OBJECTIVETo identify whether there is significant changes between the cervical neutral F-waves and cervical flexion F-waves in the patients with Hirayama disease.

METHODSThis study was performed on 25 normal subjects and 22 male patients with identified Hirayama disease (age: 15 to 44 years; height: 165 to 183 cm; duration: 6 to 240 months) between May 2010 and March 2014. Both cervical flexion F-wave (cervical flexion 45 °, 30 minutes) and conventional F-waves to median nerve stimulation and to ulnar nerve stimulation were performed in all subjects bilaterally.

RESULTSwere analyzed by t-test or Fisher exact probability.

RESULTSIn the normal subjects, all measurements of the bilateral F-waves didn't have any difference between the cervical flexion position and the cervical neutral position. On the cervical neutral position, the persistence (t = 5.209, P = 0.000), average latencies (t = 4.731, P = 0.022) and minimal latencies (t = 23.843, P = 0.006) of ulnar F-wave on the symptomatic heavier side from the patients with identified Hirayama disease were significantly lower or longer than those from the normal subjects, and the repeat F-waves were found in 3 patients (13.6%). On the symptomatic lighter side, the ulnar F-waves only had lower persistence (t = 22.306, P = 0.001) along with 5 repeat F-waves. Only lower persistence were found in the median F-wave on the both side (higher side t = 23.696, P = 0.000; lighter side t = 23.998, P = 0.000), along with 5 (22.7%) repeat F-waves on the symptomatic heavier side and 6 (27.3%) ones on the symptomatic lighter side. After cervical flexion maintaining 30 minutes, the increased maximal amplitudes (t = -2.552, P = 0.019), average amplitudes (t = -3.322, P = 0.003), duration (t = -3.323, P = 0.00), persistence (t = -2.604, P = 0.017) and frequency of repeat F-waves (9/22, 41%) (P = 0.044) were found on the symptomatic heavier side of ulnar F-wave, and 5 of 10 absent ulnar F-wave on the cervical neutral position were also recover. The median F-wave on the symptomatic heavier side mainly had increased maximal amplitude (t = -3.847, P = 0.001), average amplitudes (t = -2.188, P = 0.040) and persistence (t = -2.421, P = 0.025), and 1 of 6 absent median F-wave on the cervical neutral position were also recover after cervical flexion.

CONCLUSIONThe cervical flexion F-waves have significant regular changes compared to the cervical neutral F-waves in patients with Hirayama diseases, especially maximal and average amplitudes of F-waves.