The disc
is made up of connective tissue, which wears normally as
we age. However, many of the problems that cause neck pain
are from abnormal wear and tear. This process is called
degeneration of the intervertebral disc.
Degeneration often results from small injuries that may
not cause pain at the time the injuries actually occur.
Over time, these injuries add up and the abnormal wear and
tear can weaken the connective tissue that makes up the
disc. Once the connective tissue is weak, sudden stress,
such as a whiplash type movement, may injure the disc more
easily. The entire process of disc degeneration is sometimes
referred to as spondylolysis. You may hear your doctor refer
to your neck problem as spondylolysis of the cervical spine.
To really understand neck
pain, you need an understanding of the wear and tear process,
called disc degeneration. This will also help you later
understand what can happen to the neck when a sudden injury
can cause immediate pain and dysfunction. The next section
will explain both the process of degeneration and the
most common causes of pain in the neck.
Degenerative
Disc Disease
To help
you understand disc degeneration, compare a spinal segment
to two vanilla wafers (the "vertebrae") and
a marshmallow (the "disc"). Imagine a fresh
marshmallow between the two wafers. When you press the
wafers close together, the marshmallow gives or "squishes
out". Suppose you leave the marshmallow out for a
week and it starts to dry out. When you press it between
the wafers, it is not quite as spongy. If you press hard
enough, the outside of the marshmallow may even tear or
split. Suppose you left the marshmallow out for a month.
It would probably be so dried out it would be hard and
very thin and would not have any "shock absorbing"
ability.
As we age, the disc loses
some of its water content and, as a result, some of its
shock absorbing ability. Like the marshmallow, the first
changes that occur in the disc are tears in the outer
ring of the disc, called the annulus. Tears in the annulus
may occur without symptoms. Therefore, you may not notice
when they occur or what caused them. These tears heal
by forming scar tissue. Scar tissue is weaker than normal
tissue. Repeated injuries and tears cause more wear and
tear to the disc. As the disc wears, it loses more of
its water content. It becomes less and less "spongy",
eventually no longer able to act as a shock absorber.
As the disc continues
to wear, it begins to collapse. The space between each
vertebra becomes smaller. The collapse also affects the
way that the facet joints in the back of the spine "line
up". Like any other joint in the body, the change
in the way the bones fit together causes abnormal pressure
on the articular cartilage. Articular cartilage is the
smooth shiny material that covers the end of the bones
in any joint. Over time, this abnormal pressure causes
wear and tear arthritis (osteoarthritis) of the facet
joints.
Bone spurs may form around
the disc and facet joints. It is thought that too much
motion in a spinal segment causes the bone spurs to form.
Eventually, bone spurs can form around the nerves of the
spine, causing a condition called spinal stenosis.
Spinal
Conditions
Degeneration
of the disc and spinal segment can result in several different
spinal conditions that cause problems. These include:
mechanical neck pain, cervical radiculopathy, and spinal
stenosis. Sometimes we may injure our neck with a relatively
minor injury. These minor injuries may cause neck pain
for a few days and then go away. This is commonly referred
to as a neck, or muscle strain. Actually, we may never
fully understand what has been injured in one of these
episodes.
Muscle
Strain Of Neck
A "muscle strain"
of the neck is a common diagnosis given when a patient
presents a stiff neck. In some cases, this may represent
a true "muscle strain", or "pulled muscle"
involving the muscles around the spine of the neck. However,
muscle spasm is a common symptom that can result when
other areas of the neck are injured. Problems that are
commonly referred to as a muscle strain may also involve
injury of other soft tissues of the neck including: the
disc, the ligaments around the spinal segment, and the
muscles. Injury to any, or all, of these structures may
cause similar symptoms.
Mechanical Neck
Pain
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