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

  • supranuclear damage (central facial palsy);
  • damage to the level of the nucleus and root of the facial nerve (processes in the area of ​​the pons);
  • damage in the posterior cranial fossa (cerebellopontine angle);
  • at the entrance to the canal of the temporal bone;
  • in the nerve canal proximal to the origin of n. petrosus superficialis major (to the lacrimal gland);
  • in the canal proximal to the origin of the branch to m. stapedius;
  • between n. stapedius and chorda tympani; in the canal distal to the origin of the chorda tympani;
  • nerve damage distal to the foramen stylomastoideum.

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

Causes of unilateral weakness of facial muscles

The main causes of unilateral weakness of facial muscles:

  • Idiopathic neuropathy of the VII nerve (Bella’s palsy).
  • Familial forms of neuropathy of the VII nerve.
  • Infectious lesions (Herpes simplex is the most common cause; herpes zoster; HIV infection; polio; syphilis and tuberculosis (rare); cat scratch disease and many others).
  • Metabolic disorders (diabetes mellitus, hypothyroidism, uremia, porphyria).
  • Middle ear diseases.
  • Post-vaccination neuropathy of the VII nerve.
  • Rossolimo-Melkerson-Rosenthal syndrome (Melkersson, Rosenthal).
  • Traumatic brain injury.
  • Tumors (benign and malignant) of the nerve trunk.
  • Connective tissue diseases and granulomatous processes.
  • In the picture of alternating syndromes (with vascular and tumor lesions of the brain stem).
  • Basal meningitis, carcinomatous, lymphomatous and sarcomatous infiltration of the membranes.
  • Tumor of the cerebellopontine angle.
  • Multiple sclerosis.
  • Syringobulbia.
  • Arterial hypertension.
  • Diseases of the skull bones.
  • 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 reason. They occur somewhat more often in women in the third trimester of pregnancy (sometimes with relapses during each pregnancy), begin acutely, often accompanied by pain in the postauricular area, taste disturbances, hyperacusis and rarely impaired lacrimation; The onset of the disease is often at night. It is characterized by a detailed picture of unilateral prosopoplegia.

Familial forms of VII nerve neuropathy are rare

Their cause is not known. Often accompanied by patches of hyperpigmentation on the skin and delays in overall development. Recurrent isolated paralysis of the facial nerve is characteristic.

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

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, sometimes involving 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 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 (in children, unilateral damage to the facial nerve is more common, than in adults), childhood infections, leprosy.

Dysmetabolic disorders

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

Middle ear diseases

Otitis media and (less commonly) middle ear tumors, such as glomus tumor, can lead to facial paresis (paralysis). Paresis due to these diseases is always accompanied by hearing loss and corresponding x-ray findings.

Post-vaccination neuropathy of the facial nerve

This form of neuropathy is sometimes seen after vaccination 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 swelling of the face, cheilitis and folded tongue. A complete tetrad of symptoms occurs only in 25% of cases; swelling of the lips – 75%; swelling of the face – in 50% of cases; folded tongue – in 20-40% of cases; damage to the facial nerve – in 30-40% of cases. Prosoplegia can be unilateral or bilateral; the affected side may alternate from relapse to relapse. In families with this disease, there are patients (in different generations) with various variants of incomplete Melkerson-Rosenthal-Rossolimo syndrome. Elements of the “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 long fracture of the pyramid, nerve involvement may not appear until 14 days. Such lesions can be diagnosed otoscopic method). Possible surgical injury to the trunk of the facial nerve; The cause of neuropathy can also be birth trauma.

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), leads to slowly progressive facial palsy involving adjacent structures (eighth, fifth, sixth cranial nerves; symptoms of brain stem damage); 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, Behçet’s disease, Wegener’s granulomatosis (granulomatous inflammation of small and medium-sized 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 syndrome: facial nerve paresis (usually bilateral) in sarcoidosis with swelling of the parotid glands and visual disturbances.

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 reasons are:

Brainstem 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 rapid onset).

Multiple sclerosis

Multiple sclerosis can 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 brain stem).

Arterial hypertension

Arterial hypertension is a known cause of compressive 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.

Diseases of the bones of the skull

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

Iatrogenic forms

Iatrogenic neuropathy of the facial nerve is described after the administration of lidocaine in the facial area, isoniazid, the use of the antiseptic chlorocresol, the use of electrode pastes and some creams (transient weakness of facial muscles).

The following additional information regarding recurrent facial muscle weakness may sometimes be helpful. The latter is observed in 4-7% of all cases of Bell’s palsy.

Recurrent weakness of facial muscles

Main reasons:

  • Idiopathic neuropathy of the facial nerve (including familial).
  • Merkelson-Rosenthal syndrome.
  • Multiple sclerosis.
  • Diabetes.
  • HVDP.
  • Sarcoidosis.
  • Cholesteatoma.
  • Idiopathic cranial polyneuropathy.
  • Arterial hypertension.
  • Intoxication.
  • Myasthenia gravis.
  • Hyperostosis cranialis interna (hereditary disease manifested by thickening of the internal bone plate of the skull with tunnel cranial neuropathies).

Diagnosis of unilateral weakness of facial muscles

  • General and biochemical blood test;
  • Analysis of urine;
  • serum protein electrophoresis;
  • culture of ear discharge;
  • audiogram and caloric tests;
  • radiographs of the skull, mastoid process and pyramid of the temporal bone with tomography;
  • CT scan or MRI;
  • myelography of the posterior cranial fossa;
  • cerebrospinal fluid examination;
  • sialography;
  • Ministry of Health;
  • Serological tests for HIV infection, syphilis, and Lyme disease may be needed;
  • tuberculosis must be excluded.

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