Diagnosis for Hemifacial Spasm
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, including magnetic resonance imaging (MRI), computed tomography (CAT scan), or even angiography (arteriography), 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. 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. 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.

The more permanent treatment for hemifacial spasm, and the preferred treatment 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.