Todd paralysis

**Definition:** Temporary unilateral (or focal) weakness of a limb, face, or one side of the body after a seizure, most often a focal seizure with or without progression to bilateral tonic-clonic activity. Weakness is contralateral to the seizure focus. Typical duration is 15 minutes to 48 hours (usually <15 hours), though rare cases last up to about 36-48 hours or longer. It resolves completely without residual deficit.

**Pathophysiology (proposed, not fully established):** - Postictal neuronal exhaustion: depletion of energy substrates (e.g., glucose, ATP) after intense, hypersynchronous firing. - Active postictal inhibition: increased inhibitory neurotransmission (GABA) and activation of inhibitory networks, which suppresses the motor cortex. - Postictal cerebral hypoperfusion or neurovascular uncoupling is another proposed contributor. - The current evidence favors active inhibitory mechanisms over simple exhaustion.

**Clinical features:** - Hemiparesis, monoparesis, or focal weakness (may include facial droop) after a witnessed or suspected seizure. - Can also involve postictal aphasia (dominant hemisphere), visual loss, or sensory deficits. Todd's phenomenon is the broader term for these. - Reflexes and tone can vary. Babinski sign may be present transiently. - More common in patients with a known seizure disorder or underlying structural lesion (tumor, prior stroke, AVM, cortical dysplasia). It is more likely after prolonged or focal motor seizures.

**Diagnosis and workup:** - Diagnosis of exclusion. The main concern is that the seizure was caused by an acute stroke (hemorrhagic or ischemic), or that a stroke is mimicking Todd paralysis. - Urgent neuroimaging (non-contrast CT, then MRI) is indicated for a first seizure or if the deficit is atypical or prolonged. - Consider CT angiography or perfusion imaging if stroke is still a concern. Postictal perfusion changes can mimic stroke. - EEG may show postictal focal slowing over the contralateral hemisphere. - Check glucose, since hypoglycemia can cause both seizures and focal deficits. Also check electrolytes.

**Management:** - Supportive care. The deficit resolves spontaneously. - Treat the underlying seizure disorder or cause (antiseizure medication, address the structural lesion). - Be cautious with thrombolysis. Seizure at onset with a persistent deficit is a relative contraindication to tPA unless stroke is confirmed (e.g., by imaging). Do not give tPA based on a deficit that may be postictal.

**High-yield board points:** - Named for Robert Bentley Todd (1809-1860), who described it. - "Postictal" weakness that fully resolves = Todd paralysis. Persistent deficit means think stroke. - Distinguish from: stroke/TIA (TIA usually causes negative symptoms without preceding convulsion), hemiplegic migraine, hypoglycemia, and conversion disorder. - Not a sign of permanent brain damage, and it does not itself require specific treatment.