What is the most likely diagnosis for a patient with a history of seizures, who presents with paralysis of the right lower extremity after a witnessed grand mal seizure, with normal neuroimaging and bedside glucose results?

Todd's Paralysis

The most likely diagnosis is Todd's paralysis (Option D), a transient postictal neurological deficit that occurs after seizures and resolves spontaneously without intervention. 1, 2

Clinical Reasoning

This patient presents with the classic triad for Todd's paralysis:

• Recent witnessed grand mal (generalized tonic-clonic) seizure - Todd's paralysis is most commonly observed after partial seizures or generalized tonic-clonic seizures 2
• Transient focal neurological deficit (right lower extremity paralysis) appearing immediately after the seizure 1, 2
• Normal neuroimaging - excludes acute stroke and structural lesions requiring immediate intervention 1, 3

The patient's continued confusion is consistent with the postictal state, and the mild horizontal nystagmus may represent either a postictal phenomenon or a medication effect (given the history of seizure medication). 4

Key Distinguishing Features from Acute Stroke

Todd's paralysis can be confidently distinguished from acute stroke (Option C) in this case by:

• Temporal relationship - weakness appearing immediately after a witnessed seizure rather than as an isolated event 2, 3
• Normal neuroimaging - CT/MRI shows no acute ischemic changes, though Todd's paralysis can occasionally show transient diffusion restriction that resolves 3
• Clinical context - known seizure disorder on medication makes postictal phenomenon far more likely than coincidental stroke 1

The positive likelihood ratio for Todd's paralysis is 11.2 in patients with remote seizure etiologies or structural brain lesions. 1

Duration and Natural History

The paralysis typically resolves spontaneously:

• Duration ranges from minutes to days, depending on seizure type and whether cortical structural damage exists 2
• Most cases resolve within hours 1, 2
• No specific treatment is required beyond observation and management of the underlying seizure disorder 2, 3

Why Other Options Are Incorrect

Hemiplegia epilepsy syndrome (Option A) is not a recognized diagnostic entity in standard epilepsy classification and does not describe a postictal phenomenon. 4, 5

Psychogenic post-ictal state (Option B) is inappropriate because:

• The seizure was witnessed and therefore confirmed as organic 4
• Objective neurological findings (paralysis, nystagmus) are present on examination 4
• Normal glucose and neuroimaging support an organic postictal process rather than functional/psychogenic etiology 4

Clinical Pitfall to Avoid

The most critical error would be misdiagnosing this as acute stroke and administering thrombolytic therapy. 1, 3 Todd's paralysis is a well-recognized stroke mimic in emergency practice. The key is recognizing the temporal relationship to the seizure and the normal neuroimaging. 1, 2, 3

In patients with old stroke history, Todd's paralysis occurs in approximately 19.7% of convulsive seizures, making old stroke an independent risk factor for developing postictal paralysis. 1 This creates diagnostic complexity when weakness occurs, but the witnessed seizure and normal acute imaging clarify the diagnosis.