Wallenberg Syndrome: Understanding the Symptoms and Causes

Wallenberg syndrome, also known as lateral medullary syndrome or posterior inferior cerebellar artery (PICA) syndrome, is the most common type of brainstem infarction and a key presentation of posterior circulation ischemic stroke. The brain can be divided into the cerebral hemispheres, cerebellar hemispheres, and the brainstem, which itself consists of the midbrain, pons, and medulla oblongata. This syndrome occurs due to damage to the lateral part of the medulla oblongata, typically caused by a blockage in the blood supply from the posterior inferior cerebellar artery.

What Happens During Lateral Medullary Damage?

Each area of the brain is supplied by specific blood vessels, and the lateral medulla is primarily nourished by branches of the PICA. When this artery becomes ischemic, the neurons in this region suffer from reduced oxygen and nutrients, leading to a cascade of neurological symptoms. One of the key structures affected is the vestibular nucleus. Damage to this area results in vertigo, often accompanied by nystagmus (involuntary eye movement), nausea, and vomiting. In some cases, persistent hiccups may also occur due to disruption of the neural pathways controlling the diaphragm.

Autonomic and Sensory Effects

The lateral medulla also contains important autonomic nerve fibers, particularly those involved in the sympathetic nervous system. Injury to these fibers can lead to Horner's syndrome, which presents with a combination of symptoms including ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (reduced sweating) on one side of the face.

Movement and Coordination Issues

Damage to the lateral medulla can also affect the cerebellar connections via the spinal cerebellar tracts. As a result, patients may experience ipsilateral cerebellar ataxia — a lack of muscle coordination that can cause unsteady gait and postural imbalance. Additionally, injury to the spinal trigeminal nucleus and tract can lead to facial pain and numbness, along with impaired sensory perception on the affected side of the face.

Impact on Swallowing and Speech

Various nuclei within the medulla control essential functions such as swallowing and voice production. When these areas are affected, patients may develop dysphagia (difficulty swallowing), hoarseness, and dysarthria (slurred speech). Some may also experience a diminished sense of taste or even paralysis of the soft palate, which can lead to nasal regurgitation and difficulty in articulating words clearly.

Somatosensory Deficits

One of the hallmark features of Wallenberg syndrome is contralateral loss of pain and temperature sensation in the body, due to involvement of the spinothalamic tract. Patients may also exhibit mild weakness in the limbs on the opposite side of the body. Collectively, these symptoms form a distinct clinical pattern known as lateral medullary syndrome.