Mild traumatic brain injury is underreported in car accidents. Very often in the blur of events drivers and their passengers will not describe to the emergency personnel the exact mechanism and mechanics of a crash. Hours and days later they will begin to experience symptoms. Forgetfulness. Headaches. Pain. Disorientation. Inability to concentrate. Brains scans such as MRI may be read as normal. But the symptoms are real—and often permanent.
The medical literature has long recognized how mild traumatic brain injury (mTBI) can cause permanent neuronal degeneration.
In 2011, for example, the authors of one article noted: “Using Golgi staining, we found that dendrites were degenerated in the ipsilateral cortex after mTBI; the abnormalities included swelling with beading, a hallmark of dendritic injury, decreased numbers of branches, and shorter branch lengths. Dendrite degeneration around the epicenter was very extensive. Indeed, the volume of neuronal degeneration in the cortex was 10.3 times higher than the tissue lesion volume after mTBI.”
“In summary, we showed that although mTBI led to limited tissue lesion and cell death, it caused widespread and significant synapse degeneration in the cortical neurons that were spared,” the authors concluded. “This suggests dramatic neuronal degeneration after mTBI. The widespread synapse loss disrupts neural circuitry after mTBI would likely contribute to neurologic dysfunction. Furthermore, the spared neurons showed dramatic synapse degeneration without death after mTBI, suggesting that synapse degeneration is a program separate from neuron death and should be treated with different therapeutic approaches than those used to prevent cell death.”
Dendrites are crucial to synaptic transmission, and damage to these can interfere with the process by which neurotransmitters activate the receptors of adjoining neurons. The authors make the important distinction between neuronal death and synaptic degeneration. Too often mild TBI is mistakenly considered temporary because widespread neuronal death does not occur. “Dendrite degeneration around the epicenter was very extensive”—this explains the persistent memory loss and other cognitive deficits following a mild TBI.
Those handling this type of case should be sensitive to this area. It’s easy to become caught up in the readily-diagnosed aspects of a person’s injuries—for example, those requiring surgery—while missing the more subtle signs of a mild TBI. As well, in the presence of head injury, drivers and their passengers should seek medical attention from a neurologist as soon as possible following a car accident. In the future, we’re going to see a greater awareness to this area and ongoing progress toward more effective treatments.
All quotations from: Xiang Gao, Jinhui Chen, Mild Traumatic Brain Injury Results in Extensive Neuronal Degeneration in the Cerebral Cortex, J Neuropathol Exp Neurol. 70(3): 183-191 (2011).
