Short-latency somatosensory-evoked potential findings in two patients with complicated form of familial spastic paraplegia

We evaluated two patients who were considered as having complicated form of familial spastic paraplegia (FSP). Patient 1 was a 37-year-old male, having slowly progressive walking difficulty. Examination revealed dementia, nystagmus, slurred speech, spastic paraparesis and increased reflexes. His sensation was normal. Patient 2 was a 35-year-old male. Examination revealed dementia, dysarthria, spastic paraparesis, increased reflexes and slightly decreased vibration sense in the ankle. We examined the median and tibial short-latency somatosensory-evoked potentials (SEPs). In patient 1, N9o-P13/14o and P13/14o-N20o intervals were prolonged in the median SEPs. 'N9o' means N9 onset. N21-N30 and N30-P38 intervals were prolonged in tibial SEPs. In patient 2, P13/14o latency was normal, but N20 was lost in the median SEPs. N30 latency was normal, but P38 was lost in the tibial SEPs. The present results indicate defective transmission in the somatosensory pathway, especially in its intracranial portion, in patients with complicated form of FSP. This contrasts with findings in patients with pure form of FSP, who usually show defective transmission only in the thoracic spinal portion. SEPs showed abnormal findings, even in a patient without sensory disturbances. SEPs are useful for localizing the lesion sites and for differential diagnosis between the pure and complicated forms of FSP.