Diffusion-weighted MR neurography for the assessment of brachial plexopathy in oncological practice

Diffusion-Weighted MR Neurography with Unidirectional Motion-Probing Gradient to Evaluate Lumbar Nerve Roots at 1.5T MR

Purpose

Recent studies have demonstrated the usefulness of diffusion-weighted MR neurography (DW MRN) for assessing nerve roots. This study aimed to evaluate the utility of DW MRN with a unidirectional motion-probing gradient (MPG) for the lumbar nerve roots at 1.5T MR.

Materials and Methods

Sixty-four lumbar spine MRI scans with DW MRN using anteroposterior unidirectional MPG were retrospectively analyzed. Any changes in the 512 lumbar spinal nerve roots from L3 to S1 were evaluated using T2-weighted imaging (T2WI), contrast-enhanced T1-weighted imaging (CE T1WI), and DW MRN, with agreement and correlation analysis.

Results

T2WI revealed compression of 78 nerve roots, and CE T1WI revealed 52 instances of nerve root enhancement. Sixty-seven nerve roots showed swelling and hyperintensity on DW MRN. A total of 42 nerve roots showed changes in the CE T1WI and DW MRN sequences. Moderate to substantial agreement and moderate positive correlation were observed between DW MRN and CE T1WI, as well as DW MRN and T2WI (κ = 0.59-0.65, ρ = 0.600-0.653).

Conclusion

DW MRN with unidirectional anteroposterior MPG can help evaluate neuritis-related changes in spinal nerve roots and could serve as a sequence capable of complementing or substituting gadolinium CE imaging.

Assessment of neuropathic pain following cancer treatment

Neuropathic cancer pain (NCP) is prevalent affecting up to 58% of those with persistent pain following cancer treatment. Neuropathic pain can develop from malignancy, after neural tissue insult during surgery and/or exposure to radiation or neurotoxic agents used as part of cancer treatment regimens. Pain following cancer treatment is commonly under-treated and one barrier identified is poor recognition of pain and inadequate assessment. Recognition of the presence of NCP is important to inform pain management, which is challenging to treat and warrants the use of specific treatments to target neuropathic mechanisms. In this review, approaches for screening and classifying NCP are described. These include screening questionnaires and the application of the updated neuropathic pain grading system in a cancer context. The evidence from neuropathic pain related assessments in cancer populations is provided and highlighted under different neuropathic pain grades. Recommendations for assessment in practice are provided.

Clinical Application of Diffusion Tensor Imaging for a Brachial Plexus Injury

Brachial plexus injuries are commonly diagnosed clinically, as conventional imaging has a low sensitivity. In recent years, diffusion tensor imaging has established a clinical role in the study of the central nervous system and, while still presenting some limitations due to the technical complexity of the acquisition method, is showing promising results when applied to peripheral nerves. Moreover, deterministic fiber tracking with the Euler’s method and multishell acquisition are two novel advances in the field which contribute to enhancing the reliability of the technique reducing the respiratory and inhomogeneity artifacts in this “magnetically complex” region, and better isolating the fibers in a heterogeneous territory. Here, we report a case of brachial plexus traumatic injury, a healthy reference subject, and details on the acquisition protocol of the reconstruction algorithm.

Diagnostic performance of diffusion-weighted MR neurography as an adjunct to conventional MRI for the assessment of brachial plexus pathology

OBJECTIVE

To investigate the diagnostic performance of diffusion-weighted (DW) MR neurography as an adjunct to conventional MRI for the assessment of brachial plexus pathology.

METHODS

DW MR neurography scans (short tau inversion recovery fat suppression and b-value of 800 s/mm²) of 15 consecutive patients with and 45 randomly selected patients without brachial plexus abnormalities were independently and blindly reviewed by a 5th year radiology resident, a junior neuroradiologist, and a senior neuroradiologist.

