What is Todd's paralysis?

Todd's Paralysis: A Transient Post-Seizure Neurological Deficit

Todd's paralysis is a temporary neurological deficit characterized by focal weakness or hemiplegia that occurs following an epileptic seizure and typically resolves completely within minutes to hours without permanent consequences. 1

Clinical Characteristics

• Definition: A post-ictal (after seizure) neurological abnormality presenting as temporary limb weakness or hemiplegia
• Duration: Typically lasts minutes to hours, but can extend up to 36 hours in some cases 2
• Occurrence rate: Observed in approximately 6-13% of seizures 2
• Common presentation: Usually follows partial seizures or generalized tonic-clonic seizures 1

Risk Factors and Associations

Todd's paralysis is more likely to occur in:

• Older patients
• Those with a history of stroke
• Patients experiencing convulsive status epilepticus
• Seizures with longer duration of convulsion 3

Importantly, Todd's paralysis has been identified in 19.7% of convulsive seizures with remote etiologies, particularly those due to old stroke. These etiologies represent independent significant risk factors for Todd's paralysis compared to seizures with cryptogenic (unknown) etiology. 3

Pathophysiology

The exact mechanism remains incompletely understood, but the etiology is associated with:

• Cerebral perfusion abnormalities after seizures
• Possible neuronal exhaustion in the post-ictal period
• Transient cytotoxic edema that may be visible on diffusion-weighted MRI 4

Diagnostic Considerations

Differential Diagnosis

The most critical differential diagnosis is acute stroke, as both conditions can present with sudden-onset focal weakness. Other conditions to consider include:

1. Acute ischemic stroke - requires urgent evaluation and potential thrombolytic therapy
2. Hemiplegic migraine - typically has associated headache and visual symptoms
3. Conversion disorder - psychological factors predominate
4. Hypoglycemia - can cause focal neurological deficits

Key Distinguishing Features from Stroke

• History of seizure immediately preceding the deficit
• Resolution of symptoms within hours (versus persistent deficits in stroke)
• Normal CT/MRI findings (though transient diffusion restriction can occur)

Diagnostic Approach

When evaluating a patient with suspected Todd's paralysis:

1. Confirm recent seizure activity - witness accounts or post-ictal state
2. Perform neurological examination - document the pattern and extent of weakness
3. Consider neuroimaging - CT or MRI to rule out stroke, especially in patients without known epilepsy
4. Monitor for resolution - Todd's paralysis should improve over time

Prognostic Significance

Todd's paralysis may have prognostic implications. According to Hauser et al., Todd's paralysis predicted a higher recurrence rate (76%) of seizures 5. This suggests that patients who experience Todd's paralysis may require closer follow-up and potentially more aggressive seizure management.

Clinical Pitfalls to Avoid

1. Misdiagnosing acute stroke as Todd's paralysis - particularly dangerous as it may delay life-saving treatment
2. Failing to recognize Todd's paralysis in patients without known epilepsy - can lead to unnecessary interventions
3. Not considering Todd's paralysis in special populations - such as pregnant women 4 or post-surgical patients 6
4. Overlooking underlying structural lesions - Todd's paralysis highly suggests premorbid or comorbid structural lesions in the central nervous system 3

Management Approach

1. Supportive care during the resolution phase
2. Seizure management - optimize anti-epileptic medications
3. Neuroimaging to rule out structural causes, particularly in new-onset cases
4. Follow-up to ensure complete resolution and assess for recurrence

Todd's paralysis serves as an important clinical entity that requires careful evaluation to distinguish from other acute neurological emergencies, particularly stroke, while also potentially providing valuable information about underlying brain pathology and seizure recurrence risk.