[A case of stiff-man syndrome with head retraction like reflex myoclonus and jerky myoclonus of bilateral lower extremities which responded well to removal of mediastinal carcinoma].

A 58-year-old male presented with reflex myoclonus and stiffness of the left facial, tongue, shoulder, and lower limbs muscles. Muscle stiffness and gait progressively worsened, leading to frequent falls. Acoustic and cutaneous stimuli of head precipitated reflex myoclonus like head retraction. Cutaneous of lower extremities precipitated jerky myoclonus of bilateral lower extremities. CSF analysis were unremarkable. No anti GAD antibody or anti amphiphysin antibody was detected in the serum and CSF. On surface EMG the spasms initiated with 4-5 short burst discharges at intervals between 59 and 84 ms, followed by a tonic decrescendo activity up to 3 s. After diazepam treatment, stiffness and reflex myoclonus of lower extremities were disappeared and head retraction like reflex myoclonus was improved but remained. CT of the chest revealed a mediastinal tumor. Biopsy of the tumor revealed undifferential carcinoma. The patient further improved after the resection of the tumor. These findings suggest that this stiff-man syndrome may occur as an autoimmune paraneoplastic syndrome of CNS.