The Injured Brain
What is a Brain Injury?
The brain is made up of over a billion nerve cells (neurons) as well as other support cells and blood vessels. Brain injury occurs when groups of neurons are irreversibly damaged as a result of a stroke, a trauma, an infection, a brain tumor and other conditions. Concussion is an example of a type of brain injury where the brain is “concussed” or rattled inside the skull. Brain injury can be very mild such that the person may not show any outward signs at all. On the other hand, brain injury can be very severe, causing coma and paralysis. The brain is very susceptible to injury mostly because the nerve cells have high requirements for oxygen and glucose and when they are deprived of that nourishment, they quickly begin to die. Also, brain cells do not heal very well. After brain injury, the brain does attempt to heal itself but it is not as effective at healing as other parts of the body such as skin and bone.
What happens when the brain is injured?
It is important to note that no two brain injuries are alike, just like there are no two brains exactly alike. We all are born with a certain pattern of brain connections but this is modified by our environment and how we develop through childhood. So when a brain injury occurs it is not easy to determine how things will turn out. Most of what is discussed below refers to major brain injury where the patient requires hospitalization.
Although coma (impaired consciousness) is the most obvious immediate result of a severe head injury, many brain functions are frequently altered to some extent, temporarily, or longer term. These will be mentioned only briefly here. If any of these problems occur in an individual with brain injury, it is essential for the family to get specific information from the health care team treating that person.
Changes in mobility are probably the most common result of brain injury and may take many forms. The most deeply comatose patient may not move at all, even in response to pain. As the level of consciousness begins to improve, non-specific, generalized, REFLEX MOVEMENTS appear. The movements will be much the same, whether due to pleasurable or painful stimulation. They are not under voluntary control. The family may worry that these movements are an indication of the patient being in severe pain, but they are not.
Further improvement in the patient’s level of consciousness results in more selective and localized reflex movements in response to stimulation, as well as the beginning of some spontaneous movements. However, reflexes still predominate. For instance, stroking the palm of the patient’s hand will result in reflex closure of the hand … this should not be confused with a voluntary squeeze. As the patient begins to move more, it is sometimes noticed that spontaneous movements occur solely, or more often, on one side of the body, which indicates the presence of a HEMIPLEGIA (Lack of muscle control on one side of the body, either RIGHT or LEFT).
As the level of consciousness continues to improve, spontaneous movements increase and eventually the patient will start to produce more specific movements, more frequently, on command. (If hemiplegic, he will have normal voluntary movements only on one side.)
Movement disabilities tend to improve, often dramatically, but sometimes do not return completely to normal.
Any and all of the senses may be impaired following brain injury, including touch, smell, vision, hearing and taste. This may be due to localized damage to the sensory organ (i.e. penetrating injury of the eye) or to damage to the area of the brain involved in interpreting the sensory message. However, it is difficult to fully assess sensory function until the patient is sufficiently alert to co-operate with examination. A person with brain injury may not have full awareness of touch, pressure or temperature so it is important to watch for things around the person’s body that could injure them, for example sharp items. Also, if they are not moving around much, they may develop reddened skin in areas where most of their body weight is focused such as on their bottom or heels. This is important to watch out for.
As the patient awakens and becomes more aware of the environment, it may become apparent that there are difficulties with communication. The most common and significant problem early in the process of rehabilitation, is CONFUSION. This will be present even in patients with mild injury but frequently clears quickly.
The patient who has been intubated or who has had a tracheostomy, will have a weak, hoarse voice when he starts to talk and this may persist for weeks or months, but in the absence of other problems recovers well.
If the nerves supplying the muscles of the larynx (voice box) are badly damaged the patient will be APHONIC (unable to make sounds). This may or may not recover. Usually this problem is associated with damage to the nerves supplying the tongue and throat, so that if only partial recovery occurs, articulation is poor and speech is slurred (DYSARTHRIC). Difficulty in swallowing is usually present in these patients as well.
The most severe communication difficulties occur when the language centres in the brain (usually the left cerebral hemisphere) are damaged. This results in impairment of language function … APHASIA. The patient may not be able to find words to express himself (expressive aphasia) or may also have difficulty understanding what is said to him (receptive aphasia). Usually reading and writing are similarly affected.
4. Posttraumatic Epilepsy
There is an increased chance of a patient who has had a brain injury developing epilepsy. Epilepsy may appear early, during the initial or acute phase following trauma, or may not appear until months or years later. The overall incidence of posttraumatic (after injury) epilepsy is about 5%. However, it is much more frequent in more severely injured patients, following penetrating injuries (i.e. gunshot wounds), after injuries associated with intracerebral hematomas (blood clots), and in those patients who remain severely disabled. While epilepsy can usually be well controlled with medications, it does interfere with vocational and recreational choices.
5. Stimulation and Coma
Coma is the result of a severe disturbance of brain function from trauma or other factors. The common result, whatever the cause, is that there is an alteration of biochemical activity within the brain. Recovery from coma depends on recovery of normal biochemical function. There are many things we do to attempt to normalize brain function, some of which we understand well and some of which we do not understand completely. It is agreed by most people that stimulation of the comatose patient (familiar voices, music, touch, taste, etc.) is a good thing, but exactly what this does to the damaged brain is unknown. It appears that stimulation is one of a number of things that may favorably influence disturbed brain function, but there is little or no evidence that stimulation alone can reverse true coma or “undo” brain damage.