Head Injury
Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: Melissa Conrad Stöppler, MD
Head Injury Symptoms: When to Seek Medical Care
Medical Author: Benjamin C. Wedro, MD, FACEP, FAAEM
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
Natasha Richardson, an acclaimed actress, was apparently taking a ski lesson outside of Montreal, Canada, when she seemingly had a relatively minor fall and hit her head. Over the next hour, she complained of increasing
headache, was taken to a local hospital and by all reports was critically ill in a New York hospital,
until it was announced Ms. Richardson had passed away from the
head trauma she
suffered.
The type of brain injury she sustained was revealed as an epidural hematoma. An epidural hematoma occurs when there is bleeding between the dura mater (a tough fibrous layer of tissue between the brain and skull) and the skull bone. These occur when arteries are torn as a result of a blow to the head, and injury in the temple area is a common cause. Although the pattern of a lucid interval followed by later neurological symptoms is characteristic, only a minority of patients display this pattern of symptoms. Reported death rates from epidural hematoma vary widely, ranging from 5% to over 40%, depending upon the patient population under study.
Top Head Injury Searched Terms
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Head injury introduction
Head injuries are one of the most common causes of death
and disability in the United States. Every year, almost a quarter million people
are hospitalized because of traumatic injuries to the brain, and 50,000 people die. As well,
80-90,000 people sustain long-term or lifelong disabilities because of a brain
injury each year. Children are not excluded, with more than 2,500 deaths and
almost a half million emergency department visits per year for head injuries.
Blows to the head most often cause brain injury, it is
important to remember that the face and jaw are located in the front of the head. Brain injury may
also be associated with injuries to these structures. It is also important to
note that a head injury does not always mean that there is also a brain injury.
The brain is a rather soft, pliable material almost jelly-like in feel, and
is surrounded by a thin layer of cerebrospinal fluid
(CSF). The brain is
surrounded by thin layers of tissue called the meninges;
1) the pia mater, 2) the
arachnoid mater, and 3) the dura mater. The CSF is present in the space beneath the
arachnoid layer called the subarachnoid space.
The dura mater is very thick and has septae, or
partitions, that help support the brain in the skull. The septae attach to the
inner lining of the bones of the skull. The dura mater also helps support the
large veins that return blood from the brain to the heart.
The spaces between the meninges are usually very small but they can fill with
blood when trauma occurs, and this build-up of blood can potentially press into
the brain tissue and cause damage.
The skull protects the brain from trauma but it does not
absorb any of the
impact from a blow. Direct blows may cause fractures of the skull; there can be
a contusion or bruising and bleeding to the brain tissue directly beneath the
injury site. However, the brain can bounce around inside the skull if it is
subject to significant force and because of this, the brain injury may not
necessarily be located directly below the trauma site. A contre-coup injury
describes the situation in which the initial blow causes the brain to bounce and
is damaged by hitting the skull directly opposite the trauma site.
Acceleration/deceleration and rotation are the common types of forces that can
cause injuries away from the area of the skull that received the trauma.
Picture of the brain and potentially brain injury areas
Head injuries due to bleeding are often classified by the location of the
blood within the skull.
- Epidural hematoma: With an epidural hematoma, the bleeding is located between the dura mater and
the skull. This is often present along the side of the head where the middle
meningeal artery runs in a groove along the
temporal bone. This
bone is relatively thin and offers less protection than other parts of the
skull. As the bleeding continues, the hematoma or clot expands. There is little
space in the skull for the hematoma to grow and as it expands, the adjacent
brain tissue is
compressed. As the pressure increases, the whole brain begins to shift and
becomes compressed against the bones of the skull. The pressure tends to build
quickly because the septae that attach the dura to the skull bones create small
spaces that trap blood. Symptoms of head injury and decreased level of
consciousness occur as the pressure increases.
- Subdural hematoma: A subdural hematoma is located beneath the dura mater
(sub=below), between it and the arachnoid mater. Blood in this space is able to
dissipate into a larger space because there are no septae limiting the blood
flow. However, after a period of time, the amount of bleeding may cause
increased pressure and cause symptoms similar to those seen with an epidural
hematoma.
- Subarachnoid bleed: Subarachnoid bleeding occurs in the space beneath the
arachnoid layer where the CSF is located. Often there is intense
headache and
vomiting with
subarachnoid bleeding. Because this space connects with the spinal canal,
pressure build-up tends not to occur. However, this injury often occurs in
combination with the other types of bleeding in the brain, and the symptoms can
be compounded.
- Intracerebral bleed: Intracerebral bleeding occurs within the brain tissue
itself. Sometimes the amount of bleeding is small, but like bruising in any
other part of the body, swelling or
edema may occur over a period of time,
causing a progressive
decrease in the level of consciousness and other symptoms of head injury.
- Sheer injury: Sometimes, the damage is due to sheer injury, where
there is no obvious bleeding in the brain, but instead the nerve fibers within the brain are
stretched or torn. Another term for this type of injury is diffuse axonal
injury.
- Edema: All injuries to the brain may also cause swelling or
edema, no different than the swelling that surrounds a
bruise on an arm or leg. However, because the
bones of the skull cannot stretch to accommodate the extra volume caused by
swelling, the pressure increases inside the skull and causes the brain to
compress against the skull.
- Scull fracture: The bones of the skull are classified as flat bones,
meaning that they do not have an inside marrow. It takes a significant amount of force to break the
skull, and the skull does not absorb any of that impact. It is often transmitted
directly to the brain.
Skull fractures are described by which bone is broken, whether there is an
associated laceration of the scalp, and whether the bone is depressed and
potentially pushed into the brain tissue.
Brain injuries often occur in combination with one another. The effects of
brain injury depend upon the amount of brain tissue damaged and the level of
pressure within the skull and its effects on the brain.
Next: What are the causes of head injury? »
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