This rare but fascinating disease was first described by Cavaré1in 1853 and later in 1874 by Hartwig,2who named it intermittent spinal paralysis. It is characterized by recurrent attacks of flaccid paralysis affecting mainly the muscles of the trunk and limbs, during which the deep reflexes disappear and the muscles become inexcitable to electrical stimulation. Attacks usually come on during sleep without previous warning; they last from a few hours to three or four days. In the interval muscular power is normal and the patient is entirely well. Attacks first make their appearance during childhood or adolescence and become less frequent or disappear in later life. Males are twice as often affected as females. Sporadic cases have been reported, but the condition is usually hereditary; Holtzapple3has described seventeen cases in four generations of the same sibship. Many theories have been advanced to explain these weird