Brown-Sequard syndrome (BSS) is a rare neurological condition characterized by a lesion in the spinal cord which results in weakness or paralysis (hemiparaplegia) on one side of the body and a loss of sensation (hemianesthesia) on the opposite side.

BSS may be caused by:

• A spinal cord tumor
• Trauma – such as a puncture wound to the neck or back
• Ischemia (obstruction of a blood vessel)
• Infectious or inflammatory diseases – such as tuberculosis or multiple sclerosis

In its pure form, it is rarely seen as the trauma would have to be something that damaged the nerve fibres on just one half of the spinal cord. The classic cause is a stab wound in the back. Incomplete forms are also observed.

Magnetic resonance imaging (MRI) is used to diagnose spinal cord lesions. BSS is diagnosed by finding muscle paralysis on the same side as the lesion and deficits in pain and temperature sensation on the opposite side. The loss of sensation on the opposite side of the lesion is because the nerve fibers of the spinothalamic tract (which carry information about pain and temperature) crossover once they meet the spinal cord from the peripheries.

The prognosis for individuals with BSS varies depending on the cause of the disorder. It can advance from a typical Brown-Séquard syndrome to complete paralysis. It is not always permanent, and progression or resolution depends on the severity of the original spinal cord injury.

Generally treatment for individuals with BSS focuses on the underlying cause of the disorder. Early treatment with high-dose steroids may be beneficial in many cases. Other treatment is symptomatic and supportive.