Summary: Hereditary spastic paraplegia type 4 is the most frequent mutation of hereditary spastic paraplegias. It is commonly described as pure, with progressive weakness of the lower limbs, pyramidal syndrome and vesico-sphincter disorders. However, cognitive disorders have been reported for over 20 years, but remain poorly characterized.

Summary: Study goals 1. Prospective longitudinal data on progression in the natural course of SPG4 in presymptomatic mutation carriers prior to clinical disease onset and in early stages of disease 2. Biomarkers providing objective measures of disease activity