Chemonucleolysis
Chemonucleolysis is an interventional procedure that aims at treating back pain and
sciatica resulting from a bulging or herniated disc with percutaneous injection of the
enzyme chymopapain, under fluoroscopy and CT guidance. Chymopapain causes dissolution of
the nucleus pulposus. A discography usually precedes injection of the enzyme. This
technique, which is considered controversial, because of both questionable clinical
indications and possible severe side effects, is progressively being replaced by
percutaneous aspiration of disc material (Onik technique) (see discectomy). Also, see
chemonucleolysis.
Purpose for Chemonucleolysis
Between each vertebra lies a disk of cushioning material that keeps the spinal bones
from rubbing together and absorbs some of the shock to the spine from body movements. In
the center of the disk is soft, gelatinous material called the nucleus pulposus (NP). The
NP is surrounded by a tough fibrous coating. Sometimes when the back is injured, this
coating can weaken and bulge or tear to allow the NP to ooze out. When this happens, it is
called a herniated nucleus pulposus (HNP), or -- in common language -- a herniated disk.
When the disk bulges or herniates, it can put pressure on nerves which originate in the
spinal column, and go to other parts of the body. This causes lower back pain, and/or pain
to the hips, legs, arms, shoulders, and neck, depending on the location of the herniated
disk. Chemonucleolysis uses chymopapain, an enzyme derived from papyrus, to dissolve the
disk material that has been displaced because of injury. Herniated disks are the cause of
only a small proportion of cases of lower back pain, and Chemonucleolysis is appropriate
for only some cases of HNP.
Chemonucleolysis is a conservative alternative to disk surgery. There are three types
of disk injuries. A protruded disk is one that is intact but bulging. In an extruded disk,
the fibrous wrapper has torn and the NP has oozed out, but is still connected to the disk.
In a sequestered disk, a fragment of the NP has broken loose from the disk and is free in
the spinal canal. Chemonucleolysis is effective on protruded and extruded disks, but not
on sequestered disk injuries. In the United States, chymopapain. Chemonucleolysis is
approved only for use in the lumbar (lower) spine. In other countries, it has also been
used successfully to treat cervical (upper spine) hernias.
Other indications that a patient is a good candidate for chemonucleolysis instead of
surgery include:
- The patient is 18-50 years of age
- Leg pain is worse than lower back pain
- Other conservative treatments have failed
- The spot where the herniated disk presses on the nerve has been pinpointed by
myelography, computed tomography scan (CT scan), or magnetic resonance imaging (MRI)
- The patient wishes to avoid surgery.
Precautions before Chemonucleolysis
There are some situations in which chemonucleolysis should not be performed.
Chymopapain is derived from the papaya. About 0.3% of patients are allergic to chymopapain
and go into life-threatening shock when exposed to the enzyme. Chemonucleolysis should not
be performed on patients allergic to chymopapain or papaya. It also should not be done:
- When the patient is pregnant
- If the disk is sequestered
- If the patient has had several failed back operations
- If a spinal cord tumor is present
- If the patient has a neurological disease such as multiple sclerosis.
Other conditions may affect the appropriateness of chemonucleolysis, including
hypertension, obesity, diabetes, and a family history of strokes.
Description of Chemonucleolysis
A small gauge needle is placed in the center of the affected disk. Chymopapain is
introduced into the disk. The patient needs to remain still.
Preparation for Chemonucleolysis
Patients will need tests such as a myelogram or CT scan to pinpoint the herniated disk.
Some doctors medicate the patient 24 hours prior to the operation in order to decrease the
chances of post-operative lower back stiffness.
Aftercare
Patients may feel lower back stiffness, which goes away in few weeks. Heavy lifting and
sports activities should be avoided for at least three months.
Risks
The greatest risk is that the patient may be allergic to chymopapain. The death rate
for chemonucleolysis is only 0.02%. Complications overall are 5-10 times less than with
conventional surgery, and the failure rate is roughly comparable to the failure rate in
conventional disk surgery.
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