Posterior cord injury, also known as posterior spinal artery syndrome or dorsal cord syndrome, is an uncommon type of incomplete spinal cord injury. It involves damage specifically to the posterior columns. This condition is rare, accounting for an estimated 1% or less of all spinal cord injuries. Unlike more widespread spinal cord damage, posterior cord injury selectively affects certain sensory functions while preserving others.
Understanding Posterior Cord Injury
The spinal cord’s posterior columns, also called the dorsal columns, are a specialized region of white matter. These columns form part of the dorsal column-medial lemniscus (DCML) pathway, which transmits specific sensory information to the brain. This pathway relays sensations such as proprioception, the body’s sense of its position and movement in space. It also conveys vibration sense and discriminative touch, allowing for the precise localization of touch and the ability to distinguish between two closely spaced points.
In a posterior cord injury, damage to these columns impairs specific sensory functions. Individuals experience a loss of proprioception, vibration sense, and fine or discriminative touch below the level of the injury. Despite these sensory deficits, motor function, pain, and temperature sensation are preserved. This preservation occurs because the pathways responsible for motor control (corticospinal tract) and pain and temperature sensation (spinothalamic tract) are located in different parts of the spinal cord and are unaffected.
Causes and Clinical Presentation
Posterior cord injury can result from various causes, with non-traumatic incidents being more common. Tumors are a frequent cause, as they can compress the posterior columns of the spinal cord. Another cause is vitamin B12 deficiency, which can lead to demyelination, or damage to the protective sheath around nerve fibers, disrupting signal transmission.
Multiple sclerosis, a demyelinating disease, can also affect the posterior columns. Vascular issues, such as ischemia (lack of blood flow) to the posterior spinal artery, or disc compression from degenerative disc disease, can also contribute. While trauma is less common, hyperextension injuries to the neck or other direct impacts to the spinal cord can cause this injury.
The clinical presentation of posterior cord injury includes a pattern of sensory loss without significant motor weakness. Patients may experience a loss of vibratory sensation, particularly in the lower body, and impaired proprioception, leading to difficulties with balance and coordination. This can manifest as an unsteady gait, known as sensory ataxia, which may worsen when visual input is reduced, such as in dim lighting. Some individuals may also report pain or tingling sensations, known as paresthesia, at or below the injury level.
Diagnosis and Treatment Approaches
Diagnosing a posterior cord injury involves a comprehensive neurological examination to identify the specific pattern of sensory deficits. This includes tests for proprioception, such as evaluating the ability to detect joint position and movement, and vibration sense, often tested with a tuning fork. Discriminative touch and two-point discrimination are also assessed to determine the extent of fine touch impairment. The preservation of motor strength, pain, and temperature sensation helps differentiate posterior cord injury from other spinal cord syndromes.
Imaging techniques, particularly Magnetic Resonance Imaging (MRI), are important for confirming the diagnosis and identifying the underlying cause. MRI can visualize the spinal cord and detect areas of damage, such as compression from a tumor, disc herniation, or changes consistent with demyelination or ischemia. Electromyography (EMG) and somatosensory evoked potentials (SSEP) may also provide additional information about nerve function and the extent of neurological involvement.
Treatment for posterior cord injury is primarily directed at managing the underlying cause. If a vitamin B12 deficiency is identified, supplementation is initiated to reverse the neurological effects. In cases involving tumors or disc compression, surgical intervention may be necessary to decompress the spinal cord and relieve pressure. For inflammatory conditions like multiple sclerosis, specific medications are used to manage the disease progression.
Rehabilitation strategies are an important part of the treatment plan, focusing on improving sensory awareness and functional independence. Physical therapy aims to address issues like sensory ataxia and balance deficits through exercises that enhance proprioception and coordination. Occupational therapy helps individuals adapt to their sensory changes and learn compensatory strategies for daily activities. Assistive devices may be recommended to help with mobility and reduce the risk of falls, particularly due to impaired balance.