Systematic Review of the Use of Power Doppler Ultrasound in the Imaging of Peripheral Nerve Compression Neuropathy

Peripheral nerve ultrasound: a survival guide for the practicing radiologist with updates

Peripheral nerve injuries negatively impact patients' quality of life and healthcare resources. This review discusses using high-resolution neurosonography (HRNUS) for mapping peripheral nerves and detecting pathologic lesions. It emphasizes the importance of HRNUS in diagnosing nerve disorders and briefs the widely accepted schemes for peripheral nerve injury classification. It also highlights the non-intrusive, flexible, patient-friendly, and cost-effective nature of HRNUS, making it a valuable tool in managing nerve disorders. The authors recommend the use of HRNUS to enable precise diagnoses, prevent permanent disabilities, and contribute to the efficient utilization of healthcare resources.

Is Handheld Lower-Resolution Ultrasound Evaluation Sufficient to Measure the Cross-Sectional Area of the Median Nerve?

PURPOSE

This study aimed to assess the accuracy of median nerve cross-sectional area (CSA) measurements using a handheld ultrasound (HHUS) and a cart-based high-resolution ultrasound.

METHODS

Fifteen healthy subjects were prospectively enrolled. Each subject underwent standardized ultrasound evaluations of their median nerves with HHUS and a high-resolution ultrasound by three different providers with different levels of training in musculoskeletal ultrasound. CSA calculations were performed using a standardized method. The primary outcome was the mean difference in CSA (ΔCSA) between the gold standard high-resolution ultrasound and the lower resolution handheld ultrasound, with a noninferiority margin set at ΔCSA < 2 mm2. Inter-rater reliability was calculated using Lin concordance correlation coefficient (LCCC), and the intraclass coefficient (ICC) was used to calculate intra-rater reliability.

RESULTS

The average CSA of the median nerve across all patients and reviewers using the high-resolution US was > 0.9 mm2 for the HHUS. In paired comparisons within subjects, the ΔCSA of the median nerve using the HHUS was 1.8 mm2 (95% CI, 0.8-2.7 mm2), and the LCCC was weak 0.258 (0.018-0.470). Noninferiority was not achieved. The intrarater reliability between devices was poor at 0.201. However, the inter-rater reliability among different examiners was good when using the high-resolution device, but it was poor using the HHUS.

CONCLUSIONS

The findings suggest caution for the use of handheld ultrasound in measurements of median nerve CSA because the difference between HHUS and gold standard high-resolution ultrasound was not within the noninferiority margin of 2 mm2.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Multiparametric Ultrasound Assessment of Carpal Tunnel Syndrome: Beyond Nerve Cross-sectional Area

Carpal tunnel syndrome (CTS), the most common mononeuropathy, results from compression of the median nerve within the fibro-osseous carpal tunnel. Diagnosis is typically based on clinical evaluation and confirmed by nerve conduction studies. However, ultrasound (US) has emerged as a valuable noninvasive adjunct for CTS confirmation, offering potential advantages over electrodiagnostic testing in terms of patient comfort and diagnostic accuracy. This review begins with a concise summary of carpal tunnel anatomy and CTS pathophysiology as a foundation for exploring the diverse applications of US in CTS evaluation. B-mode US assessment is presented with a focus on cross-sectional imaging and dynamic evaluations, including the transverse translocation and longitudinal gliding of the median nerve. We also review current methods for assessing vascularization in CTS and explore the usefulness of elastography in CTS evaluation. The advantages and limitations of each US method are elucidated, highlighting their practical utility in clinical practice.

Advances in Imaging of Compressive Neuropathies

Ultrasound and magnetic resonance neurography are useful modalities to aid in the assessment of compressive neuropathies, although they are still limited in their resolution of nerve microstructure and their capacity to monitor postoperative nerve recovery. Optical coherence tomography, a preclinical imaging modality, is promising in its ability to better identify structural and potential physiologic changes to peripheral nerves, but requires additional testing and research prior to widespread clinical implementation. Further advances in nerve imaging may elucidate the ability to visualize the zone of nerve injury intraoperatively, monitor the progression of nerve regeneration, and localize problems during nerve recovery.

Mechanomyography as a Surgical Adjunct for Treatment of Chronic Entrapment Neuropathy: A Case Series

BACKGROUND

Chronic entrapment neuropathy results in a clinical syndrome ranging from mild pain to debilitating atrophy. There remains a lack of objective metrics that quantify nerve dysfunction and guide surgical decision-making. Mechanomyography (MMG) reflects mechanical motor activity after stimulation of neuromuscular tissue and may indicate underlying nerve dysfunction.

OBJECTIVE

To evaluate the role of MMG as a surgical adjunct in treating chronic entrapment neuropathies.

METHODS

Patients 18 years or older with cubital tunnel syndrome (n = 8) and common peroneal neuropathy (n = 15) were enrolled. Surgical decompression of entrapped nerves was performed with intraoperative MMG of the hypothenar and tibialis anterior muscles. MMG stimulus thresholds (MMG-st) were correlated with compound muscle action potential (CMAP), motor nerve conduction velocity, baseline functional status, and clinical outcomes.