RESULTS

Median interpretation times ranged between 20 and 30 s. Interobserver agreement was substantial (κ coefficients of 0.715-0.739). For the 5th year radiology resident, sensitivity was 53.3% (95% CI, 30.1-75.2%) and specificity was 100% (95% CI, 92.1-100%). For the junior neuroradiologist, sensitivity was 66.7% (95% CI, 41.7-84.8%) and specificity was 100% (95% CI, 92.1-100%). For the senior neuroradiologist, sensitivity was 73.3% (95% CI, 48.1-89.1%) and specificity was 95.6% (95% CI, 85.2-98.8%). Traumatic injury, metastases, radiation-induced plexopathy, schwannoma, and inflammatory process of unknown cause could be detected by the majority of readers (100% detection rate for each disease entity by at least two readers). Neuralgic amyotrophy, iatrogenic injury after first rib resection, and cervical disc herniation causing root compression were not detected by the majority of readers (0% detection rate for each disease entity by at least two readers).

CONCLUSION

DW MR neurography may be a useful adjunct when assessing for brachial plexus abnormalities, because interpretation time is relatively short and the majority of abnormalities can be detected.

KEY POINTS

• DW MR neurography interpretation time of the brachial plexus is relatively short (median interpretation times of 20 to 30 s). • Interobserver agreement between three readers with different levels of experience is substantial (κ coefficients of 0.715 to 0.739). • DW MR neurography can detect brachial plexus abnormalities with moderate sensitivity (53.3 to 73.3%) and high specificity (95.6 to 100%).

Double Fascicular Transfer Using Partially Injured Donor Nerves: Is It Powerful Enough to Restore Elbow Flexion in Acute Brachial Plexus Injuries?

BACKGROUND

 Loss of elbow flexion is a common sequela of acute brachial plexus injuries (BPIs). The Mackinnon/Oberlin-II double fascicular transfer (DFT) is a widely used method to restore this function in acute C5-6 or C5-7 injuries. This study attempted to evaluate if this technique can be applied reliably for cases involving C8 and/or T1 injuries.

METHODS

 Adult patients with acute BPIs who underwent the Mackinnon/Oberlin-II DFT in our center between 2008 and 2018 were retrospectively identified. Group I (n = 37) included patients with only C5-6 or C5-7 injury, while group II (n = 32) patients presented C5-8 ± T1 injuries. The demographic data, pre- and postoperative neurologic evaluations, electrodiagnostic studies, and grip strength assessment were collected.

RESULTS

 A total of 69 patients met the inclusion criteria. Preoperatively, the patients in group II presented poorer nerve conduction and electromyography in both the median and the ulnar nerves and the supply muscles. The percentage of M3 achievement in both groups was 91.9 versus 87.5% and M4 was 73.0 and 71.9%, respectively, which both were not statically significant but the achievement of group II was slower than the group I, 1 to 2 months slower, respectively. Both groups had 57.57 and 46.0% of the postoperative grip power compared with the healthy side, the result of shoulder abduction was not different (p = 0.480).

CONCLUSION

 With careful preoperative evaluation, early intervention, appropriate intraoperative functional fascicle selection, and aggressive postoperative rehabilitation, indications for the Mackinnon/Oberlin-II DFT technique can safely include acute C5-8 injuries and even partial T1 acute BPIs.

Preoperative imaging assessment of the paralytic upper limb

Imaging has become an essential tool in the study of the posttraumatic paralytic upper limb, in addition to the clinical examination and electroneuromyography. Upper extremity surgeons must be aware of how these different techniques contribute to the initial and preoperative assessment of nervous injuries. We review the appearance of traumatic nerve damage and muscle denervation during the initial injury assessment, focusing on the main aspects of brachial plexus injuries, paralysis after shoulder dislocation and traumatic damage to the radial nerve. Finally, we discuss the role of imaging for preoperative assessment of musculotendinous and osteoarticular palliative surgeries.

