Ocular Neuromyotonia: an update

ABSTRACT

Introduction: Ocular neuromyotonia (ONM) is a rare condition characterized by episodic involuntary extraocular muscle (EOM) contraction and spasm. ONM has many presumed causes of which radiation therapy and thyroid dysfunction are the most common. ONM symptoms can be mild, moderate, or severe and can be debilitating. This monograph reviews the current literature describing the clinical features, evaluation, and management of ONM.

Areas covered: This pathogenesis, epidemiology, clinical presentation, diagnosis and differential diagnoses, workup, and treatment options of ocular neuromyotonia are discussed in detail.

Expert opinion: ONM is a rare but highly distinctive disturbance of EOM that is typically associated with parasellar radiation therapy but can occur in other conditions such as thyroid eye disease. Neuroimaging studies are generally recommended but most cases develop in the setting of stable treated disease. Medical and surgical management of ONM is difficult with variable treatment response.

KEYWORDS:

• Ocular neuromyotonia
• myokymia
• nerve hyperexcitability
• radiotherapy

Article highlights

• Ocular neuromyotonia (ONM) is a rare condition with a characteristic history of stereotyped episodes of transient diplopia and ophthalmoplegia typically lasting up to a few minutes.

• The interval examinations between episodes of ONM may be normal but typically shows a cranial neuropathy in the affected cranial nerve.

• ONM is most commonly secondary to radiotherapy for parasellar or sellar lesions but has been reported in association with other conditions (e.g. thyroid eye disease).

• Standard workup for ONM would typically involve magnetic resonance imaging of the brain, as well as other investigations depending on clinical suspicion for other diseases (e.g. thyroid eye disease or myasthenia gravis).

• Medical treatment is sometimes effective and typically involves membrane stabilizing medications (e.g. carbamazepine).

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose

Additional information

Funding

This manuscript was not funded.