Hemifacial spasm is a paroxysmal unilateral spastic contraction of facial muscles caused by various irritating effects on the central intracranial area of the facial nerve. It is diagnosed according to the peculiarities of clinical symptoms, the characteristic pattern of electromyography. The etiology is determined by magnetic resonance imaging of the brain and cerebral vessels. Conservative (pharmacotherapy, botulinum toxin administration) and operative (decompression of the nerve trunk, removal of nerve compression formations) techniques are used in the treatment.
G51.3 Clonic hemifacial spasm
The term “hemifacial” means “affecting half of the face.” Hemifacial spasm (HFS) was first described in 1975. A detailed description of the disease was given in 1894 by the French neurologist E. Brissot, in connection with which a synonymous name is found in literary sources on neurology — Brissot’s disease. Hemifacial spasm is diagnosed with a frequency of 0.8 cases per 100 thousand population, mainly at the age of 40-50 years. Women get sick 2 times more often than men. Among persons of the Mongoloid race, the incidence is higher, due to the peculiarities of the anatomy of the skull. Bilateral hemifacial spasm is observed in exceptional cases.
The disease develops due to irritation of the root of the facial nerve coming out of the brain stem. Recent studies have shown that, along with the typical localization of the irritation zone at the outlet of the root, pathological effects on the nerve are possible throughout its central segment. The main etiofactors causing adverse effects on the facial nerve are:
- Neurovascular conflict. It occurs with a special anatomical interposition of the nerve root and nearby arteries (lower cerebellar, basilar, vertebral). Close contact of the nerve trunk with the arterial wall causes its irritation due to vascular pulsation. Excessive excitation of nerve fibers causes hyperinervation of the muscles of the corresponding half of the face.
- Cerebral vascular aneurysms. Aneurysmal vasodilatation of the cerebellar zone has a compressive effect on the facial nerve. As a result, there is an overexpression of nerve fibers, provoking the occurrence of pathological impulses in the area of facial muscles.
- Brain tumors. Neoplasms of the cerebellar angle with their mass can squeeze the facial spine. As a result, excessive excitatory impulses go along the nerve to the muscles of the face, leading to a spasm.
- The focus of demyelination. The spread of the process of destruction of myelin on the trunk of the facial nerve causes the transition of excitation from one nerve fiber to another. An increased impulse is formed, provoking a muscle spasm.
- Lacunar infarction zone. At the site of the ischemic site, a small cavity — lacuna is formed, which has an irritating effect on the facial spine. Overexpression of the nerve entails a violation of the innervation of the facial muscles, their spastic state.
The tone of the facial muscles changes under the influence of efferent impulses traveling along two facial nerves, each of which is responsible for the innervation of the homolateral half of the face. Irritating effects on the nerve trunk cause overexcitation of its fibers with an increase in efferent impulses, leading to spastic contraction of the corresponding muscles. In the pathogenesis of neurovascular conflict, arterial hypertension and progressive atherosclerosis play a special role, causing thickening of the arterial wall, the formation of vascular tortuosity. Since the roots of several cranial nerves come out of the trunk in the cerebellar region, the pathological processes of this localization can provoke irritation of two or more nerve trunks at the same time. As a result, hemifacial spasm is sometimes combined with pathology of the auditory nerve, trigeminal neuralgia.
The division of facial hemispasm into two etiological forms has historically developed due to insufficient knowledge of the etiopathogenetic mechanisms of pathology. The introduction of neuroimaging diagnostic methods allowed to identify the cause of the idiopathic form of the disease, but the separation remained. According to the etiology, hemifacial spasm is classified into:
- Primary — caused by neurovascular conflict. Previously, primary hemispasm was considered idiopathic (having no established cause).
- Secondary — caused by the compressive effect of volumetric formation (aneurysms, tumors, lacunae), demyelinating process.
The features of the clinical picture associated with the sequence of involvement in facial muscle spasm formed the basis of the clinical classification. Clinically distinguished:
- Typical HFS — spastic paroxysm begins with individual contractions of the circular muscle of the eye. It is characteristic of the primary form.
- Atypical HFS — spasm occurs in the cheek muscles, spreads to the periorbital region, forehead. It occurs in the secondary form.
In the classic (typical) version, a spastic attack starts with contractions of the muscle located around the eye. There are separate shutting of the eye, the frequency of which increases. Gradually, spastic contractions spread to all the muscles of one half of the face. The squeezing becomes so frequent that the patient loses the ability to see with the affected eye. Atypical hemifacial paroxysm begins with the cheek muscles, then the spasm covers the muscles of the lips, periorbital zone and forehead. Muscle contractions are painless, occur suddenly.
