Head injury is a major public health
problem. It occurs most commonly in teenagers and young adults who would
otherwise have been productive members of society. The disabilities that
many of them incur from their head injuries often make them dependent upon
rehabilitation services and other special care needs for the rest of their
lives. Although head injuries steal away more potentially productive years
than such common illnesses as cancer, AIDS, heart disease, and diabetes,
less research money is spent on head injury than on these other diseases.
Head injury is also commonly referred to as traumatic brain injury (TBI).
The most common cause of TBI is motor vehicle accidents. This is also the
most common mechanism in teenagers and young adults. The next most common
cause is a fall, and this mechanism is most common at the extremes of age,
i.e., pediatric and geriatric patients. Alcohol or other drug use
contributes significantly to the occurrence of many head injuries. Treatment
for head injury may be either surgical or nonsurgical. However, these
treatments are not mutually exclusive. Many of the same biochemical events
that cause damage of the brain after nonoperative TBI also occur in patients
who undergo surgery, and an operation may not be able to stop or reverse
these underlying processes.
Surgical lesions
When discussing head-injured patients,
neurosurgeons often use the term "mass lesion", which refers to an area of
localized injury that may cause pressure within the brain. The most common mass
lesions seen after TBI are hematomas and contusions. A hematoma is a blood clot
within the brain or on its surface. A contusion may be thought of as an area of
"bruised" brain. 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. Hematomas and contusions can occur anywhere within the
brain. Those hematomas between the skull and the dura, which is a thick membrane
that surrounds the brain, are called epidural hematomas. Hematomas that are
between the dura and the surface of the brain are called subdural hematomas.
Intracerebral hematomas are blood clots that are located within the brain tissue
itself. Contusions are seen most commonly at the base of the front parts of the
brain, but they can occur anywhere. Subarachnoid hemorrhage appears as diffuse
blood spread thinly over the surface of the brain. This is seen commonly after
head injury. If this is the only abnormality present on a CT scan, then
observation for a short period may be the only treatment needed.
Severe head
injuries in children (under 15 years of age)
have many features that differentiate them from head injuries in adults. In such
cases, nonsurgical treatment can not always prevent fatal herniation. We
use in such cases an
unilateral decompressive craniectomy (UDC), which was
developed by Hejazi et al. The aim of the UDC is
to decompress the midbrain and the brainstem. Our results suggest that UDC for children with severe brain
injury, not only reduces mortality but also significantly improves outcome,
especially when performed early in the first 6 hours after trauma. Craniectomy
later than 6 hours after trauma can be lifesaving but does not improve
neurological outcome as much as very early craniectomy. Although the number of
patients who can be aided by UDC is small, the use of this technique for
children with severe brain injury seems to be a viable option in the ongoing
management.
[Hejazi N,
et al.
Unilateral Decompressive Craniectomy for Children with Severe Head Injuries.
European Journal of
Pediatrics 161:99-104, 2002.], [Hejazi N, et al.
Decompressive Craniectomy for Children with Severe Brain Injuries.
Own Experiences and Review of the literature. Neurosurgery 2000;47:510.]
Diffuse injuries
The hematomas and contusions described above
generally occur in only one or a few specific parts of a patient's brain, and
they are usually easily seen on a computerized tomography (CT) scan. However,
TBI can also produce microscopic changes that cannot be seen on CT scans and
that are scattered throughout the brain. This category of injuries is called
diffuse brain injury, which can occur with or without an associated mass lesion.
One type of diffuse brain injury is diffuse axonal injury. This 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. Another type of diffuse injury is
ischemia, or insufficient blood supply to certain parts of the brain. It has
been shown that a drop in blood supply to very low levels may occur commonly in
a significant percentage of head-injured patients. This is important because a
brain that has just undergone a traumatic injury is especially sensitive to even
slight reductions in blood flow. For the same reason, changes in blood pressure
during the first few days after head injury can have an adverse effect.
