Factors associated with improvement in gait disturbance of polyneuropathy in POEMS syndrome

BACKGROUND: Distal dominant muscle weakness is one of the characteristic symptoms of polyneuropathies, largely affecting patients' quality of life. The aim of this study was to identify factors influencing gait disturbances in POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes) syndrome. METHODS: This study consists of 2 study designs: Study 1 was a cross-sectional study and Study 2 was retrospective cohort study. Study 1: a total of 60 patients with POEMS syndrome was included. Gait disturbance was assessed using the Functional Ambulation Categories (FAC), and relationships among FAC, physical functional assessments, and tibial nerve conduction studies (NCS) parameters were analyzed. Study 2: after treatment, 27 of the 60 patients were divided into the 2 groups based on FAC results: the gait improvement group (n = 14) and non-improvement group (n = 13). Factors contributing to gait improvement were assessed. RESULTS: Study 1: The median age of patients was 56 years; 26 patients walked independently, whereas the remaining 34 required assistance with walking. The median scores for manual muscle testing were 4/5 for the iliopsoas, 5/5 for the quadriceps, and 2/5 for the tibialis anterior. The median score for great toe position sense was 5/5. Gait disturbances were significantly correlated with muscle strength of the iliopsoas (rho = 0.57), quadriceps (rho = 0.64), and tibialis anterior (strongest correlation; rho = 0.82), and with great toe position sense (rho = 0.59) (all, p < 0.0001). In contrast, NCS parameters were not correlated with gait disturbances. Study 2: strength of the 3 muscles was improved after treatments in the gait improvement group, and Δ muscle strength of the iliopsoas muscles was significantly associated with gait improvement (rho = 0.54, p < 0.05). CONCLUSIONS: Whereas weakness of the distal lower limb muscles largely affects gait ability in POEMS polyneuropathy, recovery in proximal lower limb muscle strength is more important for gait improvement.