Traumatic Brain Injury (TBI)
Traumatic brain injury (TBI) is defined as a blow to the head or a penetrating head injury that disrupts the normal function of the brain. TBI can result when the head suddenly and violently hits an object, or when an object pierces the skull and enters brain tissue. Symptoms of a TBI can be mild, moderate, or severe, depending on the extent of damage to the brain. Mild cases may result in a brief change in mental state or consciousness, while severe cases may result in extended periods of unconsciousness, coma, or even death.
Many patients with moderate or severe head injuries are taken directly from the emergency room to the operating room. In many cases, surgery is performed to remove a large hematoma or contusion that is significantly compressing the brain or raising the pressure within the skull. After surgery, these patients are usually observed and monitored in the intensive care unit (ICU). Other head-injured patients may not go to the operating room immediately, but instead are taken from the emergency room to the ICU. Contusions or hematomas may enlarge over the first hours or days after head injury, so some patients are not taken to surgery until several days after an injury. Delayed hematomas may be discovered when a patient's neurological exam worsens or when their ICP increases.
At the present time, there is no medication or "miracle treatment" that can be given to prevent nerve damage or promote nerve healing after TBI. The primary goal in the ICU is to prevent any secondary injury to the brain. The "primary insult" refers to the initial trauma to the brain, whereas the "secondary insult" is any subsequent development that may contribute to neurological injury. For example, an injured brain is especially sensitive and vulnerable to decreases in blood pressure that might otherwise be well tolerated. One way of avoiding secondary insults is to try to maintain normal or slightly elevated blood pressure levels. Likewise, increases in ICP, decreases in blood oxygenation, increases in body temperature, increases in blood glucose, and many other disturbances can potentially worsen neurological damage. The prevention of secondary insults is a major part of the ICU management of head-injured patients.
Various monitoring devices may assist healthcare personnel in caring for the patient. Placement of an ICP monitor into the brain itself can help detect excessive swelling of the brain. One commonly used type of ICP monitor is a ventriculostomy, which is a narrow, flexible, hollow catheter that is passed into the ventricles, or fluid spaces in the center of the brain, to monitor ICP and to drain CSF if ICP increases. Another commonly used type of intracranial pressure monitoring device involves placement of a small fiberoptic catheter directly into the brain tissue.
External ventricular drain (EVD) a catheter is inserted into a lateral ventricle which will allow drainage of CSF (cerebral spinal fluid). A hole is drilled through the skull. The catheter is inserted through the brain into the lateral ventricle. This area of the brain contains liquid (cerebrospinal fluid or CSF) that protects the brain and spinal cord.
Intracranial pressure (ICP) monitor: Intracranial pressure monitoring uses a device, placed inside the head, which senses the pressure inside the skull and sends its measurements to a recording device. Normal measurements are between 0-20mm Hg.
Brain injury types:
- Subdural hematoma: collection of blood between the dura mater and the arachnoid layer, which sits directly on the surface of the brain.
- Epidural hematoma: collection of blood between the dura mater (the protective covering of the brain) and the inside of the skull.
- Cerebral contusion is bruising of brain tissue. When examined under a microscope, cerebral contusions are comparable to bruises in other parts of the body. They consist of areas of injured or swollen brain mixed with blood that has leaked out of arteries, veins, or capillaries
- Intracerebral hemorrhage (ICH) describes bleeding within the brain tissue, which may be related to other brain injuries, especially contusions. The size and location of the hemorrhage helps determine whether it can be removed surgically.
- Subarachnoid hemorrhage (SAH) is caused by bleeding into the subarachnoid space. It appears as diffuse blood spread thinly over the surface of the brain, and is seen commonly after TBI. Most cases of SAH associated with head trauma are mild. Hydrocephalus may result from severe traumatic SAH.
- Diffuse Axonal injury refers to impaired function and gradual loss of some axons, which are the long extensions of a nerve cell that enable such cells to communicate with each other even if they are located in parts of the brain that are far apart. If enough axons are injured in this way, then the ability of nerve cells to communicate with each other and to integrate their function may be lost or greatly impaired, possibly leaving a patient with severe disabilities.