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UNDERSTANDING SEIZURE CONTROL
A seizure is the result of a sudden uncontrolled firing of several nerve cells in the brain at the same time, usually rapidly spreading through out the entire region and occasionally short-circuiting the entire brain. Admittedly, seizures at home can be a very scary event but are rarely life threatening nor are they a medical emergency. If they are lasting longer than 15-20 minutes, the animal is cyanotic (blue color), or they do not stop at all the patient needs to be seen ASAP. If they are sporadic, less than 15 minutes in duration they are not a medical emergency and can be dealt with at a later time saving costly emergency fees and treatments.
Each individual animal and cell has a unique “threshold” below that a seizure cannot occur. This threshold is determined by genetics, the number of connections the cell has, the chemical environment around the cell and the disease state of the body. Disease both in the brain and outside of the brain can lower this threshold causing seizures or it may be set too low genetically as is seen in idiopathic epilepsy .
Extra cranial causes of seizures are the following and are investigated with a history, physical exam, blood tests and urine tests. These animals are usually clinically ill prior to showing signs of seizures with a few exceptions.
• Hypoglycemia ; low blood sugar; usually seen in toy breed puppies, hunting dogs during exercise, and in patients with pancreatic cancer.
• Hypoxia : low blood oxygen: usually have pulmonary disease, cardiac disease or carbon monoxide poisoning.
• Hepatoencephalopathy : liver disease associated: blood work may pick up, clinically ill, and seizures seem to occur around high protein meals
• Kidney disease : patient is clinically ill, blood tests and urine tests show kidney disease.
• Hypocalcemia : low blood calcium: associated with whelping, queening and nursing.
• Hyperkalemia ; high blood potassium: associated with Addison's Disease or urinary obstruction: found with some blood testing
• Hyperlipoprotienemia : High blood fat content: serum is lipemic or greasy. Blood tests show abnormal lipid panel: seizures associated with high fat meals: usually Schnauzers or Shelties
• Garbage intoxication : bacterial toxins ingested during dietary indiscretion may lead to seizures. Usually a history of eating something we shouldn't have.
Intra cranial diseases are the following and usually have an unusually history, are slowly progressive and have subtle to profoundly abnormal neurological examination findings.
• Inflammation/infection : Canine distemper virus, toxoplasmosis, cryptococosis, blastomycosis, Lyme disease, rabies, feline infectious peritonitis, and post-vaccinational encephalitis. These patients are severely ill with unusual neurological findings and progress rapidly without treatment.
• Trauma : Any head trauma may cause seizures immediately or in the future due to damaged cells having a lower threshold.
• Cancer or other masses : Usually have subtle but progressive neurological disease. REFERAL for a MRI is needed to make this diagnosis.
• Birth defects : Hydrocephalus (water head) domed cranium, open fontanel usually young at onset of seizures and may have other neurological findings. Lissencephaly & pachygyria seizures start before one year of age and only seen in Lhasa 's and Wire Haired Fox Terriers.
• Degenerative diseases : History of exposure, blood or urine tox screens are helpful here. Thiamine deficiency in cats (rarely seen today in cats on a commercial diet); strokes; poisons including the following lead, mercury, arsenic, strychnine, chlorinated hydrocarbons, organophosphates, hexachlorophene and antifreeze.
• Idiopathic epilepsy : A left over diagnosis, if no other causes can be found this is what we call the cause of the seizures.
This list is extensive but not exhaustive. What we will attempt to do is narrow it down to one or two options with a good history, physical exam, neurological exam, and some laboratory testing. When the list is eliminated the only diagnosis left is IDIOPATHIC EPILEPSY .
Now that we have found a cause of the seizures we can treat them by either eliminating the primary disease or trying to raise the seizure threshold of the patient. The goal of treating seizures is not to eliminate the seizures but to reduce the severity, frequency and duration of the seizures to less than one episode a month and durations of less than five minutes. To monitor this effect it is essential that you keep a calendar of when how and how long( yes please time them) the seizures are occurring. Only with this information can we plan or modify a treatment schedule and even know if it is working or not.
( Please bear in mind that the brain is very prone to abnormal function for 96 hours after the last seizure so clusters over 1-4 days are part of one episode and neurological exams may need to be repeated if abnormalities are found within this 96-hour window.)
If the calendar shows clustering over a 96-hour period, durations of greater than 5 minutes or frequencies greater than once a month we will recommend preventative therapy starting with Phenobarbital at 1 mg/lb twice a day. Phenobarbital is a barbiturate that raises the seizure threshold but dose not decrease its propagation once it starts. Side effects may include sedation, ataxia, and liver problems. Dosages changes take 7-10 days to stabilize so do not expect immediate results. Since it may cause some liver damage and it is a federally controlled substance annual blood work is needed while on the product or if control is less than ideal.
If the side effects are sever or we have poor control we can then add in potassium bromide, an experimental drug that has shown great promise at 20-32 mg/kg per day. KBr raises the threshold also and it decreases the propagation once a seizure starts. Side effects are rare and usually involve some vomiting, diarrhea or occasionally in coordination.
In conclusion if your dog is having seizures, keep a calendar, time them, and when needed we can start on medications to reduce the severity, frequency and duration of the seizures, however we rarely if ever totally eliminate them all together.
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