FEBRUARY 28, 2005
VOLUME 2 NO. 4
 

New imaging technique turns sciatica diagnosis on its head

MR neurography adds a pelvic twist to the sciatica story


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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