What are focal seizures?
A seizure is an abnormal surge of electrical activity within the brain. When an animal experiences a seizure, the electrical signals become hyperactive and begin firing abnormally, causing various visible effects on the body. This abnormal activity often arises without any specific trigger and is usually self-limiting (resolves on its own without treatment).
A focal seizure refers to an abnormal electrical activity surge confined to a specific area of the brain. Unlike a generalized seizure, in which the animal’s entire brain is affected, and the whole body shows signs of a seizure, a focal seizure only affects a localized region of the brain and, therefore, only has limited effects on the body. These effects may vary significantly, depending on which part of the brain is affected.
What is fly-biting?
Fly-biting seizures are a type of focal seizure in which a cat snaps at the air like she is biting at invisible flies. These episodes usually begin without warning while the cat is resting or relaxed. Some cats snap casually and intermittently at the air during these episodes, while others become frenzied and possibly aggressive. During these fly-biting episodes, cats typically remain aware of their external environment. In many cases, they can even be distracted from these episodes by their owners.
How are fly-biting and focal seizures diagnosed?
The only way to definitively determine that fly-biting and other suspected focal seizures are caused by seizure activity is through an electroencephalogram (EEG). This test allows a veterinary neurologist to record your cat’s brain waves during an episode to determine whether the behavior is caused by abnormal electrical activity within the brain. Unfortunately, fly-biting and other focal seizures often occur intermittently and unpredictably, making this test impractical in most cases.
"If your cat’s clinical signs suggest fly-biting or other focal seizures, your veterinarian will perform tests to rule out other causes of these episodes."
Therefore, fly-biting and focal seizures are typically a ‘diagnosis of exclusion’. If your cat’s clinical signs suggest fly-biting or other focal seizures, your veterinarian will perform tests to rule out other causes of these episodes. Bloodwork may be performed to assess the function of your cat’s liver, kidneys, and other internal organs. Your veterinarian will also test for the presence of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV), two viral infections associated with neurologic signs.
Your veterinarian may also recommend additional testing, such as infectious disease titers, abdominal ultrasound to assess the internal organs, brain imaging (CT scan or MRI), or cerebrospinal fluid analysis. While these tests often come back normal in patients with fly-biting or focal seizures, it is essential to perform this workup to rule out underlying medical conditions. If your cat has an underlying medical cause for fly-biting, treating that condition will be necessary for successfully managing the episodes.
Once a diagnosis of focal seizures or fly-biting has been suggested, response to treatment can often be used to confirm the diagnosis.
How are focal seizures treated?
The same anti-epileptic medications used for generalized seizures can be used to manage focal seizures and fly-biting. Medications commonly used for treating seizures in cats include phenobarbital, zonisamide, potassium bromide, and levetiracetam. These medications vary in their benefits and possible side effects, so your veterinarian will consider your cat’s individual history to determine which medication to prescribe.
"If your cat is started on anti-epileptic medication, she will likely continue them for the rest of her life."
If your cat is started on anti-epileptic medication, she will likely continue them for the rest of her life. Long-term use of anti-epileptic medications requires laboratory monitoring, although the exact requirements for monitoring vary based on the specific drug and patient. Some medications require only the monitoring of routine screening bloodwork (to assess for side effects). Other medications require monitoring the drug’s blood levels to ensure that changes in dosage are not needed.
What is the prognosis for focal seizures?
If focal seizures are infrequent, they can often be left untreated. Frequent focal seizures, however, can negatively impact a cat’s quality of life and require treatment. With treatment, many cats will experience a reduction in the frequency or severity of their focal seizures. It may take trials of several different medications to find an effective treatment. In rare situations, focal seizures (especially those that are frequent or severe) can progress over time to generalized seizures, significantly impacting the cat’s overall health and quality of life.
