Objective:To analyze the diagnostic value of preoperative electromyography and spasticity assessment for patients with hemifacial spasm, and to define a relationship between intraoperative electrophysiological examination and prognosis in order to provide help for clinical diagnosis and treatment.Methods:Thirty-one patients with hemifacial spasm were selected for the clinical spasticity scoring and divided into a general spasm group ( n=27) and a severe spasm group ( n=4). All received preoperative neurophysiological examination to record their twitch discharge, facial nerve conduction velocity (MCV), lateral spread (LSR) of the spasm, brainstem auditory evoked potential (BAEP), and blink reflex. Electrophysiological monitoring then recorded intraoperative LSR. According to whether the LSR disappeared or not, the patients were divided into the LSR disappearance group (of 15) and the LSR residual group (of 16), and facial muscle activity was recorded again one, three and six months after the operation. Results:Preoperative EMG examination of both groups showed positive LSR and that facial nerve MCV was within the normal range. There were, though, significant differences between the two groups in the twitching discharge by needle electromyography, blink reflex and preoperative BAEP. One week after the operation, one member of the residual group and 3 from the disappearance patients of the former and latter group had recovered in terms of LSR, with 3 and 7 cases significantly relieved, respectively. Two months later, the corresponding figures were 5 and 7, 3 and 6, respectively. Half of a year after the surgery, 5 from the residual group and 12 from the disappearance group had fully recovered in terms of LSR, while 9 and 2 cases were significantly relieved. Altogether, there were significant differences within the two groups in terms of recovery among all the time points, with significantly better recovery in the LSR disappearance group than the LSR residual group at 1 week after operation, while there were no significant differences between the two groups in recovery 3 and 6 months after their operation.Conclusions:Preoperative electromyography can provide objective assessments of the scope, severity, and facial nerve excitability of patients with hemifacial spasm. Real-time intraoperative electrophysiology monitoring can help surgeons to objectively assess the effect of decompression and to find and avoid nerve traction injury in surrounding areas quickly.