Seizure or fit is used to describe convulsion in which there is a powerful contortion of the body, limbs or both. Further symptoms may include sudden involuntary change in behaviour, muscle control, consciousness, and or sensation, gait problems, collapse and blindness.
Many factors may trigger seizures in susceptible horses such as hyperthermia and excessive exercise (poor electrolyte balance) and allergic reactions including chemicals and preservatives. They may be caused by an interruption of blood flow to the brain, brain tumour, injury to the brain, an allergic reaction to a drug or toxins, or inflammation of the brain due to bacterial or viral infection. Other causes are flashing lights, bright lights and fireworks and abuse or neglect.
Research has shown that more seizures occur in the autumn. This may be due to mould and bacteria in the air and may also be associated with reduced light (photoperiod) affecting the pineal gland (produces melatonin) hypothalamus, pituitary gonadal axis.
A condition called Juvenile Epilepsy primarily affects Arab foals but they usually cease having seizures by the time they are 12 months old. Appaloosas and Thoroughbreds also seem to have a higher incidence of idiopathic epilepsy and there may be a genetic factor involved so affected stock should not be used for breeding.
If the cause of a seizure cannot be diagnosed, it is termed epilepsy.
A review of relatively modern literature says that seizures are uncommon in the horse and Hayes (1987) states that epilepsy in the horse does not occur. Reference to older tomes shows that \’epilepsy\’ and \’megrims\’ were considered commonplace, are well described, and completely recognisable to any owner or trainer who has observed a seizure or convulsion taking place in their horse.
The seizure is caused by an electrical storm in the brain and can be categorised by two types:
A generalized \’Grand mal\’ , \’major motor\’ or \’tonic-clonic\’ seizure is the most severe.
The seizure begins with contraction of all skeletal muscles and loss of consciousness. The horse usually falls on its side with the legs stretched out and the head back. Sometimes it will vocalize or have facial twitching and may salivate, urinate and defecate.
The tonic portion of the seizure is usually brief and gives way to the clonic phase of the seizure. During the clonic phase rhythmic movements occur e.g. of clamping the jaws and jerking or running movements of the legs.
The seizure may last a few minutes and following the seizure, the horse may lay motionless or will get up onto its feet and may appear to be perfectly normal, but typically will show signs of including blindness, disorientation, pacing or running. This behaviour can last anywhere from hours to days after a seizure.
Infrequent or \’partial motor seizures\’ or \’petit mal\’ focal seizure is a less severe form of seizure that begins in a small area of the brain. Because the seizure starts in only a part of the brain, an underlying disease or injury is highly suspected. Usually the face is affected, resulting in twitching or blinking and mostly affects one side of the face. The horse may appear sleepy (narcolepsy).
A diary of all seizure activity (dates, description, duration, drugs) should be kept by the owner.
A complete history should be taken by your vet that will help to eliminate other health problems.
Diagnosis is based on signs and blood tests, (cell counts, immunoglobulins, protein, enzymes, hormone levels, poisons), X-rays, cerebrospinal fluid taps, electroencephalograms, magnetic resonance imaging (MRI) and neurological and ophthalmic examination that may help to diagnose a cause for the seizures. Due to the size of the horse, its temperament and psychology, the present limitations and availability of the technologies, not all the possible diagnostic technologies may be available to your horse.
Although drug therapy can be very effective, some may cause side effects that may cause other problems. Many owners and their vets are receptive to complementary methods of treating seizure disorders. These include homeopathy, chiropractors, acupuncture, herbal medicine and alternative nutritional management and should be discussed with your vet as to suitability for your horse.
The dosage of anticonvulsants may need to be lower when using herbs and supplements.
The results of this approach have been remarkable. Standard commercial diets containing synthetic chemical preservatives are replaced with naturally preserved foods. The replacement food must be of good quality and preferably of relatively low protein content. Increasing carbohydrate and reducing protein content, while maintaining high quality protein, has been shown to be beneficial for many affected horses and is also believed to have a positive effect on behaviour.
A balanced supplement with good levels of vitamin B6, folic acid, pyridoxine, vitamin C and E and manganese, zinc, magnesium and selenium as in COMPLETE and CHF are appropriate. Dimethylglycine (DMG) and MSM relieve a variety of ailments by reducing inflammation and enhancing blood flow.
Multi-strain probiotics such as BB are useful to ensure the health of the digestive system.
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