Motor neuron disease. Prognosis and epidemiology.

In order to evaluate the prognosis and possible prognostic factors associated with a bening course, 118 cases of motor neuron disease diagnosed 1948-1975 were followed up. Survival curves, based on the actuarial method showed a survival rate of 18.7 per cent (95 per cent confidence limits: 11.4-26.0) and 7.6 per cent (95 per cent confidence limits: 2.7-12.5) after 5 and 10 years respectively. Comparing the survival curves of males/females, cases with bulbar/spinal- and upper/lower extremity onset, cases with/without upper motor neuron signs, only bulbar onset was associated with a significantly poorer prognosis. However, cases with bulbar onset had a significantly higher mean age of onset. Based on cases from Funen county with a 1970-population of 432,699 we found an average annual incidence rate, mortality rate and period prevalence rate of 0.85, 0.86 and 2.5 per 100,000 respectively. Comparing the incidence per 5-year period through 1948-1972, no significant deviations indicating a changing environmental factor were found.