3 I have seen a single case of vertigo, with slight deafness on both sides, in which the sense of the position of sounds was absolutely lost.
In pigeons, injury on one side may get well, but when the canals are cut on both sides there is permanent loss of balance. In some way, then, these little organs appear to be needful to the preservation of equilibrium; and of late some interesting attempts have been made to explain the mechanism of this function. It probably depends on the varying pressure relations of the endo-lymph to the nerve-ends which lie in the membranous canals.
Wm. James of Harvard has shown that total loss of hearing is usually accompanied by lessened susceptibility to vertiginous impressions, so that the stone-deaf are not apt to be seasick or giddy from rotation, owing to their having lost the organ which responds to such impressions. It would seem also that the entirely deaf have peculiar difficulty in certain circumstances, as when diving under water, in recognizing their relations to space.
There is a general tendency to regard the cerebellum as the centre in which all the many impressions concerned in the preservation of equilibrium are generally received and made use of for that purpose. There may be several such centres, and the matter is not as yet clear. Whatever be the regulative ganglion, it seems clear that it must be in close relation to the pneumogastric centres, to account by direct connection or nerve-overflow for the gastric symptoms. But, besides this, vertigo has clinical relation to moral and mental states not easy to explain, and in extreme cases gets the brain into such a state of excitability that mental exertion, emotion, strong light, or loud sounds share with the least disorder of stomach capacity to cause an attack.
Vertigo may be due to many forms of blood-poisoning, as at the onset of fevers, inflammations, the exanthemata—notably in epidemic influenzas. It may arise in malarial poisoning, sometimes as the single symptom, as well as in diabetes, albuminuria, lithæmic conditions, and in all the disorders which induce anæmic states. Common enough as sign of brain tumor, and especially of growths in or near the cerebellum, as a result of degenerated vessels, it is also not very rare in the beginning of some spinal maladies, especially in posterior sclerosis, and is not always to be then looked upon as of ocular origin.
Alcohol, hemp, opium, belladonna, gelsemium, anæsthetics, and tobacco are all, with many others, drugs capable of causing vertigo.
In hot countries heat is a common, and sometimes an unsuspected, cause of very permanent vertigo.
Lastly, excess in venery, or, in rare cases, every sexual act, profound moral and emotional perturbations, and in some states of the system mental exertion, may occasion it, while in hysteria we may have almost any variety of vertigo well represented. Outside of the brain grave organic diseases of the heart are apt to produce vertigo, especially where the walls of the heart are fatty or feeble from any cause. Suppression of habitual discharges, as of hemorrhoids or menstrual flow, is certainly competent, but I have more doubt as to the accepted capacity of rapidly cured cutaneous disease.
The following are some of the more immediate causes of vertigo: They are disorders of the stomach or of the portal circulation; laryngeal irritation; irritation of the urethra, as passing a bougie, especially when the patient is standing up; affections of nerve-trunks; nerve wounds; sudden freezing of a nerve (Waller and the author); catarrhal congestion of the nasal sinuses; inflammation and congestion of inner ear, many irritations of the outer and middle ear; prolonged use of optically defective eyes; insufficiency of external muscles of the eye.
It will be needful to treat of some of these causes of vertigo in turn.