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Hemifacial Spasm

Many people have experienced twitching of the eyebrow, but abnormal twitching may be a symptom of hemifacial spasm (HFS), a neurological disorder characterized by involuntary, irregular contractions of the muscles on one side of the face. This condition is often referred to as "half-face spasm" as it typically affects only one side of the face, either left or right, although bilateral spasms can also occur.


Facial muscles are controlled by the seventh cranial nerve, which originates from the brainstem at the base of the skull. Hemifacial spasm often affects individuals in middle age, with a higher incidence in women than in men. The condition is caused by compression or irritation of the facial nerve at the root exit zone from the brainstem, leading to abnormal excitement of the nerve akin to an electrical short, causing involuntary twitching of the eyebrow or facial muscles.


At the onset, patients may experience uncontrollable continuous twitching or spasms of the eyelid or facial muscles, causing discomfort. As the condition worsens, one side of the face may exhibit symptoms such as eyebrow twitching, blinking, twitching of the mouth corners, and wrinkling of the skin, leading to unusual facial expressions. This can significantly affect the patient's daily life, social interactions, personal relationships, and mood.

Common causes of external pressure on the facial nerve include:

  1. Vascular Compression: The primary cause of facial muscle spasms is compression of the facial nerve by blood vessels near the brainstem. This could be due to varicosities formed by cholesterol deposits or degeneration of the vertebral or microcirculatory vessels. Alternatively, inflammation can cause blood vessels to adhere to and compress the facial nerve.

  2. Tumors: Tumors such as acoustic neuromas, cholesterol granulomas, hemangiomas, meningiomas, or epidermoid cysts can compress the facial nerve, causing symptoms.

Diagnostic methods include:

  1. Facial Muscle EMG (Electromyography): Measures and records the electrical activity of facial muscles during relaxation and contraction.

  2. Magnetic Resonance Imaging (MRI): Identifies the cause of the compression on the facial nerve.

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Treatment options include:

  1. Medication: Drugs can be effective for mild early-stage symptoms. Minor spasms may be treated with sedatives or antispasmodic medications. Doctors might start with medication for one to two weeks; if the patient responds well and prefers not to undergo surgery, or if surgery is unsuitable due to age or other conditions, medication is the first choice. However, medication is only symptomatic and not curative. Although two-thirds of patients initially find relief, they may develop tolerance, reducing the effectiveness over time. Medication can also cause side effects like confusion, drowsiness, dizziness, unsteadiness in walking, or severe sensitivity.

  2. Botulinum Toxin Injections: Targeted injection of botulinum toxin into affected facial muscles is highly effective. Botulinum toxin, a neurotoxin produced by an anaerobic bacterium, blocks the nerve impulses to muscles, preventing contractions and significantly reducing involuntary muscle movements. While safe, minor side effects such as bruising at the injection site, temporary facial droop, double vision, tearing, dry eyes, or crooked mouth may occur. These effects usually resolve within one to two weeks. However, botulinum toxin injections are not a permanent cure and require repeat treatments every three to six months.

  3. Microvascular Decompression Surgery: Retromastoid craniotomy for microvascular decompression of the facial nerve root is the most effective and definitive treatment for severe cases. This sophisticated microsurgical procedure, nearly 60 years in clinical use, is performed under general anesthesia.

The neurosurgeon operates through the space between the brain tissue and skull, placing a synthetic barrier (often Teflon) between the compressing vessel and the nerve to permanently relieve pressure. The cure rate is high, between 80-90%, with a recurrence rate of about 10% and a low risk (2%) of serious complications such as hearing loss.

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