Neurovascular compression (NVC) is typically present and more severe on the symptomatic side of the face compared to the asymptomatic side in people with hemifacial spasm.
Why this matters ?
Hemifacial spasm is characterized by involuntary painless spasms of either the left- or right-sided facial muscles and can have significant quality of life impacts. Hemifacial spasm is caused NVC of the facial nerve in most patients and commonly treated with microvascular decompressive surgery.
In patients with trigeminal neuralgia, another hemifacial condition caused by NVC, an association was found between the symptomatic side of the face and the presence and severity of ipsilateral NVC. It is possible that a similar relationship exists in people with hemifacial spasm.