Motor root conduction block in the Lewis-Sumner syndrome

The Lewis-Sumner syndrome (LSS) is a rare immune-mediated peripheral nerve disorder presenting with asymmetric upper limb sensory complaints and motor weakness. Asian patients with LSS have not been reported in the English literature.

Three Asian patients with features of LSS were prospectively studied.

Our patients tended to older, female, and have involvement of the upper limbs exclusively than those in the West. They have a markedly longer disease duration before a diagnosis was made, which could also be the result of difficulty in eliciting motor root conduction block as a sign of proximal demyelination as observed in every patient. Pain is a universal feature as is sensory nerve conduction abnormality. None responded to immunotherapy, but disease stabilization was observed over the chronic course.

Although rare, these unique observations in Asian patients with LSS differ from those reported in Western literature. The presence of motor root conduction block demonstrated for the first time is instrumental in establishing a diagnosis.