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MR Neurography from the Sonomed Imaging Center, Turkey

Best Practice
Baskan, Ozdil, M.D. Istanbul, Sonomed Imaging Center Turkey

MR Neurography

Magnetic resonance imaging (MRI) of peripheral nerves is useful in combination with standard neurological examinations and electrophysiological studies in the diagnosis of peripheral nerve disorders. MRI can define the location of nerve root pathology and secondary findings of muscle denervation.

 

MR neurography (MRN) is capable of generating high resolution images in both the longitudinal and cross sectional planes of major peripheral nerves. MRN has diagnostic utility because it is effective for demonstrating continuity, morphology and response to injury (edema) associated with many kinds of pathology.

 

The use of phase array coils has produced images with improved signal-to-noise and better resolution, improving the ability to visualize both normal and abnormal peripheral nerves.

Indications

Nerve root compression or entrapment

MRI is used to find the cause of entrapment, guided to the location of the compression by the physical findings and electrophysiological studies. Common causes of peripheral entrapment include fibrous adhesions, bands, adjacent bony structures and ganglion cysts.

 

Inflammation of adjacent fascial planes can cause secondary compression of peripheral nerves.

Secondary nerve compression can also be due to elevated pressure in an enclosed compartment due to trauma or inflamation (compartment syndrome).

 

MRN can also be used to evaluate patients with radiculopathy. 

Malignancy or pheripheral nerve masses

MRI shows the soft tissue extent of these lesions and is useful for both diagnosis and treatment planning (surgical or radiation).

Trauma

MRI may also be useful in evaluating patients with acute peripheral nerve trauma or direct nerve lacerations by localizing the site of the nerve injury pre-operatively.

Unexplained mononeuropathy and other peripheral nerve disorders

Inflammatory processes can inflame the plexus (brachial-lumbosacral) or peripheral nerves. Typical image findings include enlargement of the nerves, hypertrophy and abnormal contrast enhancement.

 

Technique

MRN is performed with a high-resolution fast spin echo imaging technique. Standard T1-weighted sequences are used to show the anatomical detail, as well as to define the bony structures and tissue planes surrounding the nerves.

 

Fat-supressed T2-weighted and STIR sequences are used to characterize lesions.

 

Gadolinium enhanced nerve imaging is limited. However it can be used in the evaluation of peripheral nerve tumors, neoplastic infiltration and postoperative procedures.

 

Our studies are well tolerated by the patients, with most of them being completed within 45 minutes. Images are obtained in at least two planes. Studies begin with sequences with a large FOV, so as to localize the exact position of the pathology.

 

Tip:

The 3-points Planscan method (3PPS) is used after defining the nerves' plane perpendicular to the longitudinal trace. This enables viewing the nerves and the pathological changes in a single slice, which is obtained in a shorter time.

 

It has also been discovered that T2-weighted TSE images are also valuable in defining anatomical details.

 

Clinical examples

Case 1: Bilateral peroneal compartment syndrome

A 29-year-old female presented with bilateral drop foot after loosing a 35 kg weight in a period of 6 months due to following a strict diet.

 

For the MRI study the Knee-Foot coil was used in combination with the Microscopy 47mm coil.

 

Conclusion:

Right knee - the images demonstrate a bright signal in the peroneal supplied muscles. The motor strength was measured to be 3/5. Proximal to the fibular head an abnormal increased signal was detected, on the sagittal/oblique ProSet images, of the peroneal nerve (white arrows).

 

Left knee - the images of the T2W fat suppressed series demonstrate a minimal, but abnormal, increased signal in the peroneal nerve. The abnormal segment is also shorter when compared with the right knee. However there were no abnormal signals detected in the muscles.

 

Note: Click on the images to enlarge them.

Right knee

Sagittal/oblique T2W TSE SPIR Axial T2W TSE SPIR Sagittal/oblique ProSet
Sagittal/oblique T2W TSE SPIR
Axial T2W TSE SPIR
Sagittal/oblique ProSet

Left knee

Coronal/oblique ProSet Coronal /oblique T2W TSE Coronal/oblique T1W TSE
Coronal/oblique ProSet
Coronal /oblique T2W TSE
Coronal/oblique T1W TSE

Case 2: Axillary schwannoma.

A 30-year-old female presented with a nodule in the left axillary region. A mass was detected distal to the brachial plexus at the level of the axillary nerve.

 

For the MRI study the SENSE Cardiac coil was used in combination with the SENSE Flex-M coil.

 

Conclusion:

The mass was an axillary schwannoma.

 

Note: Click on the images to enlarge them.

Sagittal/oblique T2W TSE Sagittal/oblique ProSet Axial T1W TSE SPIR<br> post-contrast
Sagittal/oblique T2W TSE
Sagittal/oblique ProSet
Axial T1W TSE SPIR
post-contrast

Case 3: Suspected thoracic outlet syndrome.

A 30-year-old male presented with pain in the left arm. Thoracic outlet syndrome was suspected. Compression to the subclavian vein was detected when the arm was in the abduction position during a doppler ultrasonography study. The clinician's question was if the brachial plexus was also affected.

 

For the MRI study the SENSE Cardiac coil was used.

 

Conclusion:

An old fracture of the first costa was noted on the MRI images. With the patient lying in a neutral position, an indentation to the subclavian vein was also noted. However there was no indentation to the brachial plexus. There were also no abnormal nerve signals detected.

 

Note: Click on the images to enlarge them.

Coronal T2W TSE SPIR Coronal T1W TSE Axial/oblique T1W TSE
Coronal T2W TSE SPIR
Coronal T1W TSE
Axial/oblique T1W TSE

Case 4: Suspected nodular swelling in the ankle

A 47-year-old male presented with a swelling at the level of the medial malleolus. The clinician wanted to exclude the possibility of a neural tumour.

 

For the MRI study the Microscopy 47mm coil was used.

 

Conclusion:

At the medial malleolus level the tibial and medial- lateral plantar nerves were normal with no mass detected.

Axial T2W TSE Axial T1W TSE Coronal/oblique T1W TSE
Axial T2W TSE
Axial T1W TSE
Coronal/oblique T1W TSE

Conclusion

MRI imaging of peripheral nerves is useful in the evaluation of a broad range of disorders. MRI can define the specific location of nerve entrapment and compression, post-traumatic changes and diagnose primary tumours together with malignant infiltration and invasion. MRI can also detect secondary findings of muscle denervation.

 



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