A seizure is an episode characterized by altered behavior, consciousness, movement, sensation, or autonomic function due to hypersynchronous excessive firing of a network of neurons. The differential diagnosis of seizures is listed in
Table 68-1.
Generalized seizures rapidly engage bilaterally distributed networks.
Focal seizures begin in one portion of the brain with symptoms related to that region’s function. Prior classification systems separated focal seizures into simple partial seizures (remain restricted to a region without affected alertness), complex partial seizures (spread to involve adjacent regions such that consciousness is affected), and secondarily generalized seizures (spread widely to involve the entire cortex). In the most recent International League Against Epilepsy (ILAE) classification, the terms simple and complex are replaced with the more descriptive phrases “without impairment of consciousness or awareness” and “with impairment of consciousness or awareness,” respectively, and can also be designated as “evolving to a bilateral, convulsive seizure.”
Seizures may occur in an individual with an underlying tendency to have recurrent seizures (
epilepsy) or may be secondary to an ongoing process that primarily or secondarily affects the brain (
acute symptomatic seizures). The initial evaluation of a patient with a seizure must focus on identifying and treating any underlying condition that may be causing seizures. Prolonged or multiple recurrent seizures without return to baseline mental status are called
status epilepticus. Types of seizures are listed in
Table 68-2.
Epilepsy is defined by recurrent unprovoked seizures. In more detail, the ILAE defines epilepsy as a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures and by the neurobiologic, cognitive, psychological, and social consequences of this condition. Epilepsy may be classified based on the underlying etiology as
genetic, structural-metabolic, and unknown.
Genetic refers to epilepsy caused by a known or presumed genetic defect. The genetic mutation may be known, such as a mutation in a sodium ion channel (e.g., SCN1A mutation) or may be suspected due to a family history of seizures.
Structuralmetabolic includes epilepsy related to an underlying structural or metabolic etiology. Structural defects include cortical malformations (e.g., dysplasias, tubers) or acquired defects such as strokes or trauma.
Unknown indicates that the etiology of the epilepsy is not known and may be related to an undiagnosed genetic defect or an unrecognized disorder. In some patients, the clinical history, age, seizure type, and electroencephalographic (EEG) findings can be grouped into an epilepsy
syndrome that can guide management and suggest prognosis. Common pediatric epilepsy syndromes are listed in
Table 68-3 and described in the following.
HINT: Consider acute symptomatic etiologies when evaluating a patient with a first seizure. Epilepsy (unprovoked seizures) is a diagnosis of exclusion.
DIFFERENTIAL DIAGNOSIS LIST
