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What are seizures?
Seizures (convulsions or fits) are the result of a sudden and uncontrolled burst of electrical activity within the brain. They are one of the most common neurological disorders in cats, although the prevalence is much lower than that of dogs. Seizures occur in the cerebrum, which is located in the front of the skull and is responsible for sensory and neural functions as well as behaviour.
Seizures can affect cats of any age, however as many of the underlying causes occur more in older cats, seizures are more common in middle aged to senior cats. Approximately 0.5 – 1% of cats are affected by seizures.
Seizures fall into two categories:
- Tonic-clonic seizures – Formerly known as generalised or grand mal seizures, tonic-clonic seizures are a type of seizure that affects the entire brain.
- Focal seizures (partial or local seizures) – Focal seizures are restricted to one location in the brain. Focal seizures are further divided into simple focal or complex focal. Simple focal seizures are when consciousness remains, complex focal seizures are when there is a change or loss of consciousness.
Any disease which alters the way the brain functions can potentially cause seizures. Epilepsy is the most common cause of seizures in cats and is defined as recurring seizures resulting from an intracranial cause (see below). It calls into two categories:
- Inherited, acquired or idiopathic (no known cause)
- Symptomatic epilepsy
Causes of seizures may be extracranial (problems occurring outside the brain) or intracranial (problems occurring inside the brain).
Some common causes of seizures include:
- Brain tumour, benign or cancerous (meningioma, glial cell tumours, and lymphoma)
- Head trauma
- Hydrocephalus (water on the brain)
- Brain infections or inflammation such as meningitis and encephalitis
- Bleeding into the brain
- Abnormal migration of heartworm
Intracranial diseases are the most common causes of seizures in cats.
- Heat stroke
- Portosystemic shunt
- Bacterial (tetanus) or viral infection (FIP, feline leukemia virus)
- Fungal infection (blastomycosis cryptococcosis)
- Kidney failure
- Liver disease can cause a build-up of toxins in the body, which can lead to seizures
- Certain medications (antibiotics, antihistamines)
- Poisoning – Common causes of poisoning include antifreeze, lead, insecticides, tea tree, snail bait, aspirin, marijuana, zinc, pseudoephedrine, chocolate, flea products
- Hypertension (high blood pressure)
- Metabolic disorders – Hypoglycemia (low blood sugar), hyperglycemia (high blood sugar), uremia, hypercalcemia (high blood calcium), hypocalcemia (low blood calcium), hypothyroidism
- Feline ischemic encephalopathy – A neurological disorder caused by parasitic infection of the cuterebra larvae which are located in North America, South America, and Canada.
- Lysosomal storage disease
- Thiamine deficiency
- Systemic lupus erythematosus
Symptoms can vary depending on the severity of the seizures as well as the underlying cause. Nonspecific signs may include unusual behaviour, lethargy, anorexia. There may be accompanying symptoms if there is an underlying cause.
Focal seizures affect only part of the body (for example the face), whereas clonic-tonic seizures affect the entire body. Most seizures last between 5 – 60 seconds but may be longer.
Seizures come in three phases known as preictal phase (also known as aura), ictal phase and postictal phase.
Common symptoms of seizures may include:
- Involuntary vocalisation/calling out
- Ear, eyelid and whisker fluttering or twitching
- Rigid extension of the legs
- Loss of consciousness
- Involuntary urination and/or defecation
- Loss of breathing
- Salivation/foaming at the mouth
- Champing or chewing
- Tongue biting
There may be subtle signs in your cat prior to him having a seizure such as mild changes in behaviour, pacing, crying, clinginess, and attention seeking.
Please be aware that while (and often after) a seizure has occurred, your cat may not be aware of his surroundings and it is common for him to not respond to, or recognise you. His actions are involuntary and it is important you keep a safe distance from him as it is possible you may get injured.
As soon as the seizure is over, take your cat to a veterinarian. Seizures lasting longer than five minutes are an immediate danger, seek veterinary attention immediately.
Your veterinarian will perform a complete physical and neurological examination of your cat. He will obtain a medical history from you including onset of symptoms, how many seizures your cat has had, any medications or poisons your cat could have ingested (accidentally or given by the owner), any recent accidents or illnesses when your cat was last vaccinated. Diagnosis is difficult unless your veterinarian sees your cat having an actual seizure at his practice. There is no test to diagnose seizures in cats.
- Biochemical profile, complete blood count, and urinalysis to evaluate the overall health of your cat and evaluate how the liver and kidneys are functioning.
- Imaging of the brain such as CT or MRI scan.
- Antigen testing for certain infections.
- Ultrasound to check for a portosystemic shunt.
- Fecal examination to look for the presence of parasites.
- Bile acid test to measure the performance of the liver.
- Metabolic screen to look for abnormal metabolites in the cat’s urine. This may indicate lysosomal storage disease.
- Cerebral spine fluid (CSF) analysis to check for encephalitis (inflammation of the brain).
In some cases, a cause can not be determined, in which case your cat will be diagnosed with primary or idiopathic seizure disorder.
The goal of treatment for seizures is to find the underlying cause and treat it.
Some conditions are completely reversible (such as lead poisoning, low blood sugar, certain infections for example), and once this has occurred then the seizures should stop completely.
Other conditions may be managed, but not completely eliminated, if a head trauma has occurred causing brain damage or some brain tumours which are inoperable. If this is the case, your cat may be put on anti-convulsant medications which include phenobarbital, gabapentin, levetiracetam, and zonisamide. This medication can cause some side effects including ataxia, increased appetite, thirst, and urination.
If your cat is presenting with a seizure, your veterinarian may give your cat medication such as Valium to stop a prolonged seizure.
- It is quite common for a cat who has had one seizure to have repeat seizures at a later date, therefore it is recommended he be kept indoors.
- Administer medication as instructed.
- Regular follow-ups will be necessary to ensure the medication is working and it is not causing any side effects.