The Pneumogastric Nerve.
The pneumogastric nerve has a longer course and a wider distribution than any of the cranial nerves, being distributed to the pharynx, esophagus, larynx, lungs, heart, stomach, intestines, and spleen.
Etiology.—The neucleus may be involved by hemorrhage, softening, tumors, or by degeneration, as seen in bulbar-paralysis.
The nerve-root within the skull may be disturbed by meningitis, by morbid growths, or by aneurism of the vertebral artery.
In the neck it may be disturbed by pressure from tumors, or it may be ligated in tying the carotid artery, or injured in surgical operations or by punctured or incised wounds. Neuritis from exposure or toxemia is quite rare.
Pharyngeal Branches.—Functional disturbances of the pharyngeal branches results in spasm of the muscles and mucous membrane of the larynx, as seen in nervous individuals, and generally occurs in hysterical patients, and is known as globus hystericus.
Paralysis of the branches may follow diphtheria or accompany bulbar paralysis, and causes difficulty in swallowing, the food being inclined to enter the larynx, where it gives rise to coughing or to severe choking. If the soft palate be involved, the food is regurgitated into-the nose.
Laryngeal Branches.—Functional disturbances of the laryngeal branches gives rise to spasm of the adductors—laryngismus stridulus—not infrequent in children, but rare in adults. Paralysis of the branches gives rise to stridulous respiration, cough, and hoarseness, or complete aphonia, with more or less dyspnea. It may result from diphtheria, or from pressure upon the recurrent laryngeal, from aneurisms, goitre, or morbid growths.
Pulmonary Branches.—Since the bronchial muscles are supplied by these branches, their disturbance gives rise to spasm of the intrinsic muscles, as seen in bronchial asthma.
Where paralysis occurs, respiration is slow and sometimes labored, and accompanied by cardiac disturbances.
Cardiac Branches.—The cardiac branches are motor, sensory, and trophic; hence the variety of cardiac phenomena displayed by disturbance of these branches.
Irritation of the motor branches slows the action of the heart—bradycardia—and may be due to a pure neurosis or to compression from tumors.
Paralysis of the vagus abolishes inhibitory action, when the accelerators are unrestrained, and the heart fairly runs away—tachycardia. This may follow diphtheria, wounds, accidental ligature of the nerve, or pressure from growths.
When the sensory branches are disturbed, palpitation and pain are experienced, as witnessed in angina and other painful cardiac affections.
Trophic disturbance is seen in fatty degeneration of the heart, following injury to the vagus.
Esophageal Branches.—Functional disturbances occur more frequently than paralysis; spasm of the esophagus, occurring in hysterical patients, is attended by difficulty in swallowing. Paralysis of the esophagus results in difficulty in swallowing.
Gastric Branches.—These are both motor and sensory. A disturbance of the sensory branches gives rise to pain, as seen in nervous dyspepsia and other gastric disturbances. Hunger is probably a pneumogastric sensation.
A section, or paralysis of the nerve, lessens the contractile power of the stomach, though it does not destroy it entirely. The vomiting occurring in cerebral disturbances is most likely due to irritation of these branches.
Irritation of the intestinal branches accelerates the action of the intestines, though intestinal disturbances from lesions of the vagus are so rare than little has been learned regarding them.
Treatment.—The treatment must be symptomatic. When due to specific causes, the antisyphilitics will be used. Electricity and massage should be tried in other cases. Where the lesion is functional, spasm resulting, the antispasmodics will be given, such as gelsemium, lobelia, the bromids, chloral, and like remedies.