SEIZURES AND EPILEPSY

SEIZURES AND EPILEPSY

A 29-year-old man is brought to the emergency department by ambulance after being found convulsing in his bedroom. The patient’s mother says that during the episode her son was unable to respond to her frantic cries, and she describes jerking movements that became more frequent and then stopped after approximately 1 minute. The mother says that he seemed tired and lethargic for at least 20 minutes after the episode. She then called the ambulance to bring her son to the hospital.

Definition. A seizure is a paroxysmal event due to abnormally discharging central nervous system (CNS) neurons. Epilepsy is defined as a condition of recurrent seizures due to a chronic underlying process.

Etiology. Seizures are caused by “VITAMINS”:

Vascular (stroke, bleed, arteriovenous malformation)

Infection (meningitis, abscess, encephalitis) Trauma (especially penetrating) Autoimmune (CNS vasculitis)

Metabolic (hyponatremia, hypocalcemia, hypomagnesemia, hypoglycemia, hypoxia, drug overdose/withdrawal)

Idiopathic Neoplasm pSychiatric

Clinical Presentation. A seizure is essentially a paroxysmal, involuntary event (associated with abnormal movement or change of consciousness or both). Characteristically, seizures are sudden in onset, with or without an aura. Patients often complain of disorientation, sleepi- ness, and aching muscles for minutes to hours after the event. Patients may also experience incontinence, tongue biting, and headache as a result of the seizure. It may be difficult at times to differentiate a seizure from syncope, and it is important to obtain a complete history from any individual who witnessed the event. Generally, patients with syncope will not complain of significant postictal symptoms. They will recover consciousness within several minutes of the event, and on physical exam will not have evidence of incontinence or tongue biting.

It is important to classify seizures according to their clinical features because this will deter- mine what medications will be used for treatment. Seizures can be classified as partial versus generalized and complex versus simple.

Partial seizures occur within discrete portions of the brain. The patient will often complain of involuntary jerking of a finger or hand. When consciousness is maintained for the dura- tion of the seizure, the seizure is termed a simple partial seizure. When there is a change in consciousness during the seizure, the seizure is termed a complex partial seizure. When a partial seizure progresses to a generalized seizure, it is called a partial seizure with secondary generalization. Typically, the seizure will begin focally and become generalized as the seizure activity involves both cerebral hemispheres.

Generalized seizures arise from both cerebral hemispheres spontaneously without any detect- able focal onset. Generalized tonic-clonic (grand mal) seizures are characterized by tonic contraction of muscles throughout the body followed by intermittent relaxation of various muscle groups (clonic phase). Absence seizures (petit mal) are more common in children than adults; they are characterized by sudden, brief loss of consciousness without loss of postural tone. Characteristically, the EEG will show a generalized, symmetric 3-Hz spike-and- wave discharge pattern. Atonic seizures are characterized by sudden loss of postural tone last- ing 1 to 2 seconds. Myoclonic seizures are characterized by sudden, brief muscle contraction.

Status epilepticus is defined as recurrent or continuous seizures (lasting at least 5–30 min).

Diagnosis. EEG is the test of choice for the diagnosis of epilepsy. The diagnosis of idiopathic seizures is made only after secondary precipitating factors have been ruled out. An abnormal EEG alone is not diagnostic of epilepsy. Approximately 2 to 18% of the population has an abnormal EEG. Always check serum electrolytes, glucose, toxicology, and arterial blood gas to rule out hypoxia as a cause of a patient’s seizure. CT scan or MRI of the head is usually indi- cated to rule out a structural lesion as the cause of seizure. Think of any seizure as a symptom, much like shortness of breath or chest pain, which has an extensive differential diagnosis. The evaluation of any seizing patient is to rule out reversible causes of seizure.

Treatment. The treatment of seizures can be divided into the acute management of the acutely seizing patient (status epilepticus) and the chronic management of the epileptic patient.

The first step in the treatment of any acutely seizing patient is to secure the airway, breath- ing, and circulation. Once an adequate airway is established, breathing is assured, and the patient is hemodynamically stable, the next step is to simultaneously evaluate and treat any precipitating causes of seizure. If a reversible cause is identified, treat aggressively. If the patient continues to seize, the following strategy is appropriate. The initial drug of choice    is lorazepam or diazepam, both of which are benzodiazepines. These medications work by potentiating GABA receptor function. If the patient continues to seize, add phenytoin or fosphenytoin, which inhibits sodium-dependent action potentials. CNS side effects of phe- nytoin include diplopia, dizziness, and ataxia. Systemic side effects include gum hyperplasia, lymphadenopathy, hirsutism, and rash. If the patient continues to seize add phenobarbital. Side effects include sedation, ataxia, and rash. If, despite all of the above therapy, the patient continues to seize, add midazolam or propofol.

In patients with first-time seizure, anticonvulsant therapy should be started only if the patient has an abnormal neurologic exam, presented with status epilepticus, has a strong family history of seizure, or has an abnormal EEG. Otherwise, first-time seizures are generally not treated with long-term anticonvulsant therapy.

There is no superior drug in pregnancy. Valproic acid is clearly more dangerous in pregnancy.

For primary generalized tonic-clonic seizures, valproic acid, phenytoin, lamotrigine, carba- mazepine, or levetiracetam can be used. Lamotrigine works by decreasing glutamate release. Side effects include Stevens-Johnson syndrome. Absence seizures are treated with etho- suximide as first-line therapy. If ethosuximide is not an answer choice, valproic acid is an acceptable option. For myoclonic and atonic seizures, valproic acid is the treatment of choice. Overall, there is no single antiepileptic drug that’s truly superior to the others—valproic acid, phenytoin, levetiracetam and carbamazepine are all nearly equal in efficacy.

Partial seizures, whether they are complex or simple, and whether or not they progress to secondary generalized seizures, are all treated the same. Carbamazepine and phenytoin are considered first-line therapy. Valproic acid and lamotrigine are considered acceptable alter- natives, as is levetiracetam. It is very difficult to determine when to stop therapy. Therapy may be stopped if the patient has been free of seizures for 2–3 years. Sleep-deprivation EEG may be done first to determine if the patient is at low risk of a recurrence. A normal sleep- deprivation EEG means there is a lower likelihood of seizures.