Introduction
HFS is a neuromuscular hyperactivity disorder of the facial nerve. It presents as the twitching of the musculature of facial expression, beginning with the periorbital muscles and spreading to incorporate perioral, platysma, and other facial muscles. In the vast majority of cases, this twitching takes place on just one side of the face, although bilateral manifestations occur in fewer than % of cases. HFS appears in out of 00,000 people, with a higher prevalence rate in females. The effects of HFS range from social embarrassment to functional blindness and may lead to other complications such as ocular hypertension. The disorder usually develops after the age of 40, with earlier manifestations necessitating an inquiry into possible secondary causes.,2 The disease tends to evolve progressively and seldom improves without treatment.3
HFS is commonly separated into primary and secondary forms based on its etiology. pHFS is caused by the benign compression of the facial nerve by a blood vessel in or near its root exit zon
e. The designation of secondary HFS covers several alternative sources for the same effect, including tumors, lesions, infections, and Bells palsy. The primary form of the disorder is considerably more widespread and tends to receive the most scholarly attention.,2 The pathophysiology of different forms of HFS is not yet fully understood.2 In pHFS, the conflict between the facial nerve and the offending blood vessel appears to cause hyperexcitability, generating an increased amount of action potentials that result in spasms.4 This ectopic impulse then propagates to other facial muscles.
Differential Diagnoses
The symptoms presented by the patient suggest multiple differential diagnoses that may affect the same area. In addition to pHFS, those differentials include blepharospasms, tardive dyskinesia, facial motor tics, psychogenic facial movements, focal cortical epilepsy, aberrant regeneration following damage to the facial nerve, facial myokymia, and Meige syndrome.,2,3,5 The leading possibilities to be considered in this case are: