Reliability of gadolinium-enhanced magnetic resonance imaging findings and their correlation with clinical outcome in patients with sciatica

Whole-body magnetic resonance neurography in patients with chronic inflammatory demyelinating polyneuropathy

INTRODUCTION/AIMS

Whole-body magnetic resonance neurography (MRN) is an imaging modality that shows peripheral nerve signal change in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). We aimed to explore the diagnostic potential of whole-body MRN and its potential as a monitoring tool after immunotherapy in treatment-naïve CIDP patients.

METHODS

Whole-body MRN using coronal 3-dimensional short tau inversion recovery (STIR) sampling perfection with application-optimized contrasts by using different flip angle evolution (SPACE) techniques was performed in patients being investigated for CIDP and in healthy controls. Baseline clinical neuropathy scales and electrophysiologic parameters were collected, and MRN findings were compared before and after CIDP treatment.

RESULTS

We found highly concordant symmetrical thickening and increased T2 signal intensities in the brachial/lumbosacral plexus, femoral, or sciatic nerves in five of the eight patients with a final diagnosis of CIDP and none of the healthy controls. There were no treatment-related imaging changes in five patients with CIDP who completed a follow-up study. Diffuse, symmetrical thickening, and increased T2 signal in root, plexus, and peripheral nerves were found in two patients ultimately excluded due to a diagnosis of polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin changes (POEMS) syndrome in addition to signal changes in the muscles, bony lesions, organomegaly, and lymphadenopathy.

DISCUSSION

Whole-body MRN imaging shows promise in detecting abnormalities in proximal nerve segments in patients with CIDP. Future studies evaluating the role of MRN in assessing treatment response should consider follow-up scans after treatment durations of more than 4 months.

Gadolinium Enhancement Is Not Associated With Disc Inflammation in Patients With Sciatica

STUDY DESIGN

Retrospective observational histological study.

OBJECTIVE

To evaluate the reliability of gadolinium enhancement as a marker for inflammation by associating gadolinium enhancement findings with the degree of inflammation as measured by macrophage infiltration in disc material retrieved during disc surgery in patients with sciatica.

SUMMARY OF BACKGROUND DATA

Disc inflammation often occurs in sciatica patients, a noninvasive tool that is used to assess disc inflammation is Gadolinium enhanced MR imaging.

METHODS

Disc tissue was retrieved from patients in the Sciatica trial (N = 119), a multicenter randomized controlled trial in patients with sciatica. Disc tissue was embedded in paraffin and stained with hematoxylin and CD68. Tissue samples were categorized as mild (0-10 macrophages/cm), moderate (10-100 macrophages/cm), and considerable (>100 macrophages/cm) inflammation. Of the 119 MRIs, 96 were additionally performed with contrast-enhanced gadolinium.

RESULTS

Seventy-four patients showed gadolinium enhancement of the disc herniation and 26 of the nerve root. Degree of inflammation by macrophages was not associated with gadolinium enhancement of nerve roots or herniated discs. These results did not change if the patient groups with and without Modic type 2 changes were evaluated separately. Furthermore, no associations were observed between gadolinium enhancement and presence of Modic type 2 changes.

CONCLUSION

This study found gadolinium enhanced MRI findings to be unreliable as an indicator for inflammation of disc herniation or nerve root in patients with sciatica.

LEVEL OF EVIDENCE

2.

Locating the Site of Neuropathic Pain In Vivo Using MMP-12-Targeted Magnetic Nanoparticles

Neuropathic pain remains underrecognised and ineffectively treated in chronic pain sufferers. Consequently, their quality of life is considerably reduced, and substantial healthcare costs are incurred. The anatomical location of pain must be identified for definitive diagnosis, but current neuropsychological tools cannot do so. Matrix metalloproteinases (MMP) are thought to maintain peripheral neuroinflammation, and MMP-12 is elevated particularly in such pathological conditions. Magnetic resonance imaging (MRI) of the peripheral nervous system has made headway, owing to its high-contrast resolution and multiplanar features. We sought to improve MRI specificity of neural lesions, by constructing an MMP-12-targeted magnetic iron oxide nanoparticle (IONP). Its in vivo efficiency was evaluated in a rodent model of neuropathic pain, where the left lumbar 5 (L5) spinal nerve was tightly ligated. Spinal nerve ligation (SNL) successfully induced mechanical allodynia, and thermal hyperalgesia, in the left hind paw throughout the study duration. These neuropathy characteristics were absent in animals that underwent sham surgery. MMP-12 upregulation with concomitant macrophage infiltration, demyelination, and elastin fibre loss was observed at the site of ligation. This was not observed in spinal nerves contralateral and ipsilateral to the ligated spinal nerve or uninjured left L5 spinal nerves. The synthesised MMP-12-targeted magnetic IONP was stable and nontoxic in vitro. It was administered onto the left L5 spinal nerve by intrathecal injection, and decreased magnetic resonance (MR) signal was observed at the site of ligation. Histology analysis confirmed the presence of iron in ligated spinal nerves, whereas iron was not detected in uninjured left L5 spinal nerves. Therefore, MMP-12 is a potential biomarker of neuropathic pain. Its detection in vivo, using IONP-enhanced MRI, may be further developed as a tool for neuropathic pain diagnosis and management.

Repeated 3.0 Tesla Magnetic Resonance Imaging After Clinically Successful Lumbar Disc Surgery

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To describe the naturally occurring magnetic resonance imaging (MRI) findings after successful microsurgical removal of lumbar disc herniation with repeated MRI examinations.

SUMMARY OF BACKGROUND DATA

The interpretation of MRI after spinal surgery may be particularly challenging and image findings do not always correlate to clinical findings. Early postoperative MRI has limited value in the evaluation of patients after surgery for lumbar disc herniation.

METHODS

Prospective study of 30 successfully operated patients, which underwent 3.0 T MRI within 24 h after surgery for lumbar disc herniation and repeated at 6 weeks and 3 months postoperatively. Postoperative image findings (nerve root enhancement, nerve root thickening, displacement or compression of the nerve root, and residual mass size and signal) were assessed quantitatively. Inter-rater reliability was tested.

RESULTS

Inter-rater reliability between neuroradiologists was moderate for assessed MRI variables. In the immediate postoperative phase, compression or dislocation of the nerve root at the operated level was common. A residual mass at the operated level was seen in 80%, 47%, and 33% after 24 h, 6 weeks, and 3 months, respectively. Postoperative dislocation or compression of the nerve root from residual masses was seen in 67%, 24%, and 14% after 24 h, 6 weeks, and 3 months, respectively. A residual mass with a higher signal than muscle on T2-weighted images was seen in 80%, 30%, and 17% after 24 h, 6 weeks, and 3 months, respectively.

CONCLUSION

A residual mass with compression or dislocation of the nerve root at the operated level, that disappears over 3 months, is a common MRI finding in patients successfully operated for symptomatic lumbar disc herniation. An expectant approach instead of early reoperations may perhaps be preferred in patients with residual pain and root compression due to residual masses with high T2-signal since these often seem to resolve spontaneously.

LEVEL OF EVIDENCE

3.