Epilepsy is defined as a neuro-electrical disturbance somewhere in the cerebrum or forebrain. It can be broken up into three major categories: Primary epilepsy, secondary epilepsy and reactive epilepsy. They are easiest to discuss in reverse order.
Reactive epilepsy is when the neuro-electrical disturbance comes from outside the central nervous system and is due to an underlying reactive or metabolic cause. Examples of this include low blood sugar, various toxins, kidney disease, liver disease as well as many other disease processes. Normal blood and urine work-up effectively rule out approximately 85-95% of the reactive forms of epilepsy, but some forms will not result in abnormal blood/urine work-up.
Secondary epilepsy is when the neuro-electrical disturbance comes from inside the central nervous system and it is secondary to some underlying cause. Examples of this form include brain tumors, focal or diffuse infectious or inflammatory lesions of the brain, decreased blood flow to a portion of the brain (stroke), head trauma, and other disease processes. In order to rule out secondary forms dogs have a mild seizure once every few months of epilepsy, a CT or MRI scan of the brain and cerebrospinal fluid (CSF) collection and analysis need to be performed. These are described in more detail later.
Primary Epilepsy is also referred to as idiopathic epilepsy. This is a fancy medical term meaning we have no idea what causes the condition. However, we do know that it is genetic and it occurs inside the central nervous system. This is a diagnosis of exclusion made by normal blood/urine work-up, normal CT/MRI scans, and normal cerebrospinal fluid analysis. Patients that fall in in this category typically have their first seizure episode between 6 months and 5 years of age.
Primary epilepsy is the most common cause of seizures in dogs.
Secondary or reactive forms of epilepsy are the most common cause of seizures in cats.
Dogs with epilepsy have a wide range of how severely they are affected. Some dogs have a mild seizure once every few months, while others have very severe seizures every couple of weeks. Dogs that have mild seizures once every few months frequently do not require medications to help control the seizures. Dogs who have severe or frequent seizures often require daily medications. When we see the first seizure we usually recommend bloodwork to make sure there is not an underlying medical problem that has caused the seizures. If the bloodwork is normal, the frequency of seizure episodes is low and there is absence of cluster seizures (multiple seizures in a row) we will often recommend monitoring the patient at home to gather more information about frequency and severity prior to making any further decisions. Start keeping a log of every seizure; record the length of the seizure (look at your watch; they always seem longer than in reality), record the time of day, describe the seizure, and note if anything unusual happened immediately before the seizure that may have triggered the episode. Some dogs seizure with as little stimulus as whenever company arrives, while others don't seem to have anything specific that seems to correlate with seizure activity. If we see that seizures will be very infrequent and mild, we may not need to give any medications. If the seizures become more frequent or severe, we may need to start medications to help control the frequency and/or severity of the seizures. The most frequently used medication to help control seizures is phenobarbital. It most often comes in tablet form and is given twice daily. Blood levels are monitored to help determine whether any adjustments to the dosage are necessary. Your log will identify seizure trends that will be used to determine when and how to medicate your pet.
If phenobarbital is started, blood levels should be checked in 12-14 days in order to fine-tune the dosage. The best time to draw this blood sample is just before the next dose is due ("trough" or the lowest level in the bloodstream). This test should also be run 10-12 days after any change in dosage. Once the medical treatment regimen has been customized to your pet, we recommend that a trough phenobarbital levels and a liver panel be checked every 6 months to monitor your pet's response to the medication.
If your pet's whose condition is not typical of primary or idiopathic epilepsy, more advanced diagnostic testing may be required to arrive at a definitive diagnosis. A complete neurological work-up may include:
CT or MRI scan of the brain to rule out tumors, lesions or malformations of the central nervous system
Cerebro-spinal fluid collection and analysis (for culture, cytology, titers, etc)
These tests require general anesthesia and can only be done at a specialty practice. We frequently use GVS (Georgia Veterinary Specialists) in Sandy Springs and the Veterinary Colleges at The University of Georgia and Auburn University for these services.
