Seizures

Chapter 37 Seizures



Adam Hartman




ETIOLOGY



How Common Are Seizures in Children?


Seizures occur in 3% to 5% of children. Febrile seizures occur in 2% to 4%. Epilepsy, the tendency to have recurrent unprovoked seizures, occurs in roughly 1% of children, making it one of the most common neurologic disorders in this age group.



How Are Seizures Classified in Children?


Seizures can be classified as focal or primarily generalized. In focal seizures, the first signs of neurologic dysfunction are noted in one anatomic location, then may spread to other regions of the brain. Primarily generalized seizures, in contrast, seem to affect global neurologic function from the onset. Examples of focal seizures in children include benign epilepsy with centrotemporal spikes and temporal lobe epilepsy. Examples of generalized seizures in children include febrile seizures, benign neonatal familial convulsions, infantile spasms, and childhood absence epilepsy. These are also classified as “developmentally determined” because they only appear in childhood. The differential diagnosis of seizures includes migraines, strokes, gastroesophageal reflux, breath-holding spells, dystonias, narcolepsy, night terrors, and syncope.



What Is Status Epilepticus?


Status epilepticus (SE) is currently defined as seizure activity that lasts more than 30 minutes or recurrent seizures without a return to a baseline of normal mental status for more than 30 minutes. Because 75% of seizures last less than 10 minutes, however, the definition of SE will probably be changed. Prolonged status epilepticus is dangerous for the developing brain and must be treated aggressively.



What Causes Seizures in Childhood?


The most common causes of pediatric seizures vary by age group. In the newborn period, hypoxic-ischemic encephalopathy is a common cause of seizures in the first 24 hours of life. Central nervous system (CNS) hemorrhage, infection, cerebral malformations, metabolic disorders, and drug withdrawal can also cause neonatal seizures. In infants and older children, common causes include idiopathic generalized seizures, febrile seizures, infections, tumors, strokes, hemorrhages, and neurocutaneous disorders. Some seizure types are specific to childhood.



Is There a Molecular Basis for Seizures in Children?


Studies have identified abnormal sodium or γ-aminobutyric acid (GABA) channels in some families who suffer from febrile seizures and mutations in voltage-gated potassium channels in benign familial neonatal convulsions, the so-called fifth-day fits.



What Is a Febrile Seizure?


Febrile seizures are developmentally determined seizures that occur primarily between 6 months and 5 years of age. The fever is usually high and associated with an acute infection. Febrile seizures often run in families. They need to be distinguished from seizures caused by meningitis and metabolic disorders and from underlying seizure disorders triggered by fever. Simple febrile seizures occur only once in a febrile illness, are generalized, and last less than 15 minutes. Complex febrile seizures occur more than once in a febrile illness, last longer than 15 minutes, or are focal. Approximately 30% of children will have a recurrence of febrile seizures, with 90% within 1 year after the initial seizure. Risks for recurrence include young age, family history of febrile seizures, low temperature at the time of the seizure, illness frequency, and occurrence of the seizure early in the illness episode. Children at risk for developing epilepsy include those who are developmentally abnormal, those with complex febrile seizures, or those with a family history of epilepsy.



What Are Infantile Spasms?


Infantile spasms usually start within the first year of life. These seizures may be flexor, extensor, or mixed in nature. The classic description is a “salaam” attack, during which the infant extends the arms and flexes at the neck, trunk, hips, and knees. Seizures tend to occur in clusters, particularly on awakening. Symptomatic infantile spasms have an underlying cause, including a host of structural and metabolic abnormalities, and represent about 80% of the total. Cryptogenic seizures have no identifiable underlying cause and represent about 20% of the total. The electroencephalographic pattern is highly disorganized (hypsarrhythmia). Many infants have recurrent seizures. The prognosis for normal neurologic development with symptomatic infantile spasms is poor. The differential diagnosis includes an exaggerated startle response, colic, hypnagogic jerks, the myoclonic epilepsies, and benign myoclonus.



How Do Absence Seizures Differ from Complex Partial Seizures?


Absence seizures usually occur during school age, are brief (< 30 seconds), may occur more than 20 times a day, can be induced by hyperventilation, and are characterized by an electroencephalogram (EEG) with 3-Hz spike and wave complexes. Complex partial seizures can occur at any age. They are usually longer than 1 minute, only occur a few times during the day, cannot generally be induced by hyperventilation, are associated with postictal lethargy, and show focal abnormalities on EEG.



EVALUATION



How Do I Know If a Child Had a Seizure?


The patient’s history is the best way to make a diagnosis. A precise description of the event may suggest the diagnosis. For example, an infant whose eyes suddenly rolled back, began shaking, lost consciousness for 2 minutes, then fell asleep for 15 minutes most likely had a seizure. In contrast, a toddler who was frustrated, exhaled, held his or her breath, then fell to the ground with perioral duskiness most likely had a breath-holding spell. Seizures are more likely than other paroxysmal disorders if there are focal movements (e.g., limb, face, or eye), depressed level of consciousness, and postictal paralysis (“Todd’s paralysis”) or sleep. Other important factors in the history include the length and timing of the episode, color changes (e.g., cyanosis), and associated or triggering symptoms. Review past medical, birth, and family histories, and perform a complete developmental assessment. The differential diagnosis includes gastroesophageal reflux, breath-holding spells, vasovagal episodes, migraine, stroke, tics, and dystonias. Abnormal developmental history, focal neurologic findings, or neurocutaneous findings generally mandate further workup.



When Are Laboratory Tests Needed?


Measure blood glucose in any seizing child. Choice of additional testing depends on the type of seizure, the history, and the physical examination. The American Academy of Neurology recommends an EEG after the first unprovoked seizure, but not all neurologists agree. It is important to note that EEG is most sensitive for certain conditions such as absence seizures and infantile spasms. If the diagnosis of seizurelike activity is uncertain, a normal EEG during a typical episode rules out epilepsy. EEG may identify a specific epilepsy syndrome such as juvenile myoclonic epilepsy in a teenager with occasional early morning jerks. EEG also can localize a seizure focus, which may make the patient a candidate for surgery if medicines do not work. Continuous EEG with video recording of behavior is currently used to evaluate complex patients. Imaging is recommended for the patient with focal neurologic findings to rule out a focal lesion, such as a tumor. Laboratory studies are best guided by the history and physical exam. Emergency management of seizures is discussed in Chapter 59.

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Jun 19, 2016 | Posted by in PEDIATRICS | Comments Off on Seizures

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