Subclinical motor involvement in nonsystemic vasculitic neuropathy determined by the motor unit number estimation method MScanFit.

INTRODUCTION/AIMS: Nonsystemic vasculitic neuropathy (NSVN) is characterized by a predominant lower limb involvement in many patients. Motor unit changes in upper extremity muscles have not been investigated in this subgroup but may be of interest for improving our understanding of the multifocal nature of the disease and counseling of patients about potential future symptoms. In this study we aimed to better understand subclinical motor involvement in the upper extremity muscles of patients with lower limb-predominant NSVN using the new motor unit number estimation (MUNE) method MScanFit. METHODS: In this single-center, cross-sectional study, 14 patients with biopsy-proven NSVN, with no clinical signs of upper extremity motor involvement, were investigated and compared with 14 age-matched healthy controls. All participants were assessed clinically and by the MUNE method MScanFit to the abductor pollicis brevis muscle. RESULTS: The number of motor units and peak CMAP amplitudes were significantly reduced in patients with NSVN (P = .003 and P = .004, respectively). Absolute median motor unit amplitudes and CMAP discontinuities were not significantly different (P = .246 and P = .1, respectively). CMAP discontinuities were not significantly correlated with motor unit loss (P = .15, rho = 0.4). The number of motor units did not correlate with clinical scores (P = .77, rho = 0.082). DISCUSSION: Both MUNE and CMAP amplitudes showed motor involvement in upper extremity muscles in lower limb-predominant NSVN. Overall, there was no evidence of significant reinnervation. Investigations of the abductor pollicis brevis muscle did not show a correlation with overall functional disability of the patients.

Amyloidogenicity assessment of transthyretin gene variants.

OBJECTIVE: Hereditary transthyretin-mediated amyloidosis is a treatable condition caused by amyloidogenic variants in the transthyretin-gene resulting in severe peripheral neuropathy or cardiomyopathy. Only about a third of over 130 known variants are clearly pathogenic, most are classified as variants of uncertain significance. A clear delineation of these into pathogenic or non-pathogenic is highly desirable but hampered by low frequency and penetrance. We thus sought to characterize their amylogenic potential by an unbiased in vitro approach. METHODS: Thioflavin T and turbidity assays were used to compare the potential of mammalian cell expressed wt-transthyretin and 12 variant proteins (either variants of uncertain significance, benign, pathogenic) to aggregate and produce amyloid fibrils in vitro. As proof of principle, the assays were applied to transthyretin-Ala65Val, a variant that was newly detected in a family with peripheral neuropathy and amyloid deposits in biopsies. In silico analysis was performed to compare the position of the benign and pathogenic variants. RESULTS: Transthyretin-Ala65Val showed a significantly higher amyloidogenic potential than wt-transthyretin, in both turbidity- and Thioflavin T-assays, comparable to known pathogenic variants. The other eight tested variants did not show an increased amyloidogenic potential. In silico structural analysis further confirmed differences between pathogenic and benign variants in position and interactions. INTERPRETATION: We propose a biochemical approach to assess amyloidogenic potential of transthyretin variants. As exemplified by transthyretin-Ala65Val, data of three assays together with histopathology clearly demonstrates its amyloidogenicity.

Clinical management of chronic inflammatory demyelinating polyneuropathy (CIDP) in Europe and India: An exploratory study.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an autoimmune disorder causing inflammatory demyelination of peripheral nerves and consecutive disability. Diagnostic criteria and treatments are well established, but it is unknown how clinical practice may differ in different geographical regions. In this multicentre study, clinical management of CIDP was compared in 44 patients from Germany, India and Norway regarding diagnostic and therapeutic procedures. All centres used EFNS/PNS diagnostic criteria for CIDP but diagnostic workup varied regarding screening for infectious diseases, genetic testing and nerve biopsy. Intravenous immunoglobulin and prednisolone were the most common therapies in all centres with differences in indication and dosage. Patients from the Indian cohort were the most severely affected with less diverse therapeutic approaches, whereas psychological strain did not differ significantly from the two other cohorts. Our exploratory study discloses an unaddressed issue in management of CIDP that should be further investigated to optimise standard of care for CIDP worldwide.