Can he fix it? Yes, he can!BMJ 2010; 341 doi: http://dx.doi.org/10.1136/bmj.c6645 (Published 08 December 2010) Cite this as: BMJ 2010;341:c6645
- Kelly Weston, OST21,
- Kate Bush, OST42,
- Farid Afshar, specialist registrar3,
- Steven Rowley, consultant ophthalmologist2
- 1Royal Hampshire County Hospital, Winchester SO22 5DG, UK
- 2Royal Bournemouth Hospital, Bournemouth, UK
- 3Moorfields Eye Hospital, London, UK
A 68 year old woman presented with intermittent diplopia lasting a few minutes precipitated by left gaze. Best corrected visual acuities were 6/9 right and 6/36 left. Initial examination showed only a dense left cataract, which was removed, improving vision to 6/9. Unfortunately her symptoms continued. Her diplopia was elicited during orthoptic review, showing a left exotropia, with updrift, measuring 40 prism dioptres. There was limitation of adduction and depression of the left eye. Imaging showed no structural lesion. The episodes increased in frequency to 50-100 times per day. However, she found one day, while playing with her grandson, that wearing a pair of his tight “Bob the Builder” goggles prevented the episodes from occurring (fig 1⇓).
As a result she took to wearing the goggles daily around the house, particularly to watch the television. She also tried other types of goggles, including swimming goggles, but these were not as effective. She was diagnosed with idiopathic ocular neuromyotonia affecting left lateral rectus and left superior rectus muscles. Symptom control was achieved with carbamazepine after a trial of gabapentin failed.
Ocular neuromyotonia, first described in 1970,1 is characterised by transient diplopia and strabismus that occurs spontaneously or with maintenance of eccentric gaze, resulting in tonic contraction or spasm of ocular muscles.2 It is a rare paroxysmal involuntary contraction that may affect one or more of the ocular motor muscles.
Sixth nerve myotonia is triggered by sustained action of the lateral rectus muscle, leading to intermittent exotropia with restriction of adduction. In our patient the episodes of involuntary strabismus were triggered by lateral gaze. By wearing restricted field goggles that eliminated the stimulus for lateral gaze, the patient prevented these episodes
Ocular neuromyotonia is thought to result from spontaneous neural firing from a single neurone or group of neurones, with interneural transmission resulting in a self perpetuating circuit.1 2 Eliminating this mechanism with membrane stabilising agents can lead to resolution of symptoms.2
Our patient has identified a new mechanism for preventing episodes of ocular neuromyotonia, but carbamazepine has now stabilised her condition
Cite this as: BMJ 2010;341:c6645
Contributors: All authors were involved with writing and editing this case and giving approval for publication. SR and KW act as guarantors, accepting full responsibility for the work, having had access to the data, and controlled the decision to publish.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Provenance and peer review: Not commissioned, not externally peer reviewed.