Degenerative Disc
Disease
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It is so common that
it is almost a "normal" part of our aging process. Medical studies
show that by the age of 35, 30% of people have a degenerated disc at one or
more levels in their lumbar spine. By age 60, that figure is over 90%.
The
intervertebral discs are cartilaginous plates surrounded by a fibrous ring
which lie between the vertebral bodies and serve to cushion them. Through
degeneration, wear and tear, or trauma, the fibrous tissue (annulus fibrosus) constraining the soft disc material (nucleus
pulposus) may tear. This results in protrusion of the disc or even extrusion of
disc material into the spinal canal or neural foramen. This has been called
herniated disc, ruptured disc, herniated nucleus pulposus, or prolapsed disc.
The
discs act as cushions between our vertebral bones, and as a part of walking
upright and placing stress upon our backs, these discs can start to wear out.
This is similar to a tire on a car. If you drive around a car long enough, the
tires will begin to go bald. A degenerative disc is similar to a balding tire.
Sometimes, a bald tire can become a flat tire, just as a degenerative disc can
tear and become a ruptured disc. A degenerative disc can cause problems two
ways then. It can cause local pain, if it occurs in the neck it can cause neck
pain, and if it occurs in the back it can cause back pain. Occasionally, a
degenerative disc can rupture and irritate an adjacent nerve causing pain to
radiate into an extremity. The characteristics of a degenerative disc are best
seen on an MRI.
In
the image to the left, normal discs are indicated by the white lines. In this
part of the MRI, everything that has a lot of fluid appears white. You will
notice that the normal discs have a whitish appearance to them indicating a
high fluid content. The white arrow indicates a characteristic degenerative
disc. You will notice a few things that are different about this disc. First,
it is black compared to the whitish color of the other discs. This indicates it
has a low fluid content indicating dehydration/degeneration. You will also notice
that the disc "bulges" out the back somewhat compared to the other
discs which appear flat. The significance of this posterior protrusion of the
degenerated disc is that this is the area where the nerves run that supply the
extremities. This patient was complaining of back and leg pain.
The vast majority of patients respond well to non-surgical treatment. Probably
the most important of which is time. That is to say, that no matter what is
done, most cases of acute back and neck pain slowly resolve if given enough
time to get better. Active interventions include the use of medications,
exercises/therapy, activity modifications, epidural cortisone(steroid)
injections/nerve root blocks, etc. It is only a small
percentage that ultimately require surgery.
Disc
Herniation
The intervertebral discs are cartilaginous plates surrounded by
a fibrous ring which lie between the vertebral bodies and serve to cushion
them. Through degeneration, wear and tear, or trauma, the fibrous tissue
(annulus fibrosus) constraining the soft disc
material (nucleus pulposus) may tear. This results in protrusion of the disc or
even extrusion of disc material into the spinal canal or neural foramen. This
has been called herniated disc, ruptured disc, herniated nucleus pulposus, or
prolapsed disc.
This
disc herniation may become significant if a nerve root is compressed.
Irritation of the nerve root produces pain in the distribution of that nerve,
typically down the back of the leg, side of the calf, and possibly into the
side of the foot. For this reason, a herniated lumbar disc characteristically
produces sciatica but not back pain per se. If sensory function of the impinged
nerve root is impaired, numbness will result. The exact area of numbness is
determined by the particular root, and may be in the inner ankle, the great
toe, the heel, the outer ankle, the outer leg, or a combination of these.
Impairment of motor function of the root will cause weakness which again
depends on the particular root, and may include weakness of bringing the ankle upward
or downward or raising the great toe.
The
L5-S1 disc is involved 45-50% of the time, L4-5 40-45%, and L3-4 about 5%. Disc
herniation at the other lumbar levels is rare.
Myelography with CT has
long been the gold standard, because of its excellent definition of the spaces
around the nerve roots. Its disadvantage is that it requires injection of
contrast dye through a lumbar puncture. It has to a large extent been
supplanted by MRI, but it should be viewed as a complementary rather than an
alternative test, and in many cases it is indispensable.
The
mainstay of therapy for herniated lumbar disc is conservative treatment, that
is, non-surgical. Treatment for patients with disc disorders must be
individualized to the patient. It is based on the length and severity of their
complaints, whether or not they have had prior treatments for this problem and
how they have worked, and whether or not there is any evidence of neurologic
damage such as weakness of an extremity or the loss of reflexes. Some of the
treatments used include physical therapy, anti-inflammatory medication, braces,
epidural steroid injections, or modalities such as heat, ultrasound, electrical
stimulation and massage When non-surgical means fail, and the patient no longer
wants to put up with the pain, surgery is the next appropriate step.
Surgery
for removal of a herniated lumbar disc is one of the most commonly performed procedure in this country. Surgery for patients with disc
disorders of the spine is usually reserved for those who have failed
conservative treatment. An exception to this is the patient with a neurologic
deficit in this patient, it is wise to consider early
surgical decompression to maximize the likelihood of neurologic recovery. An
incision is made vertically along the midline of the back, usually about 2
inches long. Some of the muscle overlying the bone which forms the back of the
spinal canal, called the lamina, is separated off the bone. The procedure is
performed with an operating microscope. A small window is drilled in the
laminae, about the size of a finger nail, overlying the disc herniation. The
nerve root is identified and gently retracted away to expose the offending disc
herniation. The disc material is then removed and the wound is closed in a way
which restores the normal anatomic layers.
