Utility of stimulus induced after discharges in the evaluation of peripheral nerve hyperexcitability: Old wine in a new bottle?

Limited literature is available on stimulus induced after discharges (SIAD) in patients with peripheral nerve hyperexcitability (PNH). The aim of the study was to examine the diagnostic utility of SIAD in the diagnosis and monitoring of primary PNH disorders. In this retrospective study, we studied 26 patients who were admitted with a diagnosis of primary PNH to the department of Neurology from January 2013 to April 2019. Their clinical profile, immunological characteristics were extracted from the database and nerve conduction studies were relooked for the presence of SIAD. 76% of patients in the primary PNH cohort had SIAD with 90% of them being voltage-gated potassium channel complex antibody positive; predominantly against contactin-associated protein-2 antigen and rest being paraneoplastic. There was also resolution of SIAD following treatment indicating reversible hyperexcitability. SIAD is a sensitive marker for Primary PNH syndrome with monitoring and diagnostic implications.