Hereditary spastic paraplegia (HSP) is a group of hereditary, degenerative, neurological disorders that primarily affect the upper motor neurons. Upper motor neurons in the brain and spinal cord deliver signals to the lower motor neurons, which in turn, carry messages to the muscles. In hereditary spastic paraplegia, upper motor neurons slowly degenerate so the muscles do not receive the correct messages, causing progressive spasticity (increased muscle tone/stiffness) and weakness of the legs. This leads to difficulty walking. As degeneration continues, symptoms worsen. If only the lower body is affected, HSP is classified as uncomplicated or pure. HSP is classified as complicated or complex if other systems are involved. In these cases, additional symptoms, including impaired vision, ataxia, epilepsy, cognitive impairment, peripheral neuropathy, and/or deafness, occur. The different forms of HSP are caused by mutations in different genes. Inheritance varies. There are no specific treatments to prevent, slow, or reverse HSP. Individual symptoms may be treated with medications and/or physical therapy