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A seizure is an abnormal, unregulated electrical discharge that occurs within the brain’s cortical gray matter and transiently interrupts normal brain function. A seizure typically causes altered awareness, abnormal sensations, focal involuntary movements, or convulsions (widespread violent involuntary contraction of voluntary muscles). Diagnosis may be clinical and involves results of neuroimaging, laboratory testing, and EEG for new-onset seizures or anticonvulsant levels for previously diagnosed seizure disorders. Treatment includes elimination of the cause if possible, anticonvulsants, and surgery (if anticonvulsants are ineffective).
About 2% of adults have a seizure at some time during their life. Two thirds of these people never have another one.
Terminology can be confusing.
Epilepsy (also called epileptic seizure disorder) is a chronic brain disorder characterized by recurrent (≥ 2) seizures that are unprovoked (ie, not related to reversible stressors) and that occur > 24 h apart. A single seizure is not considered an epileptic seizure. Epilepsy is often idiopathic, but various brain disorders, such as malformations, strokes, and tumors, can cause symptomatic epilepsy.
Symptomatic epilepsy is epilepsy due to a known cause (eg, brain tumor, stroke). The seizures it causes are called symptomatic epileptic seizures. Such seizures are most common among neonates (see Neonatal Seizure Disorders ) and the elderly.
Cryptogenic epilepsy is epilepsy assumed to be due to a specific cause, but whose specific cause is currently unknown.
Nonepileptic seizures are provoked by a temporary disorder or stressor (eg, metabolic disorders, CNS infections, cardiovascular disorders, drug toxicity or withdrawal, psychogenic disorders). In children, fever can provoke a seizure ( febrile seizures).
Psychogenic nonepileptic seizures (pseudoseizures) are symptoms that simulate seizures in patients with psychiatric disorders but that do not involve an abnormal electrical discharge in the brain.
Common causes of seizures (see Table: Causes of Seizures) vary by age of onset:
In reflex epilepsy, a rare disorder, seizures are triggered predictably by an external stimulus, such as repetitive sounds, flashing lights, video games, music, or even touching certain parts of the body.
In cryptogenic epilepsy and often in refractory epilepsy, a rare but increasingly identified cause is anti-NMDA ( N-methyl-d-aspartate) receptor encephalitis, especially in young women. This disorder also causes psychiatric symptoms, a movement disorder, and CSF pleocytosis. Ovarian teratoma occurs in about 60% of women with anti-NMDA receptor encephalitis. Removal of the teratoma (if present) and immunotherapy control the seizures much better than anticonvulsants.
Causes of Seizures
Seizures are classified as generalized or partial.
In generalized seizures, the aberrant electrical discharge diffusely involves the entire cortex of both hemispheres from the onset, and consciousness is usually lost. Generalized seizures result most often from metabolic disorders and sometimes from genetic disorders. Generalized seizures include the following:
In partial seizures, the excess neuronal discharge occurs in one cerebral cortex, and most often results from structural abnormalities. Partial seizures may be
Partial seizures may evolve into a generalized seizure (called secondary generalization), which causes loss of consciousness. Secondary generalization occurs when a partial seizure spreads and activates the entire cerebrum bilaterally. Activation may occur so rapidly that the initial partial seizure is not clinically apparent or is very brief.
A revised terminology for partial seizures has been proposed [ 1]. In this system, partial seizures are called focal seizures, and the following terms are used for subtypes:
This terminology is not yet in common use.
1. Berg AT, Berkovic SF, Brodie MJ, et al : Revised terminology and concepts for organization of seizures and epilepsies: Report of the ILAE [International League Against Epilepsy] Commission on Classification and Terminology, 2005–2009. Epilepsia51: 676–685, 2010.
An aura may precede seizures. Auras are simple partial seizures that begin focally. Auras may consist of motor activity or sensory, autonomic, or psychic sensations (eg, paresthesias, a rising epigastric sensation, abnormal smells, a sensation of fear, a déjà vu or jamais vu sensation). In jamais vu, a familiar place or experience feels very unfamiliar—the opposite of déjà vu.
Most seizures end spontaneously in 1 to 2 min.
