Final answer:
The right-sided hemiparesis experienced by the man with epilepsy after a generalized tonic-clonic seizure is most likely due to Todd's paralysis, a temporary and self-limiting condition that resolves within 48 hours.
Step-by-step explanation:
The best explanation for the marked right-sided hemiparesis after a generalized tonic-clonic seizure in a 33-year-old man with known epilepsy is Todd's paralysis. Todd's paralysis is a temporary neurological deficit that can follow a seizure, characterized by weakness or paralysis in a part or all of the body on one side after a seizure has occurred. This condition is a well-recognized postictal phenomenon, is self-limited, and typically resolves on its own within 48 hours. Postictal stroke, complicated postictal migraine, conversion disorder, and transient ischemic attack (TIA) are also possible considerations after a seizure. However, the presentation of a postictal neurological deficit that completely resolves, commonly without treatment, is most suggestive of Todd's paralysis. It's important to rule out a stroke or TIA, which may require urgent intervention. However, the brief duration and resolution of the symptoms, in this case, do not support these diagnoses.