What Is Todd's Paralysis?

Todd’s paralysis is a temporary medical syndrome of weakness or paralysis and loss of sensation over part of the body. This can sometimes happen after a seizure. It’s important to distinguish Todd’s paralysis from a stroke, which is a much more serious medical situation. Studies have estimated that Todd’s paralysis occurs in between 1% to 13% of people who have had a seizure.

Todd’s paralysis is also known as Todd paresis, postictal paresis, or post-epileptic paralysis. The condition was first described by an Irish physiologist, Robert Bentley Todd, back in 1849.

Todd's Paralysis Symptoms

The symptoms of Todd’s paralysis begin right after a seizure. This is sometimes called the “postictal state,” the period during which the brain recovers and returns to its normal activity. During this period, some people experience postictal symptoms such as sleepiness, headache, or confusion, even though the seizure isn't happening anymore. Todd's paralysis is a specific type of postictal symptom.

Todd’s paralysis can cause weakness or sometimes a total inability to move certain parts of your body (paralysis). The affected parts might not be able to feel sensations normally. In some cases, vision might be on the right or left side of your field of vision.

These symptoms usually affect one side of the body but not the other. For example, your right arm and right leg might be affected, or your left arm and left leg. Sometimes, symptoms might affect one side of the face as well, which might cause slurred speech. Less commonly, symptoms might occur in one leg or one arm alone. The symptoms usually affect the part of the body that was just previously involved in the seizure. These symptoms may last only for a few minutes or may persist over a couple of days.

Not everyone who has a seizure will experience Todd’s paralysis. Also, even if you’ve had an episode of Todd’s paralysis in the past, you might not have one after a future seizure.

Causes

The symptoms of Todd’s paralysis occur after a person has a seizure. This might happen after a seizure in someone who has been diagnosed with epilepsy, a medical condition that causes repeated seizures. However, it might also potentially happen in someone who has a seizure from another cause (such as an electrolyte abnormality).

For reasons that aren’t completely clear, Todd’s paralysis seems to be more common after seizures that cause physical movements during the seizure (called “clonic motor movements”). The paralysis tends to affect the areas of the body that were moving involuntarily during the seizure.

Most commonly, it occurs after partial seizures or after generalized tonic clonic seizures. Partial seizures affect only one area of the brain, and they might or might not cause loss of consciousness. Generalized tonic-clonic seizures (grand mal seizures) involve loss of consciousness and jerking motions. Todd’s paralysis may last a little longer in people who have it after a generalized tonic-clonic seizure compared to those who have it after a partial seizure.

Todd’s paralysis also sometimes happens after electroconvulsive therapy (ECT) given for depression. However, in this case the symptoms of Todd’s paralysis tend to go away even more quickly.

Underlying Causes

Though we know Todd’s paralysis sometimes occurs after seizures, researchers still don’t understand why it happens. It seems to be related to changes in brain physiology that occur from the seizure, with certain neurons not able to fire normally. But other factors may be involved as well.

Temporarily reduced blood flow to a region of the brain due to the seizure may be part of the problem. Because of this, certain areas of the brain might not be getting as much oxygen as normal. For example, if the brain area controlling the movement of the right arm and leg is affected, you might temporarily have trouble moving your right arm and leg. As the brain returns to normal, symptoms go away on their own.

Risk Factors

Older individuals seem to have a higher risk of getting Todd’s paralysis after a seizure.

Having Todd’s paralysis after a seizure is also more common in people who have had any of the following:

• Convulsive status epilepticus
• Prolonged seizures
• Epilepsy that has caused structural damage to the brain
• Previous stroke

Diagnosis

Medical history and medical exam provide the key starting points for diagnosis. The clinician assesses symptoms and learns about the individual’s medical conditions and health history.

Diagnosis may be relatively straightforward if a person has previously been diagnosed with epilepsy and their symptoms began right after someone witnessed their seizure. But if a person hasn’t previously been diagnosed with epilepsy, the diagnosis becomes trickier.

Todd’s Paralysis or Stroke?

In these situations, clinicians may be more concerned about a stroke, which can cause similar symptoms. Stroke is a much more serious medical condition with more lasting symptoms. It often requires long-term rehabilitation.

Based on symptoms alone, it is often difficult to tell Todd’s paralysis from a stroke. The diagnosis is made even trickier by the fact that a stroke can sometimes cause a seizure as well.

Distinguishing between stroke Todd's paralysis and is critical, because stroke requires a different medical treatment. Some people with certain types of strokes—those due to a blood clot or a blocked artery—may benefit from a treatment called tPA (tissue plasminogen activator). This treatment can help the blood again flow normally through brain blood vessels after a stroke. It is an extremely helpful treatment for many people who have had a stroke, and it may provide the best chance for full recovery. However, tPA comes with some risks, so clinicians don’t want to give it if a person hasn’t really had a stroke.

Medical Testing

Medical testing is often needed to help distinguish the stroke from Todd’s paralysis. Possible tests might include:

• Electroencephalogram (EEG)
• Magnetic resonance imaging (MRI)
• Computed tomography (CT) perfusion
• CT angiography

These give clues about whether the symptoms are more likely from a stroke or from a seizure.

Depending on the situation, a clinician might need to eliminate other possible causes of symptoms. For example, certain rare genetic syndromes might cause some symptoms similar to Todd’s paralysis.

Seizure Diagnosis

Other tests may also be helpful, depending on the situation. For example, if it seems like a person has had a seizure but hasn’t previously been diagnosed with epilepsy, other causes of seizure might need to be investigated. This might include:

• Basic blood tests of electrolytes
• Blood tests to assess for infection
• Tests of blood glucose
• Urine tests

These tests can’t diagnose Todd’s paralysis, but they might point to an underlying cause of a seizure in a person who hasn’t had one before. Many different types of medical problems can lead to a seizure, including infection, alcohol withdrawal, low blood sugar, and others.

A neurologist can provide guidance about whether epilepsy is the most likely cause of the seizure.

Treatment

Fortunately, the symptoms of Todd’s paralysis are short-lived. They disappear on their own without any need for treatment. Having Todd’s paralysis doesn’t cause any other medical complications.

However, the underlying cause of the seizure may need to be treated. For example, a seizure is sometimes the first symptom of untreated diabetes mellitus. Any underlying medical condition causing a seizure will need to be addressed.

In people with epilepsy, it's important to take steps to prevent future seizures. These individuals typically need to take medications long-term to help prevent future seizures. Other factors may also help you reduce your risk of future seizures, like getting enough rest and staying hydrated.

A Word From Verywell

Todd’s paralysis can be an alarming problem to have after a seizure. You may be wondering if you have a more serious problem, like a stroke. Fortunately, the symptoms of Todd’s paralysis should go away relatively quickly. Working with your medical provider to help prevent future seizures will give you more peace of mind.