Hyperexcitability restricted to the lower limb motor system in a patient with stiff-leg syndrome

We report a 29-year-old man who presented with a 2-year history of progressive stiffness and painful spasms limited to the bilateral lower limbs, exaggerated by auditory and tactile stimuli. His deep tendon reflexes were slightly increased in both lower extremities. His plantar response was flexor. His serum and cerebrospinal fluid were negative for anti-glutamic acid decarboxylase antibodies. Electromyography of antagonist muscle pairs in his distal lower limbs revealed a failure of reciprocal inhibition. We used transcranial magnetic stimulation with a paired-pulse paradigm, delivered to the cortical area of the upper and lower limbs, and revealed significantly enhanced facilitation only in the area of his lower limbs, but not that representing his upper limbs. His symptoms were improved substantially by 20 mg/day of oral diazepam. To our knowledge this is the first report of a patient with hyperexcitability limited to the lower limb motor system in a patient with stiff-leg syndrome.