Trigeminal Nerve - Wallenberg Syndrome

Wallenberg Syndrome

Wallenberg syndrome (also called the lateral medullary syndrome) is a classic clinical demonstration of the anatomy of the fifth nerve. It provides a useful summary of essential points about the processing of sensory information by the trigeminal nerve.

A stroke usually affects only one side of the body. If a stroke causes loss of sensation, the deficit will be lateralized to the right side or the left side of the body. The only exceptions to this rule are certain spinal cord lesions and the medullary syndromes, of which Wallenberg syndrome is the most famous example. In Wallenberg syndrome, a stroke causes loss of pain/temperature sensation from one side of the face and the other side of the body.

The explanation involves the anatomy of the brainstem. In the medulla, the ascending spinothalamic tract (which carries pain/temperature information from the opposite side of the body) is adjacent to the ascending spinal tract of the fifth nerve (which carries pain/temperature information from the same side of the face). A stroke that cuts off the blood supply to this area (e.g., a clot in the posterior inferior cerebellar artery) destroys both tracts simultaneously. The result is loss of pain/temperature sensation (but not touch/position sensation) in a unique "checkerboard" pattern (ipsilateral face, contralateral body) that is entirely diagnostic.