Brown-Séquard Syndrome

Brown-Séquard syndrome is an incomplete spinal cord injury caused by damage to one side of the cord. The defining examination is crossed: weakness and loss of vibration or joint-position sense occur on the same side as the lesion, while pain and temperature sensation are reduced on the opposite side. The pattern follows the routes taken by the major spinal tracts. The corticospinal tract carries voluntary motor commands after crossing in the medulla, so a lesion in the spinal cord affects motor function below it on the ipsilateral side. The dorsal columns carry vibration, proprioception, and fine touch to the medulla before crossing, producing ipsilateral loss below the lesion. Spinothalamic pain and temperature fibres cross within the spinal cord near their entry level, so damage to one side causes contralateral loss that often begins one or two segments below the lesion. The pattern may not be perfectly symmetrical or complete. Injury at the level of the lesion can add ipsilateral lower-motor-neuron weakness or segmental sensory loss, and swelling or a partial hemisection can blur the classic boundaries. The side of weakness...