Unilateral weakness of the facial muscles

Unilateral weakness of the facial muscles is caused by pathological processes that affect the facial (VII) nerve. All lesions of the facial innervation system can be localized at 8 levels:

1. supranuclear lesions (central facial nerve paralysis);
2. damage at the level of the nucleus and root of the facial nerve (processes in the area of the pons);
3. damage to the posterior cranial fossa (cerebellopontine angle);
4. at the entrance to the temporal bone canal;
5. in the nerve canal proximal to the origin of the n. petrosus superficialis major (to the lacrimal gland);
6. in the canal proximal to the branch that branches off to m. stapedius;
7. between n. stapedius and chorda tympani; in the canal distal to the origin of the chorda tympani;
8. damage to the nerve distal to the foramen stylomastoideum.

Among pregnant women, as well as patients with diabetes mellitus and arterial hypertension, neuropathy of the VII nerve occurs more often than in the rest of the population.

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Causes unilateral weakness of the facial muscles

The main causes of unilateral weakness of the facial muscles:

1. Idiopathic neuropathy of the VII nerve (Bell's palsy).
2. Familial forms of neuropathy of the VII nerve.
3. Infectious lesions (Herpes simplex - the most common cause; herpes zoster; HIV infection; poliomyelitis; syphilis and tuberculosis (rare); cat scratch disease and many others).
4. Metabolic disorders (diabetes mellitus, hypothyroidism, uremia, porphyria).
5. Diseases of the middle ear.
6. Post-vaccination neuropathy of the VII nerve.
7. Melkersson-Rosenthal syndrome.
8. Traumatic brain injury.
9. Tumors (benign and malignant) of the nerve trunk.
10. Diseases of connective tissue and granulomatous processes.
11. In the picture of alternating syndromes (with vascular and tumor lesions of the brain stem).
12. Basal meningitis, carcinomatous, lymphomatous and sarcomatous infiltration of the membranes.
13. Tumor of the cerebellopontine angle.
14. Multiple sclerosis.
15. Syringobulbia.
16. Arterial hypertension.
17. Diseases of the skull bones.
18. Iatrogenic forms.

The most pronounced paresis of the facial muscles is observed with peripheral damage to the facial nerve.

Cryptogenic or idiopathic neuropathies of the VII nerve

This is the most common cause. They occur somewhat more often in women in the third trimester of pregnancy (sometimes with relapses during each pregnancy), begin acutely, are often accompanied by pain in the parotid region, taste disturbance, hyperacusis and rarely by lacrimation disturbance; the onset of the disease is often at night. It is characterized by a detailed picture of unilateral prosopoplegia.

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Familial forms of VII nerve neuropathy are rare.

The cause is unknown. They are often accompanied by hyperpigmentation spots on the skin and a delay in overall development. Recurrent isolated facial nerve paralysis is characteristic.

Congenital facial nerve paralysis is observed in the picture of Moebius syndrome.

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Infectious lesions

Post-infectious neuropathy of the facial nerve is observed especially often after herpes zoster in the area of the intermediate nerve (Hunt's syndrome with pain and characteristic skin rashes in the ear or pharynx area, sometimes with involvement of the VIII nerve).

Other causes: HIV infection (accompanied by pleocytosis in the cerebrospinal fluid), syphilis and tuberculosis (rarely with tuberculosis of the mastoid process, middle ear or pyramid of the temporal bone); infectious mononucleosis, cat scratch disease, poliomyelitis (acute onset of paresis of the facial muscles is always accompanied by paresis and subsequent atrophy of other muscles), idiopathic cranial polyneuropathy (paresis can be unilateral), osteomyelitis of the skull bones, Lyme disease (unilateral damage to the facial nerve is more common in children than in adults), childhood infections, leprosy.

Dysmetabolic disorders

Lesions of the facial nerve in diabetes mellitus, hypothyroidism, uremia, porphyria are described as mononeuropathy or in the picture of polyneuropathy.

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Diseases of the middle ear

Otitis and (less commonly) middle ear tumors such as glomus tumors can lead to facial nerve paresis (paralysis). Paresis due to these diseases is always accompanied by hearing loss and corresponding radiographic findings.

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Post-vaccination facial neuropathy

This form of neuropathy is sometimes seen after vaccinations against diphtheria, whooping cough, tetanus, and polio.

