P351 The assessment of repeater F-waves in patients with amyotrophic lateral sclerosis

Objectives Repeater F-waves (Freps) were seen in patients with amyotrophic lateral sclerosis (ALS). The factors implicated for the presence and frequency of Freps were loss of the motor neurons and the changes in their excitability. The aim of this study was to assess the Freps in ALS patients and to compare their frequencies in thenar and hypothenar muscles. Methods Sixteen ALS patients and 11 healthy controls were recruited to the study. All patients had ⩾2 mV CMAPs recorded from the hand muscles. Ninety F-waves were recorded from abductor digiti minimi (ADM) and abductor pollicis brevis (APB). The index of repeater neurons (RN) and Freps were calculated. Results Mean index RN and index Freps values of ADM and APB muscles in ALS group (17.1 and 42.6 for ADM and 16.3 and 41.9 for APB) were significantly higher than those of healthy controls (4.7 and 13.9 for APB and 1.5 and 3.6 for ADM). ALS group had a lower persistence of F-waves for both muscles than healthy controls (56.4 and 94.6 for APB and 83.4 and 97.0 for ADM). Freps parameters were not different between thenar and hypothenar muscles, whereas persistence of F-waves was lower in the thenar (56.4%) as compared to the hypothenar (83.4%) muscles. Discussion Similar Freps parameters in the thenar and hypothenar muscles might be caused by the inclusion criteria. Lower F-persistence in the thenar muscles was in accordance with the split-hand phenomenon. Conclusion The assessment of Freps and F persistence may be useful in understanding of the electrophysiological changes in ALS.