Coma (cont.)

Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• What is a "coma"?
• What is the Glasgow Coma Scale?
• What are the causes of a coma?
• Trauma
• Bleeding (Hemorrhage)
• Epidural, subdural, and subarachnoid hemorrhages
• Tumors
• Swelling
• Infection
• Lack of oxygen
• Hypoglycemic coma
• Poisons
• How is coma assessed?
• What tests are there for coma?
• What is the outcome and prognosis for a patient in a coma?
• Induced Coma
• Patient Comments: Coma - Cause
• Coma Index

Minor head injuries can cause brief loss of consciousness, but the brain is able to turn itself back on. Similarly, patients with seizures become unconscious - but gradually waken relatively quickly as the brain recovers from the seizure's "electrical storm." Those people who cannot respond after head injury usually have had significant force applied to their head and brain.

The skull is a rigid box that protects the brain. Unfortunately, if the brain is injured and begins to swell (edema), there is no room for the additional fluid. Increased pressure within the brain (increased intracranial pressure) causes compression of the brain tissue against the skull bones. This swelling within the skull can cross the midline of the brain, and affect the undamaged hemisphere. If the intracranial pressure continues to increase without being treated, the brain will continue to swell until it pushes down through the opening at base of the skull, damaging the brain stem where the reticular activating system is located. This affects the ability of the brain to stimulate breathing and control blood pressure.

The effect of trauma on the brain is not predictable. It may or may not cause significant injury. If the brain is shaken, shear injury may occur, whereby the nerve connections within the brain are damaged. Coma may occur even with a normal CT scan in this situation. Similarly, head trauma may cause swelling of the brain without any bleeding, and coma may be the result.

Head trauma can cause different types of brain injury. The injury can occur to the brain tissue itself or may cause bleeding to occur between the brain and the skull. Computerized Tomography (CT) of the head can identify most bleeding from trauma.