Association found between TBI and neurodegenerative conditions

Excerpted from page 56 of the September 2016 edition of AOA Focus.

Over the past few years, stories of former athletes living with traumatic brain injury (TBI) have dominated the medical news headlines. The movie "Concussion," starring Will Smith, and the passing of Muhammad Ali, who lived his last several years with Parkinson's disease, have brought the topic to the mainstream.  

A recent study, published in JAMA Neurology, has recently shed more light on how TBI affects neurodegenerative diseases, such as Parkinson's or Alzheimer's, later in life. Researchers from the Icahn School of Medicine at Mount Sinai in New York and the University of Washington School of Medicine in Seattle scoured injury data of 7,130 older adults. Eight hundred and sixty-­five of those cases had experienced TBI along with a loss of consciousness. The scientists cross-referenced those patients with incidence of dementia, Alzheimer's disease and Parkinson's disease.  

They concluded that there is no association with TBI earlier in life and onset of dementia or Alzheimer's. However, they did ­find a clear link between TBI with loss of consciousness for over an hour, and Parkinson's disease.  

Anecdotally, TBI has long been associated with an increased incidence of Alzheimer's disease. According to Emergency Medicine Clinics of North America, some studies show a strong association between the two when a patient suffers extreme TBI, meaning a loss of consciousness for 24 hours or more. This is one of the first studies to differentiate between the risk of Parkinson's and Alzheimer's in persons who have experienced mild to moderate TBI. It also raises the concern that patients suffering from TBI-related neurodegeneration can potentially be misdiagnosed with Alzheimer's disease.  

A call for more action

"The most interesting part of this study is the fact that they [the researchers] are going against the grain. All of the other studies except for one point to a single traumatic brain injury being associated with Alzheimer's. They are suggesting there may be different things to look at," says Chrystyna Rakoczy, O.D., chair of AOA's Brain Injury Committee—formed under AOA's Vision Rehabilitation Section (VRS)—who practices at the James A. Haley veteran hospital in Tampa, Florida, where she is the director of the brain injury visual assessment rehabilitation program. "I think there is validity in it, but I do think that there should be quite a bit more research done on this." 

One confounding issue is the fact that patients can be unreliable when it comes to self-reporting trauma. In this study, the head injury may have happened 30 years ago or more.  

"A lot of time patients don't remember the trauma, but when they explain the situation it is pretty traumatic," Brenda Heinke Montecalvo, O.D., former chair of the VRS and one of the authors of AOA's Brain Injury Electronic Resource Manual, who practices at Nova Vision Care in Beaver Creek, Ohio. "You get used to probing for the good information. Most people deny injury. Even if they did not have to go to the emergency room, they might have hit their head pretty hard or fallen on the ice."  

For her long-term patients, Dr. Montecalvo can detect recent TBI by measuring a vertical deviation (one eye goes up, one goes down,) that may not have previously existed. Vertical deviations are highly correlated with TBI.  

Still, Dr. Montecalvo feels that a trained clinician can discern between memory loss due to TBI and that of Alzheimer's. The former can ­fluctuate day to day, while the latter worsens in progressive fashion. One thing they do have in common is how both groups benefit from staying mentally nimble.  

While patients with TBI have much more potential for regaining neurogenesis and neuroplasticity, patients with Alzheimer's who challenge themselves cognitively won't show the signs of the disease as early as those who, for example, watch TV all day. Dr. Montecalvo often prescribes Sudoku puzzles for her patients and encourages finding new mental stimulus. It's good advice even for those who have never experienced trauma. 

"The more you use your brain, the younger it stays and the better it functions," Dr. Montecalvo says.  

Read more about optometry's role in TBI management in the September 2016 edition of  AOA Focus.