From OMIM
Spastic paraplegia-8 is an autosomal dominant neurologic disorder characterized by adult onset of progressive lower limb spasticity and hyperreflexia resulting in difficulty walking. Some patients may become wheelchair-bound after several decades. Other features may include upper limb spasticity, impaired vibration sense in the distal lower limbs, and urinary urgency or incontinence (summary by de Bot et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant spastic paraplegia, see SPG3A (182600).  http://www.omim.org/entry/603563

From MedlinePlus Genetics
People with spastic paraplegia type 8 tend to be more severely affected than those with other types of hereditary spastic paraplegias; affected individuals typically require wheelchair assistance in adulthood. However, the signs and symptoms of spastic paraplegia type 8 can vary, even among members of the same family.

People with spastic paraplegia type 8 have spasticity and weakness of the leg muscles. Affected individuals may also experience exaggerated reflexes (hyperreflexia), a decreased ability to feel vibrations, and reduced bladder control. The signs and symptoms of spastic paraplegia type 8 can begin in childhood, although they typically appear in early to mid-adulthood. 

Spastic paraplegia type 8 belongs to a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) and weakness. Hereditary spastic paraplegias are divided into two types: pure and complex. The pure (also called uncomplicated) types involve only the nerves and muscles that control the legs and bladder, whereas the complex (also called complicated) types also involve the nervous system in other parts of the body. Spastic paraplegia type 8 is a pure hereditary spastic paraplegia.  https://medlineplus.gov/genetics/condition/spastic-paraplegia-type-8