A postictal state often follows generalized seizures; it is characterized by deep sleep, headache, confusion, and muscle soreness; this state lasts from minutes to hours. Sometimes the postictal state includes Todd paralysis (a transient neurologic deficit, usually weakness, of the limb contralateral to the seizure focus).
Most patients appear neurologically normal between seizures, although high doses of the drugs used to treat seizure disorders, particularly anticonvulsants, can reduce alertness. Any progressive mental deterioration is usually related to the neurologic disorder that caused the seizures rather than to the seizures themselves.
Occasionally, seizures are unremitting, as in status epilepticus.
There are several types of partial seizures.
Simple partial seizures cause motor, sensory, or psychomotor symptoms without loss of consciousness. Specific symptoms reflect the affected area of the brain (see Table: Manifestations of Partial Seizures by Site). In jacksonian seizures, focal motor symptoms begin in one hand, then march up the arm (jacksonian march). Other focal seizures affect the face first, then spread to an arm and sometimes a leg. Some partial motor seizures begin with an arm raising and the head turning toward the raised arm (called fencing posture).
Manifestations of Partial Seizures by Site
Epilepsia partialis continua, a rare disorder, causes focal motor seizures that usually involve the arm, hand, or one side of the face; seizures recur every few seconds or minutes for days to years at a time. The cause is usually
Complex partial seizures are often preceded by an aura. During the seizure, patients may stare. Consciousness is impaired, but patients have some awareness of the environment (eg, they purposefully withdraw from noxious stimuli). The following may also occur:
Oral automatisms (involuntary chewing or lip smacking)
Limb automatisms (eg, automatic purposeless movements of the hands)
Utterance of unintelligible sounds without understanding what they say
Resistance to assistance
Tonic or dystonic posturing of the extremity contralateral to the seizure focus
Head and eye deviation, usually in a direction contralateral to the seizure focus
Bicycling or pedaling movements of the legs if the seizure emanates from the medial frontal or orbitofrontal head regions
Motor symptoms subside after 1 to 2 min, but confusion and disorientation may continue for another 1 or 2 min. Postictal amnesia is common. Patients may lash out if restrained during the seizure or while recovering consciousness if the seizure generalizes. However, unprovoked aggressive behavior is unusual.
Left temporal lobe seizures may cause verbal memory abnormalities; right temporal lobe seizures may cause visual spatial memory abnormalities.
Consciousness is usually lost, and motor function is abnormal from the onset.
Infantile spasms are characterized by sudden flexion and adduction of the arms and forward flexion of the trunk. Seizures last a few seconds and recur many times a day. They occur only in the first 5 yr of life, then are replaced by other types of seizures. Developmental defects are usually present.
Typical absence seizures (formerly called petit mal seizures) consist of 10- to 30-sec loss of consciousness with eyelid fluttering; axial muscle tone may or may not be lost. Patients do not fall or convulse; they abruptly stop activity, then just as abruptly resume it, with no postictal symptoms or knowledge that a seizure has occurred. Absence seizures are genetic and occur predominantly in children. Without treatment, such seizures are likely to occur many times a day. Seizures often occur when patients are sitting quietly, can be precipitated by hyperventilation, and rarely occur during exercise. Neurologic and cognitive examination results are usually normal.
Atypical absence seizures usually occur as part of the Lennox-Gastaut syndrome, a severe form of epilepsy that begins before age 4 yr. They differ from typical absence seizures as follows:
Many patients have a history of damage to the nervous system, developmental delay, abnormal neurologic examination results, and other types of seizures. Atypical absence seizures usually continue into adulthood.
Atonic seizures occur most often in children, usually as part of Lennox-Gastaut syndrome. Atonic seizures are characterized by brief, complete loss of muscle tone and consciousness. Children fall or pitch to the ground, risking trauma, particularly head injury.
Tonic seizures occur most often during sleep, usually in children. The cause is usually the Lennox-Gastaut syndrome. Tonic (sustained) contraction of axial muscles may begin abruptly or gradually, then spread to the proximal muscles of the limbs. Tonic seizures usually last 10 to 15 sec. In longer tonic seizures, a few, rapid clonic jerks may occur as the tonic phase ends.
