Motor evoked potentials in a case of stiff-man syndrome: a longitudinal study

The clinical and neurophysiological findings in a patient with a typical st iff-man syndrome and their three-year evolution are described. The patient had high titers of anti-glutamic acid decarboxylase antibodies in both seru m and cerebrospinal fluid. Magnetic resonance imaging (MRI) of brain and sp inal cord was normal. Transcranial magnetic stimulation (TMS) revealed a di stinctive motor evoked potential (MEP) pattern in proximal lower limb muscl es consisting of markedly increased MEP amplitudes and MEP/M ratios, reduce d excitability thresholds, and absent silent period. However, MEP latencies , central and peripheral conduction times and amplitudes obtained by magnet ic spinal root stimulation were normal. Treatment with benzodiazepine and b aclofen normalized both the clinical picture and the MEP values. TMS may be useful both as a diagnostic tool and to monitor the response to drug treat ment.