hemifacial

Hemifacial is an anatomical and medical term meaning related to one side of the face. It is used as a descriptive qualifier for conditions that predominantly affect the left or right half of the face. The most commonly referenced examples are hemifacial spasm and hemifacial microsomia.

Hemifacial spasm is characterized by involuntary, intermittent contractions of the muscles on one side of the face. Onset is typically in adulthood, often starting around the eye and sometimes spreading to the cheek or mouth. The most common cause is irritation or compression of the facial nerve (cranial nerve VII), usually by a nearby blood vessel; less often, tumors, demyelinating disease, or other structural abnormalities contribute. Diagnosis is clinical and is supported by imaging, such as magnetic resonance imaging, to exclude secondary causes. Treatment options include botulinum toxin injections to reduce muscle activity; medications such as anticonvulsants may help some patients. When medication and injections fail or are unsuitable, microsurgical microvascular decompression to relieve nerve compression can provide lasting relief. The course is variable; some individuals experience years of symptoms, while others have progressive improvement with treatment.

Hemifacial microsomia is a congenital condition in which tissues on one side of the face fail to develop normally, causing asymmetry of the jaw, cheek, ear, or orbit. It is usually unilateral and ranges from mild to severe. The exact cause is not fully understood but involves disruption of early embryologic development of the first and second pharyngeal arches. Management is multidisciplinary and tailored to severity, often including jaw reconstruction, ear repair or hearing support, dental alignment, and, in some cases, facial reanimation. With appropriate care, many patients achieve functional and aesthetic outcomes, though effects vary by severity.