Hereditary myotonia in the Chow Chow

Abstract

Four related Chow Chow puppies which were presented because of stiffness in their movements were shown to have myotonia similar to myotonia congenita of man. Electromyography revealed characteristic myotonic discharges. Repetitive nerve stimulation studies showed a marked fade in the compound muscle action potential (CMAP) which was most apparent at stimulation rates of 10 per sec or higher. If stimulation was continued at a rate of 10 per sec the CMAP returned to normal or sometimes greater than normal following several seconds of the reduced response. The decremental response could be exaggerated by cooling the muscle prior to repetitive nerve stimulation. A therapeutic trial to assess the efficacy of the commonly used membrane stabilizing agents, quinidine, procainamide and phenytoin, indicated that all three drugs were beneficial in the treatment of myotonia but procainamide produced the best response. Hypocholesterolaemia was documented in one case. The possibility of a multisystem membrane defect in hereditary myotonia associated with low serum cholesterol was considered.

A Novel Mutation in CLCN1 Associated with Feline Myotonia Congenita

“…Decrement can be an electrophysiologic feature of myotonia congenita in some cases that represents the neurophysiologic counterpart of the initial weakness that patients often ‘warm-up’ out of [34]. Although not a classical finding in all cases of MC, this is not the first instance of pathologic decrement in veterinary patients with MC, as this has been reported previously in the Chow Chow dog [58]. This shared feature of pathologic decrement between the cats presented herein and these Chow Chow dogs suggests the possibility of a common molecular pathophysiology, although the molecular basis of MC in the Chow Chow will need to be addressed in order to explore this possibility.…”

Creatine kinase in the dog: A review

“…Moderate to dramatic increases of plasma CK activity were reported in congenital myopathies such as myotonia (Griffiths and Duncan, 1973;Jones et al, 1977;Farrow and Malik, 1981;Shires et al, 1983;Amann et al, 1985;Simpson and Braund, 1985) and X-linked myopathy of golden retrievers, which is an homologous model of Duchenne myopathy in humans (Kornegay, 1986;Valentine et al, 1986Valentine et al, , 1988Valentine et al, , 1989Valentine et al, , 1990Cooper et al, 1988;Kornegay et aL, 1988); whereas plasma CK is unchanged in dermatomyositis (Hargis et al, 1984Haupt et al, 1985) and myasthenia gravis (Aronsohn et al, 1984;Lefebvre, 1988Lefebvre, , 1990.…”

Progressive myotonia in foals resembling human dystrophia myotonica

“…Percussion of affected muscles results in a noticeable dimple in the muscle. Characteristic histopathologic changes in skeletal dogs.4.7,8,1 1,13,14,17,20,26,27,9 ~~~~~~i~ is an impor-muscle include formation of ring fibers and sarcoplasmic masses and internally located sarcolemmal nuclei.…”