Magnetic resonance neurography (MRN) is the direct imaging of nerves in the body by optimizing selectivity for unique MRI water properties of nerves.
It is a modification of magnetic resonance imaging yielding a detailed image of a nerve from the resonance signal that arises from in the nerve itself rather than from surrounding tissues or from fat in the nerve lining.
It has an intraneural source for the image signal.
The image provides a medically useful set of information about the internal state of the nerve such as the presence of irritation, edema, compression, pinch or injury.
Standard magnetic resonance images can show the outline of some nerves in portions of their courses but do not show the intrinsic signal from nerve water.
Magnetic resonance neurography can evaluate major nerve compressions such as those affecting the sciatic nerve (piriformis syndrome), the brachial plexus nerves (thoracic outlet syndrome), the pudendal nerve, or any named nerve in the body.
A related technique for imaging neural tracts in the brain and spinal cord is called magnetic resonance tractography or diffusion tensor imaging.
Magnetic resonance imaging (MRI) is based on differences in the physical properties of protons in water molecules in different tissues in the body.
The protons and the water molecules of which they are part have subtly different movement characteristics that relate to their biophysical surroundings.
Because of this, MRI is capable of differentiating one tissue from another; this provides tissue contrast.
Further, because they demonstrate water signal arising in the neural tissue itself, they can also reveal abnormalities that affect only the nerve and that do not affect surrounding tissues.
Diffusion MRI phenomenon to show contrast between white matter and grey matter in the brain.
MR neurography can show nerve injury and irritation.
The most significant impact of MRI neurography is on the evaluation of the large proximal nerve elements such as the brachial plexus, the lumbosacral plexus, the sciatic nerve in the pelvis, as well as other nerves such as the pudendal nerve that follow deep or complex courses.
Neurography improves image diagnosis in spine disorders, helping to identify which spinal nerve is actually irritated as a supplement to routine spinal MRI.
Standard spinal MRI only demonstrates the anatomy and numerous disk bulges, bone spurs or stenoses that may or may not actually cause nerve impingement symptoms.
Magnetic resonance neurography has greatly expanded the efficacy of nerve diagnosis by allowing uniform evaluation of virtually any nerve in the body.
MRI neurography uses optimized sequences and high-resolution imaging to visualize the nerves highlighting nerve injuries, compressions, inflammation, tumors, or other abnormalities.
This provides detailed information about the internal state of nerves, such as swelling or signal changes due to injury, which is often unattainable with conventional imaging or electrodiagnostic studies.
Its clinical uses include:
Identifying and localizing nerve compressions or entrapments.
Differentiating between nerve and muscle pathology.
Preoperative planning, especially for nerve injuries or tumors.
Assessment of conditions like brachial plexopathy, thoracic outlet syndrome, sciatic nerve entrapment, and peripheral nerve sheath tumors.
MR neurography has a limited but potentially adjunctive role in evaluating the causes .
MR neurography can help identify cranial nerve involvement in conditions such as neuralgic amyotrophy or chronic inflammatory demyelinating polyneuropathy, especially when conventional MRI is inconclusive.
The primary role of MR neurography in this context is limited to select cases where peripheral cranial nerve pathology is strongly suspected and conventional MRI is non-diagnostic.