CASE REPORT AND CLINICAL REVIEW: Unilateral facial myokymia in a dog with an intracranial meningioma

Abstract

A 23-month-old castrated male Cavalier King Charles spaniel was evaluated because of a 6-month history of unusual rippling/undulating movements of the right facial muscles that were continuous and persisted during sleep. Neurological examination revealed narrowing of the right palpebral fissure and unilateral right-sided facial myokymia that was characterised by myokymic, and to a lesser degree, neuromyotonic discharges on concentric needle electromyographic examination. After persisting unchanged for almost 2.5 years from its onset, the facial myokymia gradually disappeared over a 6-month period concomitant with the emergence of a persistent ipsilateral facial paralysis and head tilt. At 5 years and 9 months after the first examination, signs of ipsilateral lacrimal, pharyngeal and laryngeal dysfunction became evident and the dog was euthanased. Postmortem examination identified a malignant (WHO grade III) meningioma in the right cerebellopontomedullary angle that compressed the ventrolateral cranial medulla, effaced the jugular foramen and internal acoustic meatus and extended into the facial canal of the petrous temporal bone. Novel findings were the unique observation of isolated unilateral facial myokymia preceding diagnosis of a meningioma affecting facial nerve function within the caudal cranial fossa and the remarkably long duration of neurological signs (75 months) attributable to the neoplasm.

Neuromyotonia in a dachshund with clinical and electrophysiological signs of spinocerebellar ataxia

“…Myokymia and neuromyotonia are rare phenomena and have only been recently diagnosed in veterinary medicine (Reading and McKerrell 1993, Van Ham and others 2004, Galano and others 2005, Walmsley and others 2006, Holland and others 2010, Vanhaesebrouck and others 2010a). Generalised myokymia and neuromyotonia are emerging clinical phenomena in the Jack Russell terrier breed (Bhatti and others, in press).…”

Necrotizing leptomeningeal vasculitis associated with a compressive meningioma in a cat: a rare paraneoplastic syndrome

“…Recently, myokymia was reported in association with an intracranial meningioma. 17 Vasculitis, however, in conjunction with a solid neoplasm has to the knowledge of the authors, not been reported in any non human species.…”

International veterinary canine dyskinesia task force ECVN consensus statement: Terminology and classification

“…15 May be benign (eg, stress related) or indicative of underlying pathology. In veterinary patients, focal myokymia affecting the muscles of the head is often related to an identifiable brain disorder, [16][17][18] whereas generalized myokymia is most commonly seen in Jack Russell terriers 19 although other breeds are reported. 20,21 3.…”

“…May be benign (eg, stress related) or indicative of underlying pathology. In veterinary patients, focal myokymia affecting the muscles of the head is often related to an identifiable brain disorder, 16‐18 whereas generalized myokymia is most commonly seen in Jack Russell terriers 19 although other breeds are reported 20,21 Neuromyotonia Neuromyotonic discharges are high‐frequency (150‐300 Hz) bursts of decrementing discharges of motor unit potentials that originate in motor axons and have an abrupt onset and offset.…”