Case Report: Ocular Neuromyotonia

Abstract

Orthoptists and Ophthalmologists are keenly aware of the importance of stable strabismus measurements prior to extraocular muscle surgery. Disease entities such as myasthenia gravis are frequently debated in case of unstable measurements. It is important to include ocular neuromyotonia (ONM) in the differential diagnosis of variable strabismus, particularly with a history of cranial radiotherapy and to ascertain if this diagnosis is applicable preoperatively as many of these cases respond to medical rather than surgical treatment. Our experience with ONM will be described in a case report involving a 48-year-old esotropic female who had radiation therapy for a cancerous lesion of the parotid gland 15 years previously. Her initial clinical appearance was of a large esotropia with apparent right VI^th nerve paresis, eventually it was noted that an exotropia could be elicited after sustained right gaze. The exotropia lasted 15–30 seconds and is believed to be due to ONM of the right lateral rectus. This ONM, secondary to radiation/compression of the right VI^th nerve, resolved with appropriate Dilantin® levels. A small persistent esotropia was amenable to prismatic correction with no strabismus surgery required.

• ocular neuromyotonia
• abducens nerve
• palsy
• strabismus
• radiation therapy
• carbamazepine