Text book of veterinary medicine, Volume 3 (of 5)

by James Law

The explanation of cases of aural vertigo, has been sought in the physiological action of the endolymph and perilymph on the end filaments of the nerve in the membranous labyrinth, the turning of the head from one side to the other having the effect of changing the pressure in different parts and establishing currents by which the change of position is recognized; on the other hand any injury to the canals, by disturbing the pressure of the perilymph and interfering with the relative position of the canals, and the direction and force of the currents of the endolymph and perilymph, destroys all proper sense of balance. The rotation of the subject as on a wheel or in turning in a narrow circle, is held to cause circular currents in and around the membranous labyrinth which temporarily destroy all sense of equilibrium. Seasickness and railroad sickness are doubtless in part due to the swaying motions causing disturbance in the canals. The intimate relation between the root of the auditory nerve and that of the vagus in the medulla, may serve to explain the mutual interdependence of derangement of the stomach and liver on the one hand and the occurrence of vertigo on the other. Again the relation of vertigo to visual troubles, both as to cause and effect, has been attributed to the close relations of the ganglia presiding over the 3d, 4th, 5th and 6th nerves and those of the nerve of hearing.

There is a degree of deafness in nearly all cases of aural vertigo, a circumstance which may be utilized in the diagnosis of such cases, the presence of disease of the guttural pouch, or Eustachian tube, and evidence of deafness on one side rather than the other, may be taken as corroborative evidence of the affection. On the other hand James shows that the stone deaf are much less subject to both seasickness and vertigo than those that hear. The disorder that leads to vertigo implies a retention of a measure of the normal function of the internal ear, and therefore of hearing, whereas the disease that has caused complete destruction of the internal ear and consequent loss of hearing has equally destroyed the function of the labyrinth in maintaining a sense of balance, and has obviated the aural sensations of equilibrium and loss of balance.

8th. Cerebral Vertigo may be associated with derangement of the circulation, or disease in the brain or its meninges. Anæmias and congestions resulting from disease or impaired function of heart, lungs, arteries or veins have been already noticed. It remains to note the presence of cholesteatomata and other tumors, and of parasites (cysticercus cellulosa in pig; cœnurus cerebralis in sheep) in the encephalon, and of injuries from concussion, degeneration and softening of the brain substance.

9th. Nasal Vertigo has been noted by Cadeac in connection with irritation in the nose and especially by the larva of œstrus ovis (sheep), and the linguatula (dog, horse). In certain of the cases manifested by jerking of the head and diverging to one side, the recovery after section of the pes anserina indicates a nasal origin.

10th. Vertigo from Narcotics (alcohol, lolium temulentum, belladonna, solanum, various essential oils, carbon monoxide, etc.), have been already referred to.

11th. There remains to be noted cases in which no narcotic poison, no mechanical disturbance of the circulation, no visual, aural nor nasal trouble, no gastric nor hepatic disorder, and not even a distant nervous lesion can be found; the disease may in such cases be ranked for the present as essential vertigo.

Symptoms. As usually seen in the horse, vertigo often attacks the nervous, irritable animal in which the slightest occasion of irritation or disturbance causes intense suffering and quick response. This is often aggravated by the plethoric condition of the animal, kept on a liberal ration of grain and having little exercise. In some forms of the affection, however, and especially the gastric and hepatic, the subject is dull, carries the head low, and lacks vivacity and energy.

In the first form (the most common in the horse) the animal which has been full of life and vigor, slackens his pace and the tension on the reins, or stops suddenly, shakes the head, vertically or horizontally, or jerks it to one side, trembles, staggers, props his legs outward for more stable support, presses against the pole, or the other horse, or a wall, leans on the breeching or hangs on the breast strap, plunges forward, or to one side, or rears up and even falls backward, and comes to the ground. Profuse perspiration ensues, the eyes roll, the face is pinched and drawn, the prostrate animal may struggle in a helpless way, and, if the harness is loosened, he may get up in a few seconds and slowly recover. Often, however, he remains for an hour or more, nervous, sensitive, bedewed with sweat, trembling and with anxious expression. Such are the more common manifestations of what is familiarly known as blind staggers. The symptoms will vary however, with the cause.

In gastric or hepatic cases there may be more particularly dullness and lack of energy, low carriage of the head, unsteadiness of gait, lack of lustre in the eye, pupils dilated, semi-closed eyelids, pendent lips, a tendency to lean on the stall or hang on the harness, and though the animal may stagger and fall, there is not the abrupt transition from life and energy to the active excitement and uncontrollable movements. The same remarks apply in a measure to narcotic vertigo.

With optic vertigo, the attendant conditions will help to a diagnosis. The animal has come from darkness to full sunshine; there is the white, icy or snowy reflection everywhere which the animal was facing when attacked, or the glistening lake or river, the overdraw check rein, or the blind with perhaps a shining inner surface. The pupil is closed, and the eye is rolled back or oscillates in one direction or another. The symptoms are checked by covering the eyes or removing the subject into a dark building or even into the shade of a tree or shed.