Sometimes making a diagnosis
is like taking a leap of faith. Take sciatica for example,
which is caused by the pinching of the sciatic nerve.
The condition is assumed to be the result of a damaged
disc in the lower back even though the sciatic nerve cannot
be visualized, continually frustrating efforts to better
understand and treat this often devastating affliction.
Fortunately, a study using a new imaging technique called
magnetic resonance neurography (MRN) may shed some light
on its real causes.
"For the past 70 years, sciatica
has been thought to be caused by a herniated disc and
treated as such. But our study shows that it's time
for a major reassessment of how patients will be evaluated
and treated for sciatica in the future," said Dr J Patrick
Johnson, senior author of the study published in the
February issue of the Journal of Neurosurgery: Spine.
The paper reports that in the majority of sciatica patients
whose diagnosis can't be confirmed by MRI and/or who
were unsuccessfully treated surgically, their problem
lies not with a damaged disc, but with a pinched nerve
in the pelvis also called piriformis syndrome.
The MRN technique was developed
by Dr Aaron Filler, the study's lead author and a neurosurgeon
at Cedars-Sinai Medical Center in Los Angeles. In a
nutshell, MRN couples MRI to new software and hardware
to enable us to view detailed images of nerves anywhere
in the body.
Dr Filler and his colleagues decided
to use MRN's visualizing power to unravel the sciatica
mystery. They recruited 239 patients whose sciatica
had not improved following strategies aimed at dealing
with a damaged or herniated disc.
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Nine folks were indeed found to have disc trouble that
had until then eluded diagnosis and were successfully
treated via spine surgery. Of the remaining 232 patients
who underwent the MRN procedure, 162 (69%) were found
to have piriformis syndrome. The rest had a variety
of nerve, muscle or joint ailments that had escaped
MRI detection. Of the 62 patients with the syndrome
who had surgery, 51 had a great outcome, as shown by
the assessment over the next six years.
"Although sciatica is the most
common condition treated by neurosurgeons, piriformis
syndrome is not even mentioned in the majority of neurosurgery
textbooks and no more than a handful of surgeons are
trained to treat it," wrote Dr Filler. This good news
about the nature of sciatica is sadly tempered by the
lack of easy access to MRN, and specialists who can
treat it.
J Neurosurg
Spine Feb, 2005 2:99-115
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