The natural history of motoneuron loss in amyotrophic lateral sclerosis.

Using a quantitative, reliable, sensitive and valid measurement technique, we analyzed the rate and pattern of motor deterioration in 50 strictly defined ALS patients for up to 67 months. We observed that the rate of motoneuron loss was linear and symmetric. Bulbar function deteriorated more slowly than respiratory, arm, and leg function. The loss of leg strength was slower than in the arm. No correlation was observed between age at onset and rate of deterioration, or with different regions of onset. Arm strength changed more slowly in women, but other functions showed no male-female differences. These data should prove useful in the design of clinical trials and in generating testable hypotheses of the etiology of this disease.