Transcranial magnetic stimulation study in hereditary spastic paraparesis

The motor-evoked potentials and the cortical excitability by transcranial magnetic stimulation (TMS) were studied in a family with chromosome 2p linked (due to mutations in spastin) and in a family with chromosome 16q linked (due to mutations in paraplegin) hereditary spastic paraparesis (HSP), in order to evaluate the utility of these techniques in identifying the subgroups of the disease. Central motor conduction time and motor treshold to TMS were abnormal in some members of both families; the intracortical inhibition was reduced only in the affected members of the family with chromosome 2p linked HSP, even though the neurological symptoms were sometimes similar and also when clinical features reflecting cortical dysfunction were absent. The motor cortex is differentially involved in the often clinically indistinguishable forms of HSP, and TMS may help in the differential diagnosis.