Ocular Neuromyotonia: Case Reports and Literature Review

Abstract

Ocular neuromyotonia (ONM) is a rare eye movement disorder, presenting as a paroxysmal involuntary spasm of one or more extra-ocular muscles, that can persist for a few seconds up to several minutes. The phenomenon is caused by the contraction of an extra-ocular muscle, excited by a damaged nerve, which leads to delayed muscle relaxation. We present eight patients with this rare condition together with an overview of the literature on all published ONM cases. One of the presented cases is possibly secondary to hypovitaminosis D. This association has not been reported previously in the literature. A possible underlying mechanism is given.

Post-surgical left oculomotor nerve neuromyotonia: Cause or coincidence?

“…European Journal of Ophthalmology 32 (1) been described such as alcohol intake, vitamins D or B12 insufficiency, brainstem demyelination, botulinum toxin injections, myelography, cataract surgery and congenital origin. 3,4 In our case, blood testing only revealed slight hypovitaminosis D. There was no history of radiotherapy and the brain surgery involved two meningiomas situated on the right side while ONM was on the left side. Other diagnoses were considered knowing that a surgery of a temporal cavernoma occurred 12 years earlier on the left side.…”

“…Most cases of ONM described in literature are secondary to radiotherapy. [1][2][3][4] ONM also has been described in Graves' disease, or as revealing sign of vascular or brain tumour compression. Some sporadic causes have also…”

“…7 We excluded other diagnoses like myasthenia gravis, 5 superior oblique myokymia, 4,5 ischemic inflammatory diseases, 5 alcohol intake. 3 We were consequently left with a suspicion of left third nerve neuromyotonia, diagnosis comforted by the beneficial effect of carbamazepine. This suspicion required investigating that nerve along its trajectory, which was done 1 year later, highlighting neurovascular contact.…”

“…We postulate that remodelling and displacement of regional structures during surgery might be responsible for ONM. 3,4,8,9 Indeed, the opening of subarachnoid spaces and CSF removal during surgery may slightly displace regional structures and may induce or increase a neuro-vascular contact, provoking neuromyotonic manifestations.…”

“…Most cases of ONMs are unilateral but bilateral ONMs have also been described. [1][2][3][4] We report a case of left ONM in a 55-year-old female patient, several weeks after simultaneous surgical resection of two meningiomas, situated on the right side (Simpson II). The particularity of this case is linked to its puzzling presentation, its similarity with spasm of the near reflex and the putative mechanism through which surgery might have precipitated the symptoms.…”