182 SEIZURES AND EPILEPSY
Harrison’s Manual of Medicine
SEIZURES AND EPILEPSY
A seizure is a paroxysmal event due to abnormal, excessive, hypersynchronous discharges from an aggregate of CNS neurons. Epilepsy is diagnosed when there are recurrent seizures due to a chronic, underlying process.
Proper seizure classification is essential for diagnosis, therapy, and prognosis. Partial (or focal) seizures originate in localized area of cortex; generalized seizures involve diffuse regions of the brain in a bilaterally symmetric fashion. Simple-partial seizures do not affect consciousness and may have motor, sensory, autonomic, or psychic symptoms. Complex-partial seizures include alteration in consciousness coupled with automatisms (e.g., lip smacking, chewing, aimless walking, or other complex motor activities).
Generalized seizures may occur as a primary disorder or result from secondary generalization of a partial seizure. Tonic-clonic seizures (grand mal) cause sudden loss of consciousness, loss of postural control, 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 atypical absence, infantile spasms, and tonic, atonic, and myoclonic seizures.
Seizure type and age of patient provide important clues to etiology. Causes of seizures by age group are shown in Table 182-1.
Table 182-1 The Causes of Seizures
Careful history is essential since diagnosis of seizures and epilepsy is often based solely on clinical grounds. Differential diagnosis (Table 182-2) includes syncope or psychogenic seizures (pseudoseizures). General exam includes search for infection, trauma, toxins, systemic illness, neurocutaneous abnormalities, and vascular disease. A number of drugs lower the seizure threshold (Table 182-3). Asymmetries in neurologic exam suggest brain tumor, stroke, trauma, or other focal lesions. An algorithmic approach to the pt with a seizure is illustrated in Fig. 182-1.
Table 182-2 The Differential Diagnosis of Seizures
Table 182-3 Drugs and Other Substances That Can Cause Seizures
FIGURE 182-1. Evaluation of the adult patient with a seizure.
Acutely, the pt should be placed in semiprone position with head to the side to avoid aspiration. Tongue blades or other objects should not be forced between clenched teeth. Oxygen should be given via face mask. Reversible metabolic disorders (e. g., hypoglycemia, hyponatremia, hypocalcemia, drug or alcohol withdrawal) should be promptly corrected. Treatment of status epilepticus is discussed in Chap. 38.
Longer-term therapy includes treatment of underlying conditions, avoidance of precipitating factors, prophylactic therapy with antiepileptic medications or surgery, and addressing various psychological and social issues. Choice of antiepileptic drug therapy depends on a variety of factors including seizure type, dosing schedule, and potential side effects (Table 182-4 and Table 182-5). Therapeutic goal is complete cessation of seizures without side effects using a single drug (monotherapy). If ineffective, medication should be increased to maximal tolerated dose based primarily on clinical response rather than serum levels. If unsuccessful, a second drug should be added, and when control is obtained, the first drug can be slowly tapered. Approximately one- third of pts will require polytherapy with two or more drugs. Pts with certain epilepsy syndromes (e. g., temporal lobe epilepsy) are often refractory to medical therapy and benefit from surgical excision of the seizure focus.
Table 182-4 Antiepileptic Drugs of Choice
Table 182-5 First-Line Antiepileptic Drugs
For a more detailed discussion, see Lowenstein DH: Seizures and Epilepsy, Chap. 360, p. 2354, in HPIM-15.