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

Ocular Neuromyotonia: Clinical Features, Diagnosis, and Outcomes

PURPOSE

The purpose of this study was to describe the clinical features, management, outcomes, and diagnostic pitfalls in a large series of patients with ocular neuromyotonia.

DESIGN

Retrospective cohort.

METHODS

Patients diagnosed with ocular neuromyotonia from January 1, 2004, through January 1, 2023, seen at one of the 3 Mayo Clinic sites in Rochester, MN, Scottsdale, AZ, and Jacksonville, FL, comprised the study population. We ascertained patients with ocular neuromyotonia through a search using the medical records database. Only patients with an observed episode of ocular neuromyotonia were included and the medical records were reviewed. The main outcome measures were clinical features and outcomes of patients with ocular neuromyotonia.

RESULTS

Forty-two patients who were diagnosed with ocular neuromyotonia were included. The median age was 58 years (range, 16-80 years). A history of cranial radiation therapy was present in 39 patients (93%). The sixth cranial nerve was involved in 31 patients (74%). Bilateral disease was found in 2 patients (5%). The median time from onset of diplopia to diagnosis was 8 months (range, 1 month-25 years), with a high rate of initial misdiagnosis in 52%. Twenty of 42 patients (48%) were treated with oral medication, of whom 95% had significant improvement or resolution of symptoms.

CONCLUSION

Prior cranial irradiation is the most common cause for ocular neuromyotonia, affecting the sixth cranial nerve most often. Although delayed and initial misdiagnosis is common, most patients show improved symptoms on medical treatment.

Ocular neuromyotonia: a review of diagnosis and treatment

PURPOSE OF REVIEW

The current review will cover the clinical presentation, causes, epidemiology, differential diagnoses, workup, and treatment of ocular neuromyotonia (ONM) in detail.

RECENT FINDINGS

While ONM largely remains a unilateral eye movement disease affecting adults with a history of sellar radiation, recent case reports highlight an expansion of this presentation to include bilateral, pediatric, and congenital cases.

SUMMARY

ONM is a rare but recognizable ocular motility disorder involving sustained contraction of the extraocular muscle, commonly resulting in intermittent diplopia. Diagnosis of ONM relies upon a thorough history and clinical exam, with particular attention to history of radiotherapy and eccentric gaze testing. Treatment with carbamazepine remains first-line therapy, although other membrane stabilizing agents and surgical interventions can be effective.

Congenital Ocular Neuromyotonia with Partial Third Nerve Palsy

PURPOSE

We report the first case of congenital ocular neuromyotonia (ONM) and the results of strabismus surgery for this patient's co-existing cranial nerve (CN) III palsy.

PATIENTS AND METHOD

The patient presented at 18 months with strabismus that had reportedly been present since the time of birth. On exam, she had persistent exotropia (RXT) and hypertropia (RHT) with episodes of esotropia in the right eye that could be evoked by sustained left gaze. A diagnosis of ONM with partial CN III palsy was made. T1-weighted, T2-weighted, and fluid-attenuated inversion recovery magnetic resonance imaging failed to reveal intracranial pathology.

RESULTS

Gaze induced intermittent esotropia resolved with carbamazepine. Surgery was performed to improve the patient's RXT and RHT. Post-operatively, the patient's RXT had improved from 12 to 15 prism diopters (∆) at near and 20∆ at a distance to 10∆ RXT at near with no horizontal deviation at distance. Her deviation has remained stable for 13 years, as has her neurological exam and good state of health.

CONCLUSION

This case demonstrates that ONM may present congenitally and adds to the body of knowledge regarding surgical outcomes on concurrent CN palsies in these patients.

Metastatic Papillary Thyroid Carcinoma Presenting as Abducens Palsy Complicated by Ocular Neuromyotonia

Papillary thyroid carcinoma (PTC) is a type of well-differentiated thyroid cancer that accounts for the majority of thyroid malignancies. The prognosis of PTC is very good and distant metastases are rare, especially to the skull base. The authors report the case of a 47-year-old woman with biopsy-proven PTC treated with surgery and radiation therapy who presented with headache and diplopia after 5 years and was found to have clivus and cavernous sinus metastasis. Following radiation therapy for her skull base and cavernous sinus lesion, she subsequently developed sixth nerve ocular neuromyotonia. Possible causes and treatments are reviewed.

Extensive Postradiation Ocular and Diffuse Cranial Neuromyotonia Mimicking Myasthenia Gravis

BACKGROUND

Ocular neuromyotonia is a rare, but well-recognized, complication of cranial irradiation.