Tonic-clonic seizures may be
Primarily generalized seizures typically begin with an outcry; they continue with loss of consciousness and falling, followed by tonic contraction, then clonic (rapidly alternating contraction and relaxation) motion of muscles of the extremities, trunk, and head. Urinary and fecal incontinence, tongue biting, and frothing at the mouth sometimes occur. Seizures usually last 1 to 2 min. There is no aura.
Secondarily generalized tonic-clonic seizures begin with a simple partial or complex partial seizure, then progress to resemble other generalized seizures.
Myoclonic seizures are brief, lightning-like jerks of a limb, several limbs, or the trunk. They may be repetitive, leading to a tonic-clonic seizure. The jerks may be bilateral or unilateral. Unlike other seizures with bilateral motor movements, consciousness is not lost unless the myoclonic seizure progresses into a generalized tonic-clonic seizure.
Juvenile myoclonic epilepsy is an epilepsy syndrome characterized by myoclonic, tonic-clonic, and absence seizures. It typically appears during adolescence. Seizures begin with a few bilateral, synchronous myoclonic jerks, followed in 90% of cases by generalized tonic-clonic seizures. They often occur when patients awaken in the morning, especially after sleep deprivation or alcohol use. Absence seizures may occur in one third of patients.
Febrile seizures occur, by definition, with fever and in the absence of intracranial infection; they are considered a type of provoked seizure. They affect about 4% of children aged 3 mo to 5 yr. Benign febrile seizures are brief, solitary, and generalized tonic-clonic in appearance. Complicated febrile seizures are focal, last >15 min, or recur ≥ 2 times in < 24 h. Overall, 2% of patients with febrile seizures develop a subsequent seizure disorder. However, incidence of seizure disorders and risk of recurrent febrile seizures are much greater among children with any of the following:
Status epilepticus has 2 forms: convulsive and nonconvulsive.
Generalized convulsive status epilepticusinvolves at least one of the following:
The previous definition of > 30-min duration was revised to encourage more prompt identification and treatment. Untreated generalized seizures lasting > 60 min may result in permanent brain damage; longer-lasting seizures may be fatal. Heart rate and temperature increase. Generalized convulsive status epilepticus has many causes, including head trauma and rapid withdrawal of anticonvulsants.
Nonconvulsive status epilepticus includes complex partial status epilepticus and absence status epilepticus. They often manifest as prolonged episodes of mental status changes. EEG may be required for diagnosis.
Evaluation must determine whether the event was a seizure vs another cause of obtundation (eg, a pseudoseizure, syncope), then identify possible causes or precipitants. Patients with new-onset seizures are evaluated in an emergency department; they can sometimes be discharged after thorough evaluation. Those with a known seizure disorder may be evaluated in a physician’s office.
Patients should be asked about unusual sensations, suggesting an aura and thus a seizure, and about typical seizure manifestations. Patients typically do not remember generalized seizures, so a description of the seizure itself must be obtained from witnesses.
Manifestations of other conditions, such as sudden global brain ischemia (eg, due to ventricular arrhythmia), can resemble those of a seizure, including loss of consciousness and some myoclonic jerks.
History should include information about the first and any subsequent seizures (eg, duration, frequency, sequential evolution, longest and shortest interval between seizures, aura, postictal state, precipitating factors). All patients should be asked about risk factors for seizures:
Patients should also be asked about rare triggers (eg, repetitive sounds, flashing lights, video games, touching certain parts of the body) and about sleep deprivation, which can lower the seizure threshold.
In patients who have lost consciousness, a bitten tongue, incontinence (eg, urine or feces in clothing), or prolonged confusion after loss of consciousness suggest seizure.
In pseudoseizures, generalized muscular activity and lack of response to verbal stimuli may at first glance suggest generalized tonic-clonic seizures. However, pseudoseizures can usually be distinguished from true seizures by clinical characteristics:
Pseudoseizures often last longer (several minutes or more).
Postictal confusion tends to be absent.
Typical tonic phase activity, followed by clonic phase, usually does not occur.
The progression of muscular activity does not correspond to true seizure patterns (eg, jerks moving from one side to the other and back [nonphysiologic progression], exaggerated pelvic thrusting).