Rossolimo-Melkerson-Rosenthal syndrome

This eponym denotes a hereditary disease characterized by recurrent neuropathy of the facial nerve, recurrent characteristic swellings of the face, cheilitis and a fissured tongue. The complete tetrad of symptoms occurs in only 25% of cases; swelling of the lips - in 75%; swelling of the face - in 50% of cases; fissured tongue - in 20-40% of observations; damage to the facial nerve - in 30-40% of cases. Prosoplegia can be unilateral and bilateral; the side of the lesion can alternate from relapse to relapse. In families with this disease, there are patients (in different generations) with different variants of incomplete Melkersson-Rosenthal-Rossolimo syndrome. Elements of "dry" syndrome have been described in some patients with this disease.

Head injury with basal skull fracture

Traumatic brain injury, especially with a fracture of the pyramid of the temporal bone, often leads to damage to the facial and auditory nerves (with a transverse fracture of the pyramid, the vestibulocochlear nerve is immediately involved; with a fracture of the pyramid in length, the involvement of the nerve may not be apparent for up to 14 days. Such lesions can be diagnosed by the otoscopic method). Surgical injury to the trunk of the facial nerve is possible; birth trauma can also be the cause of neuropathy.

Tumors (benign and malignant) in the area of the cerebellopontine angle and posterior cranial fossa

Slowly increasing compression of the facial nerve by a tumor, especially cholesteatoma, neurinoma of the VII nerve, meningioma, neurofibromatosis, dermoid or granulomatosis at the base of the brain (or aneurysm of the vertebral or basilar artery), lead to slowly progressive paralysis of the facial nerve with the involvement of adjacent formations (eighth, fifth, sixth cranial nerves; symptoms of damage to the brain stem); the appearance of symptoms of intracranial hypertension and other symptoms.

Connective tissue diseases and granulomatous processes

Processes such as periarteritis nodosa, giant cell temporal arteritis, Behcet's disease, Wegener's granulomatosis (granulomatous inflammation of small and medium arteries, affecting mainly the respiratory system and kidneys) lead to mononeuropathies and polyneuropathies, as well as damage to the cranial nerves, including the facial nerve.

Heerfordt's syndrome: facial nerve paresis (usually bilateral) in sarcoidosis with swelling of the parotid glands and visual disturbances.

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In the picture of alternating syndromes

Peripheral facial paresis may be a manifestation of damage to the motor nuclei of the facial nerves in the caudal part of the pontine tegmentum. Common causes are:

Stem strokes manifested by Millard-Gubler syndrome (facial paresis with contralateral hemiparesis) or Foville syndrome (facial paresis in combination with homolateral lesion of the abducens nerve and contralateral hemiparesis).

Basal meningitis

Basal meningitis of various etiologies, including carcinomatous or leukemic meningeal infiltration, often leads to damage to the facial nerve (other cranial nerves are always involved; paresis is often bilateral, characterized by a rapid onset).

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Multiple sclerosis

Multiple sclerosis can quite often manifest itself as damage to the facial nerve (sometimes recurrent).

Syringobulbia is a rare cause of pathology of the VII pair (with a high localization of the cavity in the brainstem).

Arterial hypertension

Arterial hypertension is a known cause of compression-ischemic neuropathy of the facial nerve; it can lead to unilateral paralysis of the facial muscles, apparently due to impaired microcirculation or hemorrhage into the facial nerve canal.

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Diseases of the bones of the skull

Such as Paget's disease and hyperostosis cranialis interna (also a hereditary disease that leads to recurrent neuropathies of the facial nerve). In these cases, the decisive word in diagnosis belongs to X-ray examination.

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Iatrogenic forms

Iatrogenic neuropathy of the facial nerve has been described after the introduction of lidocaine into the facial area, isoniazid, the use of the antiseptic chlorocresol, the use of electrode pastes and some creams (transient weakness of the facial muscles).

The following additional information may sometimes be helpful, concerning recurrent weakness of the facial muscles. The latter is observed in 4-7% of all cases of Bell's palsy.

Recurrent weakness of facial muscles

Main reasons:

1. Idiopathic facial nerve neuropathy (including familial).
2. Merkelson-Rosenthal syndrome.
3. Multiple sclerosis.
4. Diabetes mellitus.
5. HFDP.
6. Sarcoidosis.
7. Cholesteatoma.
8. Idiopathic cranial polyneuropathy.
9. Arterial hypertension.
10. Intoxication.
11. Myasthenia gravis.
12. Hyperostosis cranialis interna (a hereditary disease characterized by thickening of the inner bone plate of the skull with tunnel cranial neuropathies).

Diagnostics unilateral weakness of the facial muscles

Complete blood count and biochemistry; urine analysis; serum protein electrophoresis; ear culture; audiogram and caloric tests; skull, mastoid, and petrous bone radiographs with tomography; CT or MRI; posterior fossa myelography; cerebrospinal fluid analysis; sialography; EMG; serologic tests for HIV, syphilis, and Lyme disease may be needed; tuberculosis must be ruled out.

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