Seizures and Epilepsy

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Table 3-2. Toxic/Metabolic Causes of Seizures Drug Intoxication Amphetamines Cocaine Lidocaine Theophylline Tricyclic antidepressants Drug withdrawal Antiepileptic drugs (AEDs) Barbiturates Benzodiazepines Ethanol Electrolyte—hypo/hypernatremia, hypo/hyperglycemia, hypocalcemia, hypomagnesemia Heavy metals—lead, mercury Hyperosmolarity Hypoxia Liver failure Porphyria Pyridoxine deficiency Thyroid storm Uremia (usually following 3 days of anuria) Cerebral ischemia is a common cause of seizures in the neonate and in the older adult but is relatively uncommon in the older pediatric population. Seizures usually occur in the more slowly growing tumors. Tumors located in the supratentorial region cause seizures more frequently than do cerebellar or brainstem tumors. CLINICAL PRESENTATION Epilepsy is divided into several categories with significant differences in the characteristics of the electrical discharges as well as the clinical manifestations. Localizationrelated epilepsy or partial epilepsy has a primary focus from which the electrical discharges arise. Complex partial seizures occur with alteration of awareness while simple partial seizures have no alteration of awareness. Jacksonian motor seizures, Rolandic epilepsy, temporal lobe epilepsy, and frontal lobe epilepsy are all examples of partial epilepsy. The Revised International Classification of Epilepsies, Epileptic Syndromes and Related Seizure Disorders divides the localization-related epilepsies as follows: 10 Idiopathic localization-related epilepsy Symptomatic or secondary localization-related epilepsy Cryptogenic localization-related epilepsy Generalized seizures are the other major seizure type. In this category of epilepsy, the seizure affects the entire cortex electrically. Several subtypes of generalized seizures have also been identified, including absence epilepsy with 3-Hz spike and wave activity, generalized tonic-clonic seizures, juvenile myoclonic epilepsy, and progressive myoclonic epilepsy. The Revised International Classification of Epilepsies, Epileptic Syndromes and Related Seizure Disorders divides the generalized epilepsies as follows 10 : Primary generalized epilepsy Symptomatic generalized epilepsy Cryptogenic epilepsy A number of seizures and epilepsies may be very difficult to categorize. The Revised International Classification of Epilepsies, Epileptic Syndromes and Related Seizure Disorders groups these disorders in the “undetermined” category. These seizures may be divided as follows10 : Both focal and generalized Situation-related epilepsy Febrile convulsions Isolated seizure Isolated status epilepticus Toxic/metabolic In each of these cases, the electroencephalographic (EEG) findings may be different. The EEG serves as a vitally important tool in the correct diagnosis of the various epilepsy subtypes and syndromes. DIAGNOSIS Seizure Types CHAPTER 3 Seizures and Epilepsy ■ 31 Generalized tonic-clonic seizures Generalized tonic-clonic seizures typically have no preceding aura but may have a prodrome of apathy or irritability. During the tonic phase, the jaw snaps shut followed by 10 to 15 seconds or longer of tonic spasms, apnea, and cyanosis. The clonic phase usually consists of 1 to 2 minutes of rhythmic generalized muscle contractions and increased blood pressure. The postictal phase lasts for minutes to hours, with confusion, somnolence, and possibly agitation. The ictal EEG usually consists of generalized spike and wave or polyspike activity. The interictal EEG is highly variable with a normal background in some patients and slowing present in others. Generalized seizures are rare in newborns. Generalized seizures occur most frequently in children secondary to fevers and metabolic derangements.
