Brown-Séquard Syndrome

Etiology

The most common causes of Brown-Séquard syndrome can be divided into traumatic and nontraumatic injuries. Traumatic injuries are far more common. Gunshot wounds, stab injuries, motor vehicle accidents, blunt trauma, or fractured vertebra from a fall are common mechanisms of injury. To a lesser extent, Brown-Séquard syndrome can result from a wide variety of nontraumatic causes, including vertebral disc herniation, cysts, cervical spondylosis, tumors, multiple sclerosis, radiation, and decompression sickness. Other vascular etiologies include spinal cord hemorrhage or ischemia. Infectious etiologies such as tuberculosis, transverse myelitis, herpes zoster, empyema, and meningitis have also been reported.[1][2][3][4][5] 

Epidemiology

Brown-Séquard syndrome is a rare form of incomplete spinal cord injury that occurs when one side of the spinal cord is damaged (hemisection), most commonly in the cervical or thoracic spinal cord. Of all spinal cord injuries, Brown-Séquard syndrome occurs in 1% to 4% of traumatic injuries.[6][7][8]

Pathophysiology

In cases of Brown-Séquard syndrome, a clean-cut hemisection is typically not visible. In contrast, a partial hemisection is evident and often includes all the nerve tracts lying along the path in the injured area. The nerve tracts involved in Brown-Séquard syndrome are discussed below.

Dorsal columns: Ipsilateral modalities of fine touch, vibration, 2-point discrimination, and conscious proprioception are affected due to injury to the dorsal columns ascending within the dorsomedial spinal cord. The gracile fasciculus carries ipsilateral sensory information from the lower extremities and truck, and the cuneate fasciculus carries sensory information from the ipsilateral upper half of the body. These afferents decussate via internal arcuate fibers, which travel ventromedially through the medullary tegmentum, cross contralaterally at the level of the caudal medulla to ascend within the medial lemniscus, and synapse on the ventral posterolateral nucleus of the thalamus. 

Anterior spinothalamic tracts: Ascending anterior spinothalamic tracts containing afferents of pain, temperature, and crude touch are transected, leading to contralateral hemisensory loss of these modalities. Afferents enter the dorsal spinal cord, synapsing within the Rexed laminae I through IV, with secondary neurons crossing midline ventrally via the anterior white commissure.[9]

Spinocerebellar tracts: Dorsal and ventral spinocerebellar tracts within the lateral region of the spinal cord carry ipsilateral afferents mediating proprioception. Hemisection of the dorsal spinocerebellar tract leads to ipsilateral loss of proprioception, whereas the ventral spinocerebellar tract contains bilateral afferent proprioceptive inputs.

Corticospinal tracts: Anterior and lateral corticospinal tracts carry efferents from the primary motor cortex to the ventral horn primary motor neurons. Hemisection of the spinal cord would produce an ipsilateral hemiplegia from the level of the lesion distally. Symptoms of upper and lower motor neuron lesions, including flaccid paralysis, changes in muscle mass, fasciculations, and decreased tone, will be present only at the level of injury. Upper motor neuron control is lost below the level of the lesion, while lower motor neuron pathways and reflex responses remain intact, resulting in spastic paralysis.[10]

History and Physical

Obtaining a detailed history and performing a thorough physical examination to determine the mechanism of injury and extent of damage are crucial to establishing future expectations regarding neurological deficits. Medical history should include past surgical history, including spinal procedures; baseline neurologic status; history of prior strokes, parkinsonism, movement disorders, dementia/cognitive decline, seizures, and related conditions; home medication regimen, including antiplatelet or anticoagulation medications, and alcohol, tobacco, and illicit substance use.

Knife injury is the most common traumatic mechanism. Other etiologies to assess include vertebral fracture, spinal epidural hematoma, and acute spinal cord ischemia in the evaluation of Brown-Séquard syndrome. Brown-Séquard-plus syndrome is differentiated and associated with neurologic deficits in the eyes, bowel, or bladder.[11] Cardiopulmonary compromise is possible if the level of injury is within the cervical region. 

