Spinal cord injury-induced cognitive impairment: a narrative review

Spinal cord injury is a serious damage to the spinal cord that can lead to life-long disability. Based on its etiology, spinal cord injury can be classified as traumatic or non-traumatic spinal cord injury. Furthermore, the pathology of spinal cord injury can be divided into two phases, a primary injury phase, and a secondary injury phase. The primary spinal cord injury phase involves the initial mechanical injury in which the physical force of impact is directly imparted to the spinal cord, disrupting blood vessels, axons, and neural cell membranes. After the primary injury, a cascade of secondary events begins, expanding the zone of neural tissue damage, and exacerbating neurological deficits. Secondary injury is a progressive condition characterized by pro-inflammatory cytokines, reactive oxygen species, oxidative damage, excitatory amino acids such as glutamate, loss of ionic homeostasis, mitochondrial dysfunction, and cell death. This secondary phase lasts for several weeks or months and can be further subdivided into acute, subacute, and chronic. One of the most frequent and devastating complications developed among the spinal cord injury population is cognitive impairment. The risk of cognitive decline after spinal cord injury has been reported to be 13 times higher than in healthy individuals. The exact etiology of this neurological complication remains unclear, however, many factors have been proposed as potential contributors to the development of this disorder, such as concomitant traumatic brain injury, hypoxia, anoxia, autonomic dysfunction, sleep disorders such as obstructive sleep apnea, body temperature dysregulation, alcohol abuse, and certain drugs. This review focuses on a deep understanding of the pathophysiology of spinal cord injury and its relationship to cognitive impairment. We highlight the main mechanisms that lead to the development of this neurological complication in patients with spinal cord injury.