Brown-Séquard syndrome (BSS) is a rare neurological condition that occurs when just one side of the spinal cord is damaged. This type of injury, known as a hemisection, distinguishes it from other spinal cord damage that affects the entire structure. The spinal cord acts as the primary communication pathway between the brain and the body for movement and sensation. Because BSS results from a partial injury, some functions below the damaged area may be preserved, leading to a unique set of symptoms.
Causes of Spinal Cord Damage
The damage leading to Brown-Séquard syndrome stems from a variety of sources, most commonly traumatic events. Penetrating injuries, such as stab or gunshot wounds, are frequent culprits because they can directly impact one half of the spinal cord. Blunt force trauma from motor vehicle accidents or falls can also cause fractures or dislocations of the vertebrae, which may compress one side of the spinal cord.
Beyond acute trauma, several non-traumatic conditions can cause the syndrome. Spinal tumors may grow to compress one side of the cord, while a blockage of blood flow to the spinal cord, known as spinal ischemia, can lead to localized damage. Additionally, infectious or inflammatory diseases like tuberculosis or multiple sclerosis can cause lesions confined to one half of the cord.
The Unique Pattern of Symptoms
The defining feature of Brown-Séquard syndrome is its distinct pattern of symptoms, which differ on each side of the body below the injury level. This occurs because different nerve fibers within the spinal cord cross to the opposite side at different locations. The result is a separation of deficits, with some functions lost on the same side of the injury (ipsilateral) and others lost on the opposite side (contralateral).
On the same side as the spinal cord lesion, individuals experience a loss of motor function, resulting in muscle weakness or paralysis. Along with this paralysis, there is a loss of proprioception, which is the sense of where one’s limbs are in space, and the ability to feel vibrations. This happens because the nerve tracts for motor control and these sensations travel up the same side of the spinal cord and cross over higher up in the brainstem.
Conversely, on the side of the body opposite the injury, the primary deficits are sensory. Individuals lose the ability to feel pain and perceive temperature changes. This loss occurs because the nerve fibers carrying pain and temperature signals cross to the opposite side of the spinal cord shortly after entering it.
This neurological arrangement creates a peculiar clinical picture. A person might be unable to move their right leg but can still feel a pinprick on it, while at the same time being able to move their left leg but unable to sense hot or cold water with it. Some individuals may also experience abnormal sensations, such as a painful burning or prickling feeling, due to the nerve damage.
Diagnosis and Treatment Approaches
The diagnostic process begins with a clinical neurological examination. A physician will test motor strength, reflexes, and different types of sensation on both sides of the body to identify the characteristic ipsilateral motor loss and contralateral sensory loss. To confirm the diagnosis and pinpoint the cause, medical imaging is employed. Magnetic Resonance Imaging (MRI) is the preferred method as it provides detailed images of the spinal cord and surrounding tissues, showing lesions, tumors, or inflammation. Computed tomography (CT) scans may also be used to visualize bone fractures or other traumatic injuries.
Treatment for BSS focuses on addressing the root cause of the spinal cord injury. If the syndrome is caused by a tumor, surgery may be performed to remove it and relieve pressure on the cord. For injuries caused by spinal compression from a herniated disc or fracture, surgical intervention may also be necessary to stabilize the spine. In cases involving infections, antibiotic or antiviral medications are administered.
Rehabilitation is a primary component of management, aimed at maximizing functional recovery. Physical therapy helps patients improve strength and mobility, while occupational therapy focuses on adapting daily activities to regain independence. Medications may be prescribed to manage associated symptoms, such as nerve pain or spasticity (involuntary muscle contractions).
Recovery and Long-Term Outlook
The prognosis for individuals with Brown-Séquard syndrome is more favorable than for those with complete spinal cord injuries. Because the injury is incomplete, the potential for recovery is significant. Many patients experience substantial improvement, particularly within the first three to six months following the injury, although neurological recovery can continue for up to two years.
Several factors influence the degree and pace of recovery, including the cause and severity of the initial lesion. A patient’s age and overall health also play a part in their ability to heal and participate in rehabilitation.
A significant majority of individuals with BSS regain a high degree of functional independence. Studies show that over 90% of patients recover bladder and bowel control, and between 75% and 90% regain the ability to walk. While some lasting deficits, such as altered sensation or mild weakness, may persist, many are able to lead active and productive lives.