Posterior Cord Syndrome

Original Editor - User Name
Top Contributors - Mason Trauger

Introduction

Posterior Cord Syndrome (PCS) is the rarest form of incomplete spinal cord injury. An individual with this form of spinal cord injury (SCI) will have intact motor function and sensations of pain, light touch, and temperature, but impairments in proprioception, vibration, kinesthesia, and combined cortical functions below the level of the lesion (see: Sensation).

The following video displays a brief overview of various spinal cord syndromes; this video does differentiate between combined degeneration and tabes dorsalis, but both tend to be generalized to PCS:

Clinically Relevant Anatomy

As the name implies, the vast majority of damage with this form of incomplete spinal cord injury is towards the posterior aspects of the spinal cord. As a result, the common location of injury in Posterior Cord Syndrome is to the posterior columns and dorsal horns of the spinal cord, which are part of the Dorsal Column Medial Lemniscal Pathway (DCML). The DCML provides the sensory information of discriminative touch (two point discrimination, stereognosis, localization of touch), deep touch, vibration, conscious proprioception, and information for combined cortical functions such as graphesthesia for all body regions except the head. The end destination of this information is then carried to the primary somatosensory cortex of the Parietal Lobe for central processing.

However, when considering the vascular anatomy of the spinal cord, specifically the posterior spinal arteries, there may be some alterations to the Corticospinal Tract or even aspects of the Spinothalamic tract due to a border zone of infusion. As there is generally not extensive damage to the corticospinal or spinothalamic tracts, voluntary motor function (corticospinal tract), and sensations of pain, crude touch, and temperature (spinothalamic tract) are preserved.

Incidence/Prevalence

There is a wide variance in global reports of incident rates for spinal cord injury. Recent estimates from the Global Burden of Disease suggest an incidence rate of 0.9 million spinal cord injuries, 20.6 million prevalent cases, and 6.2 million years lived with disability (YLD) in 2019. On average, spinal cord injuries appear to be more commonly afflicting males based on age standardized incidence rate (ASIR) and age standardized YLD rate (ASYR) , and injuries at neck level had higher ASYR than injuries below the neck. No readily available global reports suggest incidence/prevalence rates of incomplete spinal cord injury; however, the United States National Spinal Cord Injury Statistical Center reports that 67.2% of traumatic spinal cord injuries are incomplete. See Epidemiology of Spinal Cord Injury for more information.

Reports of Posterior Cord Syndrome incidence rates vary; however it is believed to be the least prevalent SCI, with estimates of 2% or less. PCS appears to have an older average age of onset compared to other spinal cord injuries, with some studies reporting an average age of onset ~62; this is likely due to most causes of PCS being atraumatic in nature.

Pathophysiology

The pathophysiology of spinal cord injury appears to follow mechanisms of primary and secondary injury. Primary injury refers to the resultant physical trauma to the spinal cord anatomy due to impingement from fractured bone or surrounding soft tissue. This damage then disrupts components of the nervous system, such as destruction of the neural parenchyma, disruption of the axonal network, and hemorrhagic disruption to glial membranes. Secondary injury is the component which generates the most damage to the spinal cord, and involves a series of chemical and mechanical changes ultimately leading to necrosis, neural apoptosis, and glial scar formation.

It is unclear what the most common mechanism of injury (MOI) is for Posterior Cord Syndrome due to its rarity. Common causes of PCS include posterior spinal artery ischemia, tumor, herniated disc, Vitamin B12 deficiency, multiple sclerosis, and trauma. Trauma appears to be the least common MOI for PCS, but is thought to be associated with hyperextension injuries, though this MOI is more commonly associated with Central Cord Syndrome.

Clinical Presentation

For a comprehensive clinical examination overview, see: Assessment of Spinal Cord Injury and Neurological Assessment

Although individuals with PCS retain their motor function, a lack of proprioception can elevate their fall risk and increase the ability to perform ambulation and other Activities of Daily Living. As a result, ataxic gait, falls, and impaired coordination below the level of lesion are common presentation characteristics. Additionally, the patient may experience paresthesia throughout the levels below the site of lesion; a lack of appropriate sensation may contribute to the development of Pressure Injuries. Typical SCI-related symptoms also occur, such as a period of spinal shock, spasticity, neuropathic pain, and neurogenic bladder.

