6th. Reflex Irritation. Perhaps no peripheral irritation more frequently causes epilepsy, than parasites. In young dogs worms in the intestines (tænia cœnurus, tænia tenuicollis, tænia serrata, tænia echinococcus, and ascarides) have been especially incriminated. Also linguatula tænioides in the nasal sinuses. In young pigs the echinorrhynchus gigas, ascarides and trichocephalus. In horses ascarides have been principally blamed.
Wounds implicating nerves, and tumors pressing on nerves, have served as sources of nervous excitement which accumulates in the cerebral ganglia and bursts forth as an epileptic explosion. Bourgelat mentions the case of a horse which fell in a fit the moment he was touched on his tender withers, also a case in which a seizure coincided with an attack of recurrent ophthalmia. Gerlach saw a horse which had an epileptic fit the instant he was touched on his sensitive withers. In kittens and puppies the irritation attendant on dentition is a common cause of attacks. In nervous dogs and pigs indigestion or constipation may serve as the occasion of an explosion. In the experimental cases of Brown-Sequard, not only did the injury to the sciatic nerve develop in the brain a latent tendency to epilepsy, but the subsequent pinching of the skin in certain areas (epileptigenous zones) promptly brought about a seizure.
Causes. Most of the causes of epilepsy have been given above under the head of pathology and morbid anatomy. The nervous predisposition may, like any other peculiarity or function, become hereditary. In the human race nothing is more certain than the tendency to some form of nervous disorder (insanity, dementia, alcoholism, morphinism, epilepsy, chorea, etc.) in a special family line. Reynal records the case of an epileptic cat (belonging to an employe of the Alfort veterinary school) the progeny of which for three generations, became affected with epilepsy and mostly died before they were a year old. Also four epileptic dogs (3 males and 1 female) which produced a number of epileptic puppies. LaNotte records the cases of two bulls affected with epilepsy, in the progeny of which numerous cases of epilepsy appeared; the cows being attacked after the first calving, and the oxen soon after they were first put to work. Breeding stallions are particularly liable to attacks, the high feeding, lack of muscular work in the open air, and above all the oft repeated nervous excitement attendant on copulation being directly exciting causes. The heredity of the artificial epilepsy induced by Brown-Sequard in Guinea pigs, serves to strengthen the doctrine of heredity in ordinary forms.
Among emotional causes fear easily heads the list. Bernard states that a horse became epileptic in connection with the terror caused by the giving way of a wooden bridge over which he was passing. Bourgelat and Reynal adduce instances, in cavalry horses when first put under fire. Reynal records the case of another which had his first attack when facing a moving locomotive, and which never again could see an engine in motion without suffering another attack. La Notte mentions the case of a horse attacked when frightened by a sky rocket; Romer, the case of a horse scared by the sudden display of a white sheet in front of him, and Friedberger and Fröhner relate cases of attacks caused by intense rays of light, as in racing toward the declining sun, or the dazzling reflection from the surface of water. Liedesdorf saw it in a dog scared by a locomotive.
A strong impression like that caused by transition from bright light into darkness, by seeing shadows of trees crossing the road, or violent suffering caused by severe forms of constraint have been named as causes.
Speaking in “Brain,” of epilepsy in man, Alexander Haig attributes the fits to the fluctuations of uric acid in the blood. Headache (migraine) he finds to be very closely allied to epilepsy and convulsions and to be a result in a susceptible system of a liberal flesh diet. By a vegetable and fruit diet he reduces the ingestion and formation of uric acid, so that the largest quantity which a patient is likely to get into his blood, shall never or only very rarely, affect the blood pressure and increase the intracranial circulation to a dangerous extent. In predisposed subjects, all flesh food, soup, and meat extracts must be avoided, while even tea, coffee, cocoa and other vegetable articles containing xanthin compounds are to be regarded as producing uric acid, and to be denied, or employed only as the merest flavoring.
This position is greatly strengthened by the fact that epilepsy is so much more frequent in the carnivora (dog, cat, bird) than in the herbivora. It also suggests very strongly a light vegetable diet for both prophylactic and curative purposes in our domestic animals. In the same line the frequent and liberal drinking of warm water, the use of diuretics and the flushing of the large intestine are indicated.
For other causes see under pathology.
Symptoms in the Horse. It has been claimed that premonitory symptoms, such as dullness, lack of energy and quick, nervous or startled movements herald an attack, but in animals as in man, the disease usually attacks suddenly without any antecedent indication.
If at work the horse stops suddenly, or if in the stable he ceases eating, seems frightened, stands for an instant immovable, braces his feet, sways, trembles, and falls heavily to the ground. Or he may remain for an instant supported on his rigid limbs, the jaws moving or firmly closed, the eyes rolling, and the facial muscles drawn or twitching. When down there are convulsive movements of the limbs, so that the animal may kick out violently, and tense contractions or twitchings may occur in the muscles of the croup, chest and abdomen. There is usually an increase of the salivary secretion with frothy accumulation about the angles of the mouth. The respiration is stertorous, dyspnœic, and interrupted, the nostrils widely dilated, the nasal mucosa of a dark brownish red, and the superficial veins distended. The pulse is weak, slow, irregular, intermittent and sometimes imperceptible. Sensation seems to be in abeyance. No attention is paid to loud sounds, nor to pinching, pricking, or even cauterizing the skin. Perspirations may break out on the flank or over the whole surface of the body.