In facial nerve palsy – colloquially called facial paralysis – (facial palsy; synonyms: Bell’s facial palsy; Bell’s palsy; Bell’s paralysis; Bell’s syndrome; facioplegia; facial nerve palsy; facial paresis; cranial nerve VII palsy; facial nerve paralysis; peripheral facial palsy; prosopodiplegia; prosopoplegia; central facial palsy; ICD-10-GM G51.0: Facial paresis) is a paresis (paralysis) of muscles innervated by the facial nerve, consequently part of the facial musculature is paralyzed.
The facial nerve is the VII cranial nerve (facial nerve). It has sensitive, sensory, motor and parasympathetic fibers and innervates large parts of the head. Thus, it supplies the mimic muscles of the face and is involved in taste sensation, tear and saliva secretion, and supplies the smallest muscle in the human body, which is located in the ear, the stapedius muscle.
The following two forms of facial nerve paresis can be distinguished according to the site of damage:
- Central (supranuclear) facial nerve palsy – damage located above the nerve nucleus (gyrus praecentralis, tractus corticonuclearis); often caused by an apoplexy (stroke) or brain tumor.
- Peripheral (nuclear, infranuclear) facial palsy (Bell’s palsy) – damage in the nerve core or peripheral course; in 60-75% of acquired peripheral facial palsy no cause can be found (= idiopathic facial palsy; Bell’s palsy).
When peripheral facial nerve palsy occurs during pregnancy with degeneration and incomplete regeneration of the VII cranial nerve, it is called Mona Lisa syndrome. The majority of cases are idiopathic paresis (paralysis of unclear cause).
Sex ratio of idiopathic facial nerve palsy: Men and women are equally affected.In women, the risk of facial nerve palsy is three times higher during pregnancy.
Frequency peak: Idiopathic facial nerve palsy occurs more frequently with increasing age.
The incidence (frequency of new cases) is 20-40 cases per 100,000 population per year. The idiopathic form occurs with an incidence of 7-40 cases per 100,000 population per year.
Course and prognosis: If it is a mild form of facial nerve palsy, the symptoms are only mild. More severe forms of facial nerve palsy are usually accompanied by changes in facial expression.The prognosis of idiopathic facial nerve palsy is good, with regression occurring in over 80% of cases within a few weeks of symptom onset (complete in >70%). In about 13% of cases, regression is incomplete, although affected individuals are not significantly impaired as a result. In 16%, reinnervation (regrowth of the nerve) is so incomplete that, for example, synkinesias (involuntary closure of the eyelids during speech), contractures (constant tension of the facial muscles), and/or autonomic disturbances such as the crocodile tear phenomenon (gustatory weeping; unilateral lacrimation that usually occurs during food intake) occur.In pregnancy, the overall course of idiopathic facial nerve palsy is less favorable, i.e., defect healing occurs more frequently. Spontaneous remission rates are 50-80%, and approximately 90% for incomplete facial paresis.Postviral (“after viral infection”) facial paresis often heals with defects.Borrelia-induced facial paresis almost always has a good prognosis.
