The aims of this study were to investigate the electrophysiological features of hemifacial spasm (HFS) and post-facial paralysis synkinesis (PFPS) that contribute to differential diagnosis.

This study was designed as a retrospective analysis, focusing on 132 patients diagnosed with HFS and 78 patients with PFPS between May and October 2023. Patient data were collected from existing medical records. The study aimed to analyze pre-existing electrophysiological data, including abnormal muscle response (AMR) and facial synkinesis, focusing on parameters such as AMR latency, amplitude, and duration.

In the HFS group, AMR could be induced in all patients, with synkinesis present in 31.8 %. In the PFPS group, AMR and synkinesis were induced in 79.5 % and 100 % of patients, respectively. Compared with the PFPS group, the HFS group had a shorter AMR latency and higher amplitude (P < 0.05). The duration of the AMR did not significantly differ between the two groups (P > 0.05). Synkinesis in the HFS group was typically accompanied or followed by an involuntary spasm episode, but not every eye closure or pouting led to synkinesis. In contrast, synkinesis in the PFPS group occurred with every voluntary movement and was synchronized with these movements.

Patients with HFS and PFPS may exhibit similar clinical symptoms. Neurophysiological tests, particularly electromyography, provide valuable information for the differential diagnosis of HFS and PFPS.