Case 1 Mechanisms of TBI (Monday morning)

The patient's traumatic brain damage was the result of a deceleration injury. As the patient's vehicle came to a violent stop, his head was catapulted into the windshield. As the movement of his skull is suddenly stopped, the front part of the patient's brain, the frontal lobes, is crushed against the inner surface of the skull (a coup injury) causing a massive contusion. This movement also impales the inferior surfaces of the temporal lobes onto the rough, bony surface of the base of the skull, resulting in lacerations and maceration. A temporary negative pressure gradient (suction) forms between the occipital lobes and the back of the skull resulting in damage to the surface of the occipital lobes (a contrecoup injury). Cavitation (the formation of microbubbles) occurs in the cerebral spinal fluid as this fluid is sloshed around within the skull, damaging cellular projections and forming cracks on the surface of the brain. Blood vessels on the brain's surface stretch and tear. Axons stretching from the front of the brain to the posterior portions of the brain snap. Swelling causes increased intracranial pressure (ICP) which places increased pressure on various structures of the brain. This increased ICP decreases blood flowing into the brain, setting the stage for ishemia. Respiratory insufficiency, abnormal respiratory patterns, cardiac abnormalities, and metabolic alterations may cause additional, secondary, damage to the integrity of the brain.

Damage to different structures in the frontal lobes of the brain can result in various cognitive and behavioral difficulties.

Damage to the orbitofrontal regions have been associated with disinhibition, inappropriate expression of emotions, impaired judgment, lack of insight, and distractibility.

Damage to the dorsolateral regions of the frontal lobes may result in so-called executive function deficits (impaired volition, planning, purposive behavior, and effective performance), perseveration, stimulus-bound behavior, and diminished verbal fluency.

Damage to the medial frontal regions of the frontal lobes have been associated with apathy, mutism or transcortical motor aphasia, lower extremity paresis, and incontinence.

Damage to the temporal lobes of the brain may result in defective auditory recognition, inability to comprehend spoken words, inability to recognize familiar voices, word-finding difficulties, impaired verbal learning, trouble organizing complex information, impaired ability to enjoy music, and impaired odor perception.

Damage to the occipital lobes can result in blindness, disruptions in visuo-perception, visual inattention, difficulty performing mathematical operations, and difficulty recognizing faces.