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<< Seizures and Status Epilepticus: Diagnosis and Management in the Emergency Department
Definitions And Classification
A seizure is a sudden change in behavior characterized by changes in sensory perception or motor activity due to an abnormal firing of neurons. The clinical spectrum of seizures is expansive and includes focal or generalized motor activity, altered mental status, sensory or psychic experiences, and/or autonomic disturbances.
The term epilepsy describes a condition of recurrent unprovoked seizures from known or unknown causes. For example, one who suffers head trauma may have a seizure acutely, but they would not be considered to have epilepsy unless they develop recurring seizures as a sequela of the brain injury. Ictus refers to the period during which a seizure occurs, and the postictal period refers to the interval after a seizure ends, but before the patient returns to baseline mental status. The postictal state usually resolves within minutes to an hour, but has been known to last several hours.
Seizures are defined by how they are manifested. A generalized seizure occurs when there is abnormal neuronal activity throughout both hemispheres which causes an alteration in mental status. A focal or partial seizure describes abnormal neuronal firing of a limited and confined population of neurons in one hemisphere of the brain. Partial seizures are further divided into simple or complex. A complex partial seizure involves some degree of impaired level of consciousness. This has been referred to in the past as temporal lobe epilepsy though this term is now archaic. The classification of seizure types is presented in Table 1.
Approximately 40% of focal seizures remain localized, but the remainder develop secondary generalization. These patients are associated with a worse outcome than those who experience generalized seizures primarily. The majority of adults who present to the ED with new onset generalized seizures in fact have partial seizures that have generalized. Of note, an “aura” or abnormal sensation prior to generalized seizure is, in reality, a focal seizure event, and is a key part of the history; consequently, the type of aura is useful in seizure focus localization.
Historically, status epilepticus has been defined as 30 minutes of continuous seizure activitiy or sequential seizures without return to normal mental baseline.1 For a number of reasons, this should not be used as a time frame to guide initial therapy.2 Prolonged seizures are associated with difficult seizure termination and considerable morbidity and mortality; therefore, treatment should not be delayed. 2, 3, 4
There is evidence that a seizure that does not spontaneously resolve in 5 to 10 minutes is unlikely to resolve quickly. In one prospective childhood study, seizure duration had a bimodal distribution at 3.6 minutes in one group (76% cases), and 31 minutes (24%) in the other.5 Nonconvulsive status epilepticus (NCSE) refers to continuous seizure activity without predominant motor activity. This should not be confused with subtle status epileptics which refers to generalized convulsive status epilepticus (SE) in which the motor findings have diminished either through high doses of administered medications or from muscular fatigue due to prolonged seizure activity.
The term epilepsy describes a condition of recurrent unprovoked seizures from known or unknown causes. For example, one who suffers head trauma may have a seizure acutely, but they would not be considered to have epilepsy unless they develop recurring seizures as a sequela of the brain injury. Ictus refers to the period during which a seizure occurs, and the postictal period refers to the interval after a seizure ends, but before the patient returns to baseline mental status. The postictal state usually resolves within minutes to an hour, but has been known to last several hours.
Seizures are defined by how they are manifested. A generalized seizure occurs when there is abnormal neuronal activity throughout both hemispheres which causes an alteration in mental status. A focal or partial seizure describes abnormal neuronal firing of a limited and confined population of neurons in one hemisphere of the brain. Partial seizures are further divided into simple or complex. A complex partial seizure involves some degree of impaired level of consciousness. This has been referred to in the past as temporal lobe epilepsy though this term is now archaic. The classification of seizure types is presented in Table 1.
Approximately 40% of focal seizures remain localized, but the remainder develop secondary generalization. These patients are associated with a worse outcome than those who experience generalized seizures primarily. The majority of adults who present to the ED with new onset generalized seizures in fact have partial seizures that have generalized. Of note, an “aura” or abnormal sensation prior to generalized seizure is, in reality, a focal seizure event, and is a key part of the history; consequently, the type of aura is useful in seizure focus localization.
Historically, status epilepticus has been defined as 30 minutes of continuous seizure activitiy or sequential seizures without return to normal mental baseline.1 For a number of reasons, this should not be used as a time frame to guide initial therapy.2 Prolonged seizures are associated with difficult seizure termination and considerable morbidity and mortality; therefore, treatment should not be delayed. 2, 3, 4
There is evidence that a seizure that does not spontaneously resolve in 5 to 10 minutes is unlikely to resolve quickly. In one prospective childhood study, seizure duration had a bimodal distribution at 3.6 minutes in one group (76% cases), and 31 minutes (24%) in the other.5 Nonconvulsive status epilepticus (NCSE) refers to continuous seizure activity without predominant motor activity. This should not be confused with subtle status epileptics which refers to generalized convulsive status epilepticus (SE) in which the motor findings have diminished either through high doses of administered medications or from muscular fatigue due to prolonged seizure activity.
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