With aural vertigo there may be similar rolling of the eyes, without the pupillary closure, the ear may be drawn down or back, and the shaking or jerking of the head is likely to be a marked feature. If there is more motion of one ear than the other, if the head is jerked to the one side, if there is a measure of deafness in the one ear (to be ascertained rather in the intervals between attacks), if there is disease of the pharynx, the Eustachian tube or pouch, or swelling about the root of the ear, if there is wax, scurf, or acarus in the ear, if the animal rubs it frequently, aural vertigo may be suspected.
Nasal vertigo. Those forms in which the head is jerked horizontally, vertically, or diagonally, the animal pressing against its mate or the pole, or outward in the harness, and getting out of its track, even if it should stop short of falling, and which appear only during work, or are aggravated by exertion, have been attributed to lesions of the ear (Fleming), but in some cases they can be warded off by wearing a net over the nostril, and can be entirely stopped by complete transverse section of the pes anserina, so that in a certain number at least they must be accounted nasal. These are not usually attended by sneezing. The simple expedient of driving with a rather close net over the nostril may enable one to diagnose many of the purely nasal forms.
Plethoric vertigo may be suspected when the attack comes on in spring, in a fleshy or fat horse, overfed and little exercised, when there is dark red congestion of the nasal mucosa and conjunctiva, and a subsidence with rest.
In the vertigo of brain lesions, the acute forms are attended by fever and marked signs of delirium or disordered nervous functions, while in the chronic forms there may be permanent hyperæsthesia or anæsthesia, general or with rather diffuse limits, and the vertiginous attacks repeat themselves frequently irrespective of weather, though they may be precipitated by faults of feeding, indigestion, severe exertion, or some of the other exciting causes above mentioned.
These cases are to be distinguished from epilepsy by the absence of any spasmodic contraction, aside from the jerking of the head and rolling of the eyes, and by the fact that consciousness is retained throughout. During the attack the animal may fail to respond to irritation of the nasal mucosa, but this appears to be due to the fact that his whole attention is engaged with a more serious trouble.
The duration of an attack is from one to two, or exceptionally five minutes. The form which is represented by jerking of the head and deviation from the direct line of motion may continue so long as exercise is kept up.
In the nasal vertigo of sheep and dogs, due to parasites, sneezing, and congestion of the mucosa are to be looked for.
In the cerebral parasitic vertigo of sheep and pigs, the symptoms vary according to the seat of the parasite. These may be blindness, turning in a circle, moving straight ahead regardless of obstacles, jerking upward of the head with nose protruded, hemiplegia, hemianæsthesia, cross hemiplegia, cross hemianæsthesia, and any one of the many forms of paralysis, or exaggerated nervous action. The animal usually turns to the side on which the parasite lies and is paralyzed on the opposite side of the trunk. A peculiarity of these cases is that while the symptoms are continuous, yet there are periodic aggravations which bear no relation to feeding, exertion or excitement, but depend on the protrusion at intervals of the heads of the parasites into the brain substance. If there are several parasites in the brain and they do this at different times the symptoms are liable to vary according to their seat, and the special organ which is irritated. This variability of symptoms is suggestive of parasitism.
While turning around in a circle has been already noticed there remains, in certain cerebral forms, the peculiar phenomenon of the animal rotating rapidly on its longitudinal axis. The patient falls on its side and rolls over and over. Among the brain lesions with which it has been experimentally identified are injuries to the middle peduncles of the cerebellum, or of the superoexternal portion of the cerebral peduncles, or of the posterior part of the encephalon, or of different parts of the hemispheres.
Cases of vertigo that occur without any appreciable lesion have been named essential vertigo. Guibert has attributed some cases to irritation of the lower part of the limbs by contact with the litter but this could only occur in an animal in which the nervous system was in a morbidly excitable condition.