Multimodality imaging of adult rhabdomyosarcoma: the added value of hybrid imaging

Rhabdomyosarcoma (RMS) represents more than 50% of paediatric soft tissue tumours. Conversely, it is extremely rare among adults, where it shows peculiar biological and clinical features that are still poorly investigated. RMS patients should be referred to a Sarcoma Centre, where the contribution of experienced radiologists plays a relevant role in the diagnostic assessment of the disease, including precise localisation, staging, image-guided biopsy, response evaluation after treatment and follow-up. Besides CT and MRI, hybrid imaging including positron emission tomography (PET)/CT and PET/MRI are giving an increasing contribution to provide functional insights about tumour biology and to improve the diagnostic accuracy of the imaging work-up. This review paper provides a revision of the pathology, clinical and radiological features of adult RMS, with a particular focus on the growing role of hybrid PET-based imaging.

Can a Partially Injured Donor Nerve Restore Elbow Flexion in an Acute Brachial Plexus Injury in Rats?

BACKGROUND

Loss of elbow flexion commonly occurs following acute brachial plexus injury. The double fascicular transfer is often used in acute C5-C6 and C5-C7 root injuries, but is rarely applied in cases involving concomitant C8 or T1 root injury. The authors designed a rat model using varying severities of lower trunk injury to determine whether partial injury to the lower trunk affects nerve transfers for elbow flexion.

METHODS

There were four different rat groups in which 0, 25, 75, or 100 percent of the donor lower trunk remained intact. One-fourth of the cross-sectional area of the ulnar nerve was then transferred to the musculocutaneous nerve immediately. The authors assessed outcomes using a grooming test, muscle mass, retrograde labeling of sensory/motor neurons that regenerated axons, and immunohistochemical stain of regenerated axons.

RESULTS

Five months after nerve transfer, rats that underwent partial injury of the lower trunk fared significantly worse than the rats in whom the donor lower trunk remained 100 percent intact, but significantly better than the rats with 0 percent intact lower trunk. Rats with 25 or 75 percent of the lower trunk intact recovered equivalent function, at both the donor and recipient sites.

CONCLUSIONS

Although relatively weak compared with the 100 percent intact donor lower trunk group, the partially injured donor nerve was still functional; even though the nerve sustained a partial injury, the residual axons reinnervated the target muscles. The power of the muscles following either 25 percent or 75 percent injuries was equal after the recovery. Resorting to this approach may be useful in cases in which no alternatives are available.

Peripheral nervous system involvement in lymphomas

The peripheral nervous system may be involved at any stage in the course of lymphoproliferative diseases. The different underlying mechanisms include neurotoxicity secondary to chemotherapy, direct nerve infiltration (neurolymphomatosis), infections, immune-mediated, paraneoplastic or metabolic processes and nutritional deficiencies. Accordingly, the clinical features are heterogeneous and depend on the localization of the damage (ganglia, roots, plexi, and peripheral nerves) and on the involved structures (myelin, axon, and cell body). Some clinical findings, such a focal or diffuse involvement, symmetric or asymmetric pattern, presence of pain may point to the correct diagnosis. Besides a thorough medical history and neurological examination, neurophysiological studies, cerebrospinal fluid analysis, nerve biopsy (in selected patients with suspected lymphomatous infiltration) and neuroimaging techniques (magnetic resonance neurography and nerve ultrasound) may be crucial for a proper diagnostic workup.

Diffusion Tensor Imaging of the Brachial Plexus: A Comparison between Readout-segmented and Conventional Single-shot Echo-planar Imaging

Purpose:

Diffusion tensor imaging (DTI) adds functional information to morphological magnetic resonance neurography (MRN) in the assessment of the brachial nerve plexus. To determine the most appropriate pulse sequence in scan times suited for diagnostic imaging in clinical routine, we compared image quality between simultaneous multi-slice readout-segmented (rs-DTI) and conventional single-shot (ss-DTI) echo-planar imaging techniques.

