cause of intermittent diplopia. Unlike most neurologic etiologies of diplopia, this syndrome can often be treated effectively with carbamazepine by stabilizing the neural cell membrane. To the authors' knowledge, this is the first presentation of ONM associated with thyroid-related orbitopathy, demonstrating bilateral but asymmetric miosis during episodes of muscle spasm.

Selected lid problems in neurologic practice

Ptosis is a common clinical finding. The many causes of ptosis include involutional (aging), myopathic, neuropathic, congenital, infectious, tumorous, traumatic, and inflammatory processes. This article reviews recent literature on some causes of ptosis and other lid conditions.

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.