Motor neuron disease (amyotrophic lateral sclerosis) arising from longstanding primary lateral sclerosis

Three men were initially diagnosed as having primary lateral sclerosis (PLS), but eventually developed amyotrophic lateral sclerosis (ALS) after 7.5, 9, and at least 27 years. Non-familial ALS and PLS might be different manifestations of a single disease or constitute completely distinct entities. The clinical diagnosis of PLS predicts a median survival that is four to five times longer than in ALS.