Hemifacial spasm: an update on pathophysiology, investigations and management

Hemifacial spasm (HFS) is characterized by involuntary, paroxysmal contractions of muscles innervated by the facial nerve that can lead to a negative impact on daily activities, including reading or driving, as well as psychosocial well-being. HFS remains a clinical diagnosis with characteristic features, however investigations can be immensely helpful. MRI, particularly heavily weighted T2 high-resolution sequences, continues to be invaluable to assess for structural abnormalities, including the presence of neurovascular conflict (NVC) in the cerebellopontine angle. The NVC, as well as its mechanistic roles in HFS, has been better characterized in recent studies, as will be summarized in this update. We will highlight the importance of MRI reporting, as false negatives may lead to delays in neurosurgical referral, while over-reporting of incidental findings can lead to inappropriate intervention and/or treatment failure. This point is reinforced by findings from recent studies, which advocate for the use of 3D techniques to further improve MRI reporting and ultimately patient outcomes. Moreover, recent investigations have shown that botulinum toxin and microvascular decompression are highly effective treatment options for HFS and additionally suggest factors that may further influence the outcomes with these interventions. The recent use of pulse radiofrequency ablation and electroacupuncture may provide alternative avenues of treatment, alongside oral medications, that can be used in HFS but require significant refinement to improve their overall efficacy, durability and safety.