Mild Traumatic Brain Injuries (MTBI)
MTBI – Most Underdiagnosed and Undertreated Brain Injury, MTBI and Sense of Smell
MTBI – Most Underdiagnosed and Undertreated Brain Injury
In what are often called “Mild” Traumatic Brain Injuries or “MTBI’s” there may be no visible bleeding at all, or only micro-vascular bleeding too small to show up on an MRI or CT. The lack of a frank bleed in the brain, a lack of a long period of loss of consciousness, and a Glasgow Coma Scale score of 13-15 (maximum), are the main reasons these traumatic brain injuries are medically defined as “mild.” But, a mild traumatic brain injury doesn't mean that the symptoms are mild. Often the short and long term consequences are more severe than those cases in which a bleed in the brain occurs. The likelihood of symptoms after trauma, and the likelihood of permanency of those symptoms increase with the number of head strikes (even sub-concussive hits).
In mTBI cases, the initial injury is physical - usually a microscopic “shearing” of the axons, dendrites and support structures of the brain on the margin between the desne white matter and less dense grey matter. This is followed by a secondary "neurochemical cascade" in the brain that disrupts the normal exchange of nutrients, ions and neuro-transmitters in the brain. This change in brain chemistry can be compounded by a sleep disruption that is frequently caused by a traumatic brain injury.
So-called “mild” Traumatic Brain Injuries, which makes up approximately 80% of all cases of TBI, never produce a visible abnormality on CT or MRI. This is because the tissue damage occurs on the cellular level, which is visible only under the microscope and is widely diffused, leaving blood vessels and major structures intact. With patients who live and who's brains cannot be examined under a microscope, the failure of mild TBI to appear on either MRI or CT, results in it being one of America's most seriously underdiagnosed and undertreated conditions.
MTBI and Sense of Smell
Many victims of MTBI lose their sense of smell (a condition called anosmia) because their olfactory nerve (Cranial Nerve I) is damaged by being rubbed between the base of the frontal lobes and the rough bony shelf beneath it called the “cribiform plate.” Yet this injury does not show up on conventional neuro-imaging like MRI and CT. We know this happens, because of autopsy findings on such patients when they die of unrelated causes. And for those survivors of MTBI, we know that many lose their sense of smell.