[Post-poliomyelitis late progressive muscular atrophy (PPMA)--clinical analyses of Japanese cases].

Clinical and epidemiologic analyses of PPMA in Japan based on the nation-wide case survey were reported, and differences between PPMA and ALS were discussed. The present survey covering the years from 1984 through 1991 cited 42 PPMA cases (30 male:12 female). The absolute incidence of PPMA is estimated 0.12/10(5) of the Japanese population (about 150 cases in total), which indicates 0.5% of the polio survivors. In Japan an actual increase of patients is noticed in these 10 years, which reflects the big epidemic of polio around 1950-60. The antecedent poliomyelitis occurred at the mean age of 2.6, mostly between 1940 and 1960. Residual paralysis was generally absent or only minimal. Late muscular atrophy and weakness were noticed at age from 16 to 63 y (mean:41.5), with the mean latency of 40.1 years after polio. Both polio-affected and unaffected site of the limb were equally involved by PPMA, but the left leg tends to be predominantly involved. Neurological symptoms were summarized as an asymmetrical proximal muscular atrophy and flaccid motor paresis in one or two limbs with decreased tendon reflexes. Fasciculation in 45.2%, myalgia in 28.6%, and hypesthesia in 28.5% were noticed. Electromyography and muscle CT scan showed marked selective neurogenic changes. In most cases symptoms are stable or slowly progressive, with some recovery by rest or rehabilitation and deterioration by over work and/or trauma. On regarding these clinical features, PPMA is essentially different from classical ALS. Long-term hyperfunction of survived neurons with potential fragility by polio infection is suspected to mediate PPMA.(ABSTRACT TRUNCATED AT 250 WORDS)