Generalized Myokymia and Neuromyotonia in a Yorkshire Terrier

Abstract

An eight-year-old female Yorkshire terrier presented with episodes of hyperpnea and stiffness of the limbs. A physical and neurological examination revealed rhythmic, undulating movement across the muscles of the trunk and limbs. This movement was characteristic of myokymia. An electromyogram demonstrated myokymicdischarges. The cisternal cerebrospinal fluid (CSF) showed mononuclear pleocytosis, which was indicative of inflammatory central nervous system disease. The MRI of the brain was unremarkable. A clinical diagnosis of myokymia/neuromyotonia with inflammatory brain disease was made, and the dog was treated with antibiotics, zonisamide and procainamide. A follow-up CSF analysis performed 5 months after the initial examination was normal. At present, 11 months after the diagnosis, the dog is still being treated with zonisamide and procainamide. No episodes of hyperpnea or stiffness of the limbs have been observed, and the myokymia has decreased markedly in frequency and severity.