Brain Disease in Dogs: Causes of Seizure Disorders in Older Dogs

The most common types of disease in dogs, older than 5 years old, that cause seizures are cancerBrain Disease in Dogs: Causes of Seizure Disorders in Older Dogs (neoplasia), metabolic diseases, acquired epilepsy, toxins and trauma.  Toxicities and trauma are straightforward causes of seizures in animals.  Many chemical intoxicants can produce seizures, the most common being organophosphates (commonly used to control parasitic disease in dogs), chlorinated hydrocarbons, strychnine, and lead.  Trauma can cause a seizure immediately after or within a few days of a severe head injury, but can occur up to 2 years following the traumatic event.

Neoplastic (cancerous) disease in dogs that cause seizures.

Primary or metastatic neoplastic disease in dogs can affect the cerebral cortex and rostral brain stem, resulting in seizures as well as behavioral abnormalities.  Neoplasia (cancer) can occur at any age, but is more common in older animals.  Signs may have a slow rate of onset, and worsen as the tumor and secondary edema surrounding the tumor involves a larger area of the brain.  Partial seizures or partial seizures which secondarily generalize are often associated with tumors of the cerebral cortex.  Computerized tomography (CT) is often necessary to localize the tumor and determine the size and extent of the disease.  Skull radiographs are sometimes beneficial if the tumor is involving the bone of the skull rather than the brain itself, but CT is still the preferred imaging modality.  Thoracic radiographs are often advised to screen for metastatic disease that could have also spread to the brain.  Treatment of choice for primary brain tumors is surgery often followed with radiation therapy.

Insulinomas is a type of cancer disease in dogs that involves the pancreas, not the brain, but can result in seizures due to low blood glucose levels.  Insulinomas produce increased amounts of insulin in the blood stream, which causes the blood glucose of the dog to drop, resulting in signs of weakness, mental confusion and seizures.  Treatment with surgical removal is most effective at controlling the disease, but is rarely curative.  As the disease advances various medical treatments exist that may be of benefit of controlling signs of the disease.

Metabolic disease in dogs that cause seizures.

The most common metabolic disease in older dogs that causes seizures is acquired hepatic vascular shunts.  Like congenital hepatic shunts, this is a condition where blood bypasses the liver, which results in blood not being filtered of metabolic waste products by the liver.  The result is a build up of these waste products that can have a negative impact on brain function, causing signs of disease in dogs, including possible seizures.  Unlike a congenital hepatic shunt, new vessels develop that cause blood to bypass the liver rather any an existing blood vessel that does not close the way it was intended to.  The cause is typically a response of the body to liver cirrhosis, which is a severely damaged, nonfunctional liver.  This condition can be managed medically, but long-term prognosis is poor.

Renal (kidney) failure is a disease in dogs that can result in dementia, seizures and comas.  Like the liver, the kidneys are involved in removing toxic wastes from the body.  If these substances are not removed, they can build-up in the blood and affect normal metabolism of the brain and interfere with normal nerve transmission.  Diagnosis is easily detected in routine blood chemistry evaluations.  Prognosis is typically poor as it reflects the terminal stages of renal failure.

Acquired epilepsy as a disease in dogs that can cause seizures.

Acquired or non-inherited epilepsy is a brain disease in dogs that develops as a result of some cerebral insult to the brain that produces permanent damage.  The damage is often mild and produces no neurological defects other than the seizures.  A previous inflammatory, traumatic, toxic or metabolic insult may produce this form of brain disease in dogs.  Although the active disease process that caused the brain insult may be resolved, the animal continues to have periodic seizures.  This type of epilepsy typically is seen in older dogs compared to the inherited form of epilepsy.  Treatment typically involves the use of anti-convulsants (anti-seizure drugs). Click here to learn more about characteristics of seizures and current treatments.

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Dr Stephen Atwater

Stephen W. Atwater, DVM, MS, Diplomate ACVIM (oncology) is a board-certified veterinary oncology specialist. His professional interests include utilizing emerging therapies for difficult to treat cancers.

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