Lewis–sumner syndrome of pure upper‐limb onset: Diagnostic, prognostic, and therapeutic features

Abstract

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 (> or =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.

Long-term treatment of Lewis–Sumner syndrome with subcutaneous immunoglobulin infusions

“…Protein concentration is often elevated in cerebrospinal fluid (CSF) [2][3][4]. Further laboratory work-up is not helpful, slightly raised anti-GM1 antibody titers are rarely observed (b 5%), yet no high titers have been reported [5]. The classification of this neuropathy in relation to MMN and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) has repeatedly been discussed [1][2][3][4]6], but most experts consider LSS as a variant or atypical form of CIDP, since the treatment response resembles that of CIDP patients [7].…”

Magnetic resonance imaging in bilateral brachial neuritis with pure sensory involvement

“…There are reported cases of focal upper limb demyelinating neuropathies in the literature. But they all have both motor and sensory conduction abnormalities indicative of demyelinating process [9,10]. Motor conduction examinations of the upper limb were normal in our patient, and neither upper limb motor involvement nor lower limb nerve involvement were detected at subsequent electrophysiological investigations.…”

Do patients having a decrease in SNAP amplitude during the course of MMN present with a different condition?

“…These patients did not fit the criteria of multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy or Lewis-Sumner syndrome [10], because they did not have objective sensory loss and because SNAP amplitudes were normal at the time of the initial electrophysiological examination. Furthermore, three of the four patients with decreased SNAP amplitude had high titers of IgM anti GM1 antibodies, which are not seen in the Lewis-Sumner syndrome [16,18,19]. Chronic inflammatory demyelinating polyneuropathy (CIDP) is unlikely in patients of group 2, since the clinical and electrophysiological abnormalities were in the distribution of individual peripheral nerves and because CSF protein level was not elevated, per our laboratory normative data [9].…”