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.

View Full Profile

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.

View Full Profile

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

Bleeding within the brain (intracerebral hemorrhage) may be small, but can be associated swelling that may cause damage to the brain and result in coma.

The lining of the brain has multiple layers, and these layers can act as potential spaces where bleeding can occur. Bleeding on the outside of the brain and under the brain lining, and subdural bleeding may not cause coma immediately, but as the bleeding continues, it compresses the injured side of the brain and shifts it to the unaffected side. Now both cerebral hemispheres are affected and loss of consciousness or coma may occur; the more swelling, the deeper the coma.

Subarachnoid hemorrhage (bleeding beneath the arachnoid layer) occurs in the layer of the brain lining where cerebrospinal fluid (CSF) is located. CSF is the nutrient fluid that bathes the brain and spinal cord. Bleeding here may be without symptoms or it may cause significant problems, such as paralysis. Bleeding is often associated with a significant headache and neck stiffness.

Bleeding can occur within the skull or brain without trauma. Some medical causes include:

• Hypertension (high blood pressure): when blood pressure is too high, and not controlled, blood vessels in the brain may not be able to tolerate the high pressure and may leak blood.
• Cerebral aneurysm, or an area in a blood vessel that is congenitally weak and ruptures. Some people are born with blood vessels that have a weak wall that can gradually balloon, like a weak spot in an inner tube. At some time in their life, or perhaps never, the weak spot gives way and blood is spilled into the brain.
• Arteriovenous malformations (AVMs) are abnormal blood vessels where arteries connect to veins and cause potential weak spots that can leak blood. Normally, arteries branch into smaller and smaller vessels until they form the smallest set of vessels called capillaries. Capillaries form meshes where chemicals, nutrients, oxygen and carbon dioxide are exchanged from the blood stream to individual cells. The capillaries then merge to form larger blood vessels, the veins. In AVMs, this relationship of artery to capillary to vein is abnormal and is at risk for bleeding.
• Tumors, either benign or malignant, can be very vascular (composed of many veins and capillaries) and have significant bleeding potential.

Picture of the brain and potentially brain injury areas