Posterior Cord Syndrome

Posterior cord syndrome is a rare type of incomplete spinal cord injury that affects the dorsal columns of the spinal cord (found in the posterior—or backside—region of the spinal cord), responsible for the perception of fine-touch, vibration, sense of self-movement, and body positioning (proprioception).

The spinal cord is an important part of the central nervous system that serves as a highway for information to travel between the brain and the rest of the body. This information is transmitted by highly specialized spinal tracts or columns that carry sensory and motor information up and down the spinal cord. Ascending tracts, such as the posterior or dorsal columns and spinothalamic tract, carry sensory information from different parts of the body to the brain. Specifically, the dorsal columns carry delicate sensations, such as vibration, fine-touch (also known as discriminative touch), and proprioception. The spinothalamic tract, on the other hand, carries sensory information about pain, temperature, and crude touch (also known as non-discriminative touch). Descending tracts, such as the corticospinal tract, carry motor information from the brain towards the muscles of the trunk (torso) and limbs.

Interruption of these nervous pathways—either by trauma, external compression, or degeneration—can result in a spinal cord syndrome, which can be classified as complete or incomplete. A complete spinal cord syndrome occurs when damage to the spinal cord causes a complete loss of sensory and motor function below the site of injury. Conversely, an incomplete spinal cord syndrome occurs when only a portion of the spinal cord is damaged, causing various symptoms that depend on the specific spinal tracts that have been injured. In addition to posterior cord syndrome, other examples of incomplete spinal cord syndromes include central cord syndrome, anterior cord syndrome, and Brown-Séquard syndrome.

Posterior cord syndrome occurs as a result of damage to the posterior columns of the spinal cord. Such damage can be caused by trauma to the spinal cord and damage to the protective myelin sheath that surrounds nerve fibers (i.e. demyelinating disorders). Examples of demyelinating disorders include vitamin B₁₂ deficiency, multiple sclerosis and late syphilis infection, also known as tabes dorsalis (neurosyphilis). Other, less common causes, include external compression of the posterior spinal cord by tumors or mechanical degeneration of the cervical spine, as well as hereditary neurodegenerative disorders, such as Friedrich’s ataxia. Finally, posterior cord syndrome can occur as a result of a blockage in the posterior spinal artery, which supplies blood to the posterior columns of the spinal cord. Since there are two posterior spinal arteries, damage to one of the arteries will only affect one side of the body.

Individuals with posterior cord syndrome typically present with sensory ataxia, or impaired voluntary movement coordination caused by a lack of proprioception. Sensory ataxia can result in decreased balance, poor coordination, unsteady walking, and frequent falls. These symptoms typically worsen in dark environments or when a person closes their eyes, as the body can no longer rely on sight to maintain balance. In addition, some individuals may experience sensory losses including impaired sensation of vibration and fine-touch, while their sensation of pain and temperature is preserved.

In some cases, large spinal cord lesions can also affect surrounding spinal tracts, such as those responsible for motor function and involuntary body functions (e.g. blood pressure, digestion, breathing). Involvement of these tracts can subsequently lead to various clinical manifestations, including muscle weakness and spasticity, decreased tendon reflexes, urinary or bowel incontinence, or low blood pressure, depending on the severity of the lesion.

Since motor function is carried by the corticospinal tract (i.e. descending motor tracts) of the anterior spinal cord, most people with posterior cord syndrome are able to walk. However, some individuals may experience increased loss of balance and unsteady walk due to a decreased perception of the sensory information (i.e. proprioception) which helps maintain balance and posture.

Posterior cord syndrome can be diagnosed with clinical tests to assess neurological function. Sensory problems can be assessed by asking an individual to identify different sensations (e.g. temperature, pain, vibration) while touching the skin with specific tools (e.g. dull needle, tuning fork, cotton swabs, etc.). 

Additionally, Romberg’s test can be used to demonstrate sensory ataxia. This test is performed by asking an individual to close their eyes and stand straight with their feet together while the examiner looks for signs of loss of balance. If the individual is not able to stand straight without opening their eyes or swaying to either side, the result is considered to be positive for sensory ataxia.

Once posterior cord syndrome has been diagnosed, further tests are often required to identify the cause of spinal injury. This may include performing blood tests to check for vitamin deficiencies or markers of syphilis infection, as well as performing imaging tests to look for signs of demyelination, external compression of the spinal cord, or degenerative disorders.

Treatment of posterior cord syndrome will depend on the cause of spinal damage and severity of the condition. For instance, individuals with vitamin B₁₂ deficiency can be treated with vitamin B₁₂ supplements, whereas individuals with late syphilis infection can be treated with antibiotics like penicillin. In cases of external compression of the spinal cord, surgery may be necessary to prevent further damage. Regardless, most individuals with posterior cord syndrome can benefit from physical and occupational therapy to improve balance and voluntary movement coordination.

Posterior cord syndrome is a rare type of incomplete spinal cord injury that affects the dorsal or posterior columns of the spinal cord, which are responsible for the perception of vibration, fine-touch and body positioning (i.e. proprioception). People with posterior cord syndrome can present with poor balance, unsteady walking, and frequent falls, which typically worsen in dark environments. This syndrome can be seen in individuals with vitamin B₁₂ deficiency, late syphilis infection, multiple sclerosis, and neurodegenerative disorders, among other causes. Damage to the posterior columns of the spinal cord can be demonstrated by clinical tests to assess sensory function and balance. Treatment will depend on the specific cause of spinal injury and severity of the condition, although physical and occupational therapy can be recommended to improve quality of life in most individuals.