Lateral Medullary Syndrome

Definition

Wallenberg syndrome is a type of brain stem stroke manifested by imbalance, vertigo, difficulty swallowing, hoarseness of voice, and sensory disturbance. It is caused by blockage in one of the arteries supplying the medulla and cerebellum.

Description

The first clinical description was given by Gaspard Viesseux in 1808 and published by Alexander John Gaspard Marcet in 1811. But it wasn't until 1895 that Adolf Wallenberg eloquently described the different symptoms and signs and confirmed the findings during autopsy. The syndrome is also known as lateral medullary infarct (LMI) or posterior inferior cerebellar artery syndrome (PICA).

It usually affects people over 40 years of age. They tend to have vascular risk factors such as hypertension, high cholesterol, and diabetes. Wallenberg syndrome can also occur in younger people, but the underlying causes are different.

Demographics

Wallenberg syndrome is rare, and accurate estimates about incidence are unavailable. In a large stroke registry in Sweden gathered by Norving and Cronquist in 1991, only about 2% of all strokes over a six-year period were caused by LMI.

Causes and symptoms

The stroke occurs in the medulla and cerebellum. The medulla controls such important functions as swallowing, speech articulation, taste, breathing, strength, and sensation. The cerebellum is important for coordination. The blood supply to these areas is via a pair of vertebral arteries and its branch, called the posterior inferior cerebellar artery (PICA).

Initially, the PICA was thought to be the blocked major artery, but this has been disproved from autopsy studies. In eight out of 10 cases, it is the vertebral artery that is occluded due to plaque buildup or because of a clot traveling from the heart. In younger patients, the vertebral artery dissection causes the infarct. The area of the stroke is only about 0.39 in (1 cm) vertically in the lateral part of the medulla and does not cross the midline.

Fully 50% of patients report transient neurological symptoms for several weeks preceding the stroke. During the first 48 hours after the stroke, the neurological deficit progresses and fluctuates. Dizziness, vertigo, facial pain, double vision, and difficulty walking are the most common initial symptoms. The facial pain can be quite bizarre with sharp jabs or jolts around the eye, ear, and forehead. Patients feel "seasick" or "off-balance" with nausea and vomiting. Objects appear double, tilted, or swaying. Along with gait imbalance, it becomes nearly impossible for the patient to walk despite good muscle strength. Other symptoms include hoarse voice, slurred speech, loss of taste, difficulty swallowing, hiccups, and altered sensation in the limbs of the opposite side.

The eye on the affected side has a droopy eyelid and a small pupil. The eyes jiggle when the person moves around; this is called nystagmus. There is decreased pain and temperature perception on the same side of the face. The limbs on the opposite side show decreased sensory perception. Voluntary movements of the arm on the affected side are clumsy. Gait is "drunken," and patients lurch and veer to one side.

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Author Info: Chitra Venkatasubramanian MBBS, MD, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Neurological Disorders, 2005

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