Homozygous or compound heterozygous mutation of Strumpellin and Spartin proteins necessary for axonal integrity maintenance at locus 13.3q induces Troyer syndrome, an HSP form SPG20/SPART [83] with ankle clonus, atrophy of the cerebellar vermis, loss of white matter volume, skeletal abnormalities with high arched feet, muscular weakness, and hyperreflexia with oromotor dysfunction [84]. The gene discussed is SPART; the disease is Troyer syndrome.