Lewis-Sumner syndrome of pure upper-limb onset: Diagnostic, prognostic, and therapeutic features

Lewis-Sumner syndrome (L-SS) represents the asymmetric variant of chronic inflammatory demyelinating polyneuropathy (CIDP). The characteristics and specificities of L-SS of pure upper-limb onset, as initially described by Lewis et al. [Multifocal demyelinating neuropathy with persistent conduction block. Neurology 32:958-964, 1982], have not been studied. We describe 8 such patients and review 82 previously reported cases. Distal involvement predominates and is mixed, sensory and motor from onset in only 50% of patients. Pain is a feature in about 20%. Subsequent lower-limb involvement occurs in <40% of cases. Electrophysiologically, upper-limb-onset L-SS is characterized by the presence of motor conduction blocks in arm nerves in about 90% of cases, and other demyelinating motor abnormalities are significantly less frequent. Cerebrospinal fluid (CSF) protein levels are raised in about 40% of cases and are moderate in most. Mildly raised anti-GM1 antibody titers are rare (<5%), but very high titers (≤1: 6400) have not been reported. Over 80% of treated patients respond, and intravenous immunoglobulins may be more effective than steroids. The prognosis is favorable in 40% of patients who eventually stabilize without treatment. We also reviewed 36 cases of other forms of L-SS, and present a further 2 cases. The upper-limb-onset variant is significantly less likely to spread to other limbs and may be less likely to have raised CSF protein levels. This could reflect a more localized disease process in upper-limb-onset L-SS. This variant may represent a separate entity, to be distinguished from other asymmetric forms of CIDP.