Hemifacial spasm is usually diagnosed by its symptoms – the characteristic tic is the best evidence of the diagnosis. An expert evaluation of a patient must include testing for the presence of a tumor or a vascular malformation, or for multiple sclerosis. When those conditions are ruled out, the assumption is that the hemifacial spasm is being caused by a small blood vessel pressing on the seventh cranial nerve at the brainstem.
The usual diagnostic imaging tools included magnetic resonance imaging (MRI), computed tomography (CAT scan), or, rarely, angiography (arteriography). They are not completely effective in locating the source of the nerve irritation, since the blood vessel causing the pressure is often too small to be seen on those scans. New FIESTA (fast imaging employing steady-state acquisition) MRI imaging has significantly increased our ability to visualize the offending blood vessel. If those scans do not show a tumor or lesion, however, the presumed cause is pressure from a blood vessel.
Initial treatment of hemifacial spasm usually consists of injections of botulinum toxin (Botox), which causes a small, partial paralysis of the muscle and stops the spasm. The paralysis is temporary, so injections need to be repeated approximately every six months. Botulinum toxin alters the facial muscles, and with long-term use may result in flattening of the face on the treated side. An accurate diagnosis is critical to successful treatment, so Botox injections should not be given until imaging scans and other testing rule out the presence of a tumor or lesion (see Doctors Who Treat Hemifacial Spasm).
The more permanent and preferred treatment for hemifacial spasm in more severe cases is a surgical procedure called microvascular decompression. This procedure is a highly effective microsurgery procedure that involves repositioning the artery that irritates the nerve as it comes out of the brainstem. Relief is usually immediate (see Surgery for Hemifacial Spasm).
Reviewed by: Philip E. Stieg, PhD, MD
Last reviewed/last updated: April 2021