In a large study of more than 72,000 traumatic brain injury patients and more than 200,000 controls, over a period of six years, researchers have recently reported an increased risk of multiple sclerosis after traumatic brain injury.
Multiple sclerosis is a disease of the central nervous system, in which the myelin sheath (white matter) is attacked, resulting in a wide range of neurological problems, including blindness and motor impairments. It has been suggested that one of the potential triggers of multiple sclerosis is a previous brain trauma, but no previous research has been able to support this. The current study suggests that traumatic brain injury, in combination with genetic and other environmental influences, may contribute to the development of multiple sclerosis.
There is a limitation to the study in that it was based in China. Other studies based in other nations have failed to find the same association between traumatic brain injury and multiple sclerosis. It is unknown if these differences are due to genetic profiles (China has a relatively low rate of multiple sclerosis) or other environmental factors.
However, another issue is that reporting measures are not consistent between nations. For instance, other studies may have included only more severe cases of brain injury. Severe cases of traumatic brain injury might "mask" symptoms of multiple sclerosis, and may have therefore led to skewed results. The current study included all cases of traumatic brain injury, and the researchers felt that their results represented an accurate view of multiple sclerosis in China.
Kang J-H, & Lin H-C. Increased risk of multiple sclerosis after traumatic brain injury: A nationwide population-based study. Journal of Neurotrauma. (December 2011).