[Slowly progressive dysarthria in primary lateral sclerosis].

Slowly progressive dysarthria over many years may be the only sign of primary lateral sclerosis (PLS). Clinically it presents as pseudobulbar palsy which can be differentiated from amyotrophic lateral sclerosis (ALS) by the longer disease duration (> or =4 years), central pathological magnetic-evoked potentials to the tongue and lack of denervation in EMG. In contrast, hereditary spastic paraplegia (HSP) is characterized by a primary spasticity of the lower limbs, mostly later onset, the fact that other family members are affected and in isolated cases by positive genetic testing for mutations.