Chapter 586 - Seizures in Childhood
Michael V. Johnston
A seizure or convulsion is a paroxysmal, time-limited change in motor activity and/or behavior that results from abnormal electrical activity in the brain. Seizures are common in the pediatric age group and occur in approximately 10% of children. Most seizures in children are provoked by somatic disorders originating outside the brain, such as high fever, infection, syncope, head trauma, hypoxia, toxins, or cardiac arrhythmias. Other events, such as breath-holding spells and gastroesophageal reflux, can cause events that simulate seizures (see Chapter 587 ). A few children also exhibit psychogenic seizures of psychiatric origin. Less than one third of seizures in children are caused by epilepsy, a condition in which seizures are triggered recurrently from within the brain. For epidemiologic classification purposes, epilepsy is considered to be present when two or more unprovoked seizures occur at an interval greater than 24?hr apart. The cumulative lifetime incidence of epilepsy is 3% and more than half of cases begin in childhood. However, the annual prevalence of epilepsy is lower (0.5–0.8%) because many children outgrow epilepsy. Although the outlook for most children with symptomatic seizures or those associated with epilepsy is generally good, the seizures may signal a potentially serious underlying systemic or central nervous system (CNS) disorder that requires thorough investigation and management. For children with epilepsy, the prognosis is generally good, but 10–20% have persistent seizures refractory to drugs, and those cases pose a diagnostic and management challenge.
Evaluation of the First Seizure.
Initial evaluation of an infant or child during or shortly after a suspected seizure should include an assessment of the adequacy of the airway, ventilation, and cardiac function as well as measurement of temperature, blood pressure, and glucose concentration. For acute evaluation of the first seizure, the physician should search for potentially life-threatening causes of seizures such as meningitis, systemic sepsis, accidental and nonaccidental head trauma, and ingestion of drugs of abuse and other toxins. The history should attempt to define factors that may have promoted the convulsion and to provide a detailed description of the seizure and the child's postictal state. Most parents vividly recall their child's initial convulsion and can describe it in detail.
The first step in an evaluation is to determine whether the seizure has a focal onset or is generalized. Focal seizures may be characterized by motor or sensory symptoms and include forceful turning of the head and eyes to one side, unilateral clonic movements beginning in the face or extremities, or a sensory disturbance such as paresthesias or pain localized to a specific area. Focal seizures in an adult usually indicate a localized lesion, but investigation of focal seizures during childhood may be nondiagnostic. Motor seizures may be focal or generalized and tonic-clonic, tonic, clonic, myoclonic, or atonic. Tonic seizures are characterized by increased tone or rigidity, and atonic seizures are characterized by flaccidity or lack of movement during a convulsion. Clonic seizures consist of rhythmic muscle contraction and relaxation, and myoclonus is most accurately described as shocklike contraction of a muscle. The duration of the seizure and state of consciousness (retained or impaired) should be documented. The history should determine whether an aura preceded the convulsion and the behavior of the child immediately preceding the seizure. The most common aura experienced by children consists of epigastric discomfort or pain and a feeling of fear. The posture of the patient, presence and distribution of cyanosis, vocalizations, loss of sphincter control (particularly of the urinary bladder), and postictal state (including sleep and headache) should be noted.
In addition to the assessment of cardiorespiratory and metabolic status described above, examination of a child with a seizure disorder should be geared toward the search for an organic cause. The child's head circumference, length, and weight are plotted on a growth chart and compared with previous measurements. A careful general and neurologic examination should be performed. The eyegrounds must be examined for the presence of papilledema, retinal hemorrhages, chorioretinitis, coloboma, and macular changes, as well as retinal phakoma. The finding of unusual facial features or associated physical findings such as hepatosplenomegaly point to an underlying metabolic or storage disease as the cause of the neurologic disorder. A search for vitiliginous lesions of tuberous sclerosis using an ultraviolet light source, examination for adenoma sebaceum, shagreen patch, multiple café-au-lait spots, or a nevus flammeus, and the presence of retinal phakoma would indicate a neurocutaneous disorder as the cause of the seizure.
Localizing neurologic signs such as a subtle hemiparesis with hyperreflexia, an equivocal Babinski sign, and a downward-drifting extended arm with eyes closed might suggest a contralateral hemispheric structural lesion, such as a slow-growing temporal lobe glioma, as the cause of the seizure disorder. Unilateral growth arrest of the thumbnail, hand, or extremity in a child with a focal seizure disorder suggests a chronic condition such as a porencephalic cyst, arteriovenous malformation, or cortical atrophy in the opposite hemisphere.