Electrophysiological features of anti-neurofascin-155 autoimmune nodopathy: Preferential involvement of distal and proximal segments

Objective: Anti-neurofascin-155 (NF155) antibody-associated autoimmune nodopathy (NF155-AN) is associated with distinct clinical features, yet its electrophysiological characteristics remain unclear. This study aimed to identify electrophysiologic features of treatment-naïve NF155-AN. Methods: We conducted a multicenter retrospective analysis of nerve conduction data from 10 treatment-naïve patients with NF155-AN and compared them with 22 patients with seronegative chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The terminal latency index (TLI) was calculated to assess distal nerve involvement, while the intermediate segment F-ratio, a new parameter, was used to evaluate proximal nerve conduction. Results: Patients with NF155-AN more often exhibited subacute onset, sensory ataxia, tremors, and cranial nerve involvement, and were classified as atypical CIDP with poor responses to intravenous immunoglobulin and corticosteroids. Electrophysiologically, NF155-AN patients had significantly longer distal latencies in the peroneal and tibial nerves. The TLI of the ulnar, peroneal, and tibial nerves was lower, while the intermediate segment F-ratio of the ulnar and tibial nerves was higher in the NF155-AN group. Conclusions: NF155-AN patients exhibit prominent proximal and distal nerve slowing, suggesting unique patterns of nerve dysfunction distinct from seronegative CIDP. Significance: These findings provide enhanced insight into the unique electrophysiological features of NF155-AN, offering clues to its pathophysiology and aiding in differentiation from CIDP.