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. © 2009 Wiley Periodicals, Inc. Muscle Nerve 39: 206–220, 2009