WHAT TRAUMA DOES TO THE BRAIN
Blows and sudden jerks tend to cause linear forces, in which the brain moves in a straight line inside the skull. However, some injuries to the head cause rotational forces within the brain.
Traumatic brain injuries (TBIs) are defined by the Centers for Disease Control as jolts, blows or penetrating injuries to the head that alter the victim’s mental state. Although most of us understand that a sudden blow can cause a concussion, it’s important to know that you don’t need to strike your head to sustain a dangerous brain injury: Simply whipping your head hard can cause the brain---which floats in a layer of cerebrospinal fluid--to slam into the interior of the skull, and both a blow and a jolt can stretch, tear and/or bruise the neural tissue.
The direction of force matters, too. Blows and sudden jerks tend to cause linear forces, in which the brain moves in a straight line inside the skull. However, some injuries to the head cause rotational forces within the brain. “Rotatory movement is probably more dangerous because the brain can shift more and there’s twisting and tearing of fibers,” says Julian Bailes, MD, chairman of the Department of Neurosurgery and co-director of NorthShore University HealthSystem’s Neurological Institute in Chicago. The severity of TBIs can be ranked on different official medical scoring systems, such as the Glasgow Coma Scale or the Abbreviated Injury Scale, but generally concussions can be described as mild, moderate or severe. To some degree, all TBIs can change the way a person thinks, feels and acts; they can also affect language and cause sleep disturbances. People who sustain mild TBIs may lose consciousness for a few minutes, or they may remain awake but simply be confused or “dazed” following an injury. They may experience memory loss that persists for up to a day. Other symptoms common following milder TBIs include fatigue, headaches, dizziness, blurred vision, nausea or vomiting, loss of balance, increased
irritability or other emotional disturbances, sensitivity to bright lights or loud noises, ringing in the ears, and depression. Sometimes these signs can be subtle and easy to miss, and they may persist for weeks or in some cases symptoms may last for a year or more.
Although recovery from mild TBIs is usually uneventful, it can take a minimum of six weeks for the neural tissues to fully heal. During that time, damage from an additional blow to the head would be cumulative: A second TBI might cause serious long-term complications or prove fatal, even if neither blow alone would have been life-threatening. (For that reason, physicians suggest not riding or participating in other high-risk sports until the brain has had time to heal.)
More moderate to severe TBIs cause unconsciousness for 30 minutes or longer, ranging up to coma, and when awake, these patients may experience extensive memory loss. The period of unconsciousness is a sign of much more serious injury. “If a person is knocked unconscious, it usually means their brain experienced enough strain to disrupt transmission pathways. A loss of consciousness typically means the head impact was more severe than when the symptoms are a headache and dizziness,” says biomechanical engineer Stephanie Bonin, PhD, PE, of MEA Forensic Engineers & Scientists in Laguna Hills, California.
These patients almost always need to be hospitalized, possibly in intensive care. Blows to the head hard enough to cause serious TBIs may also be complicated by issues such as skull fractures, hemorrhage or subdural hematoma (the pooling of blood between the brain and the skull), all of which can place pressure on the brain and cause seizures, breathing difficulties and other lifethreatening conditions.
People who survive moderate and severe TBIs are likely to require extensive rehabilitation. Long-term effects are common and may include:
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Over the long term, TBI---even a mild one---may leave a person at an increased risk for developing epilepsy, Parkinson’s disease, Alzheimer’s disease and other neurological disorders.