What Is Hemifacial Spasm And How Is It Diagnosed?

Hemifacial spasm is a neurological movement disorder that causes involuntary twitching or contractions on one side of the face. It most commonly affects the muscles around the eye before potentially spreading to other muscles on the same side of the face.

Although hemifacial spasm is not usually harmful in itself, the repeated involuntary movements can be disruptive and may affect everyday activities, confidence and quality of life.

Getting an accurate diagnosis is important because several conditions can cause facial movements or twitching.

What causes hemifacial spasm?

Hemifacial spasm is often associated with irritation or compression of the facial nerve, also known as the seventh cranial nerve.

In many cases, a nearby blood vessel comes into contact with the facial nerve where it leaves the brainstem. This can interfere with the nerve's normal function and contribute to involuntary contractions of the facial muscles.

Less commonly, hemifacial spasm can have other causes. This is why specialist assessment and appropriate imaging can be important when symptoms develop.

What does hemifacial spasm feel like?

The main characteristic is involuntary movement affecting one side of the face. It often begins with intermittent twitching around one eye. Over time, contractions may involve other areas supplied by the facial nerve, including the cheek, mouth or jaw.

The spasms can vary in frequency and intensity. They may occur occasionally at first and become more noticeable over time.

Importantly, facial twitching does not automatically mean someone has hemifacial spasm. Benign eyelid twitching and other movement disorders can produce similar symptoms, while facial movements can occasionally have different neurological causes.

How is hemifacial spasm diagnosed?

Diagnosis generally starts with a detailed clinical assessment.

Medical and symptom history

A specialist will ask about when the facial movements started, which areas are affected and how frequently the spasms occur. They may also ask whether the movements have changed over time and whether they are consistently restricted to one side.

A neurological history can help identify features that distinguish hemifacial spasm from other causes of facial movement.

Neurological examination

A neurological examination allows the specialist to observe the facial movements and assess the function of the facial nerve and other cranial nerves.

The pattern of involuntary contractions can provide important clues. In classic hemifacial spasm, the movements follow the distribution of the facial nerve and remain predominantly on one side.

MRI scanning

Magnetic resonance imaging (MRI) is commonly used when investigating suspected hemifacial spasm.

An MRI can provide detailed images of the brain and the structures around the facial nerve. Specialist imaging may help identify whether a blood vessel is contacting or compressing the nerve.

Is hemifacial spasm the same as blepharospasm?

Hemifacial spasm and blepharospasm can both cause involuntary movements around the eyes, but they are different neurological conditions.

Blepharospasm generally involves involuntary contractions of the muscles around both eyes, although the presentation can vary. Hemifacial spasm typically affects one side of the face and can extend beyond the eye to other facial muscles.

Distinguishing between these conditions is important because their underlying mechanisms and treatment approaches can differ.

When should you see a specialist?

Occasional eyelid twitching is common and can have many temporary causes. However, persistent or progressively frequent involuntary facial movements, particularly when they consistently affect one side of the face, should be assessed by a healthcare professional.

Specialist assessment can help establish whether the symptoms are consistent with hemifacial spasm and whether further imaging is appropriate.

What happens after a diagnosis?

Treatment depends on the severity and pattern of symptoms, the underlying cause and the individual's circumstances.

For some patients, hemifacial spasm treatment may focus on reducing the frequency and severity of spasms. In selected cases where facial nerve compression is identified, a neurosurgical approach may be considered.

The most appropriate treatment is therefore not determined by an MRI finding alone. Specialists consider the patient's symptoms, examination, imaging and overall clinical picture before recommending a treatment pathway.

Hemifacial spasm can sometimes be mistaken for other causes of facial twitching. A careful clinical assessment can help establish an accurate diagnosis and identify whether the facial nerve is being affected by an underlying structural cause.

For patients experiencing persistent unilateral facial spasms, specialist neurological assessment can provide greater clarity about what is causing the symptoms and which treatment options may be appropriate.

Explore Queen Square's specialist neurological services to learn more about the diagnosis and treatment of complex cranial nerve conditions, including hemifacial spasm.