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Many terms are used by health care professionals to describe injury, damage, or degeneration to the
spinal discs. The purpose of this article is to describe these terms. A brief review of spinal
anatomy is necessary to understand these terms.
One important note: a disc herniation cannot be seen on regular X-rays; it can only be seen on
MRI. Regular X-rays show disc degeneration, which shows up as a decrease in space between the
vertebrae.
ANATOMY
The spinal column is comprised of 24 bones called vertebrae. These 24 vertebrae are divided into
three areas: the neck or cervical spine which has seven vertebrae, the middle back or thoracic
spine which has 12 vertebrae, and the lower back or lumbar spine which has five vertebrae. The
bone at the base of the spine is called the sacrum. At the end of the sacrum is the coccyx.
In between each pair of vertebrae is a disc or shock-absorbing cushion. There are 23 discs in the
spine starting between the second and third cervical (neck) vertebrae and continuing to the last
disc between the fifth lumbar (low back) vertebra and the sacrum (bone at base of spine). The discs
are named by using the vertebrae above and below, i.e., C2-C3, T5-T6, and L4-L5. The letter "C"
stands for cervical, the letter "T" stands for thoracic (mid-back), the letter "L" stands for
lumbar and the letter "S" stand for sacrum. In the example above, C2-C3 is the disc between the
second and third cervical vertebrae.
The spinal cord is a direct continuation of the brain that passes through a hole in the skull
(foramen magnum or big hole) and through holes in each vertebra called the spinal canal. In-between
each pair of vertebrae are holes on both the right and left through which branches of the spinal
cord run called a nerve roots. In the cervical spine these nerve roots travel down the arm and
control the muscles of the arms and all the muscles around the shoulder and shoulder blades as
well as the feeling in the arms. In the thoracic spine they run around the ribs and to the
internal organs and in the lumbar spine they run to the sexual organs and the hips, thighs,
legs, and feet.
The disc is comprised of a strong outer material called the annulus fibrosis that has concentric
rings quite similar to a cut tree trunk as seen from above. These concentric rings receive
nutrients through osmosis, as they have no arteries or veins directly. The center of the disc
is called the nucleus pulposus. This fluid (water)-filled jelly sack, similar to the inside of
the gum you can bite into and the middle squirts out, can be pushed out by compressive forces
down the spinal column. The disc provides a shock absorbing effect that dissipates these
compressive forces across multiple levels in the spine and still allows for the flexibility
required for performing normal activities of daily living. Thus, as the body twists, bends,
flexes and extends; the discs are constantly changing their shape.
DISC TERMINOLOGY
Over a lifetime the disc can be damaged by acute injuries like auto accidents and falls or by
chronic insult like poor posture, weak and inflexible supporting muscles, and poor body mechanics.
These injuries can cause the annulus, the outer layer of the disc, to tear.
A disc bulge is due to tears in the annulus allowing disc material to enlarge the disc in the form
of a bulge; similar to the way an old tire might bulge out. The nucleus (jelly like middle) of the
disc "squirts" through some of the torn annular fibers, but not through all the fibers. This bulge
may press straight back or to either side, depending on location of the annular tears. A bulge may
or may not cause symptoms.
A disc herniation, also called a subligamentous disc, occurs when the nuclear (inner jelly-like
portion of the disc) material protrudes into the tears in the annulus in one area and has displaced
surrounding anatomical structures, like the spinal cord or nerve roots, i.e. pinched nerve.
However, the outer ring of the annulus has not been breached, in other words, no disc material
has completely squirted through the outer edges of the disc.
MRI reports frequently use the term disc protrusion interchangeably with disc herniation. A disc
protrusion generally refers to a broad-based or slightly asymmetric bulging of the disc with an
intact annulus and reflects disc degeneration (see below). Sometimes you may even see the term
focal disc protrusion, which usually means the same thing as a disc herniation.
An extruded disc, or transligamentous disc, occurs when the annulus tears all the way through and
some disc material actually pushes out beyond the boundaries of the disc and nearby ligaments, but
has not broken away from the disc itself.
Finally, a sequestered disc is the end stage of an extruded disc, when the herniated disc material
completely separates from the disc and becomes a free fragment, which floats around, just like a
loose piece of cartilage in the knee.
Two other general terms are used when describing disc herniations: contained and uncontained.
The distinction is important because contained disc herniations generally will respond well to
conservation care (chiropractic adjustments and exercise rehabilitation) while uncontained
disc herniations may not. Contained disc herniations include the terms disc bulge, disc
herniation, disc protrusion and focal disc herniation. Uncontained disc herniations include
the terms extruded disc and sequestered disc. A sequestered disc will need surgical intervention,
while in the case of an extruded disc; conservative care should be tried first with surgery as a
last resort.
Patients with disc herniations in the cervical, thoracic, or lumbar spine can present with neck
pain, back pain, arm pain, leg pain or any combination of the above. The pain may be due to the
bugling or herniated disc pressing on either the spinal cord or a nerve root. If the herniation
occurs in the neck and causes pressure there, it may cause pain that radiates into the shoulder,
arm, and hand; if it occurs in the back, the pain produced may radiate down into the hip, groin,
leg, and foot. Sometimes, patients with large disc herniations can present with weakness in an
extremity or signs of spinal cord compression such as difficulty with gait, incoordination, or
loss of bladder/bowel control. If symptoms include incoordination or loss of bladder/bowel
control, immediate medical attention is necessary.
In many cases, people have disc herniations, but do not have pain. Conversely, the pain that a
patient has may not be completely caused by the disc causing pressure on the nerve. It may come
from the inflammation that occurs at the joints in the spine as well as tightness or spasm of the
surrounding muscles. All these issues must be addressed when treating this problem.
Effective treatment includes many different forms of chiropractic manipulation, Active Release
Technique®, Graston Technique, Kinesiotaping, Ergonomic changes, Postural changes, and proper
rehabilitative exercise.
DISC DEGENERATION (Degenerative Disc Disease)
As a part of the aging process, the discs begin to lose their high water content and their
ability to dissipate force as efficiently. By the age of 35, approximately 30% of people will
show evidence of disc degeneration at one or more levels. By the age of 60, greater than 90%
of people will show evidence of disc degeneration at one or more levels on MRI. In some patients,
this disc degeneration can be asymptomatic; in others, disc degeneration can lead to intractable
back pain. The amount of disc degeneration - what many doctors call degenerative disc disease -
frequently has no relationship to pain at all. Lack of flexibility and muscle weakness must be
addressed when treating disc degeneration.
Disc degeneration cannot be reversed, but can be effectively slowed down and treated with
chiropractic adjustments, exercise, and nutritional support (bromelain for acute pain and
glucosamine supplements for long term care).
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Disc Herniations