This patient should receive an antiepileptic drug (AED), such as carbamazepine. His seizure was unprovoked. The 2-year risk of recurrence after a single unprovoked seizure is approximately 40%. On the basis on this estimate, most experts do not recommend starting an AED for a first seizure unless the patient has risk factors that increase the likelihood for future events. This patient, however, has several risk factors for future seizures, including previous head trauma with loss of consciousness, a focal brain lesion on MRI, and postictal Todd paralysis of the right arm (focal weakness after a seizure). His risk of future seizures is high, and he should be treated with an AED. In this patient, the brain injury involving the contralateral parietal lobe is likely the source of the seizure, with the abnormal sensation experienced at seizure onset representing a sensory aura. He most likely had a simple partial seizure starting in the parietal lobe that spread to the motor cortex, which led to the dystonic posture of his hand and subsequent tonic-clonic seizure.

Ambulatory electroencephalography (EEG) is an outpatient test that can be useful to exclude the presence of unrecognized seizures and provide a more sensitive evaluation of interictal discharges than a 30-minute EEG. This test, however, is not performed in the emergency department and does not have to be completed before starting treatment in this patient, who had a witnessed seizure and has a high risk of recurrent seizure.

Clinical observation is appropriate management of a single unprovoked seizure only in patients with no risk factors for future seizures.

A lumbar puncture is indicated in some patients with a first seizure if they have symptoms or signs of infection or have altered mental status. In this patient with a clear reason for a partial seizure, a normal mental status, and no signs of infection, a lumbar puncture is unnecessary.