West J Med. 2001 August; 175(2): 99–103.
PMCID: PMC1071497
Copyright © Copyright 2001
BMJ Publishing Group
Straight to the Point
Seizure disorders: Part 1.
Classification and diagnosis
Sandra Kammerman and Lloyd Wasserman
Department of Medicine New York University School of Medicine
Bellevue Hospital
462 First Ave New York, NY 10016
EPIDEMIOLOGY
CLASSIFICATION OF SEIZURES
* Seizures are the most common acute neurologic problem in the United States
* Epilepsy (recurrent seizures) is the third most common serious neurologic disorder, following stroke and Alzheimer's disease.
* The age-adjusted incidence of newly diagnosed epilepsy is 44 per 100,000 person-years.
* The incidence of epilepsy increases with advanced age; people over 75 are twice as likely to develop new-onset epilepsy as all adult age groups under 65.1
* By age 74, 3% of all people will have had epilepsy at some point in their lives. For those living to 85, the cumulative incidence rises to 4.4%.1
* The prevalence of active epilepsy is 0.68%. The prevalence of all unprovoked seizures (including epilepsy) is 0.82%.2
Table 1
Terminology
* Seizure: an uncontrolled, paroxysmal neuronal discharge in any part of the brain; it may cause physical or mental symptoms and may be convulsive or nonconvulsive
* Convulsion: involuntary contraction of body muscles
* Epilepsy: two or more unprovoked, recurrent seizures. Seventy-five percent of epilepsy is primary (idiopathic); 25% is secondary to another CNS disorder.1
* Simple seizure: no alteration of consciousness
* Complex seizure: alteration of consciousness
* Status epilepticus: epileptic seizures that last more than 30 minutes or occur so frequently that consciousness is not restored between seizures
Partial (focal) seizures
* These seizures account for almost 60% of new cases of epilepsy.
* Simple partial seizures occur in about 15% of patients with seizures. Depending on the area of cerebral cortex involved, symptoms may be motor, cognitive, sensory, autonomic, or affective. Consciousness is not impaired.
* Complex partial seizures, also known as temporal lobe or psychomotor seizures, occur in approximately 35% of patients with seizures. Consciousness is partially or completely impaired, but there is no initial generalized tonic-clonic activity. Clinical presentation is variable, but patients usually experience an aura, automatism, postictal confusion, or tiredness. They have no memory of the events during the seizure.
* Partial seizures evolving to generalized seizures begin locally but then generalize.
This system classifies seizures by clinical symptoms and is easy to use. Another widely used but more complicated system classifies epileptic “syndromes” and includes other data such as family history, exposure history, physical examination, electroencephalography (EEG), imaging, and biochemical studies.
Generalized seizures
* These seizures account for 40% of patients with epilepsy.
* Initial manifestations indicate involvement of both hemispheres, most commonly impairment of consciousness with bilateral motor involvement.
* Patients usually forget the events of the seizure.
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Types and characteristics.
* Six types of generalized seizures and their presenting signs are described in table 1
* Absence (petit-mal) seizures occur in 5% of patients with seizures, primarily in children
* Tonic-clonic (grand-mal) seizures occur in 25% of all patients with seizures and are the most common type of generalized seizure in adults.
Types and characteristic signs of generalized seizures
Distinguishing secondarily generalized partial seizures from primary generalized seizures.
* Many patients with partial seizures that generalize incorrectly report their seizures as “grand mal.”
* Distinguishing factors favoring secondarily generalized partial seizures are as follows:
o Preceding the seizure: period of unresponsiveness and staring, aura, automatisms, focal motor phenomena
o Past occurrence of any of the above factors without impairment of consciousness
o Focal findings on neurologic examination, magnetic resonance imaging (MRI)
o Focal activity on the electroencephalogram (EEG)
o Adult onset of seizures
DIAGNOSIS
General approach
For a first seizure, it is important to distinguish between an isolated event that is caused by an unusual stress, such as alcohol withdrawal, high fever, or hypoglycemia, and an unprovoked event that may be the initial manifestation of a recurrent seizure disorder (epilepsy).
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Table 4
Causes of nonepileptic seizures
* Alcohol withdrawal
* Benzodiazepine withdrawal
* Massive sleep deprivation
* Excessive use of stimulants, cocaine, etc
* Psychogenic (conversion disorder, somatization, factitious disorder, malingering)
* Acute head trauma (within 1 week)
* Central nervous system infection or neoplasm
* Uremia
* Eclampsia
* High fever
* Hypoxemia
* Hyperglycemia or hypoglycemia
* Electrolyte disorders
Neurocysticercosis and malaria are common causes of seizures worldwide and should be considered in patients from high-risk areas.
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Common precipitants
* Emotional stress
* Hyperventilation
* Menstrual cycle
* Sleep deprivation
* Alcohol withdrawal or excess
* Photic stimulation (strobe lights, television)
* Febrile seizures are very rare in adults
Refer patients to the Epilepsy Foundation , an excellent resource for group support, information, and counseling.
Patients with epilepsy are protected by the Americans with Disabilities Act.
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