My Spine - Lumbar
Figure 2.2
These two illustrations demonstrate
the dermatomes of the body. A der-
matome is the area of the skin that is
being supplied with sensation by a spe-
cific spinal nerve.
Your specialist will use this map to get
an idea of which nerve is being com-
pressed in nerve root mediated pain
(radiculopathy). ote for instance that
compression of the fourth lumbar
nerve (L4) will cause pain over the
shin and compression of the fifth nerve
root (L5) will cause pain over the outer
part of the shin and on top of the foot.
The whole body is divided into der-
matomes and the dermatome map is an
invaluable aid for your specialist.
These areas are, however, not com-
pletely fixed and there is some overlap
and certainly differences between the
exact location of dermatomes from
patient to patient.
It is important to confirm the nature of nerve compression with an MRI scan
or CT myelogram (see the chapter Tests and Scans). Radicular or nerve root
pain is felt in a specific dermatome and should not be confused with referred
pain, which is pain that spreads from inflamed tissue such as the disc and the
facet joints to non-specific areas on the skin. These referred pains are fre-
quently said to be non-dermatomal, indicating that, as they do not comply
with dermatomal patterns, they are unlikely to be nerve root-related pain.
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