Treatment.—In addition to removing the cause, when this is possible, recovery of function may be promoted by the administration of drugs, such as potassium iodide, strychnin, or iron, by the application of blisters, or by massage and electricity. These measures are most useful in cases due to blows or exposure to cold. When the nerve is accidentally divided in the course of an operation on the face, it should immediately be sutured. So long as the electrical reactions of the affected muscles indicate an incomplete lesion, recovery may be confidently expected (Sherren). When the reaction of degeneration is present and the paralysis has lasted for more than six months, there is little hope of recovery, and recourse should be had to operation, to restore the function of the nerve by grafting its distal end on to the trunk of the hypoglossal nerve. To prevent paralysis of the tongue the lingual nerve may be divided, and its proximal end anastomosed with the distal end of the hypoglossal.
The facial may be grafted on the accessory nerve, but the associated movements of the face which then accompany movements of the shoulder often prove inconvenient.
Facial Spasm.—Clonic contraction of the facial muscles (histrionic spasm) occasionally results from irritative lesions in the cortex or pons. Sometimes all the muscles are involved, sometimes only one, for example the orbicularis oculi (palpebrarum)—blepharospasm. This condition may be induced reflexly from irrigation of the trigeminal nerve, notably of branches that supply the nasal cavities and the teeth.
The treatment consists in removing any source of peripheral irritation that may be present, in employing massage, and in administering nerve tonics, bromides, and other drugs. In severe cases, the facial nerve may be stretched with benefit, either at its exit from the stylo-mastoid foramen or on the face.
VIII. Acoustic or Auditory Nerve.—The acoustic nerve is liable to be damaged along with the facial in tumours of the cerebello-pontine angle, and in fractures which traverse the internal auditory meatus. Both nerves also may be torn across just before they enter the meatus in severe brain injuries apart from fracture. Complete and permanent deafness results. Effusion of blood into the nerve sheath, or into the internal or middle ear, causes transitory deafness, and the patient suffers from noises in the ear, giddiness, and interference with equilibration.
IX. The Glosso-pharyngeal Nerve is comparatively seldom injured. When it is compressed by a tumour in the region of the medulla, there is interference with speech and deglutition, ulcers form on the tongue, and œdema of the glottis may supervene.
X. The Vagus or Pneumogastric Nerve is seldom injured within the cranial cavity.
In the neck, it is liable to be divided or ligated in the course of operations for the removal of malignant or tuberculous glands, for goitre, or for ligation of the common carotid. Division of the nerve on one side, or even removal of a portion of it, is not as a rule followed by any change in the pulse or respiration. If it is irritated, however, for example by being grasped with an artery forceps, there is inhibition of the heart, and if it is accidentally ligated, there may be persistent vomiting.
Division of the main trunk, or of its recurrent branch on one side, results in paralysis of the corresponding posterior crico-arytænoid muscle—the muscle that opens the glottis. This condition is known as unilateral abductor paralysis, and is accompanied by interference with inspiration and phonation. If both nerves are divided, bilateral abductor paralysis results: the vocal cords flap together, producing a crowing sound on inspiration and embarrassment of breathing, and tracheotomy may be necessary to prevent asphyxia.
The vagus and recurrent nerves have been successfully sutured after having been divided accidentally.