Intensity may wax and wane.
Vital signs, including temperature, usually remain normal.
Patients often actively resist passive eye opening.
Physical examination rarely indicates the cause when seizures are idiopathic but may provide clues when seizures are symptomatic (see Table: Clinical Clues to the Causes of Symptomatic Seizures).
Clinical Clues to the Causes of Symptomatic Seizures
Testing is done routinely, but normal results do not necessarily exclude a seizure disorder. Thus, the diagnosis may ultimately be clinical. Testing depends on results of the history and neurologic examination.
If patients have a known seizure disorder and examination results are normal or unchanged, little testing is required except for blood anticonvulsant levels. Additional testing is indicated if patients have symptoms or signs of a treatable disorder such as trauma, infection, or a metabolic disorder.
If seizures are new-onset or if examination results are abnormal for the first time, neuroimaging is required. Patients with new-onset seizures or atypical manifestations also require laboratory testing, including blood tests (serum electrolytes, BUN, creatinine, glucose, Ca, Mg, and P levels), and liver function tests. Other tests may done based on disorders that are suspected clinically:
Meningitis or CNS infection with normal neuroimaging results: Lumbar puncture is required.
Unreported use of recreational drugs that can cause or contribute to seizures: Drug screens may be done, although this practice is controversial because positive results do not indicate causality and test results can be inaccurate.
Cryptogenic epilepsy: Testing for the anti-NMDA receptor antibody should be considered, especially in young women (as many as 26% may test positive); a positive result suggests anti-NMDA receptor encephalitis.
Neuroimaging (typically head CT, but sometimes MRI) is usually done immediately to exclude a mass or hemorrhage. Some experts say that CT can be deferred and possibly avoided in children with typical febrile seizures whose neurologic status rapidly returns to normal.
Follow-up MRI is recommended when CT is negative. It provides better resolution of brain tumors and abscesses and can detect cortical dysplasias, cerebral venous thrombosis, and herpes encephalitis. An epilepsy-protocol MRI of the head uses high-resolution coronal T1 and T2 sequences, which can detect hippocampal atrophy or sclerosis. MRI can detect some common causes of seizures, such as malformations of cortical development in young children and mesial temporal sclerosis, traumatic gliosis, and small tumors in adults.
EEG is critical in the diagnosis of epileptic seizures, particularly of complex partial or absence status epilepticus, when EEG may be the most definitive indication of a seizure. EEG may detect epileptiform abnormalities (spikes, sharp waves, spike and slow-wave complexes, polyspike and slow-wave complexes). Epileptiform abnormalities may be bilateral, symmetric, and synchronous in patients with primarily generalized seizures and may be localized in patients with partial seizures. EEG findings may include the following:
Epileptiform abnormalities in temporal lobe foci between seizures (interictal) in complex partial seizures originating in the temporal lobe
Interictal bilateral symmetric bursts of 4- to 7-Hz epileptiform activity in primarily generalized tonic-clonic seizures
Focal epileptiform discharges in secondarily generalized seizures
Spikes and slow-wave discharges occurring bilaterally at a rate of 3/sec and usually a normal interictal EEG in typical absence seizures
Slow spike and wave discharges usually at a rate of < 2.5/sec, typically with interictal disorganization of background activity and diffuse slow waves, in atypical absence seizures
Bilateral polyspike and wave abnormality at a rate of 4- to 6-Hz in juvenile myoclonic epilepsy
However, normal EEG cannot exclude the diagnosis of epileptic seizures, which must be made clinically. EEG is less likely to detect abnormalities if seizures are infrequent. The initial EEG may detect an epileptiform abnormality in only 30 to 55% of patients with a known epileptic seizure disorder. Serial EEG may detect epileptiform abnormalities in up to 80 to 90% of such patients. In general, serial EEG with extended recording times and with tests done after sleep deprivation greatly increases the chance of detecting epileptiform abnormalities in patients with epileptic seizures.
Inpatient combined video-EEG monitoring, usually for 2 to 7 days, records EEG activity and clinical behavior simultaneously. It is the most sensitive EEG testing available and is thus useful in differentiating epileptic from nonepileptic seizures.
