|
|
Introduction
to Seizures Return to MD Home Page
M. Kutscher, MDFaced with a paroxysmal neurological event, the practitioner must first decide whether or not the event is a seizure. There is a large and varied differential diagnoses that must be considered. Once the event has been determined to be a seizure, it must be classified to help determine appropriate work up, prognosis, and treatment. Seizure Disorders Epidemiology and Classification Seizures occur over a lifetime of about 11% of all people, although only 3% of the population will have epilepsy. Two different schemes are utilized in the classification of epileptiform events: classification by type of seizure and classification by epilepsy syndrome. The term "seizure" refers to the specific neurological event, such as an absence seizure or a tonic-clonic seizure. The term "epilepsy syndrome" refers to a full syndrome consisting of the type(s) of seizures seen in that syndrome, EEG findings, typical age of patient, typical prognosis, etc. For example, "absence seizure" refers to the specific event of staring for several seconds; whereas "petit mal epilepsy" refers to a syndrome of young, neurologically normal children whose EEG shows 3/second spike-wave discharges and who are likely to outgrow their seizures. The seizures and their corresponding epilepsy syndromes are divided into two broad categories: generalized and partial. By definition, generalized seizures are those that start simultaneously from both hemispheres. Partial seizures start from one hemisphere. The epilepsy syndromes are similarly divided into the generalized and partial epilepsies. The classification of seizures and the major childhood epilepsies are summarized in Table 1.
Table 1: Seizure/Epilepsy Classification Generalized (start both hemispheres)
Partial (start in part of one hemisphere)
This distinction between generalized and partial seizures is important for several reasons; and affects the history, work up, and treatment of a child with seizures. During the history, we must ask if the seizure has any signatures of a focal onset: Did the seizure start or affect one part of the body more than the others? Was there an aura? The latter question is important since a well defined aura means that the seizure began focally. This is because the "aura" of a seizure is actually just its focal onset. During an aura, the rest of the brain is "watching" that part of the brain have its seizure. In contrast, a generalized seizure does not have a well defined aura. This is because consciousness requires one working cerebral hemisphere and a brainstem. A generalized seizure, though, affects the entire brain at its onset, and thus usually leaves "no one there" to be aware of the spell. Determination of an aura, then, is extremely useful. We should remember to ask both the observer and the child about the specific onset of the seizure. Young children may be unable to verbalize an aura, and may just start acting unusually or run to their parent. Also, the aura or focal onset of a seizure may be so brief that it may not be noticed before there is secondary generalization of the seizure. Thus, a focal seizure does not nescessarily have an identifiable aura. Since focal seizures are more likely to have underlying focal structural abnormalities, classification of focal vs. generalized seizures may affect the child’s work up. In addition, different anticonvulsants are chosen on the basis of the type of epilepsy classification.
The Generalized Seizures Absence seizures Typical absence seizures are very "clean" seizures. Like all generalized seizures, there is no aura. They consist of brief (3-30 second) staring spells, accompanied by a cessation of activity. Sometimes, there is some eye fluttering, mild lip movements, or twitches. There is no post-ictal state after a typical absence seizure. Tonic-Clonic seizures "Tonic" refers to continuous stiffening of the extremities. "Clonic" refers to the rhythmic alternating contraction and relaxation of the muscles. A "tonic-clonic" seizure is one which starts with continuous tonic stiffening and is then followed by a clonic phase of rhythmic jerks. Note that partial seizures may have such rapid secondary generalization that they may be clinically indistinguishable from true primary generalized tonic-clonic seizures. Minor Motor seizures There are two basic types of "minor motor" seizures. Myoclonic seizures are brief jerks, often occurring in irregular flurries. Atonic (a.k.a. akinetic) seizures a drop attacks. They are so brief that consciousness has been regained by the time the child hits the floor.
The Partial Seizures Partial seizures are classified into three types: simple partial, complex partial, and partial seizures with secondary generalization. Simple and complex partial seizures are, in effect, one big aura. Simple partial seizures Simple partial seizures begin focally in one hemisphere and do not impair the level of consciousness. They may consist of virtually any task of which the brain is capable, such as jerking of just one extremity, abnormal sensation of one part of the body, a feeling of deja-vu etc. Complex partial seizures Complex partial seizures (previously called "psychomotor seizures" or "temporal lobe epilepsy") begin focally in one hemisphere and do impair the level of consciousness. There is usually a well defined aura followed by confusion which is accompanied by lip smacking, fumbling, or eye fluttering. Unlike absence seizures, these spells tend to last several minutes and are accompanied by an aura and post-ictal states. Partial seizures with secondary generalization Although the secondary generalization may be the most striking feature to the family, it is the partial onset of these seizures that matter most to the clinician. A "Jacksonian march" is the label given to a seizure which spreads along the cortex with resultant spread of the clinical seizure along one hemisphere. The children may be aware of this focal spread along one side of their body, and then loose consciousness as the seizure spreads to the other hemisphere during secondary generalization.
Selected Epilepsy Syndromes Comprehensive discussion of the specific epilepsy syndromes is beyond the scope of this chapter. Although a few comments will be given here about some prototypical epilepsies, the reader is referred to standard texts,. Typically, children with these conditions are managed by their primary caregiver in conjunction with a neurologist with special competancy in child neurology.