A hemifacial attack is provoked by psycho-emotional stress, overwork. Unlike other hyperkineses that disappear during sleep, hemifacial spasm can be observed in a sleeping patient. The symptom of Babinsky’s synkinesia is considered pathognomonic: on the side of the lesion, the closing of the eyelids is accompanied by raising of the eyebrow, which is due to the simultaneous contraction of the circular muscle of the eye and the frontal muscle of the forehead.
The disease has a chronic course, accompanied by the gradual formation of moderate paresis of the facial muscles. In some cases, HFS is combined with pathology of other cranial nerves. 5% of patients have trigeminal neuralgia, 15% have hearing loss of varying severity due to damage to the auditory root. Some patients complain of noise in the ear from the affected side, which occurs due to the involvement in spasm of the muscle that moves the auditory bones.
Without posing a serious danger to health, HFS significantly worsens the quality of life of the patient. The main complications are psychological in nature, associated with psycho-emotional discomfort experienced by patients due to the occurrence of an aesthetic defect. The disease restricts social activity, is an obstacle in professional activity, and can cause depression. In 60% of patients there is a deterioration of visual function.
Hemifacial spasm is diagnosed by a neurologist according to clinical data: the nature of seizures, the presence of synkinesia symptoms, the presence of paroxysms during sleep. The absence of other neurological symptoms is important. Patients with hearing impairment need to consult an otolaryngologist. In order to confirm the diagnosis, establish the etiology of HFS, additional studies are being conducted:
- Electromyography. Two types of myographic patterns characteristic of HFS are described. A pathognomonic sign is the phenomenon of abnormal muscle response — when one of the branches of the facial nerve is electrically stimulated, the muscles innervated by its other branches contract.
- MRI of the brain. Allows you to diagnose the cause of root compression: tumor, focus of demyelination, vascular malformation, lacuna. According to MRI data, it is possible to judge the primary or secondary nature of HFS.
- Cerebral MR angiography. It is performed in addition to brain MRI to visualize neurovascular conflict. The detectability of the latter depends on the caliber of the conflicting vessel: for large vessels it is 100%, for smaller vessels it is 76%.
It is necessary to differentiate HFS from idiopathic blepharospasm, the initial manifestations of which are often unilateral. The main distinguishing feature is the location of the eyebrow with spastic closing of the eyelids: with HFS, the eyebrow is raised, with blepharospasm, it is drawn into the eye socket. Differential diagnosis is also performed with facial myokemia, psychogenic spasm, paroxysms of focal epilepsy.
Hemifacial spasm treatment
It is possible to use conservative and neurosurgical techniques. Conservative therapy is carried out for a long time, and therefore leads to side effects. Neurosurgical treatment allows to radically eliminate the cause of the disease, but does not exclude recurrence.
- Pharmacotherapy. It is carried out by antiepileptic drugs (carbamazepine, levetiracem, clonazepam), muscle relaxants (baclofen). The long-term results of drug therapy have not been sufficiently studied, and are considered doubtful by some authors.
- Introduction of botulinum toxin. Injections of the drug are made every 3-4 months subcutaneously and intramuscularly in the area of the affected muscle groups. The method is effective in 75% of patients, gives good results at the start of therapy in the initial stages of the disease.
- Microvascular decompression. It is carried out with neurovascular conflict. The operation consists in separating the nerve trunk and the vessel with a Teflon protector at the point of their contact. The main postoperative complications are dysfunction of the vestibulocochlear nerve (2-3%), facial paresis (3.5-4.8%), often of a transient nature.
- Surgical treatment of aneurysms. It is performed by clipping the aneurysm neck or its endovascular occlusion. It prevents the rupture of the thinned vascular wall at the point of protrusion, leading to intracerebral hemorrhage.
- Removal of a cerebral tumor. It is made with the help of microsurgical equipment. The volume of the operation depends on the size and type of neoplasm, it is corrected intraoperatively according to the results of histological examination.
Prognosis and prevention
Hemifacial spasm is characterized by a chronic course. There are cases of spontaneous regression of symptoms, amounting to 10%. Relapses of the primary form of the disease after microvascular decompression, according to various data, reach up to 20%. The prognosis of the secondary form depends on the cause of the pathology. There is no specific prevention. Prevention of vascular changes that contribute to the occurrence of neurovascular conflict includes measures to prevent hypertension and atherosclerosis.