If surgical resection of areas of epileptic foci is being considered, advanced imaging tests to identify such areas are available in epilepsy centers. Functional MRI can identify functioning cortex and guide surgical resection. If EEG and MRI do not clearly identify the epileptic focus, magnetoencephalography with EEG (called magnetic source imaging) may localize the lesion, avoiding the need for invasive intraoperative mapping procedures. Single-photon emission CT (SPECT) during the peri-ictal period may detect increased perfusion in the seizure focus and help localize the area to be surgically removed. Because injection of contrast is required at the time of seizure, patients must be admitted for continuous EEG-video monitoring when SPECT is done during the peri-ictal period.
Neuropsychologic testing may help identify functional deficits before and after surgery and help predict social and psychologic prognosis and capacity for rehabilitation.
With treatment, seizures are eliminated in one third of patients with epileptic seizures, and frequency of seizures is reduced by > 50% in another third. About 60% of patients whose seizures are well-controlled by drugs can eventually stop the drugs and remain seizure-free.
Epileptic seizures are considered resolved when patients have been seizure-free for 10 yr and have not taken anticonvulsants for the last 5 yr of that time period.
Sudden unexplained death in epilepsy (SUDEP) is a rare complication of unknown cause.
Optimal treatment of seizures is to eliminate the causes whenever possible.
If the cause cannot be corrected or identified, anticonvulsants are often required, particularly after a 2nd seizure; usefulness of anticonvulsants after a single seizure is controversial, and risks and benefits should be discussed with the patient. Because the risk of a subsequent seizure is low, drugs may be withheld until a 2nd seizure occurs, particularly in children. In children, certain anticonvulsants cause important behavior and learning problems.
During a generalized tonic-clonic seizure, injury should be prevented by loosening clothing around the neck and placing a pillow under the head. Attempting to protect the tongue is futile and likely to damage the patient’s teeth or the rescuer’s fingers. Patients should be rolled onto their left side to prevent aspiration. These measures should be taught to the patient’s family members and coworkers.
Because partial seizures can become generalized, patients are at risk of losing consciousness and thus should be advised to take certain precautions. Until seizures are controlled, patients should refrain from activities in which loss of consciousness could be life threatening (eg, driving, swimming, climbing, operating power tools, bathing in a bathtub). After seizures are completely controlled (typically for > 6 mo), many such activities can be resumed if appropriate safeguards (eg, lifeguards) are used, and patients should be encouraged to lead a normal life, including exercise and social activities.
In a few states, physicians must report patients with seizures to the Department of Motor Vehicles. However, most states allow automobile driving after patients have been seizure-free for 6 mo to 1 yr.
Patients should be advised to avoid cocaine and some other illicit drugs (eg, phencyclidine, amphetamines), which can trigger seizures, and to avoid alcohol. Some drugs (eg, haloperidol, phenothiazines) may lower seizure threshold and should be avoided if possible.
Family members must be taught a commonsense approach toward the patient. Overprotection should be replaced with sympathetic support that lessens negative feelings (eg, of inferiority or self-consciousness); invalidism should be prevented.
Institutional care is rarely advisable and should be reserved for severely cognitively impaired patients and for patients with seizures so frequent and violent despite drug treatment that they cannot be cared for elsewhere.
Most seizures remit spontaneously in several minutes or less and do not require emergency drug treatment. However, status epilepticus and most seizures lasting > 5 min require drugs to terminate the seizures, with monitoring of respiratory status. Endotracheal intubation is necessary if there is any indication of airway compromise.
The sooner anticonvulsant therapy is started, the better and the more easily seizures are controlled.
IV access should be quickly obtained, and patients are given lorazepam 0.05 to 0.1 mg/kg IV (typically a 4-mg IV dose for adults) at a rate of 2 mg/min. Larger doses are sometimes required. After lorazepam is given, a second, longer-acting anticonvulsant is indicated.
There is no consensus or evidence-based guideline indicating which longer-acting anticonvulsant is preferred. Many experts choose one of the following:
If seizures persist after these doses are used, an additional 5 to 10 PE/kg of fosphenytoin or 5 to 10 mg/kg of phenytoin can be given.
