Cellular Brain Damage: Diffuse Axonal Injury
Particularly when the brain injury involves diffuse axonal injury (DAI), the primary injury is to the brain cells, cellular brain damage, predominantly the neuron. While the neuron may only be stretched at the time of the initial trauma, that stretching can cause a defect in the cell membrane that allows brain chemicals, principally calcium, to invade the neuron in abnormal ways, resulting in cell death, “even days or weeks after injury.”
(Greenfield’s Neuropathology, 1996, page 197.)
Cellular brain damage is thought to occur primarily to axons. The axon is the long thin extension of the neuron. It is covered by a fatty sheath that increases the speed of the nerve transmission, the part which the cell signal travels down on its way to the axonal bulb, the transmitting part of the neuron. Axonal damage is one of the most common and most important causes for traumatic brain injury. This is a result of a blow to the head. It is associated with long periods of unconsciousness and the outcome is not good. Normally axons are soft and flexible but when exposed to brain trauma they become brittle and cause cellular brain damage. Rapid stretch of axons can damage the axonal cytoskeleton, resulting in a loss of elasticity and impairment of axoplasmic transport.
As stated in the page dedicated to axon with in our TBILaw Site, Axons are like electrical wires. An example would be a vacuum cleaner cord. I know myself have done this many times. In the course of vacuuming I have let the blades of the vacuum head sit on the cord, unknowingly. Will the vacuum cleaner quit working because the wires are bare? No, it will continue to vacuum but if I touch the part of the cord in which the rubber has been worn off, I will get an electrical shock. This is because the “insulation” from the electricity is no longer there and now it is exposed to do damage. Our anatomy has all types of protection equipment or insulation against unexpected force. The brain is insulated by your skull. Our nerves, arteries, veins and organs are insulated or protected by our skin. If any one of the insulation factors of our bodies is damaged, the parts that it was placed there to protect is now exposed and injury will occur.