FSP and HSP simply describe the characteristics of the disease in medical terms. Use of any one name does not mean that the individual has a different disorder than another who is given a different diagnosis in the above list but has the same symptoms. No matter what name is used or what diagnosis is given, the basic symptoms of the disorder affect people from the waist down, with variable degrees of muscle stiffness, difficulty with fluid movement of the legs, weakness in some leg muscles, and difficulty with bladder control. Onset of symptoms can occur from age 1 year to the 80's. The age of onset is variable both within and among families.
Symptoms generally get worse over time.
In some people with FSP, the nervous system has been studied after death. Abnormalities are seen in selected areas of the spinal cord called tracts . These tracts carry messages from brain to muscles. It appears that such areas have deteriorated. Their functioning has been likened to that of a frayed electrical cord that sparks, shorts, and surges.