Postoperative
recovery is relatively short. Patients are up walking the same night and
discharged home the next day. The vast majority of patients experience
permanent relief of pain. Recovery of motor function is variable. Relief of leg
pain depends upon how badly the nerve has been compressed and for how long.
Some patients are relieved of pain immediately, while others may take months to
be rid of all of the pain.
General Data
radiculopathy-dysfunction of a nerve root with pain, sensory
disturbances, weakness, and hypoactive reflexes in that root's distribution.
myelopathy-spinal
cord compression with weakness, increased tone, hyperactive reflexes, gait
difficulties, and possible bowel/bladder signs.
sciatica-radiculopathy
of a root contributing to the sciatic nerve (L4, L5, or S1).
mechanical low back pain-may result from strain of the paraspinal muscles and/or ligaments or irritation of facet
joints. No anatomically identifiable lesion. The most common
form of low back pain.
Most common cervical disk herniation is
at the C6/7 level (70%), C5/6 is 20%.
Lumbar disk herniations
are most common at L5/S1 (45%) and L4/5 (40%).
Neurogenic claudication is pain in the distribution of a nerve that is incited by variable
amounts of exercise or prolonged maintenance of a given posture in a patient
who has narrowing of the spinal canal due to degenerative changes in the facet
joints or hypertrophy of the ligamentum flavum (yellow ligament). The pain is slowly relieved with
rest and peripheral pulses as well as skin temperature of the feet are normal,
all of which help to distinguish neurogenic claudication
from vascular claudication. Treated
with decompressive/foraminotomy at the appropriate
levels.
Degenerative disc disease (DDD)
It is part of the natural process of growing older.
Unfortunately, as we age, our intervertebral discs lose their flexibility,
elasticity, and shock absorbing characteristics. The ligaments that surround
the disc called the annulus fibrosis, become brittle and they are more easily
torn. At the same time, the soft gel-like center of the disc, called the
nucleus pulposus, starts to dry out and shrink. The combination of damage to
the intervertebral discs, the development of bone spurs, and a gradual
thickening of the ligaments that support the spine can all contribute to
degenerative arthritis of the lumbar spine.
Degenerative disc disease is as certain as death and taxes,
and to a certain degree this process happens to everyone. However, not everyone
who has degenerative changes in their lumbar spine has pain. Many people who
have "normal" backs have MRIs that show
disc herniations, degenerative changes, and narrowed
spinal canals. Every patient is different, and it is important to realize that
not everyone develops symptoms as a result of degenerative disc disease.
When degenerative disc disease becomes painful or
symptomatic, it can cause several different symptoms, including back pain, leg
pain, and weakness that are due to compression of the nerve roots. These
symptoms are caused by the fact that worn out discs are a source of pain
because they do not function as well as they once did, and as they shrink, the
space available for the nerve roots also shrinks. As the discs between the
intervertebral bodies start to wear out, the entire lumbar spine becomes less
flexible. As a result, people complain of back pain and stiffness, especially
towards the end of the day.
Symptoms
The most common symptom of degenerative disc disease
is back pain. When DDD causes compression of the nerve roots, the pain often
radiates down the legs or into the feet, and may be associated with numbness
and tingling. In severe cases of lumbar DDD, where there is evidence of nerve
root compression, individuals may experience symptoms of sciatica and back
pain, and sometimes even lower extremity weakness.
Diagnosis
The diagnosis of degenerative disc disease begins with
a complete physical examination of the body, with special attention paid to the
back and lower extremities. Your doctor will examine your back for flexibility,
range of motion, and the presence of
certain
signs that suggest that your nerve roots are being affected by degenerative
changes in your back. This often involves testing the strength of your muscles
and your reflexes to make sure that they are still working normally. You will
often be asked to fill out a diagram that asks you where your symptoms of pain,
numbness, tingling and weakness are occurring.
A routine set of x-rays is also usually ordered when a
patient with back pain goes to see a doctor. If degenerative disc disease is
present, the x-rays will often show a narrowing of the spaces between the
vertebral bodies, which indicates that the disc has become very thin or has
collapsed. Bone spurs begin to form around the edges of the vertebral bodies
and also around the edges of the facet joints in the spine. These bone spurs
can be seen on an x-ray, where they are called osteophytes. As the disc
collapses and bone spurs form, the space available for the nerve roots starts
to shrink. The nerve roots exit the spinal canal through a bony tunnel called
the neuroforamen, and it is at this point that the
nerve roots are especially vulnerable to compression.
In many situations, doctors will order a MRI or a CT scan in
order to evaluate the degenerative changes in the lumbar spine more completely.
A MRI scan is very useful for determining where disc herniations
have occurred and where the nerve roots are being compressed.
Treatment
Your doctor will be able to discuss with you what your
diagnosis means in terms of treatment options. For most people who do not have
evidence of nerve root compression with muscle weakness, the first line of
therapy includes non-steroidal anti-inflammatory drugs and physical therapy. A
soft lumbar corset is often prescribed in order to allow the back to have a
chance to rest. Surgery is offered only after physical therapy, rest, and
medications have failed to adequately relieve the symptoms of pain, numbness
and weakness over a significant period of time