The Seventh or Facial Nerve.
Synonyms.—Facial Paralysis; Bell's Palsy.
Etiology.—Paralysis of the seventh or facial nerve may be supra-nuclear, nuclear, or peripheral in origin.
Supranuclear Paralysis.—This form is due to lesions of the cortex, corona radiata, or internal capsule, and is usually associated with hemiplegia.
Tumors, cerebral softening, hemorrhage, and abscess or chronic inflammation, may be responsible for this lesion.
It differs from the peripheral form in that the upper branches of the facial nerve are intact, enabling the patient to wink and wrinkle the forehead. The normal electrical excitability of both nerves and muscles are also preserved.
The emotional movements are not so impaired in this form of paralysis as the voluntary.
Nuclear Paralysis.—This form is more rare and may be due to tumors, hemorrhages, or softening, affecting the nucleus. This center has also been involved in diphtheria and anterior poliomyelitis.
The symptoms are those of the peripheral type.
Peripheral or Intranuclear Paralysis.—When the nerve trunk is involved within the pons, it is usually due to hemorrhage, a tumor, or softening. When affected at its point of exit, it may be due to syphilis, meningitis, tumors, or fractures at the base of the skull. Caries of the bone, or disease of the middle ear, may affect the nerve in the Fallopian tube, and at its emergence from the styloid foramen it may be influenced by pressure, as from tumors of the parotid gland, or from forceps in instrumental delivery.
Symptoms.—In facial paralysis, the appearance of the affected side presents a picture that is characteristic. The tissues are lax and immobile, the natural lines and furrows are diminished or entirely effaced, especially noticeable in elderly people, the skin of the forehead being smooth and without wrinkles. The lower lid droops, and the patient is unable to close the eye, owing to paralysis of the orbicularis palpebrarum; the eye waters, and the affected eye remains open during sleep.
Voluntary and emotional movements are lost, the corner of the mouth drops and the mouth is drawn to the affected side. In protruding the tongue it appears as though it were drawn to the affected side, but examination reveals the tongue in normal position, the distortion being due to the drawing of the mouth away from the affected side. The sagging of the mouth causes the saliva to dribble. The patient can not whistle, whisper, or lift the angle of his mouth. In drinking, the lips are not perfectly closed and the fluid is apt to escape from the mouth. Owing to paralysis of the buccinator, the food collects in' the teeth and cheek of the affected side. The patient is unable to sniff, owing to paralysis of the nasal muscles.
Where the nerve is involved within the canal between the geniculate ganglion and the region of the chorda tympani, taste is lost upon the anterior two-thirds of the tongue.
There is often abnormal sensitiveness to sound, though if there has been disease of the middle ear, sensitiveness is lost or materially lessened.
Spasmodic twitching of the affected muscles may occur late in the disease.
Where the paralysis is due to cold, the facial muscles alone are involved, hearing and taste being preserved, and electrical reactions remain good. Recovery takes place in from one to four weeks.
Diagnosis.—The diagnosis is readily made by noting the characteristic picture as given above.
Prognosis.—The prognosis is generally favorable, though it may last several months. If due to traumatism, tumors, or softening, it will most likely be permanent.
Treatment.—The treatment will depend upon the cause giving rise to the lesion. If due to cerebral tumors, softening, and like causes, but little result will be obtained from medication. If the result of middle-ear diseases, thorough drainage must be secured. If due to syphilis, potassium iodid, echinacea, berberis aquifolium, corydalis formosa, thuja, and Donovan's solution will give good results.
If due to cold, gelsemium, bryonia, macrotys, rhamnus Californica, and other anti-rheumatics will be suggested.
Galvanism should receive a thorough trial.