The Incremental Value of Magnetic Resonance Neurography for the Neurosurgeon: Review of the Literature

Intravenous contrast does not improve detection of nerve lesions or active muscle denervation changes in MR neurography of the common peroneal nerve

OBJECTIVE

To evaluate the effect of intravenous (IV) contrast on sensitivity, specificity, and accuracy of magnetic resonance (MR) neurography of the knee with attention to the common peroneal nerve (CPN) in identifying nerve lesions and active muscle denervation changes.

MATERIALS AND METHODS

A retrospective search for contrast-enhanced MR neurography cases evaluating the CPN at the knee was performed. Patients with electrodiagnostic testing (EDX) within 3 months of imaging were included and those with relevant prior surgery were excluded. Two radiologists independently reviewed non-contrast sequences and then 4 weeks later evaluated non-contrast and contrast sequences. McNemar's tests were performed to detect a difference between non-contrast only and combined non-contrast and contrast sequences in identifying nerve lesions and active muscle denervation changes using EDX as the reference standard.

RESULTS

Forty-four exams in 42 patients (2 bilateral) were included. Twenty-eight cases had common peroneal neuropathy and 29, 21, and 9 cases had active denervation changes in the anterior, lateral, and posterior compartment/proximal muscles respectively on EDX. Sensitivity, specificity, and accuracy of non-contrast versus combined non-contrast and contrast sequences for common peroneal neuropathy were 50.0%, 56.2%, and 52.3% versus 50.0%, 56.2%, and 52.3% for reader 1 and 57.1%, 50.0%, and 54.5% versus 64.3%, 56.2%, and 61.4% for reader 2. Sensitivity, specificity, and accuracy of non-contrast and combined non-contrast and contrast sequences in identifying active denervation changes for anterior, lateral, and posterior compartment muscles were not significantly different. McNemar's tests were all negative.

CONCLUSION

IV contrast does not improve the ability of MR neurography to detect CPN lesions or active muscle denervation changes.

Pathophysiology and Molecular Imaging of Diabetic Foot Infections

Diabetic foot infection is the leading cause of non-traumatic lower limb amputations worldwide. In addition, diabetes mellitus and sequela of the disease are increasing in prevalence. In 2017, 9.4% of Americans were diagnosed with diabetes mellitus (DM). The growing pervasiveness and financial implications of diabetic foot infection (DFI) indicate an acute need for improved clinical assessment and treatment. Complex pathophysiology and suboptimal specificity of current non-invasive imaging modalities have made diagnosis and treatment response challenging. Current anatomical and molecular clinical imaging strategies have mainly targeted the host's immune responses rather than the unique metabolism of the invading microorganism. Advances in imaging have the potential to reduce the impact of these problems and improve the assessment of DFI, particularly in distinguishing infection of soft tissue alone from osteomyelitis (OM). This review presents a summary of the known pathophysiology of DFI, the molecular basis of current and emerging diagnostic imaging techniques, and the mechanistic links of these imaging techniques to the pathophysiology of diabetic foot infections.

Pathophysiology and Molecular Imaging of Diabetic Foot Infections

Diabetic foot infection is the leading cause of non-traumatic lower limb amputations worldwide. In addition, diabetes mellitus and sequela of the disease are increasing in prevalence. In 2017, 9.4% of Americans were diagnosed with diabetes mellitus (DM). The growing pervasiveness and financial implications of diabetic foot infection (DFI) indicate an acute need for improved clinical assessment and treatment. Complex pathophysiology and suboptimal specificity of current non-invasive imaging modalities have made diagnosis and treatment response challenging. Current anatomical and molecular clinical imaging strategies have mainly targeted the host's immune responses rather than the unique metabolism of the invading microorganism. Advances in imaging have the potential to reduce the impact of these problems and improve the assessment of DFI, particularly in distinguishing infection of soft tissue alone from osteomyelitis (OM). This review presents a summary of the known pathophysiology of DFI, the molecular basis of current and emerging diagnostic imaging techniques, and the mechanistic links of these imaging techniques to the pathophysiology of diabetic foot infections.

Imaging features and atypical signs of symptomatic vertebral haemangioma: a retrospective single-centre analysis of 118 patients

OBJECTIVES

Symptomatic vertebral haemangioma (SVH) can present with atypical imaging features. Thus, this study analysed the imaging features of SVH using CT and MRI to improve SVH awareness.

METHODS

We retrospectively analysed CT and MRI characteristics of 118 patients with clinically and pathologically confirmed SVH.

