Spinal Cord Injury Results in Neurogenic Osteoporosis

  • The parents were in the hospital room with their boy lying motionless in the bed. Tears swelled in their eyes when I told them that their son would never walk again. And that was just the beginning of the medical problems this young man faced for the rest of his life.

     

    Besides the obvious paralysis that comes with a spinal cord injury, a tetraplegia or paraplegia faces many inherent medical problems. The bowel and bladder cease to work properly, leading to chronic constipation and urinary tract complications. Blood pressure can be difficult to manage to the point of an emergency situation even with a simple hang-nail as a trigger. Skin can breakdown as a result of the endless pressure from sitting in a chair. And last but not least, the bones deteriorate rapidly within the first two years following a spinal cord injury. Within 15 years, upwards of 40% of spinal cord injury patients will encounter a fragile bone fracture.

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    What happens to the bones after a spinal cord injury that leads to profound osteoporosis? Scientists have been baffled by that question for years because the bone loss is dramatic. The first thought was that the bones thinned merely because of the lack of use (both lack of muscle activity and lack of weight bearing) and that initial theory was termed "disuse osteoporosis". This theory has since fallen out of favor because the recent medical evidence points to the role of the nervous system in bone strength and structure. The pattern of bone loss is particular to the level of injury. Bones below the level of the spinal cord injury are more severely affected than bones above the spinal cord injury including the spine. Those people with spinal cord injuries above the level of T6 seem to have the most profound spinal bone mineral loss (Spine, 2010, Vol.35, Num 9, pp 958-962). All of these observations point to the fact that the nervous system and its subsequent disruption is a major influential factor for what is now called "neurogenic osteoporosis". Additionally, scientists now know that there is also a disrupted hormonal balance, particularly the parathyroid axis that influences bone loss. With the bones at the mercy of the nervous system and hormonal system, those with a spinal cord injury fall victim to osteoporosis despite the best treatment.

     

    None of the traditional or non-traditional treatments used for traditional osteoporosis have really proven very effective against neurogenic osteoporosis. Calcium and Vitamin D supplementation is risky because of the possibility of inducing urinary stones in those with a spinal cord injury because they excrete calcium rapidly in the urine. Bisphosphonate medications do not seem to slow down the bone loss in this special population with any significance. And exercise, even with elaborate machines, does not counteract the deleterious effects of the disrupted nerve signals to the bone. Bone loss seems to happen no matter what treatment is used in tetraplegics and paraplegics. This puts the medical community in a defensive mode of prevention. Prevent the spinal cord injuries. Prevent the bone fractures once a spinal cord injury occurs.

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    What does this teach us about bone health? Bone health is a complicated orchestra of hormones, minerals, vitamins, physical forces, nerve function, and health. If just one member of this orchestra is out of tune, the entire boney skeleton can suffer from lack of strength and density. The fragility of the skeleton leaves the individual at risk for fractures, infections, and deformity. Now, is a nineteen year-old going to be thinking about all of this when he jumps off a rock into the river? Probably not. Preventing this accident from happening is the best way to prevent neurogenic osteoporosis. Let's be careful out there!

     

Published On: August 22, 2010