Diagnostic utility of F waves in cervical radiculopathy: electrophysiological and magnetic resonance imaging correlation

OBJECTIVE: F wave study is a simple, non-invasive method commonly utilized for evaluation of cervical root lesions. Its diagnostic sensitivity is low. There are no large series comparing F wave studies with MRI as a reference standard. PATIENTS AND METHODS: We performed F wave studies in 30 controls (15 men; mean age: 50 years; standard deviation: 17.9 years; range: 21-80 years) and, prospectively, 31 patients (19 men; mean age: 48 years; standard deviation: 16.2 years; range: 26-79 years) referred for evaluation of cervical spondylotic radiculopathy (CSR). All patients' MRIs were compared with F wave parameters. RESULTS: Combined utilization of minimal F latency, F chronodispersion, F persistence and side to side differences resulted in 55% sensitivity and 100% side concordance for detecting CSR, with MRI as a comparison standard. F wave parameters also provided complementary information to needle electromyography in the diagnostic evaluation of CSR. Although F waves were not indicative of radiculopathy levels, 4/31 (13%) of cases had at least one abnormal F wave parameter, despite normal electromyography findings. CONCLUSIONS: Combined utilization of multiple F wave parameters is a useful, diagnostic adjunct in the electrophysiological evaluation of CSR.