Glossary of Terms

Any injury to the brain sustained after birth. Such injuries include blows to the head, lack of oxygen from suffocation, smoke inhalation or near drowning, hemorrages, brain tumors, infections and penetrating wounds.

A person who receives a blow to the head that is sufficiently firm to cause brief loss of consciousness (minutes, not hours) and/or amnesia (loss of memory for the event).   These types of injuries do not show up as an abnormality on any testing.   Recovery is usually complete with-out any special treatment, but occasionally ability to concentrate and short term memory may be affected for several months afterwards.

When a blow to the head is strong enough to cause temporary loss of consciousness (minutes to hours) and amnesia with tests showing bruises in the brain, the injury is called a cerebral contusion.  The bruises are called  hemorragic contusions and may be large or small, single or multiple.  Their size, number and location determines whether there will be any associated speech difficulties, reading or writing problems, or any weakness of the arms or legs.  Recovery may be spontaneous and complete or may require many months or years of treatment.

Focal (localized) or diffuse edema (swelling) of the brain frequently accompanies traumatic brain injuries.  Edema with cerebral contusions, hemorrages or brain tumors is often focal (localized to one area of the brain) or may be diffuse. With infections or lack of oxygen, the edema is generally diffuse. Diffuse edema usually signals a prolonged recovery frequently requiring long term treatment.  Cerebral edema following a TBI usually lasts from 3 - 10 days.

Hemorrages of TBI may be outside or inside the brain.  Inside the skull the brain is surrounded by a protective triple-layered covering known as the meninges.  These consist of a thick outer layer called the dura, a very fine middle layer called the arachnoid and a third fine layer adherent to the surface of the brain called the pia.   Within the brain are 4 narrow fluid filled cavities called ventricles; they produce cerebro-spinal fluid,  a clear colorless fluid that constantly bathes the brain.

Cerebral hemorrages are named according to their anatomical location:

1. Epidural hemorrage: Between the skull and the outer (dura) covering.
   


2. Subdural hemorrage: Between the outer (dura) and middle (arachnoid) coverings.
   


3. Subarachnoid hemorrage: Between the middle (arachnoid) and inner (pia) coverings.
   


4. Intracerebral hemorrage: Within the  parenchyma or meat of the brain.  (Different anatomical sites may be given, i.e. frontal, temporal, etc.).
   


5. Intraventricular hemorrage: Within the fluid filled cavities of the brain.
   

Hemorrages may have a single anatomical location, or in very severe TBI's may have several anatomical locations.  Hemorrages injure the brain by compression of brain cells and pathways, or by mechanical disruption and tearing of the cells and pathways.

Skull fractures may be linear, undisplaced (like a crack in a dinner plate), stellate with multiple linear fracture lines diverging from a central point, depressed with a fragment of bone indenting or cutting into the brain, diastatic with a wide separation of the fracture margins, suggesting a massive underlying hemorrage or severe diffuse swelling of the brain, egg shell with multiple fractures in different parts of the skull. A compound fracture of the skull is one in which there is an open wound of the skin over the fracture.  A skull fracture is not always accompanied by brain injury, but the more severe the fracture, the greater the likelihood of brain injury.  Conversely, a blow to the head may injure the brain without fracturing the skull.

Penetrating wounds are those that involve an object penetrating the skin, the bone, the brain coverings and the brain.  These include but are not limited to gun shot wounds, knife wounds, axe wounds, ice pick wounds, harpoon wounds, metallic fragment wounds, hard wood wounds, nails, masonry and others.  Depending on the site of the penetration, the size of the object and the degree of the brain injury, recovery may be complete and rapid or partial and slow.

Whenever an insufficient amount of oxygen reaches the brain, the term anoxia or hypoxia is applied.  Anoxia is a total absence of oxygen.  The brain cannot survive more than 2 minutes without oxygen.  Hypoxia is an insufficient amount of oxygen.   These types of injury to the brain usually occur after a near drowning, a suffocation, smoke inhalation or a crush injury to the chest.  In older individuals, hypoxia or anoxia accompanies a stroke, a heart attack or a pulmonary arrest (cessation of breathing).  Hypoxic or anoxic brain injuries frequently have an initial episode of diffuse brain swelling (edema).  The duration and the degree of oxygen deprivation dictates the subsequent degree of injury to the brain, but the exact duration and degree are often unknown so the extent of injury may not be recognized until days, weeks or months following the event.

Growths or tumors in the brain may be single or multiple.  They may invade or compress brain cells.  Depending on their location in the brain and their behavior (slow growing or fast growing) they will cause minimal or major injury to the brain.