CASE REPORT

Using figures and videos, we report a 52-year-old man with extensive ocular, brainstem, and lower cranial nerve neuromyotonia postradiation therapy for a fourth ventricle glioma who, in the context of an apparently positive edrophonium test, was initially misdiagnosed with myasthenia gravis.

CONCLUSIONS

This is the first case of postirradiation neuromyotonia to be reported with such extensive cranial nerve and brainstem involvement.

Therapy of Vestibular Paroxysmia, Superior Oblique Myokymia, and Ocular Neuromyotonia

OPINION STATEMENT

Neurovascular compression syndromes are characterized by recurrent attacks of neurological symptoms and clinical signs depending on the cranial nerve affected. It is assumed that pulsatile compression of the nerve is caused mainly by an artery. The result is segmental demyelination of the transition zone or the central part of the cranial nerve, which is covered by oligodendrocytes, and subsequent ephaptic axonal transmission. Compression of the vestibular nerve can cause attacks of spinning or non-spinning vertigo: vestibular paroxysmia. Compression of the trochlear nerve is characterized by attacks of monocular oscillopsia: superior oblique myokymia. Damage to ocular motor nerves due to local radiation or rarely neurovascular compression can also lead to oscillopsia and double vision precipitated by sustained excentric gaze: ocular neuromyotonia. It is important to note that controlled trials have so far not been performed for any of these three syndromes, mainly because of their low prevalence. Therefore, treatment recommendations are based on single cases or small case series and thus have the lowest level of evidence. The sodium channel blockers carbamazepine (50 to 200 mg tid) or oxcarbazepine (100 to 300 mg tid) are evidently effective in most of the patients who have these three syndromes. However, one should always keep in mind the contraindications, side effects, and interactions with other drugs of carbamazepine ( http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682237.html ) All patients require regular laboratory examinations. Alternatives are other sodium channel blockers such as phenytoin (100 to 300 mg tid), gabapentin (100 to 600 mg tid), or valproic acid (100 to 300 mg tid). Furthermore, there are also few reports on the effects of beta blockers, which may be explained by their reduction of the amplitude of blood pressure. Patients who do not respond to pharmacotherapy require further diagnostics to determine the possibility of other etiologies. Some of these patients benefit from surgical decompression of the affected nerve.

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.

Ocular Neuromyotonia Associated with Chronic Inflammatory Demyelinating Polyneuropathy

Ocular neuromyotonia (ONM) is a neuro-ophthalmic disorder characterized by episodic diplopia caused by contraction of one or more ocular muscles due to spontaneous excitation of the respective ocular motor nerve. We report a patient whose ocular neuromyotonia arose in the setting of a subacute demyelinating polyneuropathy consistent with chronic inflammatory demyelinating polyneuropathy (CIDP) and subsequently resolved following the initiation of intravenous immunoglobulin (IVIg) for her neuropathy. Our patient provides additional evidence towards the role of demyelination and ephaptic neurotransmission in ocular neuromyotonia and also represents the first reported case of ocular neuromyotonia associated with a systemic neurological condition.

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

A 56-year-old female complained of diplopia immediately after surgical excision of a recurrent left skull base tuberculum meningioma. She was found to have a left sixth nerve palsy, which was subsequently treated with botulinum toxin injection to the medial rectus muscle. Three months post injection, the patient had partial recovery of the sixth nerve palsy and new-onset ocular neuromyotonia.

A novel association of ocular neuromyotonia with brainstem demyelination: two case reports

Ocular neuromyotonia (ONM) is a rare disorder of ocular mal-alignment in which painless, transient spontaneous or gaze-induced abnormal deviation of the eye manifests as episodic diplopia. With only a few cases reported in the literature, ONM mostly follows months to years after cranial irradiation for sellar or suprasellar lesions. Here we present two patients with this rare ocular condition, secondary to brainstem demyelination, the association of which is hitherto unreported in the literature. Both patients were 15-year-old girls who presented to us with episodic forced-eye deviation with diplopia. Examination during these attacks revealed ONM involving the superior rectus and medial rectus in the first and second patient, respectively. There was clinical evidence of intrinsic brainstem involvement with downbeat nystagmus and skew deviation in one patient without any other cerebellar or long tract signs. MRI showed evidence of demyelination involving the brainstem in both, with CSF showing positive immunological markers and with positive aquaporin-4 antibody in one patient. Both patients responded remarkably to immunomodulatory therapy and are asymptomatic at follow-up. That ONM can occur with brainstem demyelination has not been reported in the literature. This association may help in explaining the pathophysiology of ONM as secondary to segmental demyelination.