Skull fractures
No treatment is required for most linear skull
fractures, which are simple breaks or "cracks" in the skull. Of greater concern
is the possibility that forces strong enough to cause a skull fracture may also
have caused some damage to the underlying brain. Fractures of the base of the
skull are worrisome if they cause injury to nerves, arteries, or other
structures. If a fracture extends into the sinuses, there may be leakage of
cerebrospinal fluid (CSF) from the nose or ears. Most such leaks will stop
spontaneously. Sometimes, it may be necessary to insert a lumbar drain, which is
a long, thin, flexible tube that is inserted into the CSF space in the spine of
the lower back. This provides an alternate route of CSF drainage so that the
dural tear that is responsible for the CSF leak in the base of the skull has
time to seal. Depressed skull fractures are those in which part of the bone
presses on or into the brain. These may require surgical treatment. The damage
caused by depressed skull fractures depends upon the region of the brain in
which they are located and also upon the possible coexistence of any associated
diffuse brain injury.
Like all trauma patients, persons with head
injury need a systematic yet rapid evaluation in the emergency room. Cardiac and
pulmonary function are the first priority. Next, a rapid examination of the
entire body is performed.
Neurological examination
An accurate neurological examination is
important to categorize the severity of a patient's injuries and to plan further
evaluation and possible treatment. The standard for objectively assessing the
severity of head injury is the Glasgow Coma Scale (GCS). This scale assigns
points to each patient based upon three categories: verbal function, eye
opening, and best motor (movement) response. Patients with a GCS score of 13-15
are usually classified as having mild head injuries. Those with a GCS score of
9-12 have moderate head injuries, and those with a score of 3-8 are usually
described as having severe head injuries. Any patient who is not obeying
commands (for example, to follow instructions to hold up two fingers) is also
often considered to have a severe head injury, even if the GCS score may be
slightly higher than eight. In addition to the GCS, the ability of the pupils to
become smaller in bright light is also important after head injury. In patients
with large mass lesions or with high intracranial pressure (ICP), one or both
pupils may be very wide or "blown". The presence of a wide, or dilated, pupil on
only one side suggests that a large mass lesion may be present on the same side
as the dilated pupil.
Radiologic assessment
CT scanning is the gold standard for the
radiologic assessment of a head-injured patient. A CT scan is easy to perform
and is an excellent test for detecting the presence of blood and fractures,
which are the most important lesions to identify in emergency situations. Plain
x-rays of the skull are recommended by some people as a way to evaluate patients
with only mild neurologic dysfunction. However, most centers in the United
States have readily available CT scanning, which is a more accurate test. For
this reason, the routine use of skull x-rays for head-injured patients has
declined. Magnetic resonance imaging (MRI) is not commonly performed for acute
head injury because it takes longer to perform an MRI scan than a CT scan,
because MRI is not as useful as CT for acute trauma, and because transporting an
acutely injured patient from the emergency room to the MRI scanner is difficult.
However, after a patient has stabilized, MRI may demonstrate the existence of
lesions that could not be detected by CT. Such information is generally more
useful for determining prognosis than for influencing treatment.
Surgical
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 first taken from the emergency room
to the ICU. However, contusions or hematomas may enlarge over the first hours or
days after head injury, so that some patients are not taken to surgery until
several days after an injury. Sometimes these delayed hematomas are discovered
when a patient's neurologic exam worsens or when the ICP increases. On other
occasions, a routine follow-up CT scan that was ordered to see if a small lesion
has changed in size indicates that the hematoma or contusion has enlarged
significantly. In many of these cases, removing the lesion before it enlarges
and causes neurologic damage may be safest for the patient. At surgery, the hair
over the appropriate part of the head is shaved. After the scalp incision is
made, the bone that is removed is usually taken out in a single piece or "flap",
which is then replaced after surgery. Sometimes, however, the bone may be
shattered or heavily contaminated. In these cases, the contaminated or shattered
fragments may be removed and not replaced. The next structure encountered is the
dura, which is carefully cut to reveal the underlying brain. After any hematoma
or contusion is removed, the surgeon makes sure that the area is not bleeding.
