Progressive spastic paraparesis: hereditary spastic paraplegia and its relation to primary and amyotrophic lateral sclerosis.

The syndrome of insidiously progressive spastic weakness of both legs occurs in a number of etiologically distinct disorders including hereditary spastic paraplegia (HSP), primary lateral sclerosis (PLS), and sometimes in amyotrophic lateral sclerosis (ALS). This review summarizes the clinical and pathologic relationship between these disorders.