F-wave
Late response in nerve conduction studies representing antidromic activation of motor neurons.
Full Definition
The F-wave is a late electrophysiological response recorded during nerve conduction studies that occurs when an electrical stimulus travels antidromically (backward) along a motor axon to the anterior horn cell and then orthodromically (forward) back to the muscle. This response appears 25-35 milliseconds after the direct motor response (M-wave) and represents the integrity of the entire length of the motor pathway. F-waves are particularly useful for detecting proximal nerve pathology that might be missed by standard distal nerve conduction studies, such as radiculopathies or proximal neuropathies.
Usage
Usage note: Hyphenate when used as an adjective (F-wave latency) but not when used as a noun (the F wave).
In Context
- "F-wave latencies were prolonged bilaterally, suggesting proximal conduction abnormalities." — Nerve conduction study report
- "The F-wave was absent on the affected side, indicating severe axonal loss." — Electrophysiology findings