RESULTS

Overall, 118 patients were diagnosed with SVH, including 79 females and 39 males (mean age, 45.76 ± 16.36 years). The thoracic spine (n = 86) was the most common location of SVH, followed by the lumbar spine (n = 17). Involvement of multiple spinal segments was observed in 15 patients (12.71%). A total of 101 lesions (85.59%) were centred in the vertebral body, 15 lesions (12.71%) were centred in the posterior attachment, and two lesions (2%) were centred in the paraspinal region. CT showed 39 lesions (33.05%) without a typical honeycomb or polka-dot pattern. Compression fracture was observed in 23 patients (19.49%). Extraosseous extension was present in 111 patients (94.1%), and 17 lesions (14.41%) presented with foraminal extension. Epidural bony compression was observed in 46 patients (38.98%). 20 lesions (16.95%) had atypical T₂ weighted MRI signals, and 8 lesions (10.26%) showed atypical enhancement.

CONCLUSION

SVH was predominantly located in the thoracic spine. Involvement of multiple segments, posterior attachment localisation, absence of honeycomb or polka-dot signs, compression fracture, and atypical T₂ weighted imaging signals and enhancement were uncommon. Epidural bony compression was not uncommon and has important clinical significance.

ADVANCES IN KNOWLEDGE

The imaging features of SVHs are not fully understood. We examined the largest series of SVH cases reported to date.

Imaging Review of Peripheral Nerve Injuries in Patients with COVID-19

With surging numbers of patients with coronavirus disease 2019 (COVID-19) throughout the world, neuromuscular complications and rehabilitation concerns are becoming more apparent. Peripheral nerve injury can occur in patients with COVID-19 secondary to postinfectious inflammatory neuropathy, prone positioning-related stretch and/or compression injury, systemic neuropathy, or nerve entrapment from hematoma. Imaging of peripheral nerves in patients with COVID-19 may help to characterize nerve abnormality, to identify site and severity of nerve damage, and to potentially elucidate mechanisms of injury, thereby aiding the medical diagnosis and decision-making process. This review article aims to provide a first comprehensive summary of the current knowledge of COVID-19 and peripheral nerve imaging.

Post-Contrast 3D Inversion Recovery Magnetic Resonance Neurography for Evaluation of Branch Nerves of the Brachial Plexus

PURPOSE

To compare 3.0 Tesla brachial plexus three-dimensional (3D) T2-weighted short tau inversion recovery fast spin echo (STIR-FSE) MRI sequences before (pre-contrast STIR) and after (post-contrast STIR) administration of gadolinium intravenous contrast.

METHOD

Eighteen patients were included. Each patient was imaged before and after intravenous contrast administration during the same session. 3D STIR-FSE sequences were obtained at 3.0 Tesla using two 16-channel flexible coils positioned over the lower neck and chest wall region. Three musculoskeletal radiologists qualitatively assessed degree of vascular signal suppression, visualization of the axillary, musculocutaneous, and suprascapular nerves, diagnostic confidence in nerve evaluation, and lesion conspicuity. Marginal ordinal logistic regression models were used to compare subjective ratings between sequences. Pre- and post-STIR lesion conspicuity was compared using Wilcoxon signed-rank test. Inter- and intra-observer agreements were assessed using Gwet's agreement coefficient.

RESULTS

Vascular signal suppression significantly improved following contrast administration (odds ratio, OR = 209.9, 95% confidence interval, CI: 21.0-2094.6, p < .001). The post-contrast STIR technique significantly improved nerve visualization (OR = 8.4, 95% CI: 3.6-19.9, p < .001) and diagnostic confidence in evaluation (OR = 13.2, 95% CI: 4.8-36.0, p < .001) across all nerve segments. Post-contrast STIR improved lesion conspicuity by 1 point, but statistical significance was not reached (Reader 1: p = 0.5, Reader 2: p = 0.063). Post-contrast STIR imaging demonstrated substantial to near-perfect inter- and intra-rater agreement coefficients for both nerve visualization (inter-rater: 0.74-1.0, intra-rater: 0.94-1.0) and diagnostic confidence (inter-rater: 0.79-1.0, intra-rater: 0.94-1.0). Quantitatively, post-contrast STIR demonstrated a 24% increase in mean C6 nerve-to-muscle signal intensity ratio (p = 0.017).

CONCLUSIONS

Post-contrast STIR improved nerve-to-muscle contrast ratio, allowing for enhanced visualization and diagnostic confidence in evaluation of branch nerves of the brachial plexus.