Muscle stiffness triggered by potassium in 12 cats

Abstract

CASE DESCRIPTION: 12 European shorthair cats (6 males and 6 females; age range, 2 months to 3 years) from 1 household were evaluated for clinical signs of recurrent and progressive muscle spasticity. Genetic relationships among the cats were suspected but were not known. CLINICAL FINDINGS: Physical examination of all cats revealed a thin to mildly emaciated body condition and signs of suppurative rhinitis. Results of neurologic evaluations revealed no abnormalities in any cats at rest, but exercise- and stress-induced episodes of muscle spasticity were observed. Results of hematologic (7/12 cats) and CSF (4) analysis, diagnostic imaging (including radiography [7] and magnetic resonance imaging [4]), electromyography (4), motor nerve conduction tests (4), screening for metabolic storage diseases (4), provocation tests via exercise in a cold (4°C [39.2°F]) environment (7), and gross pathological and histologic examination (5) revealed no abnormalities that could potentially explain the clinical signs. However, consumption of a potassium-enriched diet resulted in severe aggravation of clinical signs in 7 of 7 cats, leading to a diagnosis of potassium-aggravated muscle stiffness. TREATMENT AND OUTCOME: 5 cats were euthanized after initial examination because of poor physical condition and severe clinical signs. Spasticity in the 7 remaining cats was improved during a 6-week follow-up period as they reduced their own activity. Further investigation and treatment were declined. CLINICAL RELEVANCE: Channelopathies are rarely recognized diseases in domestic animals. In addition to conventional diagnostic evaluation methods, provocation tests in a clinical environment can be used in the assessment of channelopathies.