He then closes the dura, replaces the bone, and closes the scalp. (If the brain
is very swollen, some surgeons may decide not to replace the bone until the
swelling goes down, which may take up to several weeks.) The surgeon may elect
to place an ICP monitor or other types of monitors if these were not already in
place. The patient is then returned to the ICU for observation and additional
care.
Medical
At the present time, there is no drug or
"miracle treatment" that can be given to prevent nerve damage or promote nerve
healing after TBI. The best treatment that can be performed in an ICU is to
prevent any secondary injury to the brain. The "primary insult" refers to the
initial trauma to the brain, whereas a "secondary insult" is any subsequent
development that may contribute to neurologic injury. For example, as mentioned
above, an injured brain is especially sensitive and vulnerable to decreases in
blood pressure that might otherwise be well tolerated. Thus, one way of avoiding
secondary insults is to try to maintain the blood pressure at normal or perhaps
slightly elevated levels. Likewise, increases in ICP, decreases in blood
oxygenation, increases in body temperature, increases in blood glucose, and many
other disturbances can potentially worsen neurologic damage. Thus, the
prevention of secondary insults is a major part of the ICU management of
head-injured patients.
Various monitoring devices may assist the physicians 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 also to drain CSF if the ICP increases.
Placement of an oxygen
sensor into the jugular vein can detect how much oxygen is in the blood that is
coming from the brain and in this way can give an indication of how much oxygen
the brain is using. This may be related to the degree of brain damage. Many
other monitoring techniques are currently under investigation to see if they can
help to improve outcome after head injury or provide other critical information
about caring for these patients.
Once they leave the acute-care hospital, some
head-injured patients may benefit from an aggressive rehabilitation program.
Such patients usually had less severe initial injuries or have begun to show
significant improvement from severe injuries. In some cases, their further
recovery may be expedited by transfer to a rehabilitation hospital or to the
rehabilitation service of a large hospital. For more severely injured patients
or for those whose recovery is slow, constant vigilance is required to prevent
the gradual onset of problems with joint mobility, skin integrity, respiratory
status, and many other physiologic functions. Patients with moderate or mild
injuries, as well as severely injured patients who have improved sufficiently,
may be candidates for outpatient therapy. Regardless of the setting, most
head-injury rehabilitation centers emphasize compensatory strategies, which
essentially help patients learn to reach the maximum level of function allowed
by their impairments. The concept of cognitive retraining, which presumes that
at least some of the brain's cognitive capacity can be restored by constant
repetition of certain simple tasks, is more controversial but is also emphasized
at many centers. Another major goal of head injury rehabilitation is working
with patients' families to educate them about what they can realistically expect
and how they can best help their injured family member.
One of the most widely used systems to
classify outcome from head injury is the Glasgow Outcome Scale, which is
summarized below. Patients with mild head injury (usually defined as
Glasgow Coma Score
13-15) tend to do well. They may sometimes be troubled by headaches, dizziness,
irritability, or similar symptoms, but these gradually improve in most cases.
Patients with moderate head injuries fare less well. Approximately 60% will make
a good recovery, and another 25% or so will be left with a moderate degree of
disability. Death or a persistent vegetative state will be the outcome in
roughly 7-10%. The remainder are left with a severe degree of disability. Not
surprisingly, the group comprised of severely head-injured patients has the
worst outcomes. Only a quarter to a third of these patients have good outcomes.
Moderate disability and severe disability each occur in about a sixth of
patients, with moderate disability being slightly more common. Roughly a third
of these patients die. The remaining few percent remain persistently vegetative.
