A 68-year-old man is seen in the emergency room after an unwitnessed syncopal episode. His wife heard a strange noise and found him confused and on the floor of the living room where he had been watching television. His wife tells you that he has no ongoing medical problems, does not take any medications, and does not use alcohol or illicit drugs. On examination the patient is drowsy, has a tongue laceration, and his pants are wet with urine. Serum electrolytes (including calcium) are normal and urine drug screen is negative.
Which of the following is the best next step in evaluation?
A. MRI scan of brainThough syncope is usually due to a cardiovascular cause, the presence of a tongue laceration and urinary incontinence suggest syncope due to a seizure. Furthermore, patients with syncope due to cardiac causes usually recover normal mentation within a few minutes. Prolonged drowsiness is a common postictal phenomenon that can follow a generalized seizure. These findings all point to the likelihood of an unwitnessed seizure in this patient. Juvenile myoclonic epilepsy is the most common cause of generalized seizures in young persons. Usually beginning in childhood or adolescence, juvenile myoclonic epilepsy tends to run in families and is associated with morning myoclonic jerks. Seizures that begin in older adults are more likely due to structural brain disease. The evaluation of a new seizure in an older adult includes an electroencephalogram (EEG) to confirm the diagnosis, but the EEG will be nondiagnostic in about one-half of patients. An MRI is the best test to look for structural brain disease, such as a brain tumor, old stroke, brain abscess, or vascular malformation. Even small lesions can provide the trigger for a seizure, so the more sensitive MRI is preferred to CT scanning in this circumstance. Amphetamines, cocaine, and other illicit drugs may cause seizures, and urine toxicology is appropriate in patients with new-onset seizures. Though often performed, routine blood tests are rarely helpful in the evaluation of seizures. Lumbar puncture is performed only if meningitis or encephalitis is suspected. Holter monitoring is used to detect rhythm disturbances that can be associated with syncope, but cardiac syncope is rarely associated with seizures. Another cause of cardiac syncope is aortic stenosis that could be detected by echocardiography, but syncope associated with aortic stenosis is almost never associated with seizures.