Epilepsy by Dr M L Ferrara B.V.Sc. Ph.D

Absolute credit is given to the Author Dr M L Ferrara B.V.Sc. Ph.D for this health issue article.

One of the most frightening experiences an owner can have with their pet, is to see it lose consciousness then convulse for what might seem an eternity, although it may be only moments.

Often the animal seems to fall down dead, then a few seconds later begins to fit. This may involve severe muscle spasms, jaw champing and frothing at the mouth, frantic paddling leg movements, (running on the spot), whining or crying and sometimes emptying the bladder and bowel.

Convulsions may occur in cases of poisoning, fever (high blood temperature), hypoglycaemia (low blood sugar), hypocalcaemia (low blood calcium due to eclampsia or vitamin D abnormalities),hydrocephalus (water on the brain), liver and kidney disease, encephalitis (infection of the brain) or after physical injury such as a blow to the head. Some cases, however, will be due to the well known but poorly understood disease called Epilepsy.

Epilepsy is not a true disease in itself. Rather, it is a definition of a group of symptoms associated with recurrent seizures or fits. True or idiopathic epilepsy is generally considered to be that group of recurrence seizures without an identifiable cause. Symptomatic epilepsy has an acquired or identifiable organic (physical) cause, such as brain tumour, head injury or brain damage due to non-fatal oxygen depletion.

Symptomatic epilepsy is obviously not inherited. However, idiopathic epilepsy is generally classified as hereditary, or having a strong tendency to be hereditary.

Not all forms of this problem involve major fits or obvious loss of consciousness. Seizures are in fact any periods of abnormal central nervous system (Brain) function due to excess electrical discharge of the nerve cells of the brain. The abnormal electrical activity occurs after over-stimulation of the cells. The resultant fit may be Grand Mal (major), Petit Mal (minor), or psychomotor or focal (usually mild with behavioural changes rather than convulsions). Most seizures first occur between the ages of one and two years in dogs.

Grand Mal

Grand Mal seizures are often preceded by an aura. In humans, this can last from a split second to a number of seconds. There may be hallucinations of taste, smell, sound or vision, feeling of deja vu (familiarity with new or strange surroundings) or changes in the normal behaviour patterns. In dogs, many owners report that the dog seems restless or different prior to the occurrence of Grand Mal convulsions, so this period of abnormal behaviour may be taken as the aura. This alteration is noted 12 to 24 hours before the start of convulsions, rather than just a few seconds prior to fitting. Grand Mal seizures involve loss of consciousness then major muscle spasms and jaw champing.

Status Epilepticus

If these activities continue, without a normal intervening period, the seizure is termed "Status Epilepticus". Such fits will rapidly exhaust the dog and also cause a steady rise in its body temperature, which in turn overstimulates the brain. If Status Epileticus is left untreated the dog will die either of heat exhaustion or physical exhaustion.

Provided the dog is not in Status Epilepticus, a single Grand Mal fit will not cause death in an otherwise healthy animal. It is important, however, to insure that the dog is not in a position to injure itself during the convulsion phase of the fit. It is best if moved away from areas such as swimming pool surrounds, stairs, or where sharp objects could cause injuries. Many dogs seem to have some underlying awareness of either touch or the spoken words of their owners whist fitting, so it is generally a good idea to gently stroke the dog or talk calmly to it - probably the last thing most owners feel like doing at that moment. Take note of the duration of the seizure and any pertinent details, for example, whether the patient is unconscious, champing, paddling or loses bladder or bowel control. These details can be relayed to your veterinarian when the dog has its check-up after the fit, if it has not had such a medical history previously. Do not attempt to stop the dog "swallowing" its tongue! It will not and you could get badly bitten by the champing jaws.

After the convulsions cease, the dog enters the post ictal phase. This is a stage of mild disorientation and sometimes depression. this phase may last up to 24 hours, and the dog may react abnormally to what might be fairly commonplace occurrences. Many dogs exhibit fear and nervousness in this phase, probably as they cannot understand what has happened to them. Human epileptics can at least be told they had a fit and that all is now well. This is not the best time to decide to take Fido for a visit to dear old Aunt Agatha or a dog show. It is better to keep the next 24 hours routine as normal and as quiet as possible with the exception of visiting a veterinarian for a check-up to eliminate other causes and to institute therapy if appropriate. Often therapy will not begin after the first fit, rather when the frequency has been determined.

Petit Mal

Petit Mal seizures, like Grand Mal, are due to generalised symmetrical brain dysfunction, usually originating in the forebrain. They are quite common in people but relatively uncommon in dogs. There may be an aura beforehand, but the fit itself is of short duration, sometimes only seconds in length. Although consciousness is lost, it is often for such a short time that the dog or person remains standing or seated, and merely appears inattentive or absent minded. Usually there is muscle twitching around the eyes or face, while the body muscles appear slack or loose. This is the most common Form of fitting in children and may be "grown out of". Many owners would be unaware that their pet has suffered one of these seizures, which might in part explain why this is not commonly diagnosed in domestic pets.

