Ocular Neuromyotonia: Hypovitaminosis as a Possible Underlying Cause
Catherine Cassiman; Anne-Catherine Stockman; Maria Van Lammeren; Hilde Janssens; Veerle Van Bellinghen;
Liesbet Beelen; Maria Dieltiens
University Hospital Leuven
Leuven, Belgium, Europe
Introduction: Ocular neuromyotonia (ONM) is a rare eye movement disorder, observable as a paroxysmal involuntary spasm of one or more extra-ocular muscles. The phenomenon is caused by a contraction of an extraocular muscle by a damaged nerve, which leads to delayed muscle relaxation.
Methods: Ten patients presented with ONM at the ophthalmology department of the University Hospital of Leuven, Belgium. The clinical picture and the underlying aetiology will be given as well as the response to treatment.
Results: The diagnosis of ONM was made after a thorough orthoptic examination. Four out of 10 patients had a history of cranial irradiation. In 2 patients thyroid dysfunction was found. Three patients had demonstrable hypovitaminosis (vitamin D and B12). In 1 patient no underlying cause could be demonstrated. All patients were symptom free after correction for the underlying pathology or with membrane stabilizing drugs.
Discussion: ONM is a rare eye movement disorder. Patients complain of intermittent diplopia and strabismus. ONM is a clinical diagnosis, therefore is important to recognize the symptoms and observe the eyes in primary position at rest and again after sustained eccentric gaze. In the absence of a history of cranial irradiation, un underlying disease must be ruled out. A hypovitaminosis can possibly provoke ONM by inducing nerve membrane instability.
Conclusion: We present 10 patients with ONM. The clinical picture and work up is presented. Two patients with ONM were presumably provoked by hypovitaminosis, an hypothesis for the underlying mechanism is given.
References: Ricker VK, Mertens HG. Okulare Neuromyotonie. KlinMonatsblAugenheilk 1970;156:837-842
Roper-Hall G, Chung SM, Cruz OA. Ocular neuromyotonia: differential diagnosis and treatment. Strabismus 2013;21(2):131-136