Methods:

Institutional Review Board (IRB) approved study including 10 healthy volunteers. The supraclavicular brachial plexus, covering the nerve roots and trunks from C5 to C7, was imaged on both sides with rs-DTI and ss-DTI. Both sequences were acquired in scan times <7 min with b-values of 900 s/mm² and with isotropic spatial resolution.

Results:

In rs-DTI image, the overall quality was significantly better and distortion artifacts were significantly lower (P = 0.001–0.002 and P = 0.001–0.002, respectively) for both readers. In ss-DTI, a trend toward lower degree of ghosting and motion artifacts was elicited (reader 1, P = 0.121; reader 2, P = 0.264). No significant differences between the two DTI techniques were found for signal-to-noise ratios (SNR), contrast-to-noise ratios (CNR) and fractional anisotropy (FA) (P ≥ 0.475, P ≥ 0.624, and P ≥ 0.169, respectively). Interreader agreement for all examined parameters and all sequences ranged from intraclass correlation coefficient (ICC) 0.064 to 0.905 and Kappa 0.40 to 0.851.

Conclusion:

Incomparable acquisition times rs-DTI showed higher image quality and less distortion artifacts than ss-DTI. The trend toward a higher degree of ghosting and motion artifacts in rs-DTI did not deteriorate image quality to a significant degree. Thus, rs-DTI should be considered for functional MRN of the brachial plexus.

An Update on the Management of Neonatal Brachial Plexus Palsy-Replacing Old Paradigms: A Review

IMPORTANCE

Neonatal brachial plexus palsy (NBPP) can result in persistent deficits for those who develop it. Advances in surgical technique have resulted in the availability of safe, reliable options for treatment. Prevailing paradigms include, "all neonatal brachial plexus palsy recovers," "wait a year to see if recovery occurs," and "don't move the arm." Practicing by these principles places these patients at a disadvantage. Thus, the importance of this review is to provide an update on the management of NBPP to replace old beliefs with new paradigms.

OBSERVATIONS

Changes within denervated muscle begin at the moment of injury, but without reinnervation become irreversible 18 to 24 months following denervation. These time-sensitive, irreversible changes are the scientific basis for the recommendations herein for the early management of NBPP and put into question the old paradigms. Early referral has become increasingly important because improved outcomes can be achieved using new management algorithms that allow surgery to be offered to patients unlikely to recover sufficiently with conservative management. Mounting evidence supports improved outcomes for appropriately selected patients with surgical management compared with natural history. Primary nerve surgery options now include nerve graft repair and nerve transfer. Specific indications continue to be elucidated, but both techniques offer a significant chance of restoration of function.

CONCLUSIONS AND RELEVANCE

Mounting data support both the safety and effectiveness of surgery for patients with persistent NBPP. Despite this support, primary nerve surgery for NBPP continues to be underused. Surgery is but one part of the multidisciplinary care of NBPP. Early referral and implementation of multidisciplinary strategies give these children the best chance of functional recovery. Primary care physicians, nerve surgeons, physiatrists, and occupational and physical therapists must partner to continue to modify current treatment paradigms to provide improved quality care to neonates and children affected by NBPP.

Diffusion weighted imaging demystified: the technique and potential clinical applications for soft tissue imaging

Diffusion-weighted imaging (DWI) is a fast, non-contrast technique that is readily available and easy to integrate into an existing imaging protocol. DWI with apparent diffusion coefficient (ADC) mapping offers a quantitative metric for soft tissue evaluation and provides information regarding the cellularity of a region of interest. There are several available methods of performing DWI, and artifacts and pitfalls must be considered when interpreting DWI studies. This review article will review the various techniques of DWI acquisition and utility of qualitative as well as quantitative methods of image interpretation, with emphasis on optimal methods for ADC measurement. The current clinical applications for DWI are primarily related to oncologic evaluation: For the assessment of de novo soft tissue masses, ADC mapping can serve as a useful adjunct technique to routine anatomic sequences for lesion characterization as cyst or solid and, if solid, benign or malignant. For treated soft tissue masses, the role of DWI/ADC mapping in the assessment of treatment response as well as recurrent or residual neoplasm in the setting of operative management is discussed, especially when intravenous contrast medium cannot be given. Emerging DWI applications for non-neoplastic clinical indications are also reviewed.

