Brown-Sequard Syndrome is a condition associated with hemisection of spinal cord, which usually damages descending corticospinal tracts, ascending dorsal column tracts and spinothalamic tracts.
That's why, most of the time, individuals with Brown-Sequard Syndrome will only present with an incomplete hemisection, and some sensory or motor problems, depending on which tracts are damaged.
In Brown-Sequard syndrome, a vertebral bone fracture or any kind of penetrating trauma, like a gunshot injury or stab wound in the back can lead to the hemisection of the spinal cord.
Besides those three tracts, very rarely, a hemisection of the spinal cord above the T1 spinal level can also damage the sympathetic chain that runs alongside the spinal cord and supplies the facial region.