Brown-Sequard syndrome is a neurological condition that results from an injury or damage to one side of the spinal cord. This condition results in weakness or paralysis on one side of the body (hemiparaplegia) and a loss of sensation on the opposite side (hemianesthesia). Brown-Sequard syndrome most commonly occurs in the the thoracic spine (upper and middle back). There are several causes of Brown-Sequard syndrome, including: a spinal cord tumor, trauma (such as a puncture wound to the neck or back), infectious or inflammatory diseases (tuberculosis or multiple sclerosis), and disk herniation.