Objective To investigate the involvement of posterior auricular muscle (PAM) and the effect of botulinum toxin type A (BTX-A) injection into PAM in patients with hemifacial spasm (HFS)complicated by auricular symptoms.Methods Sixty-three consecutive HFS patients with auricular symptoms such as tinnitus or murmur,"ticking" or a "clicking" sound and discomfort on the same side,referred to our department between July,2009 and January,2010,were enrolled,and the diagnosis of idiopathic HFS was clinically made.The patients were largely randomized into two groups according to the order of referral.One was regular group including 33 cases whose injection sites were routinely at the frontal,orbicularis oculi,zygomaticus and buccinator muscles while another was PAM group including 30 cases,in which 4 units of BTX-A was additionally injected to the PAM.Before and after injection,the test of blink reflex was performed and lateral spread of blink reflex to orbicularis oris(OO)and PAM,I.e.Abnormal muscle response(AMR),were recorded,and the peak-peak amplitude of AMR was measured.The patients were followed up clinically and electrophysiologically at least 4 weeks((29.5±2.5)days) later.Results(1)The patients reported that their auricular symptoms subsided after injection in both groups.The remission rate was 45.5%(15/33)in the regular group and 76.7%(23/30)in the PAM group,respectively,with a higher rate in the PAM group(x2=6.40,P=0.011).(2)In both groups the AMR amplitude decreased significantly after injection.In the regular group,the OO amplitudes (μV) before and after injection were 304.0±30.3 and 129.3±9.6(t =5.820,P =0.000),and PAM amplitudes,298.0±33.3 and 184.7±20.2(t=2.818,P=0.014),respectively.In the PAM group,OO amplitudes were 405.3±66.7 and 116.0±10.0(t=4.214,P=0.001),PAM amplitudes,390.0±53.6 and 72.0±9.7(t=6.011,P=0.000),respectively.(3)The decrease of PAM amplitudes in the PAM group was more significant compared with those in the regular group (t=4.237,P=0.001).Conclusions In HFS patients with auricular symptoms,the electrophysiological studies are helpful for the guidance of treatment;and the auricular symptoms could be better improved after BTX-A injection into PAM in addition to those regular injection sites.