ttp://www.bsava.com
LETTER TO THE EDITOR Canine hemifacial spasm: a misnomer? Recently, we have encountered two dogs (Labrador retriever, 7-yearold neutered-male; cocker spaniel, 1-year-old female-entire) that have been diagnosed with idiopathic hemifacial tetanus. Haematology, serum biochemistry, thyroid function and pre- and post-contrast MR imaging of the brain were unremarkable in each dog. On the affected side of the face, there was a slightly narrowed palpebral fissure, the upper and lower lips appeared contracted and displaced caudally, the ear appeared slightly elevated and the nose was deviated towards the affected side. At induction of general anaesthesia the hemifacial tetanus resolved in both dogs. Electromyography (EMG) was carried out under general anaesthesia and showed doublets (Labrador retriever: 40–48 µV at intervals of 20 ms; cocker spaniel: 170–180 µV at intervals of 20 ms) (Fig 1) and fibrillation potentials in the affected facial muscles. No treatment was given to both dogs. The Labrador retriever was re-evaluated after 12 months and the cocker spaniel after 6 months. The hemifacial tetanus remained unchanged in both dogs. Electromyography findings have never been reported in dogs with hemifacial tetanus. Doublets are double discharges of the same motor unit at intervals of 2–20 ms (De Risio et al. 2006, Kimura 2013). In humans with hemifacial spasm, doublets are not a typical EMG feature (Kimura 2013). Commonly, in humans doublets accompany tetany (Kimura 2013) and they have been detected in a dog with focal tetanus (De Risio et al. 2006). The clinical and EMG features in the dogs under study suggest that the hemifacial muscle contractions are a form of tetanus (de Lahunta & Glass 2009) and, therefore, it is suggested that this specific clinical condition should be referred as canine idiopathic hemifacial tetanus. The human disorder is truly a spasm of the facial muscles and is often related to an aberrant position of an artery at the internal acoustic meatus. Muscle spasms are never seen in affected dogs, only a tetanus of the affected facial muscles.
480
FIG 1. Concentric-needle electromyography of the affected orbicularis oris muscle in a Labrador retriever with hemifacial tetanus. Note the series of doublets
Luca Motta and Alexander de Lahunta* Chester Gates Veterinary Specialists (CVS LTD), Gates Lane, Telford Court, Unit F/E, Chester, Cheshire, CH1 6LT *College of Veterinary Medicine, Cornell University, PO Box 907, Rye, NH 03870, USA References De Risio, L., Zavattiero, S., Venzi, C., et al. (2006) Focal canine tetanus: diagnostic value of electromyography. Journal of Small Animal Practice 47, 278-280 de Lahunta, A. & Glass, E. (2009) Lower motor neuron: general somatic efferent, cranial nerve. In: Veterinary Neuroanatomy and Clinical Neurology. Eds. A. DeLahunta and E. Glass. Saunders, Elsevier St. Louis, MO, USA, pp 150-151 Kimura, J. (2013) Types of electromyographic abnormalities. In: Electrodiagnosis in Diseases of Nerve and Muscle: Principle and Practice. Ed. J. Kimura. Oxford University Press, New York, NY, USA. pp 361-392
Journal of Small Animal Practice
•
Vol 56
•
July 2015
•
© 2015 British Small Animal Veterinary Association
LETTER TO THE EDITOR Canine hemifacial spasm: a misnomer? Recently, we have encountered two dogs (Labrador retriever, 7-yearold neutered-male; cocker spaniel, 1-year-old female-entire) that have been diagnosed with idiopathic hemifacial tetanus. Haematology, serum biochemistry, thyroid function and pre- and post-contrast MR imaging of the brain were unremarkable in each dog. On the affected side of the face, there was a slightly narrowed palpebral fissure, the upper and lower lips appeared contracted and displaced caudally, the ear appeared slightly elevated and the nose was deviated towards the affected side. At induction of general anaesthesia the hemifacial tetanus resolved in both dogs. Electromyography (EMG) was carried out under general anaesthesia and showed doublets (Labrador retriever: 40–48 µV at intervals of 20 ms; cocker spaniel: 170–180 µV at intervals of 20 ms) (Fig 1) and fibrillation potentials in the affected facial muscles. No treatment was given to both dogs. The Labrador retriever was re-evaluated after 12 months and the cocker spaniel after 6 months. The hemifacial tetanus remained unchanged in both dogs. Electromyography findings have never been reported in dogs with hemifacial tetanus. Doublets are double discharges of the same motor unit at intervals of 2–20 ms (De Risio et al. 2006, Kimura 2013). In humans with hemifacial spasm, doublets are not a typical EMG feature (Kimura 2013). Commonly, in humans doublets accompany tetany (Kimura 2013) and they have been detected in a dog with focal tetanus (De Risio et al. 2006). The clinical and EMG features in the dogs under study suggest that the hemifacial muscle contractions are a form of tetanus (de Lahunta & Glass 2009) and, therefore, it is suggested that this specific clinical condition should be referred as canine idiopathic hemifacial tetanus. The human disorder is truly a spasm of the facial muscles and is often related to an aberrant position of an artery at the internal acoustic meatus. Muscle spasms are never seen in affected dogs, only a tetanus of the affected facial muscles.
480
FIG 1. Concentric-needle electromyography of the affected orbicularis oris muscle in a Labrador retriever with hemifacial tetanus. Note the series of doublets
Luca Motta and Alexander de Lahunta* Chester Gates Veterinary Specialists (CVS LTD), Gates Lane, Telford Court, Unit F/E, Chester, Cheshire, CH1 6LT *College of Veterinary Medicine, Cornell University, PO Box 907, Rye, NH 03870, USA References De Risio, L., Zavattiero, S., Venzi, C., et al. (2006) Focal canine tetanus: diagnostic value of electromyography. Journal of Small Animal Practice 47, 278-280 de Lahunta, A. & Glass, E. (2009) Lower motor neuron: general somatic efferent, cranial nerve. In: Veterinary Neuroanatomy and Clinical Neurology. Eds. A. DeLahunta and E. Glass. Saunders, Elsevier St. Louis, MO, USA, pp 150-151 Kimura, J. (2013) Types of electromyographic abnormalities. In: Electrodiagnosis in Diseases of Nerve and Muscle: Principle and Practice. Ed. J. Kimura. Oxford University Press, New York, NY, USA. pp 361-392
Journal of Small Animal Practice
•
Vol 56
•
July 2015
•
© 2015 British Small Animal Veterinary Association