Infantile Spasms Table 2: Moro response vs. myoclonic seizures
Infantile spasms (also known as West syndrome) is an epilepsy syndrome of infants with myoclonic seizures and an EEG finding of hypsarrhthymia (a triad of multifocal spikes, disorganized background, and burst-suppression). These momentary seizures may appear as myoclonic "startle" jerks, as a momentary loss of tone, or as forceful extension or flexion. The features distinguishing myoclonic seizures from the normal Moro response are given in Table 2 . However, the distinction is not always clear. Since early treatment (typically ACTH steroid injections) appears to be critically important in an attempt to maintain neurologic function, immediate referral should be made to a pediatric neurologist whenever the question is raised. Children with an identifiable underlying neurological abnormality have a worse prognosis in regards to both developmental outcome and tendancy to go on to other seizures (typically Lennox-Gastaut syndrome).
Classic Absence ("petit-mal") Epilepsy Classic absence epilepsy is commonly referred to as "petit mal." This epilepsy syndrome occurs in neurologically normal preschool and school age children who have absence seizures. These appear as brief staring spells during which the children stop their activity and are unresponsive to even strong stimuli. The EEG shows 3/second spike and wave activity, especially during hyperventilation--an office maneuver which may precipate spells. About 10 percent of children with absence epilepsy will develop tonic/clonic seizures. Prognosis for outgrowing the seizures is excellent. Treatment is usually with valproate or ethosuccimide. Benign Rolandic Epilepsy Benign Rolandic Epilepsy is a fairly common type of focal epilepsy in school age children. Seizures are often markedly focal, such as just a rhthymic twitch of the mouth. A clue to the diagnosis is their predominance during sleep. The EEG may be totally normal during wakefulness, yet sleep records show prominent stereotyped central-temporal spikes. Prognosis is excellent; in fact, the word "Benign" is built into the name of this epilepsy syndrome. When treatment is indicated, carbamazepine is the usual anticonvulsant of choice.
Diagnostic Procedures As an initial step, non-epileptiform conditions need to be considered and evaluated as appropriate. This would include cardiac arrhthymias, prolonged QTc interval, etc. Evaluation of seizures per se usually includes CBC, SMA20, an EEG (preferentially containing sleep), and an MRI. A non-contrast CT scan is frequently used as an initial screen in the emergency room, but is not by itself generally a sufficient neuroimaging technique when evaluating seizures. It should be followed soon by a contrast CT scan, or quite preferentially, a MRI scan. Lumbar puncture should be performed if meningitis or encephalitis is a consideration. Toxicology screen may also be appropriate.
Treatment of seizures Decision to treat The family needs to know that it is unlikely--although certainly not impossible--to be hurt or die from a seizure. The decision to treat with anticonvulsants is often jointly made by the family, the primary practioner, and the neurologist. Factors in the decision include: the type of seizures (including focality and duration), type of epilepsy syndrome, age of the child, family concerns, EEG, and MRI. In general, most neurologists do not give anticonvulsants to children with a first, generalized, brief seizure in the setting of a normal EEG and MRI. Overall, a child with a single seizure has less than a 1/3 chance of having another. However, the care for each child must be individualized, taking into account the risks of seizures vs. the risks of medication.
Choice of anticonvulsants An appropriate anticonvulsant is chosen on the basis safety, side effects, and the type of epilepsy. As demonstrated in table 18- , certain anticonvulsants work better for particular types of seizures. Carbamazepine, phenytoin, and phenobarbital are targeted mainly at the partial seizures, but additionally work well for tonic/clonic seizures. When possible, carbamazepine is usually chosen in order to avoid the hyperactivity frequently seen with phenobarbital; and the gum hypertrophy and facial hirsuitism of phenytoin. However, phenobarbital is usually used first in children less than a few years of age. Valproic acid works particularly on generalized seizures, including primarily generalized tonic/clonic and absence seizures. Valproate appears effective with partial seizures as well. Risk factors for valproate hepatic failure include young age, neurological impairment, and concommitent use of other anticonvulsants. Ethosuximide is limited to absence seizures. The newer anticonvulsants such as gabapentin (Neurontin), topiramate (Topamax), tiagabine (Gabatril), and lamotrigine (Lamictal) are generally currently indicated as add-on therapy for partial seizures in children >12 years of age. These new medications are described in detail in published reviews.
Spectrum of Standard Anticonvulsants
Laboratory testing on these anticonvulsants needs to be individualized. In general, though, CBC,diff, liver function tests, and drug levels are monitored 2 weeks into treatment, then monthly for several months, and then every six months.
Discontinuation Typically, children are treated with anticonvulsants for a period of two years without seizures. At that point, the EEG is repeated, and consideration with the family is given to the taper of the anticonvulsant over a two month period. Risk factors for a relapse include: difficulty obtaining seizure control initially, partial seizures, and an abnormal EEG.
First aid and accident precautions For any child with periods of altered levels of consciousness--whether due to seizures or not--it is appropriate to counsel families regarding first aid and reasonable accident precautions (below). These precautions apply particularly until one year symptom free at the beginning of diagnosis as well as with significant changes in anticonvulsant regimens. Practicioners should be famililar with their state driving laws for patients with seizures and/or loss of consciousness.
First aid for seizures Stay calm. Lay the child down with head to the side. Loosen tight clothing. Place something soft under the head. Do not place anything in the child’s mouth. If the seizure persists for more than a few minutes, is followed by a prolonged "post-ictal" state, or is atypical, the child should be taken to the emergency room. All first seizures require prompt medical attention.
Accident precautions
|