Hereditary spastic paraplegia.

Hereditary spastic paraplegias (HSPs) are a group of neurodegenerative disorders which involve the corticospinal tracts and present with distinct spasticity and weakness of the lower extremities. The estimated prevalence of HSP is around 1.8/100,000 cases for both autosomal dominant and autosomal recessive types. Classification of HSP is based on inheritance pattern, clinical phenotype, and molecular pathophysiological mechanisms. The most common neuropathological sign is the axonal degeneration involving the lateral corticospinal tracts in both the cervical and thoracic spinal cord. The target of this review article is to provide a comprehensive overview of the HSP classification, neuropathology, and differential diagnosis.