The imaging features of neurovascular compression in hemifacial spasm patients

Neurovascular compression is considered the main cause of primary hemifacial spasm. However, it also occurs on the asymptomatic facial nerves in primary hemifacial spasm patients and in healthy controls. This study aimed to compare neurovascular compression features among the three groups: the facial nerves on the symptomatic and asymptomatic sides in primary hemifacial spasm patients, and the bilateral facial nerves in healthy controls. Magnetic resonance imaging features of the facial nerves were retrospectively analyzed in 181 primary hemifacial spasm patients and 88 age- and sex-matched healthy controls. The assessed neurovascular compression features included presence, number, location, severity, direction, and offending vessels. Logistic regression analysis was performed to evaluate the associations between these features and the presence of spasm symptoms. Neurovascular compression was present on the symptomatic side in 98.34% of primary hemifacial spasm patients ( P < 0.001). Among these neurovascular compressions, 96.13% were located in the susceptible segment ( P = 0.027), and 34.25% were in the most-sensitive segment ( P < 0.001). These proportions were significantly higher than those observed on the asymptomatic side and in healthy controls. Similar differences were observed in the number, direction, and severity of neurovascular compression. Neurovascular compressions in the susceptible and most-sensitive segments were positively associated with the presence of spasm symptoms, particularly in the susceptible segment. In contrast, grade 1 compression was negatively associated with spasm symptoms. Neurovascular compression located in the susceptible and most-sensitive segments was positively associated with the presence of spasm symptoms, whereas grade 1 compression was associated with lower odds of spasm symptoms. Anatomical subdivision of the root entry/exit zone of the facial nerve could improve clinical imaging assessment of neurovascular compression features.