A seizure is a momentary, involuntary disruption of normal brain function. It may transpire once as the result of illness or trauma and never repeat again. Seizures that occur in repeated episodes over a period of time are called epilepsy. Epileptic seizures are either idiopathic (primary) and have no known cause, or symptomatic (secondary) and have an identifiable medical cause. Several types of seizures can present in dogs for a variety of reasons.
Generalized, or tonic-clonic, seizures are typically associated with idiopathic epilepsy. They can be grand mal or mild. Grand mal seizures are considered classic seizures. They present with loss of consciousness, apnea, rigid limbs, paddling, facial twitching, chewing, pupil dilation, urination and defecation. They usually last less than two minutes. The dog may bounce back immediately but most likely will recover slowly over several hours. In a mild generalized seizure, the dog usually does not lose consciousness and there's very little limb rigidity or paddling.
Petit Mal Seizures
Petit mal, or absence, seizures are either very rare in dogs or so slight that they simply go unnoticed. Most professionals agree that a petit mal cannot be properly diagnosed without an EEG. As opposed to other types of seizures, they create inhibition in the brain rather than excitation, resulting in a unique EEG pattern. These seizures manifest with a brief lapse into unconsciousness, a blank stare, loss of muscle tone and momentary eye rotation.
Partial, or focal, seizures are generally associated with symptomatic epilepsy. They're restricted to one area of the body and typically manifest as movement in one limb, muscle jerking, turning the head, bending the trunk or facial twitches. Partial seizures can progress and be mistaken for generalized seizures, but the prognosis can be established by determining if the seizure began in one body part.
Complex Partial Seizures
Also called psychomotor or behavioral seizures, complex partial seizures are generally associated with symptomatic epilepsy. They occur in the part of the brain connected with emotion and manifest with odd, repeated behaviors such as lip-smacking, aggression, cowering, hiding, vocalization, flank biting or hysterical running. Physical symptoms include lack of awareness, abdominal distress, salivation, vomiting, diarrhea, blindness, unusual thirst or appetite. Symptoms can last a few minutes to several hours and may be followed by a generalized seizure.
More common in large breed dogs, cluster seizures are multiple seizures that occur within a period of time. In cluster seizures, the dog will seize, almost recover, then seize again. This cycle can repeat again and again over a few to 24 hours, and may possibly culminate in status epilepticus (continuous seizure). Cluster seizures are a true medical emergency and should be treated immediately by a veterinarian.
Status epilepticus is a continuous seizure lasting 30 minutes or more, or a series of continuous seizures with no recovery in between. It's associated with both idiopathic and symptomatic epilepsy, but can also arise suddenly in dogs who have never seized before or shown signs of illness. Often confused with cluster seizures and just as dangerous, status epilepticus is an urgent-care situation requiring immediate veterinary care.