Spastic paraplegia is a form of paraplegia defined by spasticity of the affected muscles, rather than paralysis. See also: spastic diplegia. Paraplegia is a condition in which the lower part of a persons body is paralyzed and cannot willfully function. ... Spasticity is a disorder of the bodys motor system in which certain muscles are continuously contracted. ... Paralysis is the complete loss of muscle function for one or more muscle groups. ... Spastic diplegia refers to a type of cerebral palsy that is a neuromuscular condition of hypertonia and spasticity in the muslces of the lower extremities, usually those of the legs, hips and pelvis. ...