Veterans exposed to improvised explosive devices exhibit neurodegenerative disease similar to that observed in athletes sustaining head injuries. The injuries lead to personality changes, dementia, and neurodegeneration in later years.
Chronic traumatic encephalopathy (CTE) results from head trauma and is characterized by abnormal accumulation of tau protein. Tau also forms the neurofibrillary tangles seen upon autopsy of patients with Alzheimer's disease and frontotemporal dementia. Athletes who exhibited elevated tau, on autopsy, also had histories of anger outbursts, risk and rash decision-making behaviors, impaired attention and memory, and alcohol or drug abuse. Both suicidal and accidental deaths in athletes prompted examination of long-term consequences of blows to the head.
Bennet Omalu, the chief medical examiner in San Joaquin County, California, and colleagues discovered tau tangles characteristic of CTE upon autopsying the brain of a Marine who committed suicide. The Marine had experienced 2 IED encounters while in Afghanistan. He was diagnosed with posttraumatic stress disorder upon return to the United States and experienced forgetfulness, irritability, and alcohol abuse. Interestingly, Omalu and his associates were the first to report CTE in a professional football player in 2005.
Lee Goldstein of Boston University and Ann McKee, a neuropathologist at the Bedford Veterans Affairs Medical Center in Massachusetts, have developed a mouse model that reflects CTE. Mice are placed in a tube and exposed to compressed gas. The gas creates a shock wave similar to an IED. Blast-exposed mice showed inflammation, damage to axons and capillaries of the brain, and tau accumulations as soon as 2 weeks after blast exposure. If the head was not immobilized during the blast injury, neurons in the hippocampus were damaged. The hippocampus is important in learning and memory. Damage to that region may explain some of the forgetfulness and other cognitive problems seen in veterans.
Future research will focus on ways to detect tau accumulations prior to autopsy. Also, researchers are interested in determining whether tau is the cause of CTE or a symptom. More in-depth information is needed to determine the number and type of hits or blast exposures that can be experienced prior to long-term damage. With more information to assist in prevention of CTE and better diagnostic abilities, perhaps the devastating impact of these injuries can be decreased.
Source: Miller G. Blast injuries linked to neurodegeneration in veterans. ScienceMobile: News and Analysis: Neuropathology. 2012;336:6083, 790-791. DOI:10.1126/science.336.6083.790.
Submitted by: Robin E. Pattillo, PhD, RN, CNL, News Editor at [email protected].