Paramyotonia Congenita without Cold Paralysis: A Case Report

A 27-year-old-woman with paramyotonia congenita was reported. She began to suffer from myotonia since infancy. Myotonia was aggravated by cold, but with intense cooling myotonia did not change to flaccid paralysis. Four generations of her family showed the same symptoms that suggested autosomal dominant inheritance. Neurological examinations revealed no impairments of mental function, cranial nerves and sensory system. Muscular atrophy or hypertrophy was not observed. Percussion myotonia of the tongue and thenar muscles could be elicited at room temperature. Myotonia was aggravated by cold. An oral intake of potassium chloride (7 grammes) did not provoke any muscle weakness or flaccid paralysis. Routine laboratory data and findings of head CT scan, cerebrospinal fluid and electroencephalogram were normal. The nosological distinction between paramyotonia congenita and hyperkalemic periodic paralysis has been debated since 1956. Paralysis induced by cold is thought to be a feature of paramyotonia congenita, thus raising a possible relationships to hyperkalemic periodic paralysis. In our case cold paralysis never occurred spontaneously and could not be provoked by immersion in ice water or by potassium loading. This finding confirms the existence of paramyotonia congenita without cold paralysis and may provide a nosological distinction between paramyotonia congenita and hyperkalemic periodic paralysis.