In inherited periodic spasticity, episodic, involuntary muscle contractions or spasms involving the hind limbs are associated with postural and locomotor disturbances, as well as spasticity. The condition may progress to hind limb paresis or plegia. Inherited periodic spasticity occurs most frequently in Holstein and Guernsey cattle 3–7 years old. It is regarded as a genetic disease and is attributed to inheritance of an autosomal dominant gene with incomplete penetrance. The pathology and pathophysiology remain obscure.
Clinical Findings of Inherited Periodic Spasticity in Cattle
Clinical signs of inherited periodic spasticity may vary in severity, duration, and frequency. Usually, some stimulus provokes the onset of clinical signs, such as the effort associated with rising or any factor that induces a notable emotional reaction. Pain, particularly in the feet or joints, may precipitate an episode of clinical signs. An animal may be unable to move forward, stand trembling, and characteristically extend its hind limbs backward. Between episodes, the animal can ambulate normally.
Treament of Inherited Periodic Spasticity in Cattle
Periodic spasticity is progressive, and because of the possibility of genetic transmission, animals (particularly bulls used for artificial insemination) are best eliminated from the breeding pool as soon as a positive diagnosis is made. Palliative treatment for animals in the peak of production may be helpful. The spinal cord depressant mephenesin (30–40 mg/kg, PO, in three divided doses administered every 8 hours for 2–3 days) may be given during an episode and is reported to mitigate the more severe clinical signs.