Radiological testing:
Magnetic resonance imaging (MRI)
What it is:
It consists of the placement of a patient in the center of a very
intense magnetic field of a specific frequency. The machine's magnetic
pull directs the electrons of certain body substances toward the
magnetic field's source. At that moment, an image is captured, showing
the shape of the tissues formed by that substance.
What it allows:
MRI is the process that permits a better viewing of "soft tissues",
that is, all non-bony spinal components, such as the intervertebral
disc, the spinal cord or nerve roots, or the presence of postoperative
fibrosis. Although it allows bone imaging, bone is better seen
with CT scans.
Risks:
MRI does not expose the patient to any potentially hazardous radiation
and is painless. It requires the patient to be still during 15 minutes
in a small tunnel, which may be unpleasant for nervous persons or
those with a tendency to claustrophobia.
Indications:
MRI is the procedure of choice when soft tissues, such as intervertebral
discs, must be visualized. Some of the existing recommendations
based on scientific evidence advise performing an MRI:
- Immediately in those cases where:
- It is suspected that the back pain has causes other than
common
back pain, for example in patients with a previous history
of cancer or those who present with a widespread neurological
deficit.
- Data suggest the need for urgent surgery, such as sphincter
disturbance -patient has no urinary or fecal control -, severe
or progressive motor loss, or saddle anesthesia (complete
absence of perineal and inner upper thigh sensitivity).
- After the recommended 6-week wait, in patients with sciatica
-leg radiating pain following the nerve root pathway- which is
resistant to treatment.
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Diagnostic tests
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