Cystic degeneration of the tibial nerve: magnetic resonance neurography and sonography appearances of an intraneural ganglion cyst

Extra- and intraneural ganglion cysts have been described in the literature. The tibial nerve ganglion is uncommon and its occurrence without intra-articular extension is atypical. The pathogenesis of cystic degeneration localized to connective and perineural tissue secondary to chronic mechanical irritation or idiopathic mucoid degeneration is hypothesized. Since the above pathology is extremely rare and the magnetic resonance imaging examination detects the defining characteristics of the intrinsic alterations of the tibial nerve, the authors illustrate such a case of tibial intaneural ganglion cyst with its magnetic resonance neurography and sonography appearances.

MRI-guided lung SBRT: Present and future developments

Stereotactic body radiotherapy (SBRT) is rapidly becoming an alternative to surgery for the treatment of early-stage non-small cell lung cancer patients. Lung SBRT is administered in a hypo-fractionated, conformal manner, delivering high doses to the target. To avoid normal-tissue toxicity, it is crucial to limit the exposure of nearby healthy organs-at-risk (OAR). Current image-guided radiotherapy strategies for lung SBRT are mostly based on X-ray imaging modalities. Although still in its infancy, magnetic resonance imaging (MRI) guidance for lung SBRT is not exposure-limited and MRI promises to improve crucial soft-tissue contrast. Looking beyond anatomical imaging, functional MRI is expected to inform treatment decisions and adaptations in the future. This review summarises and discusses how MRI could be advantageous to the different links of the radiotherapy treatment chain for lung SBRT: diagnosis and staging, tumour and OAR delineation, treatment planning, and inter- or intrafractional motion management. Special emphasis is placed on a new generation of hybrid MRI treatment devices and their potential for real-time adaptive radiotherapy.

Whole-body MR neurography: Prospective feasibility study in polyneuropathy and Charcot-Marie-Tooth disease

PURPOSE

To evaluate the feasibility of whole-body magnetic resonance neurography (WBMRN) in polyneuropathy for technical feasibility, distribution of nerve abnormalities, and differentiation.

MATERIALS AND METHODS

Twenty WBMRN examinations were performed on a 3T scanner over 2 years. Patient demographics including history of hereditary and acquired neuropathy were recorded. The images were evaluated by two independent readers with nerve imaging experience for quality. The nerve signal and size alterations were measured in the brachial plexus, lumbosacral plexus, and femoral and sciatic nerves; diffusion tensor imaging parameters (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]) were determined in plexuses, and tractography was performed. Nonparametric Wilcoxon rank sum test, receiver operating characteristic (ROC) analysis, and intraclass correlation coefficients (ICCs) were obtained.

RESULTS

Excellent image quality was obtained for the majority of lumbosacral (LS) plexus (18/20) and 50% of brachial plexus (10/20) regions. Qualitatively among cases, the nerve hyperintensity and/or thickening involved the brachial plexus (11/11), LS plexus (7/11), and both plexuses (7/11), with most nerve thickenings observed in Charcot-Marie-Tooth disease type 1. The nerve signal intensity alterations were significantly different for both brachial (P < 0.05) and LS (P < 0.05) plexuses in cases versus controls. The femoral and sciatic nerve size alterations were different (P < 0.05), while signal intensity differences were not significant (P = 0.1-0.97). Transverse dimensions of C8 (4 mm), L5 (6.2 mm) and S1 (5.1 mm) nerve roots, and sciatic nerves (10.2 mm) were the most accurate diagnostic performance measures in distinguishing cases from controls.

CONCLUSION

WBMRN is feasible for use in the clinical practice for the identification and potential characterization of polyneuropathy. J. Magn. Reson. Imaging 2016;44:1513-1521.