Seizures are sudden neurological events that cause changes in consciousness and involuntary movements. Seizures may manifest in many ways, but the clinical signs are usually the same each time for an individual pet. The duration of a seizure ranges from a few seconds to several minutes.
Seizures are classified as generalized grand mal (involving all of the body) or focal partial (involving just one area of the body).
Seizures can be classified into three categories:
Primary brain abnormalities such as a tumor or congenital defect
Metabolic or toxins that affect brain function
A cause that cannot be identified aka idiopathic epilepsy.
If a pet is diagnosed with seizures before the age of 7 it is more likely that the cause is due to idiopathic epilepsy, and if after 7 years of age it is more likely to have a brain abnormality.
What is Primary Epilepsy?
Primary or idiopathic epilepsy is the major cause of recurrent seizures in dogs between 1 and 5 years of age. Since no obvious evidence of brain injury is found in primary epilepsy, the probable cause of seizures may be related to a pre-existing or hereditary chemical or functional defect in the brain. The typical seizure due to primary epilepsy is a one to two minute generalized convulsion characterized by collapse, stiffening and/or paddling of the limbs, jaw-chomping, salivation, occasional loss of urine and/or feces, and unconsciousness.
Primary Epilepsy may also present with mild focal seizures. Dogs suffering from focal seizures may have odd facial or limb twitching and occasionally odd behavior changes such as sudden episodes of rage.
A seizure event is typically followed by a “post-ictal” or post-seizure period characterized by incoordination, exhaustion, and disorientation.
Diagnostic Work-up for Epilepsy
It is important to rule out other causes of seizures before concluding that a dog has primary epilepsy.
Evaluation of an animal with seizures includes physical and neurological examinations, routine laboratory tests (bloodwork and urinalysis), and sometimes x-rays. Bloodwork to assess the liver and kidney are typically included in the initial work-up since these organs are responsible for breaking down and removing anti-epileptic medications from the body. Additional testing may be recommended based on the results of these baseline tests or if a metabolic or toxic cause is suspected.
Advanced testing may include magnetic resonance imaging (MRI), computed tomography (CT), cerebrospinal fluid analysis, etc. These advanced tests may help identify a specific brain disorder, or certain infections of the brain, and may be necessary if neurological signs are present between seizures or if the seizures are responding poorly to antiepileptic drug therapy.
Home observations are also helpful when diagnosing seizure disorders. It is important to keep a journal of each seizure episode. The journal should include date the seizure occurs, how long the episode lasts, behaviors occurring during the seizure (ictal period), environmental events that occur prior to the seizure that may have precipitated the seizure, and finally any strange behaviors that occur before the seizure (pre-ictal), after the seizure (post-ictal), and between seizures (inter-ictal). Things to watch for and document include changes in behavior, circling, paw knuckling, drunken walking, localized twitching, etc.
When to Start an Antiepileptic Drug and When to Recheck
Antiepileptic drugs are often started after all other causes for seizures have been ruled out via diagnostic testing as outlined above. We advise starting an antiepileptic drug if your pet has an average of 2 or more seizures per month, has one seizure that is very prolonged (more than 5 minutes), or has seizures which occur in a “cluster” (2 or more seizures in one 24 hour period). The goal of drug therapy is to decrease the number and severity of the seizures. A complete “cure” is rarely achieved and dosage changes are often needed. For optimal seizure control, close monitoring of seizure frequency and severity is essential.
Recheck appointments should be scheduled for bloodwork monitoring a few weeks after starting an antiepileptic medication and then yearly. A recheck is also recommended if the medications are not controlling seizures or if the seizures are increasing in duration and frequency.
Potential Treatment Options
For many causes of seizures, there is no cure, however we can help control the frequency, duration and severity of seizures with medications. It can take weeks to months to get your pets seizure activity under control and therefore close monitoring and communication with your veterinarian for monitoring blood levels of medications is essential.
Oral medication is the mainstay of treatment for controlling seizures, and specific treatments are chosen based on whether your pet has primary epilepsy or secondary epilepsy (epilepsy due to another cause). Once your pet is started on a seizure medication, you should not suddenly stop giving the medication because withdrawal seizures may occur.
The following are common medications used:
Zonisamide– This is a relatively new medication in veterinary medicine due to availability of generic variations that are less cost prohibitive. It is often used as a first line anti-epileptic medication due to it being well tolerated in many dogs with few side effects. Zpnosamide is administered twice daily. Most common side effects include decreased appetite, sedation, or incoordination. In rare cases this medication can cause liver damage and decreased tear production. Because this medication is related to the sulfa class of drugs, we do not suggest this medication if your pet is sensitive to sulfa medications.
Levetiracetam (keppra) – Another new medication that recently became available in a cost effective generic. Keppra can be used as a first line anti-epileptic medication. Keppra is administered every 8 to 12 hours. Keppra is one of the safest anticonvulsants with few side effects. Rare side effects include decreased appetite, sedation, or incoordination. In severe rare cases this medication can cause kidney damage.
Phenobarbital – This medication has been a mainstay of anti-seizure medication for a long time, but has become less prescribed due to newer medications becoming more cost-effective with less side effects. The most common side effects include increased thirst and urination, incoordination, and sedation. In addition, this medication can damage the liver, so bloodwork monitoring is performed routinely. Phenobarbital levels can also be monitored by blood work.
Potassium Bromide – Sometimes abbreviated as KBr, is one of the traditional anticonvulsant medications used to treat epilepsy. It is frequently used together with Phenobarbital or Zonisamide, rarely used by itself to control seizure activity. When starting potassium bromide, your vet might recommend an initial loading dose that is higher than the recommended maintenance dose. Potassium bromide is a safe drug with minimal side effects. The most common side effects include increased thirst and appetite and hind limb weakness. Sedation can also be seen initially or if the serum level is higher than therapeutic level. Vomiting is rarely reported.
All pets receiving seizure medication should have bloodwork before beginning the medication to establish base line, then bloodwork is rechecked in 4-6 weeks after starting medication, and then yearly to make sure the liver and kidney are tolerating the medication well. Bloodwork is also monitored following a dosage change.
Prognosis for animals with idiopathic epilepsy is usually good because many of these seizures can be controlled with medications and proper monitoring. Over time the condition may progress and medication doses will need to be adjusted or multiple medications may need to be used in combination.
With other types of seizure disorders, prognosis depends on the underlying cause. If the underlying cause can be resolved the prognosis is good. If the cause cannot be determined or cannot be treated, prognosis is guarded.