Peripheral nerve hyperexcitability syndrome: A clinical, electrophysiological, and immunological study

Peripheral nerve hyperexcitability syndrome (PNHS) is characterized by muscle fasciculations and spasms. Nerve hyperexcitability and after-discharges can be observed in electrophysiological studies. Autoimmune mechanisms play a major role in the pathophysiology of primary PNHS.We retrospectively conducted a case-control study recruiting patients with clinical and electrophysiological features of PNHS. Control patients were diagnosed with other neuronal or muscular diseases. Contactin-associated protein2 (CASPR2) and leucine-rich glioma-inactivated1 (LGI1) antibodies were examined.A total of 19 primary PNHS patients and 39 control patients were analyzed. The most common symptoms for the case group were fasciculations (11/19) and muscle spasms (13/19). Case group patients were likely to demonstrate electrodiagnostic findings of nerve hyperexcitability (17/19) and after-discharges in the tibial nerve (19/19). We found high prevalence of CASPR2 (9/19) and LGI1 (6/19) antibodies in the case group.Primary PNHS patients were likely to show after-discharges in the tibial nerve. The pathogenesis of PNHS is autoimmune CASPR2 and LGI1 antibodies are possible pathogenic antibodies for primary PNHS.