Citations

ABSTRACT Introduction/Aims The clinical significance of stereotyped post‐F‐wave discharges remains uncertain. We aimed to characterize F‐wave‐induced repetitive discharges (FIRDs) and their associated clinical and electrodiagnostic findings. Methods We searched the Mayo Clinic electrodiagnostic database (January 1997–December 2025) using “F‐wave” and “repetitive discharges” and reviewed retrieved waveforms. FIRDs were defined by repetitive discharges following F‐wave activation, reproducible morphology within a train, and regular or semiregular firing. Results The study included 20 patients with FIRDs (median age 61 years, range 21–83 years; 10 male). Routine motor conduction attributes were normal in 90% of patients and F‐wave latencies were normal in all. FIRDs consisted of brief, reproducible discharges with a regular or semi‐regular firing pattern, individual durations of 2–10 ms, firing frequencies of 100–500 Hz, and amplitudes of 120–1000 μV. Neurogenic abnormalities on needle electromyography were seen in the distribution of the FIRD nerve in 65%. FIRDs were transient in a subset of patients who had repeat studies (5/5). Clinical and electrophysiological diagnoses included peripheral neuropathy (30%), radiculopathy (25%), polio (5%), brachial plexopathy (5%), and chronic inflammatory demyelinating polyradiculoneuropathy (5%). Six patients (30%) had no clinical or electrophysiological evidence of a neuromuscular disorder. Discussion FIRDs represent an uncommon electrophysiological phenomenon seen in both chronic neurogenic disorders and patients without neurologic disease. Recognition may aid waveform interpretation, but their presence alone does not establish a specific neuromuscular diagnosis.