Lateral Medullary Syndrome

What is lateral medullary syndrome?

Lateral medullary syndrome is a neurological condition caused by a stroke in the brainstem. This relatively uncommon type of stroke is often the result of a blockage of the vertebral artery or posterior inferior cerebellar artery (PICA).  These arteries provide blood to the medulla oblongata, a brain structure that plays a critical role in sending and receiving signals between the brain and spinal cord. Lateral medullary syndrome is also known as Wallenberg's syndrome or PICA syndrome. Lateral medullary syndrome consists of several symptoms that can occur from this type of brain stem stroke.

Symptoms may include:

• Difficulty swallowing
• Hoarseness
• Dizziness
• Nausea and vomiting
• Rapid involuntary movements of the eyes (nystagmus)
• Problems with balance and walking
• Lack of pain and temperature sensation on only one side of the face
• Uncontrollable hiccups, which may be very disruptive and last for weeks
• Different symptoms on opposite sides of the body—for example:
  • Feeling paralyzed or numb on the right side of the face while having weak or numb arms and legs on the left side of the body
  • Losing the sense of taste on one side of the tongue, while keeping it on the other side

Some people with Wallenberg's syndrome say that the world seems to be tilted in a disturbing way. This makes it difficult for them to keep their balance when they walk. 

Another common presentation in people with lateral medullary syndrome is a collection of symptoms known as Horner syndrome, which features a smaller pupil in one eye, a drooping eyelid, and decreased sweating on one side of the body. 

Who is more likely to get lateral medullary syndrome?

Lateral medullary syndrome is caused by a blood clot in the arteries that feed the brainstem (called an ischemic stroke of the brainstem).  

Risk factors for Wallenberg syndrome and other strokes include:

• High blood pressure
• Smoking
• Diabetes
• Elevated cholesterol

In younger people, lateral medullary syndrome is most commonly caused by an injury or tear (trauma) to the vertebral artery. Vertebral arteries run through the vertebrae in the neck that make up the spinal column.

How is lateral medullary syndrome diagnosed and treated? 

Diagnosing lateral medullary syndrome

Because it is a type of stroke and can be very serious, people with suspected lateral medullary syndrome should be seen by a doctor as soon as possible. The medical team will order imaging tests, including MRI (magnetic resonance imaging) or CT (computed tomography) scans. It is important to rule out a head injury, which shares many of the same symptoms of lateral medullary syndrome. 

Learn more about assessing and treating stroke. 

Treating lateral medullary syndrome

Because lateral medullary syndrome is a type of acute ischemic stroke, the most effective treatment is to quickly restore blood flow. Tissue plasminogen activator (tPA) is a drug that can help break up clots and restore blood flow in the brain, but it must be administered within 4.5 hours of symptom onset. This is why it is important for someone suspected of stroke to be seen by a doctor as soon as possible. 

Once blood flow in the brain is restored, treatment for Wallenberg's syndrome focuses on easing the symptoms of the disorder. If swallowing is very difficult, a feeding tube may be necessary. Speech/swallowing therapy can help, too.  

It is important that people who have had Wallenberg syndrome manage their risk factors to prevent future strokes. A doctor may prescribe medications to reduce the risk of another stroke. These can include long-term treatment with aspirin or clopidogrel (Plavix) to prevent clotting and statins to reduce cholesterol. If the person also has atrial fibrillation, they may be placed on a blood thinner to prevent blood clots. 

The outlook for people with lateral medullary syndrome depends on the area of the brainstem that is damaged by the stroke. Some people's symptoms may improve within weeks or months. Others may have neurological disability for years.

Learn more about stroke recovery. 

How can I or my loved one help improve care for people with Wallenberg's syndrome?

Consider participating in a clinical trial so clinicians and scientists can learn more about Wallenberg's syndrome and related disorders.  Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with Wallenberg's syndrome at Clinicaltrials.gov.