Potential causes of seizures

  • Primary Epilepsy – also known as idiopathic, genetic, or inherited epilepsy. Epilepsy is assumed to inherited when no diagnostic evidence can be found to explain the cause of seizures. It is a case of ruling out every other possibility. The first seizure in a dog with primary epilepsy usually occurs between the ages of 6 months and 5 years. The age of onset and family history may suggest a genetic basis for primary epilepsy if there is a familial history of seizures.

 

  • Secondary Seizures –refers to seizures for which an underlying cause can be determined. Some possible causes include:
    • Hypoglycemia (low blood sugar)
    • Hypothyroidism (low thyroid)
    • Drug reactions in dogs with the MDR1 mutation
    • Infections causing brain damage (such as canine distemper, Cryptococcosis, etc.)
    • Toxicity (ingestion of lead paint chips, insecticide, poisons, etc.)
    • Brain tumor
    • Portosystemic shunts. Improperly routed intestinal blood vessels bypass the liver (one of the body’s important waste-product detoxifiers)
    • Cobalamin malabsorbtion
    • Neuronal ceroid lipofuscinosis
    • Acepromazine – can reduce the seizure threshold and thus bring on a seizure.
    • Trauma
  • In dogs less than one year of age, the most commonly-found causes of seizures can be broken down into the following classes: degenerative (storage diseases); developmental (hydrocephalus); toxic (lead, arsenic, organophosphates, chlorinated hydrocarbons, strychnine, tetanus); infectious (distemper, encephalitis, and others); metabolic (such as transient hypoglycemia, enzyme deficiency, liver or kidney failure); nutritional (thiamine, parasitism); and traumatic (acute injury). In dogs 1-3 years of age, a genetic factor is most highly suspected. In dogs 4 years of age and older, seizures are commonly found in the metabolic (hypoglycemia, cardiovascular arrhythmia, hypocalcemia, cirrhosis) and neoplastic (brain tumor) classes. Under each age category (the age when seizures first occurred), the possible causes (etiology) are approximately listed as the most likely first and the least likely cause last.
    • Less Than 1 Year of Age
      • Anomaly: hydrocephalus.
      • Inflammatory:
      • Infectious – Viral: canine distemper; parasitic; bacterial; fungal
      • Immune mediated
      • Metabolic:
        • Hepatic – portosystemic shunt; Autoimmune thyroiditis (early stage: TgAA positive); Hypoglycemia; Electrolyte disorders
        • Toxic: Single or combination vaccines; Lead; Drug related; Other exposures
        • Trauma: Acute; Delayed
        • Degenerative: Storage disorders
        • Primary (Idiopathic) Epilepsy
      • Between 1 – 5 Years of Age
        • Primary (Idiopathic) Epilepsy
        • Inflammatory:
          • Infectious – Viral: canine distemper; parasitic; bacterial; fungal
          • Immune mediated
          • Metabolic:
            • Hepatic – Thyroid dysfunction; portosystemic shunt; Hypoglycemia; Electrolyte disorders
            • Anomaly: hydrocephalus
            • Trauma: Acute; Delayed
            • Toxic: Single or combination vaccines; Lead;
            • Drug related; Other exposures
            • Neoplasia: Primary; Metastatic
      • 5 Years of Age and Older
        • Neoplasia: Primary; Metastatic
        • Metabolic:
          • Thyroid dysfunction; Hypoglycemia – insulinoma;
          • Hepatic – cirrhosis; Electrolyte disturbances
          • Vascular:  Focal ischemia – Thromboembolism; vasospasm
          • Hemorrhage: hypertension; vasculitis
          • Inflammatory:  Infectious – Viral: canine distemper; parasitic; bacterial; fungal
          • Immune mediated
          • Primary (Idiopathic) Epilepsy
          • Degenerative
          • Toxic: Lead; Drug related; Other exposures

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