Wallenberg's syndrome is a neurological condition caused by a stroke in the brain stem, specifically in one of the arteries that provides blood to the cerebellum. The cerebellum coordinates and regulates muscular activity in the body. Symptoms may include:

• Difficulty swallowing
• Hoarseness
• Dizziness
• Nausea and vomiting
• Rapid involuntary (automatic) movements of the eyes (known as nystagmus)
• Problems with balance and walking
• Lack of pain and temperature sensation on only one side of the face

• Uncontrollable hiccups
• A pattern of 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.

The outlook for people with Wallenberg's symptoms depends on the area of the brain stem that is damaged by the stroke. Some people's symptoms may decrease within weeks or months. Others may have significant neurological disabilities (such as epilepsy, learning disabilities, autism, attention deficit disorder, brain tumors, or cerebral palsy, among others) for years after the first symptoms appear.

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 may help. In some cases, drugs may help reduce or eliminate pain. Some doctors report that the anti-epileptic drug gabapentin appears to help people with chronic (long-term) pain.

The most common underlying cause of Wallenberg syndrome is a brain stem stroke in the vertebral or posterior inferior cerebellar arteries of the brain stem. However, several other disorders or conditions reportedly have been associated with Wallenberg syndrome, including:

• mechanical trauma to the vertebral artery in the neck
• vertebral arteritis (inflammation of the wall of the artery)
• metastatic cancer
• hematoma
• aneurysm of the vertebral artery
• herpetic brainstem encephalitis (relating to herpes)
• head injury
• arteriovenous malformations (AVMs)
• multiple sclerosis
• varicella infection
• brainstem tuberculoma (a rare form of tuberculosis)

• pain and temperature sensory loss on one side of the face as well as on the opposite side of the body
• rapid involuntary movements of the eyes (nystagmus)
• problems with balance and gait (walking) coordination
• vomiting
• vertigo
• nystagmus
• dysphagia
• hoarseness
• uncontrollable hiccups
• Horner syndrome (decreased pupil size, a drooping eyelid and decreased sweating on the affected side of the face) with visual deficits