The video below is of two kittens from the same litter with myotonia congenita. This is a rare presentation and even more so having two related kittens presented at once. The owner of these kittens consented for the video to be shown to raise awareness of this rare condition. Myotonia congenita (MC) is a skeletal muscle channelopathy characterized by the inability of the muscle to relax following voluntary contraction. These kittens had a tendency to 'freeze' when jumping off a height which was one of the presenting complaints and what we tried to recreate by letting them jump off a very small height in this video to illustrate that presentation. After collapsing, they both slowly recover normal muscle tone and use, described for this condition as 'warm-up' phenomenon. Other common clinical signs include blepharospasm following digital stimulation of the medial or lateral canthus and a tendency to keep the jaw open again for a short period of time until the warm-up occurs as illustrated on this video.

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Needle electromyography demonstrated repetitive spontaneous discharges, which waxed and waned and sounded like a revving motorcycle - see video.

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