Table 2.

Classification of HSP.

Criteria for Classification	Types
Symptoms and signs (Harding’s classification)	Pure HSP Complex HSP
Age and onset of spasticity (Harding’s classification)	Type I HSP (Early onset < 35 years) Type II HSP (Classical/late onset > 35 years)
Inheritance pattern	Autosomal dominant HSP Autosomal recessive HSP X-linked HSP Mitochondrial HSP De Novo
Intracellular involvement	Membrane/organelle trafficking Axonal transport Dysfunction of mitochondria Defective lipid metabolism Abnormalities in the myelination process