Infections of the brain may be caused by bacteria or by viruses.  A bacterial infection may be localized, forming an abscess, or diffuse, causing a cerebritis or encephalitis. Viral infections tend to be diffuse, causing a viral encephalitis.  If the coverings of the brain are infected, the term meningitis is used.  When an infection involves the ventricles, a ventriculitis is diagnosed.  These infections may occur in association such as in a meningo-encephalitis.  The severity of the injury to the brain depends on the virulence of the bacteria or virus and the degree of inflammation and swelling that it provokes in the brain.

Several terms are used in a neurological or neurosurgical setting to define levels of consciousness:

1. Alert: Eyes open, able to follow some directions, signs of awareness of surroundings.
   


2. Lethargic: Sleepy, but arousable. Cooperates when aroused. Aware of surroundings when aroused.
   


3. Obtunded: Difficult to arouse. Shows some signs of awareness when aroused, but drifts back to sleep in mid-sentence or mid-activity, requiring frequent stimulation to re-arouse.
   


4. Stuporous: Can only be aroused to point of eye-opening, and only very briefly.
   


5. Coma: Unarousable or as yet unaroused.
   


6. Brain death: Complete cessation of all brain activity.
   

The next section includes descriptions of various examinations and tests that are used to evaluate an individual's function.

Clinical examinations attempt to evaluate an individual's function.  Tests consist of different studies designed to give a black and white objective image, graph or numerical value to a finding.

The simplest bedside clinical exam performed in TBI is the GCS, evaluating eye opening ability, vocal or verbal ability, and best movement ability.  The score ranges from a low of 3 (no detectable function) to a high of 15 (fully alert).  A score of 8 or less indicates coma. A single score has no predictive or prognostic value, but a series of scores over hours, days and weeks indicate a trend.

The standard neurological exam requires an assessment of mental status (level of consciousness, orientation to time, person and place, understanding of instructions, ability to read and understand reading), function of the twelve cranial nerves (that innervate the eyes, face, hearing, mouth and throat), mobility (of the extremities and of the body), muscle tone, abnormal movements, reflexes, sensory functions, balance and coordination.  This exam may be quite time consuming when done completely in an alert individual, or may be very brief in a poorly responsive person.

The Profile assesses seven levels of 3 sensory functions and 3 motor functions giving a 42 box grid that supplies in a simple and reproducible way an extrememly comprehensive view of brain function, regardless of the degree of the person's responsiveness, and quickly localizes the level of function as brain stem, midbrain or cortical, unilateral or bilateral.

Blood pressure, heart rate, respiratory pattern and temperature in the first days following a TBI give an indication of intracranial pressure and status of infection.   Increasing blood pressure with a decreasing heart rate and changes in respiratory pattern suggest increasing intracranial pressure from a space occupying lesion such as hemorrage or a tumor, or from edema (swelling) of the brain.

If increasing intracranial pressure is suspected, an intracranial pressure monitor is inserted through a tiny opening in the skull to provide information about intracranial pressure before changes in vital signs or in clinical exam appear, allowing for more rapid and more effective treatment.

Also known as lumbar puncture, this test involves inserting a fine needle into a sac of fluid at the base of the spine.  The fluid in the sac is the same fluid that bathes the brain and the spinal cord.  The test is done if an infection is suspected or if a hemorrage that has not declared itself on any other test is being entertained.

This is the best test to demonstrate skull fractures.

CAT or CT scan is a computer generated radiological image of axial slices through the brain. This is the best test to demonstrate hemorrages, penetrating injuries, swelling, and size of the ventricles of the brain.  The test may also show contusions of the brain and brain tumors.

Magnetic Resonance Imaging is a type of scan generated by a powerful magnet and provides images of the brain in slices through three different planes (axial, sagittal, coronal) and is more sensitive than the CT scan for subtle findings or for brain tumors.

The ElectroEncephaloGram is a recording of the electrical activity of the brain, just as an electrocardiogram records the electrical activity of the heart.  A major difference between the two is that the EEG must record microvolts throught the thickness of the skull which, in places, may reach 1/2 inch.  The test is useful to follow the evolution of seizures, the course of an infection and to determine brain death.

Three types of evoked potential tests may be performed: Visual Evoked Potential (VER), Brain Stem Auditory Evoked Potentials (BAER) and Somato Sensory Evoked Potentials (SSEP).   Each of these tests uses computerized EEG analysis of brain recordings of different sensory stimuli (visual, auditory, or peripheral sensory) to provide information about the integrity of the respective pathways.

It is important to remember that a test only gives information about a condition that it is measuring at that given moment in time.  The test has no prognostic value, in other words, the tests are not predicting the future.