Focal or Psychomotor

Focal or Psychomotor seizure are quite common in pets. Those referred to as focal usually involve asymmetric brain dysfunction, with muscle twitching or repeated meaningless movement (usually of a limb) occurring somewhere on the opposite side of the body to the side of the brain affected. This called contralateral symptoms.

Psychomotor seizures, originating in the temporolimbic brain region, involve a change in the behaviour of an animal. This is usually seen as aggression, biting at imaginary objects (fly catching), flank sucking (side suckers) or tail chasing (sometimes almost non-stop). The aura and post limbic phase are rarely distinguishable to the owner. Certainly two of these syndromes, flank sucking and tail chasing, often prove to be highly irritating to the owner and can cause physical damage to portions of the affected animal’s anatomy.

In all cases, therapy in the form of anticonvulsant drugs is available, but some drugs are better suited to one form of seizure or to an individual than others are. Rarely will an animal which has only very occasional fits (once or twice a year) be put on medication. Medication is usually provided when fitting becomes common and results is a highly disrupted lifestyle for both the animal and its owner. High stress levels in the dog will increase the level or rate of seizures.

Medications commonly used in dogs are phenobarbitol, diazepam (Valium) - especially for status epilepticus and in cats, primidone (Mysoline) and clonazepam.

These drugs may be used alone or in combination (reducing the dosage and side effects of each one). One drug not usually beneficial in Grand Mal seizures, but which seems to normalize some psychomotor epileptic patients who are unresponsive to other drugs is carbamazepine (Tegretol).

A number of breeds are commonly afflicted by "cluster" fits. These are fits which follow one after the other in a short period of time, but are not quite status epilepticus which may develop in time. These breeds, Saint Bernard, Irish Setter, Belgian Tervurens, are more difficult to control with anticonvulsant drugs as cluster fits and status epilepticus are less affected by the drug’s mode of action.

The hereditary mode of epilepsy is still in a confused state. Seizures are about four times more common in males than in females, implying some sex linked action. By contrast, the offspring of affected females (in humans) are more likely to be affected than the offspring of affected males, so there is also some form of direct maternal influence not of a classic hereditary nature.

It must also be remembered that even true (idiopathic) epilepsy is not just one disease, but a grouping of diseases with very similar clinical symptoms. Most theories refer to the condition as due to simple recessive inheritance, but more recent theories prefer a polygenetic inheritance, possibly with a threshold nature, for most forms of true epilepsy. Only two forms of epilepsy, both uncommonly diagnosed in dogs, but not rare in people, have been confirmed in their inheritance pattern. One of these is due to a simple autosomal dominant gene, the other is due to a recessive autosomal gene. A third rare form so far fits the simple dominant pattern. Most of the remaining forms of epilepsy seem to fit the aforementioned polygenetic patterns, but they do seem to be of variable penetrance and markedly affected by the maternal influence and by some environmental conditions.

Given the variable expression and apparent range of inheritance pattern for the epilepsy group, it is difficult to give a hard and fast policy for the eradication of the problem. Basic precautions, of course, include avoiding the use of idiopathic epileptic animals in your breeding program, this may require extensive tests and good history of affected animal to be sure you do not remove an animal with symptomatic epilepsy (not hereditary) from breeding stock.

As in most diseases, there will be times when it is still more valuable to the breed to selectively breed from an affected animal in order to select from unaffected offspring. This is made difficult because most seizures do not begin until 18 months of age onwards, but it is still possible for larger kennels or small breeds. In some breeds, notably Saint Bernard's, fitting may begin at a very early age - commonly six to eight weeks which makes selection easier.

The maternal effect noted in epilepsy in people should encourage breeders to avoid using female epileptics as brood bitches. If it is necessary to use epileptic stock, the condition is more easily eliminated from the offspring or affected males than females.

Commonsense indicates that breeders should not linebreed or inbreed on an affected animal or on one which has thrown an above average percentage of affected offspring. Record keeping is invaluable in finding such trends within a kennel or breed. <. Such fits will rapidly exhaust the dog and also cause a steady rise in its body temperature, which in turn overstimulates the brain. If Status Epileticus is left untreated the dog will die either of heat exhaustion or physical exhaustion. swallowing its tongue! It will not and you could get badly bitten by the champing jaws. <. Many owners would be unaware that their pet has suffered one of these seizures, which might in part explain why this is not commonly diagnosed in domestic pets. cluster fits. These are fits which follow one after the other in a short period of time, but are not quite status epilepticus which may develop in time. These breeds, Saint Bernard, Irish Setter, Belgian Tervurens, are more difficult to control with anticonvulsant drugs as cluster fits and status epilepticus are less affected by the drug’s mode of action.

 

Disclaimer: The articles contained on the Britfeld Weimaraners web site are for information purposes only and can never replace the advice and/or opinion of a professional.  If you have any doubts about the health and well being of you dog, please seek the advice of such individuals.