Hemifacial Spasm

Conflitti Neuro-vascolari

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Definition and Etiology

Neurovascular conflicts include a set of syndromes caused by the compression of cranial nerves, in general in correspondence with their entry point into the brainstem (root entry zone or REZ).

The REZ is the point in which the sheath (myelin) of central origin (oligodendrocytes) transforms into peripheral myelin (Schwann cells).

Hemifacial spasm is a disorder characterised by a unilateral, involuntary and intermittent contraction of the facial muscles.

The facial nerve controls the muscles of facial expressions (forehead, eye, neck, and cheeks).

Initially, the hemifacial spasm can affect the eyelids with small blinking movements, which can however lead to a more continuous spasm with persistent eye closure. In other cases, the spasm can initiate in the forehead or lower part of the face. A hemifacial spasm starting from the lower part of the face has the distinctive characteristic of deviating the mouth.

Occasionally the spasm can involve the surface muscles on the front of the neck.

The main cause is related to the pulsations of a blood vessel coming into contact with the nerve on the point in which the facial nerve emerges from the brainstem.

The contact (conflict) between the blood vessel and the nerve irritates the latter and determines the spasm.

However, other causes can be a tumor or any other kind of process taking up space close to the nerve or an anomaly in the brainstem.

Symptoms

Symptoms usually affect one side of the face. Hemifacial spasm generally starts with a gradual progression until it reaches stability and rarely deteriorates. Often hemifacial spasm occurs during sleep.

The disorder generally affects people over 40 years of age and is more frequent in women. In most cases, it occurs spontaneously and is only rarely the consequence of a facial trauma.

Factors that may aggravate this disorder are: stress, fatigue, driving, intense light, watching TV or reading.

Diagnosis

Performing a brain Magnetic Resonance (MRI) is indicated in people who present these symptoms, both to rule out the presence of lesions taking up space, and to document the possible conflict.

Treatment

Conservative treatment

Two types of therapy can be performed: oral medical therapy and local injection of drugs.

Oral therapy

Oral pharmacological therapy to treat hemifacial spasms has proven to be scarcely effective. The most commonly used drugs are: Carbamazepine, Phenytoin, Baclofen, and Clonazepam. All these medicines, however, present side effects such as mental confusion, memory disorders, and sedation. Carbamazepine can furthermore alter the hematochemical and hepatic function. Moreover, these treatments are not very effective.

Local infiltrative treatment

The most effective treatment for hemifacial spasms is injecting botulinum toxin. In most subjects affected by hemifacial spasm, a treatment with botulinum toxin can be effective.

The botulinum toxin is injected directly into the muscle affected by the spasm or under the skin, on the surface of the muscle. The toxin paralyses the muscle partially and relaxes it thereby reducing, or at times even eliminating, the spasms.

However, the effect is temporary, from 3 to 6 months, after which the treatment needs to be repeated.

There are potential, albeit infrequent, side effects such as skin irritation on the site of the injection, a burning sensation during the injection itself, and excessive muscle weakness. Excessive hyposthenia (reduction of strength) of the periocular muscles can lead to a temporary difficulty in closing an eye or lowering an eyelid. This will require the instillation of eye drops. Other side effects include double vision or the appearance of scotomas (seeing dark spots).

If the muscle weakness affects the lower part of the face, a facial asymmetry may appear (deviation of the mouth).

All these complications are temporary and do not require any specific treatment.

Surgical treatment

While the oral medical therapy and the local administration of botulinum toxin merely control the symptoms of the pathology, surgical therapy, on the contrary, can cure the cause.

Vascular decompression performed with microsurgery is a neurosurgical methodology consisting in distancing the blood vessel from the facial nerve by placing a small foam swab between them to prevent contact.

In this manner, by eliminating the adherence between the nerve and the blood vessel, 85% of all cases lead to a total cure of the spasms. Often the improvement is gradual (a few days). Relapses are rare and can benefit from a second procedure.

The main complications of the procedure are the reduction (or loss) of hearing and a possible paresis of the facial nerve (both events are very rare with an incidence of 3-5%).

Age, other concomitant diseases, and the severity of the hemifacial spasm are other elements used to establish if a patient can be subjected to this procedure or not.

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