Movement disorders are increasingly recognized in veterinary medicine. Perhaps we’ve had a shared patient where I have proclaimed this diagnosis, and you’ve thought… “It’s a what?” Let’s spend this TidBit Tuesday talking about movement disorders, and specifically, movement disorders related to a common storage disorder called Lafora’s Disease.
What is a movement disorder?
A movement disorder is classified by clinical appearance, anatomic origin or etiology in human medicine. In veterinary medicine we classify them as hyperkinetic (those associated with increased muscle movement) and hypokinetic (those with reduced or absent muscle activity). Even more confusingly, some of the hyperkinetic movement disorders can be associated with seizures. Myoclonus, a type of hyperkinetic movement disorder, is one of the more common movement disorders that we see. An example of a myoclonus is a rapid lip twitch, eyelid twitch or even hiccups! Although probably annoying, they haven’t been shown to result in brain damage, or respond well to anticonvulsants, so generally treatment is benign neglect.
What is Lafora’s Disease?
Lafora’s disease is an autosomal recessive storage disorder that is unique compared to some of the other lysosomal storage disorders. Signs of Lafora’s Disease onset in adult hood, typically between 6-9 years of age. Dachshunds are commonly affected. Most other lysosomal diseases are juvenile onset. What it does is clog up the inner workings of the brain with these Lafora’s bodies resulting in blindness, behavioral changes (aggression) and, yes, myoclonus. Some dogs will also develop seizures, too. The myoclonus is typically visually stimulated. When something briskly approaches the dog’s face the eyes will shutter rapidly, and the dog may move its head and neck rapidly back and forth. Myoclonus can occur for reasons UNRELATED to Lafora’s disease but in combination with loss of vision, and possibly seizures or behavioral changes, I would suspect Lafora’s Disease in a patient with mature adult onset visually stimulated myoclonus. Sadly, we do not have any treatment to date for Lafora’s Disease. The disease is progressive, and unresponsive to anticonvulsants, however some dogs may temporarily improve with muscle relaxants.
Key Points:
· Movement disorders are not seizures and can be hyperkinetic (increased movement) or hypokinetic (decreased movement).
· Myoclonus is a type of hyperkinetic movement disorder
· Lafora’s Disease causes myoclonus, blindness, behavioral changes and sometimes seizures
· Animals with Lafora’s Disease often have visual myoclonus that can be triggered by a visual stimulus
· No treatment is available for Lafora’s Disease
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