A seizure is a transient occurrence of signs or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Epilepsy is diagnosed when there is a risk of recurrent seizures due to a chronic, underlying process.
| APPROACH TO THE PATIENT | ||
SeizureSeizure classification: Essential for diagnosis, therapy, and prognosis (Table 184-1 Classification of Seizuresa ). Seizures are focal or generalized: focal seizures originate in networks limited to one cerebral hemisphere, and generalized seizures rapidly engage networks distributed across both hemispheres. Focal seizures are further divided based on presence or absence of cognitive impairment. Generalized seizures may occur as a primary disorder or result from secondary generalization of a focal seizure. Tonic-clonic seizures (grand mal) cause sudden loss of consciousness, loss of postural control, and tonic muscular contraction producing teeth-clenching and rigidity in extension (tonic phase), followed by rhythmic muscular jerking (clonic phase). Tongue-biting and incontinence may occur during the seizure. Recovery of consciousness is typically gradual over many minutes to hours. Headache and confusion are common postictal phenomena. In absence seizures (petit mal) there is sudden, brief impairment of consciousness without loss of postural control. Events rarely last longer than 5-10 s but can recur many times per day. Minor motor symptoms are common, while complex automatisms and clonic activity are not. Other types of generalized seizures include tonic, atonic, and myoclonic seizures. Etiology: Seizure type and age of pt provide important clues to etiology (Table 184-2 Causes of Seizures). |
Careful history is essential since diagnosis of seizures and epilepsy is often based solely on clinical grounds. Differential diagnosis (Table 184-3 Differential Diagnosis of Seizures) includes syncope or psychogenic seizures (“pseudoseizures”). General examination includes search for infection, trauma, toxins, systemic illness, neurocutaneous abnormalities, and vascular disease. A number of drugs lower the seizure threshold (Table 184-4 Drugs and Other Substances That Can Cause Seizures). Asymmetries in neurologic examiation suggest brain tumor, stroke, trauma, or other focal lesions. An algorithmic approach is shown in Fig. 184-1. Evaluation of the Adult Pt with a Seizure.
Routine blood studies are indicated to identify the more common metabolic causes of seizures such as abnormalities in electrolytes, glucose, calcium, or magnesium, and hepatic or renal disease. A screen for toxins in blood and urine should be obtained especially when no clear precipitating factor has been identified. A lumbar puncture is indicated if there is any suspicion of CNS infection such as meningitis or encephalitis; it is mandatory in immunosuppressed pts even in the absence of symptoms or signs suggesting infection. Testing for autoantibodies in the serum and CSF should be considered in pts presenting with an aggressive form of epilepsy associated with cognitive disturbances.
All pts should be evaluated as soon as possible with an EEG, which measures electrical activity of the brain by recording from electrodes placed on the scalp. The presence of electrographic seizure activity during the clinically evident event (i.e., abnormal, repetitive, rhythmic activity having an abrupt onset and termination) clearly establishes the diagnosis. The absence of electrographic seizure activity does not exclude a seizure disorder, however. The EEG is always abnormal during generalized tonic-clonic seizures. Continuous monitoring for prolonged periods may be required to capture the EEG abnormalities. The EEG can, but does not always, show abnormal discharges during the interictal period that support the diagnosis of epilepsy and is useful for classifying seizure disorders, selecting anticonvulsant medications, and determining prognosis.
Brain Imaging
All pts with unexplained new-onset seizures should have a brain imaging study (MRI or CT) to search for an underlying structural abnormality; the only exception may be children who have an unambiguous history and examination suggestive of a benign, generalized seizure disorder such as absence epilepsy. Newer MRI methods have increased the sensitivity for detection of abnormalities of cortical architecture, including hippocampal atrophy associated with mesial temporal sclerosis, as well as abnormalities of cortical neuronal migration.
| TREATMENT | ||
Seizures and Epilepsy
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