Cortical plasticity causes useless hand syndrome in multiple sclerosis: a neurophysiological study in a rare case.

Background: Useless Hand Syndrome (UHS) is a rare clinical manifestation of an upper cervical cord lesion, which is most commonly associated with multiple sclerosis (MS). The pathophysiological mechanism underlying UHS remains unclear.

Case: We report a 25-year-old woman, who described numbness in her left upper extremity. Cervical magnetic resonance imaging revealed a posterior upper cervical cord lesion. There was no cortical lesion that could explain the clinical findings. We measured (1) short-latency afferent inhibition (SAI) by obtaining motor evoked potentials as an indicator of sensorimotor integration and (2) somatosensorial temporal discrimination threshold (STDT) to display central somatosensory pathway function. In the right cerebral hemisphere, we found an excessive increase in STDT and no inhibition in the SAI paradigm.

Conclusions: These findings indicate that impairment of sensorimotor integration and central processing of sensory stimuli cause useless hand syndrome.