Neurology · Seizure Disorders
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Todd paralysis is a transient postictal focal deficit (classically unilateral weakness/hemiparesis) appearing immediately after a seizure and resolving spontaneously within 48 hours.
It is a diagnosis of exclusion; sudden hemiparesis without a witnessed seizure must be treated as an acute stroke until proven otherwise.
Workup uses non-contrast head CT first to exclude hemorrhage, then MRI brain and CT angiography to rule out acute ischemic stroke or large-vessel occlusion.
The deficit maps to the homunculus region of the seizure focus and is often accompanied by confusion and transient expressive aphasia.
Pathophysiology involves postictal neuronal metabolic exhaustion (ATP depletion, lactic acidosis) and GABA-mediated cortical hyperpolarization.
Management is entirely supportive with airway protection, plus optimization of the antiepileptic drug regimen to prevent future seizures.
tPA is contraindicated if the deficit is definitively postictal, but if the seizure was caused by an acute stroke, standard stroke protocols must be activated.
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A 58-year-old man is brought to the ED after a witnessed generalized tonic-clonic seizure lasting two minutes. On arrival he is confused and has 2/5 strength in the left arm and leg with a normal sensory exam. A non-contrast head CT is unremarkable, and MRI with diffusion-weighted imaging shows no acute infarction. Over the next several hours his confusion clears and his left-sided strength returns to 5/5.
Which of the following is the most likely diagnosis?
Todd paralysis
A transient unilateral motor deficit appearing immediately after a witnessed seizure and resolving within 48 hours, with negative diffusion-weighted MRI, is characteristic of Todd paralysis. The lack of restricted diffusion excludes acute ischemic stroke, the principal mimic that must always be excluded first.
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High yield triage
Etiology / Epidemiology
A transient postictal focal neurological deficit occurring immediately after a seizure.
Clinical Manifestations
Presents as acute unilateral weakness or paralysis that typically resolves spontaneously within 48 hours.
Diagnosis
A clinical diagnosis of exclusion; must urgently use MRI brain and CT angiography to rule out acute ischemic stroke.
Treatment
Supportive care with close observation and optimization of baseline antiepileptic drug (AED) therapy.
Prognosis
Excellent prognosis with complete spontaneous resolution of motor deficits expected.
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Epidemiology & Etiology
Occurs in up to 13% of patients following focal seizures, particularly those with a prominent motor component. The exact etiology represents a transient postictal exhaustion of the primary motor cortex. It is most strongly associated with generalized tonic-clonic or focal motor seizures. Recurrent episodes of focal weakness in a patient with a known seizure disorder should prompt immediate re-evaluation of medication adherence and seizure control.
Pertinent Anatomy
Primarily involves the contralateral cerebral hemisphere corresponding to the affected, weakened limb. The focal deficit localizes precisely to the primary motor cortex (precentral gyrus) or the specific cortical area involved in the preceding seizure discharge.
Pathophysiology
Intense, high-frequency neuronal firing during a seizure leads to severe metabolic exhaustion of the involved cortical neurons. This results in localized ATP depletion, transient intracellular lactic acidosis, and temporary hypoxia within the focal epileptogenic zone. Additionally, there is a profound postictal hyperpolarization mediated by increased inhibitory neurotransmitter release, specifically GABA, rendering the motor cortex temporarily refractory to normal stimuli.
Clinical Manifestations
Presents as acute, focal motor weakness or paralysis (often hemiparesis) immediately following a clinically evident seizure. Deficits are typically unilateral and map to the homunculus region affected by the seizure focus. Associated postictal features frequently include confusion, lethargy, and transient expressive aphasia. Sudden onset hemiparesis without a clearly witnessed preceding seizure is a major red flag and must be treated as an acute stroke until proven otherwise.
Diagnosis
It is fundamentally a diagnosis of exclusion, as the critical step is differentiating it from an acute ischemic stroke or intracranial hemorrhage. Non-contrast head CT is the first-line test to rule out acute bleeding, followed by MRI brain and CT angiography (CTA) to exclude acute infarction or large vessel occlusion. Continuous EEG monitoring typically shows prominent focal slowing over the affected hemisphere but should not demonstrate active epileptiform discharges during the paralytic phase.
Treatment
Management is entirely supportive as the condition is self-limiting and requires no acute intervention for the weakness itself. The primary goal is ensuring airway protection and hemodynamic stability during the postictal phase. Long-term management requires optimization of the patient's antiepileptic drug (AED) regimen to prevent future seizures. Thrombolytic therapy (tPA) is strictly contraindicated if the focal deficit is definitively known to be postictal, but if the seizure was secondary to an acute stroke, standard stroke protocols must be activated.
Prognosis
The prognosis is highly favorable, with complete spontaneous resolution of all neurological deficits. Recovery typically begins within hours and is fully complete by 48 hours, though rarely it can persist for up to several days. Permanent neurological deficits indicate an alternative pathology, such as an underlying structural lesion or missed cerebral infarction.
Differential Diagnosis
1. Acute Ischemic Stroke: Presents with sudden focal neurological deficits that persist and requires emergent MRI brain or CT perfusion to differentiate from a postictal state.
2. Hemiplegic Migraine: Characterized by unilateral weakness accompanied by a severe, throbbing headache and often a positive family history.
3. Hypoglycemia: Can cause focal neurological deficits acting as a stroke mimic, but is rapidly reversible with IV dextrose and confirmed via a bedside fingerstick glucose.
4. Intracranial Neoplasm: Causes progressive, rather than abrupt, focal weakness and often serves as the structural nidus for the focal seizure itself.