Magnetic Resonance Neurography

Taking Pictures of Sciatica

Woman enters an MRI machine.
Having an MRI. Chris Ryan/ OJO Images/ Getty Images

MR Neurography

MR Neurography, also known as either magnetic resonance neurography or MRN, is a type of MRI that shows clearly what’s going on in your nerves.  It was first developed in the early 1990s, and since then numerous studies have been done that attest to its ability to help doctors truly see the condition of nerves.

For example, Zhang, et., al., examined magnetic resonance neurographs of 137 patients who had sciatica.

  Some of these patients had nerve root compression, a spinal condition in which a herniated disc or other structure presses on the nerve at the place where it branches off from the spinal cord. Most people call the resulting symptoms of a nerve root compression, in other words – pain, weakness, numbness, pins and needles, tingling, electrical shock and/or other electrical feelings all down one leg only - sciatica. The researchers reported that in all 137 images, the picture was clear.  They said they could see the sciatic nerve, and that its main branches were differentiated and easily visible.

Related:  3 Common Causes of Sciatica

Zhang’s study, entitled “Morphological analysis in patients with sciatica: a magnetic resonance imaging study using three-dimensional high-resolution diffusion-weighted magnetic resonance neurography techniques,” was published in the April 2009 issue of the journal Spine.

Nerve Entrapment and Sciatica

MR neurography can show where nerves are entrapped, and it is used to evaluate the brachial plexus for symptoms felt in the neck, shoulders and/or arms.  As far as sciatica goes, it can show piriformis syndrome which is a condition in which your sciatic nerve becomes compressed by a tight or misaligned hip muscle known as the piriformis.

Related:  Piriformis Syndrome

Up until the development of MRN (and currently, as well), radiologists relied on x-rays, MRI, CT scans and nerve conduction tests to determine the causes of nerve symptoms. To a great extent, then, their determinations were made indirectly.  But now, with this still relatively new imaging test, some doctors say they are able to more confidently diagnose nerve problems, including rare conditions often otherwise overlooked in the process.

In his study entitled “Magnet resonance neurography and diffusion tensor imaging: origins, history and clinical impact of the first 50,000 cases with an assessment of efficacy and utility in a prospective 5000 patient study group,” which was published in the October 2009 issue of the journal Neurosurgery, MRN originator Aaron Filler says that neurography shows a number of things relevant to a clinical diagnosis including: Mechanical distortion of nerves, hyperintensity (i.e., nerve irritation), nerve swelling, discontinuity, relations of nerves to masses, and image features revealing distortion of nerves at entrapment points.

  Filler comments that these findings are comparable to the kinds of things nerve conduction tests may reveal.

While MRN is good for showing the condition of peripheral nerves, a related technology, known as diffusion tensor imaging, reveals the inside of the brain and spinal cord.  Generally, diffusion tensor imaging is studied right alongside MRN.

Related:  How Much Radiation are You Exposed to During a Diagnostic Imaging Test?

Sources:

Filler, A., Magnetic resonance neurography and diffusion tensor imaging: origins, history, and clinical impact of the first 50,000 cases with an assessment of efficacy and utility in a prospective 5000-patient study group. N eurosurgery. 2009 Oct;65(4 Suppl):A29-43. doi: 10.1227/01.NEU.0000351279.78110.00. http://www.ncbi.nlm.nih.gov/pubmed/19927075

Zhang Z1, Song L, Meng Q, Li Z, Pan B, Yang Z, Pei Z. Morphological analysis in patients with sciatica: a magnetic resonance imaging study using three-dimensional high-resolution diffusion-weighted magnetic resonance neurography techniques. Spine (Phila Pa 1976). 2009 Apr 1;34(7):E245-50. doi: 10.1097/BRS.0b013e318197162e. http://www.ncbi.nlm.nih.gov/pubmed/19333087

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