Alternative anticonvulsants include the following:
If IV access cannot be obtained, options include IM fosphenytoin and sublingual or rectal benzodiazepines.
Seizures that persist after use of lorazepam and phenytoin (or another 2nd anticonvulsant) define refractory status epilepticus.
Recommendations for a 3rd anticonvulsant vary and include phenobarbital, propofol, midazolam, levetiracetam, and valproate. Dose of phenobarbital is 15 to 20 mg/kg IV at 100 mg/min (3 mg/kg/min in children); continued seizures require another 5- to 10-mg/kg dose. A loading dose of valproate 20 to 40 mg/kg IV is an alternative.
At this point, if status epilepticus has not abated, intubation and general anesthesia are necessary. The optimal anesthetic to use is controversial, but many physicians use propofol 1 to 2 mg/kg at 100 mg/min or pentobarbital 5 to 8 mg/kg (loading dose) followed by infusion of 2 to 4 mg/kg/h until EEG manifestations of seizure activity have been suppressed. Inhalational anesthetics are rarely used.
After initial treatment, the cause of status epilepticus must be identified and treated.
Drugs are given to prevent seizures if head injury causes significant structural injury (eg, large contusions or hematomas, brain laceration, depressed skull fracture) or a Glasgow Coma Scale (GCS) score of < 10. These drugs reduce risk of seizures during the first week after injury but do not prevent permanent posttraumatic epilepsy months or years later. They should be stopped after 1 wk unless seizures occur.
If seizures begin > 1 wk after head injury, long-term treatment with drugs is required.
Anticonvulsants may be required indefinitely, but many types of seizures (eg, most febrile seizures, seizures due to alcohol withdrawal, seizures that do not recur) do not require treatment with anticonvulsants.
No single drug controls all types of seizures, and different patients require different drugs. Some patients require multiple drugs. The drugs preferred vary according to type of seizure (see Table: Choice of Drugs for Seizures). For more detailed drug-specific information, see Drug Treatment of Seizures : Anticonvulsant Choice for Long-Term Treatment.
About 10 to 20% of patients have intractable seizures refractory to medical treatment and are potential surgical candidates. If seizures originate from a focal, resectable area in the brain, resection of the epileptic focus usually improves seizure control markedly. If the focus is in the anteromesial temporal lobe, resection eliminates seizures in about 60% of patients. After surgical resection, some patients remain seizure-free without taking anticonvulsants, but many still require the drugs, but in reduced doses and possibly as monotherapy.
Because surgery requires extensive testing and monitoring, these patients are best treated in specialized epilepsy centers.
Intermittent electrical stimulation of the left vagus nerve with an implanted pacemaker-like device (vagus nerve stimulator) is used as an adjunct to drug therapy in patients who have intractable seizures and are not candidates for epilepsy surgery. This procedure reduces the number of partial seizures by ≥ 50% in about 40%. After the device is programmed, patients can activate it with a magnet to abort an imminent seizure.
Adverse effects of vagus nerve stimulation include deepening of the voice during stimulation, cough, and hoarseness. Complications are minimal.
Duration of effectiveness is unclear.
Common causes of seizures include birth defects or injuries, developmental defects, and metabolic disorders in children < 2 yr; idiopathic seizure disorders in children 2 to 14 yr; head trauma, alcohol withdrawal, tumors, and strokes in adults; and tumors and strokes in the elderly.
Loss of consciousness is likely to be caused by seizures if patients have bitten their tongue, are incontinent (eg, urine or feces in clothing), or are confused for a long time after loss of consciousness.
Evaluate patients with seizures for signs of possible causes (eg, fever, stiff neck, focal neurologic deficits, neuromuscular irritability and hyperreflexia, papilledema), and test accordingly.
Evaluate all patients who have new or unexplained seizures with neuroimaging, EEG, and blood tests.
Talk to patients about how to avoid or minimize seizure triggers and how to reduce risk of seizure complications (eg, by not driving and not swimming alone).
Anticonvulsants may be required indefinitely, but many types of seizures (eg, most febrile seizures, seizures due to alcohol withdrawal, seizures that do not recur) do not require anticonvulsant treatment.
Consider surgery if therapeutic doses of ≥ 2 anticonvulsants do not control seizures.
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