A neurological examination should comprise a detailed motor and sensory evaluation. Clinically, there would be an ipsilateral sensory loss of pressure, vibration, position, and flaccid paralysis at the level of the lesion, and spastic paraparesis below the level of the lesion; contralaterally there would be a loss of pain and temperature, usually 1 to 3 levels above the level of injury. Hemiplegia may initially present as flaccid due to acute spinal shock, so close monitoring of the neurologic examination is necessary. Injuries within the superior thoracic and cervical spine may also involve the spinal adjacent sympathetic chain, and evaluation for possible Horner Syndrome (miosis, anhydrosis, and ptosis) is warranted.[10]

Evaluation

The diagnosis of BSS is made through neurologic examination, mechanism of injury, and imaging studies. Laboratory tests common to all trauma presentations should be performed until a definitive diagnosis is determined, including complete blood count (CBC), comprehensive metabolic panel (CMP), prothrombin time/partial thromboplastin time (PT/PTT), international normalized ratio (INR), and type and screen. Imaging studies such as chest x-ray, computed tomography (CT) of the chest/abdomen/pelvis, CT of the head, and CT of the cervical, thoracic, and lumbar spine should be completed to determine the extent of the traumatic injury, which may involve surrounding structures. Magnetic resonance imaging (MRI) of the spinal cord without contrast at the level of injury provides the most detailed information and evidence supporting the diagnosis and information on injury etiology (mechanical compression from epidural fluid collection, bony fracture compression, or ischemic injury).[10]

Treatment / Management

Individual treatment starts with cardiopulmonary support if needed. Spinal precautions should be followed until the extent and stability of the injury is determined. Further management of BSS depends on the mechanism and extent of injury and is focused on preventing complications. The use of steroids (high-dose intravenous methylprednisolone) in traumatic spinal cord injuries is controversial due to the elevated risk of infection and other complications with no significant improvement in neurologic outcome. However, standard perioperative prophylactic antibiotics are recommended. Decompression surgery is considered for patients who have mechanical spinal canal stenosis/compression.[12][13][14](A1)

Nonoperative treatment focuses on supporting individuals with less dependency during daily activities and improving quality of life through a multidisciplinary approach involving spinal cord injury physicians, nurses, physical therapists, occupational therapists, and social workers. Specific devices such as wheelchairs, limb supports, and hand splits can help improve patients' quality of life and daily activities. If the patient has difficulty breathing or swallowing, various aids can be applied; cervical collars can also be used depending on the level of paralysis. In the case of thoracolumbar region involvement, spinal orthotic devices can be used. 

Differential Diagnosis

Differential diagnoses should include stroke, tumors, and cysts; other causes of spinal cord injury and compression include epidural hematoma, epidural abscess, syringomyelia, anterior cord syndrome, and central cord syndrome. A careful recording of history to help establish the baseline functionality of the patient before and after the injury is very important. Chronicity of a new neurologic deficit is a key feature, and an acute presentation is less likely in cases of cysts, tumors, congenital malformation, or chronic infection.[15] Fluctuating asymmetric symptoms would suggest spinal cord demyelinating disorders such as multiple sclerosis over BSS.

Prognosis

The prognosis for individuals with BSS varies depending on the mechanism of injury and the extent to which the spinal cord is damaged. Generally, BSS is an incomplete spinal cord injury, and the potential for significant recovery is strong. Notably, BSS has a better long-term prognosis than anterior and central cord syndrome. More than half of BSS patients recover well, and the majority of posttraumatic patients recover motor function. Recovery becomes slower throughout 3 to 6 months, and ongoing neurological recovery can take up to 2 years.[16] Damage to ipsilateral autonomic fibers generally does not affect sphincter function. Most patients will regain some strength in the lower extremities, and a significant portion will regain functional walking ability.[17]

Complications

Untreated BSS may lead to complications such as hypotension or spinal shock, depression, pulmonary embolism, and infections, most commonly in the lungs and urinary tract. Respiratory support is critical for patients with high thoracic and cervical lesions. Long-term complications, such as atelectasis, deep venous thrombosis, and pressure ulcers, are primarily due to poor ambulation.