As the years go by, the adult brain slowly atrophies, like a desiccated orange detaching from its rind. The shrinkage can cause problems. Cerebral veins are tethered to the superior sagittal sinus, the large blood vessel that runs front to back along the underside of the skull. As the brain contracts, these bridging veins must stretch, making them vulnerable to shearing forces caused by rapid head movements or even modest contusions. Without sufficient brain tissue to support and compress the bleeding site, small, low-pressure venous leaks may go unstanched. The blood seeps into the gap between the arachnoid membrane that encloses the brain and the lining of the skull, or dura mater. Bleeding into this space is called a subdural hematoma.
Acute subdural hematomas result from severe head trauma and expand quickly. Chronic subdural hematomas, on the other hand, often spread slowly—and without visible symptoms. What really scares emergency physicians—and has me repeating to patients and their families, "Return if there's any change in behavior"—is that older people who have fallen can look fine for weeks before the bleeding causes symptoms. By then, relatives will have forgotten the long-ago head knock, attributing Granddad's confusion to the heat, the cold, or a dizzy spell. Without that critical, sometimes lifesaving clue, precious time is lost.
Vital Signs: Why is Grandpa Falling?
A seemingly simple stumble provides clues to serious injury.
By Tony Dajer
DISCOVER Vol. 27 No. 08 | August 2006 |
