Epidemiology
Brown-Séquard syndrome is rare as the trauma would have to be something that damaged the nerve fibres on just one half of the spinal cord. History
Charles-Édouard Brown-Séquard studied the anatomy and physiology of the spinal cord. He described this injury after observing spinal cord trauma which happened to farmers while cutting sugar cane in Mauritius. French physician, Paul Loye, attempted to confirm Brown-Séquards observations on the nervous system by experimentation with decapitation of dogs and other animals and recording the extent of each animals movement after decapitation. Notes
Sources
Egido Herrero JA, Saldanã C, Jiménez A, Vázquez A, Varela de Seijas E, Mata P (1992). "Spontaneous cervical epidural hematoma with Brown-Séquard syndrome and spontaneous resolution. Case report". J Neurosurg Sci. 36 (2): 117–19. PMID 1469473. Ellger T, Schul C, Heindel W, Evers S, Ringelstein EB (June 2006). "Idiopathic spinal cord herniation causing progressive Brown-Séquard syndrome". Clin Neurol Neurosurg. 108 (4): 388–91. doi:10.1016/j.clineuro.2004.07.005. PMID 16483712. S2CID 35644328. Finelli PF, Leopold N, Tarras S (May 1992). "Brown-Sequard syndrome and herniated cervical disc". Spine. 17 (5): 598–600. doi:10.1097/00007632-199205000-00022. PMID 1621163. S2CID 37493662. Hancock JB, Field EM, Gadam R (1997). "Spinal epidural hematoma progressing to Brown-Sequard syndrome: report of a case". J Emerg Med. 15 (3): 309–12. doi:10.1016/S0736-4679(97)00010-3. PMID 9258779. Harris P (November 2005). "Stab wound of the back causing an acute subdural haematoma and a Brown-Sequard neurological syndrome". Spinal Cord. 43 (11): 678–9. doi:10.1038/sj.sc.3101765. PMID 15852056. Henderson SO, Hoffner RJ (1998). "Brown-Sequard syndrome due to isolated blunt trauma". J Emerg Med. 16 (6): 847–50. doi:10.1016/S0736-4679(98)00096-1. PMID 9848698.
Pathophysiology
The hemisection of the cord results in a lesion of each of the three main neural systems:
the principal upper motor neuron pathway of the corticospinal tract
one or both dorsal columns
the spinothalamic tractAs a result of the injury to these three main brain pathways the patient will present with three lesions:

The corticospinal lesion produces spastic paralysis on the same side of the body below the level of the lesion (due to loss of moderation by the UMN). At the level of the lesion, there will be flaccid paralysis of the muscles supplied by the nerve of that level (since lower motor neurons are affected at the level of the lesion). The lesion to fasciculus gracilis or fasciculus cuneatus (dorsal column) results in ipsilateral loss of vibration and proprioception (position sense) as well as loss of all sensation of fine touch. The loss of the spinothalamic tract leads to pain and temperature sensation being lost from the contralateral side beginning one or two segments below the lesion.In addition, if the lesion occurs above T1 of the spinal cord it will produce ipsilateral Horners syndrome with involvement of the oculosympathetic pathway. Diagnosis
Magnetic resonance imaging (MRI) is the imaging of choice in spinal cord lesions.Brown-Séquard syndrome is an incomplete spinal cord lesion characterized by findings on clinical examination which reflect hemisection of the spinal cord (cutting the spinal cord in half on one or the other side).