The above statistics apply to patients with so-called closed head injuries. For
penetrating head injuries, which in modern society are caused most commonly by
handguns, outcomes follow a different pattern. Over half of all patients with
gunshot wounds to the head who are alive upon arrival at a hospital go on to die
because their initial injuries are so severe. However, most of the remaining
patients tend to do fairly well, largely because their injuries are relatively
mild (Glasgow Coma Scale score of 13-15). Relatively few patients suffer
injuries of intermediate severity (that is, with a Glasgow Coma Scale score of
6-12) from gunshot wounds, but it is this group that has the most variability in
outcomes. It must be emphasized that, despite its usefulness, the Glasgow
Outcome Scale is not a good tool with which to measure subtle emotional or
cognitive problems. Several months after a severe head injury, patients who have
a good score on the Glasgow Outcome Scale may in fact have significant
neuropsychological disabilities. Tremendous effort is being directed into
finding better ways to evaluate these problems, into improving the quality of
prehospital, acute, and rehabilitative care, and into research to learn more
about the effects of head injury and their possible treatment.
Table1: Glasgow Coma Scale (GCS)
| SCALE VALUE |
BEST MOTOR RESPONSE |
BEST VERBAL RESPONSE |
BEST EYE OPENING RESPONSE |
| 6 |
Obeys commands |
-- |
-- |
| 5 |
Localizes stimulus |
Oriented |
-- |
| 4 |
Withdraws from stimulus |
Conversant, but confused |
Eyes open spontaneously |
| 3 |
Flexes arm |
States recognizable words or phrases |
Eyes open to voice |
| 2 |
Extends arm |
Makes unintelligible sounds |
Eyes open to painful stimulus |
| 1 |
No response |
No response |
Remain closed |
Table2:
Glasgow Outcome Scale (GOS)
|
OUTCOME |
SCORE |
DESCRIPTION |
| Good Recovery (GR) |
5 |
Minor disabilities, but able to resume
normal life. |
| Moderate Disability (MD) |
4 |
More significant disabilities, but still
able to live independently. Can use public transportation, work in an
assisted situation, etc. |
| Severe Disability (SD) |
3 |
Conscious, but dependent upon others for
daily care. Often institutionalized. |
| Persistent Vegetative State (PVS) |
2 |
Not conscious, though eyes may be open
and may "track" movement. |
| Death (D) |
1 |
Self-explanatory. |
AXON
- The part of a nerve cell that usually sends signals to other nerves or
structures.
CONTUSION
- A bruise; an area in which blood that has leaked out of blood vessels is mixed
with brain tissue.
CSF
- Cerebrospinal fluid.
DEPRESSED
SKULL FRACTURE - A break in the
bones of the head in which some bone is pushed inward, possibly pushing on or
cutting into the brain.
DIFFUSE
AXONAL INJURY - Damage to the
axons of many nerve cells that lie in different parts of the brain.
DIFFUSE
BRAIN INJURY - Damage to the brain
that can affect many parts of the brain, often in a subtle fashion; examples
include diffuse axonal injury and inadequate blood flow.
DURA
- Dura mater.
EPIDURAL
HEMATOMA - A blood clot between
the dura mater and the inside of the skull.
GCS
- Glasgow Coma Scale.
GLASGOW COMA SCALE - The most widely used
system of classifying the severity of head injuries or other neurologic
diseases.
GLASGOW
OUTCOME SCALE - A widely used
system of classifying outcome after head injury or other neurologic diseases.
INTRACEREBRAL
HEMATOMA - A blood clot within the
brain.
ICP
- Intracranial pressure.
ISCHEMIA
- Inadequate blood flow; if prolonged or severe, may lead to a stroke.
LUMBAR DRAIN
- A device (usually a long, thin, flexible tube) inserted through the skin into
the cerebrospinal fluid space of the lower back; provides a method of draining
cerebrospinal fluid.
PUPIL
- The black part of the eye through which light enters; enlarges in dim light
and decreases in size in bright light.
SUBARACHNOID
HEMORRHAGE - Blood in, or bleeding
into, the space under the arachnoid membrane, most commonly from trauma or from
rupture of an aneurysm.
VENTRICULOSTOMY
- An opening into the ventricles of the brain, such as by inserting a small,
thin, hollow, flexible catheter.