Epilepsy has several causes. Its most likely cause in individual patients relates to the age at onset. Seizures usually begin between 5 and 20 years of age but may start later in life. No specific cause can be identified, and there is no other neurologic abnormality.
Symptoms and Signs of Epilepsy
Nonspecific changes such as headache, mood alterations, lethargy, and myoclonic jerking alert some patients to an impending seizure hours before it occurs. These prodromal symptoms are distinct from the aura which may precede a generalized seizure by a few seconds or minutes and which is itself a part of the attack, arising locally from a restricted region of the brain.
In most patients, seizures occur unpredictably at any time and without any relationship to posture or ongoing activities. Occasionally, however, they occur at a particular time (eg, during sleep) or in relation to external precipitants such as lack of sleep, missed meals, emotional stress, menstruation, alcohol ingestion (or alcohol withdrawal; see below), or use of certain drugs. Fever and nonspecific infections may also precipitate seizures in known epileptics. In a few patients, seizures are provoked by specific stimuli such as flashing lights or a flickering television set (photosensitive epilepsy), music, or reading.
Clinical examination between seizures shows no abnormality in patients with idiopathic epilepsy, but in the immediate postictal period, extensor plantar responses may be seen. The presence of lateralized or focal signs postictally suggests that seizures may have a focal origin. In patients with symptomatic epilepsy, the findings on examination will reflect the underlying cause.
Laboratory and Other Studies of Epilepsy
Initial investigations should always include a full blood count, blood glucose determination, liver and renal function tests, and serologic tests for syphilis. The hematologic and biochemical screening tests are important both in excluding various causes of seizures and in providing a baseline for subsequent monitoring of long-term effects of treatment.
Electroencephalography may support the clinical diagnosis of epilepsy (by demonstrating paroxysmal abnormalities containing spikes or sharp waves), may provide a guide to prognosis, and may help classify the seizure disorder. Classification of the disorder is important for determining the most appropriate anticonvulsant drug with which to start treatment. For example, absence (petit mal) and complex partial seizures may be difficult to distinguish clinically, but the electroencephalographic findings and treatment of choice differ in these two conditions. Finally, by localizing the epileptogenic source, the electroencephalographic findings are important in evaluating candidates for surgical treatment.
Differential Diagnosis of Epilepsy
The distinction between the various disorders likely to be confused with generalized seizures is usually made on the basis of the history. The importance of obtaining an eyewitness account of the attacks cannot be overemphasized.
Treatment of Epilepsy
For patients with recurrent seizures, drug treatment is prescribed with the goal of preventing further attacks and is usually continued until there have been no seizures for at least 3 years. Epileptic patients should be advised to avoid situations that could be dangerous or life-threatening if further seizures should occur. State legislation may require clinicians to report to the state department of public health any patients with seizures or other episodic disturbances of consciousness.
Choice of medication
The drug with which treatment is best initiated depends upon the type of seizures to be treated (Table 24–3). The dose of the selected drug is gradually increased until seizures are controlled or side effects prevent further increases. If seizures continue despite treatment at the maximal tolerated dose, a second drug is added and the dose increased depending on tolerance; the first drug is then gradually withdrawn. In treatment of partial and secondarily generalized tonic-clonic seizures, the success rate is higher with carbamazepine, phenytoin, or valproic acid than with phenobarbital or primidone. Gabapentin, topiramate, lamotrigine, oxcarbazepine, levetiracetam, and zonisamide are newer antiepileptic drugs that are effective for partial or secondarily generalized seizures. Felbamate is also effective for such seizures but, because it may cause aplastic anemia or fulminant hepatic failure, should be used only in selected patients unresponsive to other measures. Tiagabine is another adjunctive agent for partial seizures. In most patients with seizures of a single type, satisfactory control can be achieved with a single anticonvulsant drug. Treatment with two drugs may further reduce seizure frequency or severity, but usually only at the cost of greater toxicity. Treatment with more than two drugs is almost always unhelpful unless the patient is having seizures of different types.
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