Many things can tip the balance between excitation and inhibition in the brain toward too much excitation. Keep in mind, we’re talking about the excitatory influences on nerve cells in the brain, not the dog’s emotional state. Once a certain threshold of excitation has passed, any animal may seize. Things that can push an animal past that threshold include toxins, metabolic diseases, and direct damage to the brain.
Some plants have evolved toxins which cause seizures as a defense against insects or other plant-eating animals. If your pet eats such plants, they could be similarly affected. We utilize some of these plant toxins and related chemicals as insecticides to protect our pets from fleas and our tomatoes from horn worms and these insecticides can cause seizures if used inappropriately. Other toxins, such as lead and some industrial chemicals, can also cause seizures. Thus your veterinarian will need to know about potential exposure to these compounds if your pet has a seizure.
Seizures and metabolic state of the pet
The metabolic state of the pet will also influence the brain and can secondarily cause seizures. If the brain doesn’t get an adequate supply of oxygen and nutrients to fill its needs, the excitability of the cells may increase and seizures result. Thus low blood sugar or heart disease may cause seizures. Electrolytes (different salts normally present in the body) play important roles in brain function. Alterations of these electrolytes (particularly sodium and calcium) can cause seizures. Low calcium levels can be a problem in a nursing mother. Toxic byproducts are constantly being produced in our body from normal activities of the organs. The liver and kidneys have the job of getting rid of these toxic byproducts. If either of these organs isn’t able to do its job, these byproducts can accumulate and seizures may be one of the results. If your pet is having seizures, your veterinarian will recommend blood tests both to determine if one of these metabolic diseases is the cause and to provide a base line to watch for potential side effects of the antiepileptic drugs which may be used.
Damage to the brain from seizures
Physical damage to certain areas of the brain can produce an epileptic focus. This is a small area of the brain that initiates focal seizures which in turn can lead to generalized seizures. We don’t know how local damage causes the electrical storm in that area, but we do know that many types of damage can have this effect. Thus head trauma, brain tumors, infections in the brain (encephalitis), strokes, just about anything that damages the brain can lead to seizures. If your veterinarian suspects such brain damage as the cause, they may refer you to a veterinary neurologist for brain scans, spinal taps, or other tests to be sure there isn’t a brain tumor or other explanation for the seizures. We become especially worried about such acquired damage if the dog falls outside the age range where we typically see hereditary epilepsy, that is if they are less than one year or more than 3-5 years old. Sometimes, removing the cause of the damage cures the epilepsy. Other times, the damage has been done, and even if we can’t remove the tumor or control the infection, the pet is often left with epilepsy. Even if we don’t cure the epilepsy, the seizures will be easier to control without the continuing damage from an untreated tumor or infection. In addition, such a disease left untreated may well cause other, potentially even more serious problems.
Source: Seizures: What You Need to Know; Hurricane Animal Hospital