32 ■ Section 2: Common Pediatric Neurologic Problems Absence seizures Absence seizures typically have no preceding aura or prodrome. An absence seizure usually lasts for only several seconds to minutes. There is a sudden interruption of consciousness, staring, 3-Hz blinking, and less frequently automatisms. There is no postictal confusion. 11 The ictal EEG usually consists of 3-Hz generalized spike and wave activity with some slowing of the discharge frequency during the seizure. The interictal EEG usually has a normal background. Atypical absence seizures have generalized spike and wave activity but usually have a frequency less than 3 Hz. 12 Absence seizures typically start between ages 4 and 10 years and resolve by age 20 years. Atypical absence epilepsy usually occurs in children who are neurologically or developmentally abnormal. 13 Febrile seizures Febrile seizures occur with a prodromal fever. A simple febrile seizure occurs as a brief generalized tonic clonic seizure occurring after the onset of fever. A complicated febrile seizure has prolonged seizure activity or focal seizure activity. Febrile seizures are covered in detail in Chapter 4. Juvenile myoclonic epilepsy The seizures associated with juvenile myoclonic epilepsy typically have no preceding aura but may have a prodrome of morning myoclonus. The seizures may consist of generalized tonic-clonic activity; however, absence seizures may also occur. The postictal phase is variable depending on the seizure type. 11 The ictal EEG usually consists of generalized polyspike and slow wave activity. The interictal EEG is typically unremarkable. 12 The age of onset of juvenile myoclonic epilepsy is typically 10 to 20 years. Patients are usually developmentally and neurologically normal. 13 Progressive myoclonic epilepsy The family of disorders known as the progressive myoclonic epilepsies (Table 3-3) consists of a number of loosely related disorders. These epilepsy subtypes are quite rare and have complex presentations and diagnostic findings. Most of these disorders have a genetic basis, though sporadic cases have occurred in some cases (Table 3-4). The EEG associated with these disorders is variable. The background is often slow. The seizures are typically generalized. 11 Infantile spasms West syndrome typically begins between 3 months and 3 years of age. 14–16 The seizures associated with West syndrome consist of a jack-knifing movement and myoclonus. The EEG consists of a hypsarrhythmia pattern with bursts of asynchronous slow waves; spikes and Table 3-3. Progressive Myoclonic Epilepsies Dentorubral-pallidoluysian atrophy Juvenile neuroaxonal atrophy Lafora disease Late infantile and juvenile GM2 gangliosidosis Myoclonic epilepsy and ragged red fibers (MERRF) Neuronal ceroid lipofuscinosis (NCL) (also known as Batten disease) Noninfantile Gaucher disease Sialidosis Unverricht–Lundborg disease (Baltic myoclonus) sharp waves alternate with a suppressed EEG. 17 The clinical features of West syndrome include infantile spasms and mental retardation, which varies according to the etiology of the spasms. Aicardi syndrome is an X-linked disorder present from birth that is associated with infantile spasms. The seizures are described as infantile spasms, but alternating hemiconvulsions may also be seen. The clinical features of Aicardi syndrome include coloboma, chorioretinal lacunae, agenesis of the corpus callosum, vertebral anomalies, and seizures. 18 Lennox–Gastaut syndrome Lennox–Gastaut syndrome typically begins between 1 and 10 years of age. There are multiple seizure types, associated with variable degrees of mental retardation. The EEG reveals a slow spike wave complex with a frequency of 1 to 2.5 Hz, multifocal spikes, and generalized paroxysmal fast activity (GPFA). 19 Partial seizures: localization-related epilepsy Jacksonian motor seizures are simple partial seizures with no alteration of consciousness. These seizures begin with tonic contractions of the face, fingers, or feet and transform into clonic movements that march to other muscle groups on the ipsilateral hemibody. There is no alteration in consciousness, but postictal aphasia may occur if the primary epileptogenic zone involves the dominant hemisphere. Simple partial seizures may involve autonomic (Table 3-5), sensory, motor, or psychic functions. Complex partial seizures Benign Rolandic epilepsy. Benign Rolandic epilepsy usually begins between ages 5 and 10 years and is transmitted in an autosomal dominant pattern with variable penetrance. It is fairly common, with an incidence of
Page 1: CHAPTER 3 DEFINITIONS AND EPIDEMIOL
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