Comparison of Lewis–Sumner syndrome with chronic inflammatory demyelinating polyradiculoneuropathy patients in a tertiary care centre

Background and purpose Whether the Lewis–Sumner syndrome (L‐SS) is a distinct entity from other types of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP‐ot) remains controversial. Method The clinical/electrophysiological characteristics and long‐term outcomes of 45 L‐SS and 35 CIDP‐ot patients were retrospectively compared. Results The CIDP‐ot group was composed of 11 patients with a typical CIDP, 17 with a pure sensory form, four with a distal form and three with a pure motor form. In the L‐SS group, asymmetric ( P < 0.001) and monomelic involvement ( P = 0.04) of the upper limbs ( P < 0.001) was significantly more frequent; paucisymptomatic forms (Overall Neuropathy Limitations Scale ≤ 1) were less frequent ( P < 0.001); electroneuromyography showed that conduction block in intermediate nerve segments was the main demyelinating feature, with frequent F‐wave abnormalities on nerves without conduction block (44%). Long‐term prognosis was globally poorer in the L‐SS group with more frequent aggravation during treatment ( P = 0.02), less frequent treatment withdrawal ( P = 0.03) and longer time to achieve successful withdrawal (39 vs. 15 months). Conclusions Our study suggests that L‐SS patients have a less favourable therapeutic response rate and long‐term outcomes. Rapid differentiation of L‐SS from other forms of CIDP is important in order to anticipate a more complicated disease course management, with from one side the inefficacy or even harmfulness of corticosteroids and from the other side a difficult weaning procedure. A prospective study is necessary to confirm these results.