Introduction

A seizure is a transient event due to abnormal and excessive neuronal activity in the brain, specifically the forebrain (cerebrum and dien­cephalon). Characteristics of seizures include autonomic signs (salivation, urination, defe­cation, pupillary dilation), tonic or tonic- clonic movements, and rhythmic contractions of facial or appendicular muscles.

Seizures can be characterized by type and pattern. Seizures are often classified as generalized, partial, and complex partial or psychomotor. A generalized seizure, also known as “grand mal,” shows bilateral clinical signs and involves both cerebral hemi­spheres. A partial seizure has clinical signs that reflect restriction to one cerebral hemi­sphere; therefore only one area of the body is affected. A complex partial seizure, also known as a limbic or psychomotor seizure, involves abnormal mentation and some kind of repetitive motor activity like lip smacking. These seizures typically have a significant emotional component, a distinct lack of awareness (no loss of consciousness), and may manifest as aggression, fear, vocaliza­tion, or hysterical running. Most seizures occur as single, discrete events. More than one seizure in a 24-hour period is considered a cluster event. Status epilepticus is often defined as continuous seizure activity for a certain minimum duration (>5-30 minutes) or more than two seizures without regaining full consciousness between episodes.

The terminology for seizure disorders is changing. Epilepsy, in essence, means recur­rent seizures. Currently, what was previously known as idiopathic epilepsy is now called either genetic epilepsy (known genetic defect) or unknown epilepsy (unidentified genetic defect). Structural epilepsy encompasses symptomatic epilepsy, meaning seizures sec­ondary to things like tumors, trauma, or men­ingitis. Cats with seizures and a normal neurologic examination but no diagnostic tests and survive more than 2 years are consid­ered to have presumptive unknown epilepsy.