On clinical examination, the following components may be utilized, not only to identify functional deficits, but to rule out additional locations of injury:

• Quantitative Sensory Testing (for a comprehensive overhaul of sensory testing)
• Sensation (identifying greater deficits in deep sensation and combined cortical sensation would support a PCS diagnosis)
• Weber Two-Point Discrimination Test
• Somatosensation
• Proprioception
• Romberg Test - tends to be positive due to impaired proprioceptive input

The following video shows a brief clinical examination of PCS:

Diagnostic Procedures

When there is suspicion of a spinal cord injury, it is common for imaging to be ordered. Plain radiography, computed tomography (CT), and magnetic resonance imaging (MRI) are used to assess trauma/injury to soft tissue, including CT and MR angiography to assess for vascular compromise.

To differentiate between levels of impairment, the International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) are utilized to differentiate between specific subtypes and identify the level of lesion in spinal cord injury. The American Spinal Injury Association (ASIA) Impairment Scale is the assessment performed; however, some clinicians suggest that Posterior Cord Syndrome can be overlooked and potentially mis-diagnosed without thoroughly assessing vibration and proprioception during the ISNCSCI exam.

Differential Diagnosis

• Neurosyphilis
• Central Cord Syndrome
• Brown-Sequard Syndrome
• Disc Herniation
• Cauda Equina Syndrome
• Conus Medularis Syndrome

Management / Interventions

Medical management is primarily dependent on the cause of spinal cord injury

• If related to trauma, a laminectomy may be performed to alleviate spinal compression
• If related to cancer, the appropriate aspects of oncology management should be utilized
• If due to demyelination of the spinal cord as a result of Vitamin B12 deficiency, supplementation through either oral or parenteral routes are indicated

For physiotherapy management, please refer to the following pages:

• Therapeutic Interventions for Spinal Cord Injury
• Physiotherapy Management of Individuals with Spinal Cord Injury
• Locomotor Clinical Practice Guideline Recommendations (for ambulatory individuals greater than 6 months after acute onset of CNS injury)
  • Strong evidence supports the use of task-specific activities such as walking to improve locomotor function when performed at moderate or high intensities
  • Strong evidence supports the use of virtual reality (VR) based training (for augmented feedback) to improve locomotor function
  • Strong evidence does NOT support the use of balance training without VR, body-weight supported treadmill training, or robotic-assisted training to improve walking speed or distance
  • Weak evidence suggests that VR-based balance training, strength training, and moderate to high intensity circuit and cycling training may improve walking distance and speed
• Note: due to symptom presentation and location of nervous system damage, respiratory and contracture management are likely not needed for individuals with PCS after the acute stages, but clinical judgement should monitor these conditions.

Prognosis

Generally, the prognosis for incomplete spinal cord injuries have favorable prognoses compared to complete SCI.No reports detail long-term prognosis specifically for PCS, however 20-75% of incomplete spinal cord injury recover their ability to ambulate within a year, and most functional recovery will plateau within 18 months.See Prognosis and Goal Setting in Spinal Cord Injury for more information.

Outcome Measures

For all suspected spinal cord injuries, the American Spinal Injury Association (ASIA) Impairment Scale is performed to assess long-term prognosis. General standards of practice are to perform this assessment within 72 hours of suspected injury to reliably predict the likelihood of recovery.

See Spinal Cord Injury Outcome Measures Overview for all relevant outcome measures for SCI. (Note: based on typical PCS presentation, they typically present as ASIA Impairment Scale category of D - Motor Incomplete. Refer to the pertinent outcome measures for a patient's respective ASIA level.

Resources

• See the American Physical Therapy Association's Academy Of Neurologic Physical Therapy's Neuro Compendium: https://www.neuropt.org/education/physical-therapy-educators/compendium/comp-docu
  • Click on "Spinal Cord Injury Lesions" for an interactive learning module
  • Enjoy the other links as appropriate!

Case Studies

• Posterior Cord Syndrome After Spinal Cord Stimulation Electrode Lead Insertion: A Case Report
• A Rare Case of Posterior Spinal Cord Syndrome Following Commando Surgery: A Case Report and Review of Literature
• Rehabilitation of a Patient with Posterior Cord Syndrome