RESULTS

After nerve decompression, MMG-st significantly reduced, the mean reduction of 0.5 mA (95% CI: 0.3-0.7, P < .001). On bivariate analysis, MMG-st exhibited significant negative correlation with common peroneal nerve CMAP ( P < .05), but no association with ulnar nerve CMAP and motor nerve conduction velocity. On preoperative electrodiagnosis, 60% of nerves had axonal loss and 40% had conduction block. The MMG-st was higher in the nerves with axonal loss as compared with the nerves with conduction block. MMG-st was negatively correlated with preoperative hand strength (grip/pinch) and foot-dorsiflexion/toe-extension strength ( P < .05). At the final visit, MMG-st significantly correlated with pain, PROMIS-10 physical function, and Oswestry Disability Index ( P < .05).

CONCLUSION

MMG-st may serve as a surgical adjunct indicating axonal integrity in chronic entrapment neuropathies which may aid in clinical decision-making and prognostication of functional outcomes.

Sensitivity and Specificity of Examination Maneuvers for Carpal Tunnel Syndrome: A Meta-Analysis

Our purpose was to assess the diagnostic validity (sensitivity (Sn) and specificity (Sp)) of physical examination maneuvers for carpal tunnel syndrome (CTS). This meta-analysis utilized the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. Studies assessing exam maneuvers (including components of the CTS-6) for CTS were identified in MEDLINE (Medical Literature Analysis and Retrieval System Online) and Embase (Excerpta Medica Database) databases. Assessed maneuvers assessed included: Phalen's test, Tinel's sign, Durkan test, scratch-collapse test, Semmes-Weinstein monofilament (SWM), and static 2-point discrimination (2PD) test. Data extracted included: article name, total number of subjects/hands, type of exam, and exam Sn/Sp. Forest plots were presented to display the estimated Sn/Sp and boxplots were used to demonstrate the locality, spread, and skewness of the Sn/Sp through the quartiles. After screening 570 articles, 67 articles involving 8924 hands were included. Forty-eight articles assessed Phalen's test, 45 assessed Tinel's sign, 21 assessed the Durkan test, seven assessed the scratch-collapse test, 11 assessed SWM, and six assessed the static 2PD test. Phalen's test demonstrated the greatest median Sn (0.70, (Q1, Q3): (0.51, 0.85)), followed by the Durkan test (0.67, (Q1, Q3): (0.46, 0.82)). 2PD demonstrated the highest median Sp (0.90, (Q1, Q3): (0.88, 0.90)), followed by SWM (0.85, (Q1, Q3): (0.51, 0.89)). There is considerable variability with respect to the validity of physical exam tests used in the diagnosis of CTS. Upper-extremity surgeons should be aware of inherent limitations for individual exam maneuvers. In the absence of a uniformly accepted diagnostic gold standard, a combination of exams, along with pertinent patient history, should guide the diagnosis of CTS.

Future Considerations in the Diagnosis and Treatment of Compressive Neuropathies of the Upper Extremity

Compressive neuropathies of the upper extremity are among the most common conditions seen by hand surgeons. The diagnoses of carpal tunnel syndrome and cubital tunnel syndrome have traditionally been made by a combination of history, physical examination, and electrodiagnostic testing. However, findings can be nonspecific and electrodiagnostic testing is invasive for the patient. The diagnosis of compressive neuropathies continues to evolve as technology advances, and newer diagnostic modalities predominantly focus on preoperative diagnostic imaging with ultrasound and magnetic resonance imaging/neurography. With the advent of cheaper, faster, and less invasive imaging, the future may bring a paradigm shift away from electrophysiology as the gold standard for the preoperative diagnosis of compressive neuropathies. Intraoperative imaging of nerve health is an emerging concept that warrants further investigation, whereas postoperative imaging of nerve recovery with ultrasound and magnetic resonance imaging currently has a limited role because of nonspecific findings and potential for misinterpretation. Advances in surgical treatment of compressive neuropathies appear to center around the use of imaging for less invasive neurolysis techniques and other adjunctive treatments with nerve decompression. The management of failed peripheral nerve decompressions and recurrent compressive neuropathies remains challenging.

Ultrasonography for the diagnosis of carpal tunnel syndrome: an umbrella review

BACKGROUND

Numerous sonographic modalities and parameters have been used to diagnose carpal tunnel syndrome (CTS), with varying accuracy. Our umbrella review aimed to summarize the evidence from systematic reviews and meta-analyses regarding the use of ultrasound imaging to diagnose CTS.

METHODS

Systematic reviews and meta-analyses meeting the inclusion criteria were searched in PubMed, Embase, Medline, Web of Science, and Cochrane databases from inception to March 2022. Critical appraisal, data extraction, and synthesis were performed in accordance with the criteria for conducting an umbrella review.

RESULTS

Sixteen reviews were included. Three reviews were classified as high quality, one as moderate, four as low, and eight as critically low. The cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet demonstrated the best reliability and diagnostic accuracy among multiple parameters. A cutoff CSA value of 9-10.5 mm2 gave the highest diagnostic performance in the general population. The degree of CSA enlargement was correlated with CTS severity. Sonoelastography and Doppler ultrasound might provide additional insights into CTS evaluation as median nerve stiffness and vascularity at the wrist were increased in these patients.

CONCLUSIONS

Sonography is a reliable tool to diagnose CTS, with inlet CSA being the most robust parameter. Sonoelastography and Doppler ultrasound can serve as auxiliary tools to confirm CTS diagnoses. Further studies are needed to expand the use of sonography for diagnosing CTS, especially in the presence of concomitant neuromuscular disease(s).