Median Nerve Cross-Sectional Area and Carpal Tunnel Syndrome in Specific Populations: Sonographic Analysis of Patients with Type 2 Diabetes or Bifid Anatomy

OBJECTIVES

Evaluate diagnostic accuracy of median nerve cross-sectional area (CSA) to determine severity versus presence of carpal tunnel syndrome (CTS) across existing electrodiagnostic-based (EDX) classification systems in patients with type 2 diabetes or bifid anatomy.

METHODS

Retrospective analysis of cross-sectional patient data. Receiver operating characteristic analysis used to determine median nerve CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS in patients with type 2 diabetes or bifid anatomy. Determine shifts in diagnostic probability based on established cutoff values and associated likelihood ratios. Distal CSA measured at or near carpal tunnel inlet, proximal CSA at level of pronator quadratus muscle, and delta CSA by subtracting proximal from distal.

RESULTS

Binary categorizations of CTS were statistically superior to consolidated categorizations of CTS severity in patients with type 2 diabetes or bifid anatomy. Binary categorizations established reasonably consistent median nerve CSA cutoff values across all EDX-based classifications examined resulting in the following for distal CSA or delta CSA: ≤10 or ≤4 mm2 to rule out and ≥11 or ≥5 mm2 to rule in CTS, respectively. These cutoff values resulted in small shifts in diagnostic probability in patients with type 2 diabetes and small to conclusive shifts in diagnostic probability in patients with bifid anatomy.

CONCLUSIONS

Binary categorizations to rule out or rule in CTS based on the proposed cutoff values provide the most meaningful information about shifts in diagnostic probability across all EDX-based classifications examined. The use of median nerve CSA to categorize severity of CTS is not recommended in patients with type 2 diabetes or bifid anatomy.

Sonographic Measurement of Median Nerve Cross-Sectional Area to Determine Severity of Carpal Tunnel Syndrome: A Cautionary Tale

OBJECTIVES

Evaluate the diagnostic accuracy of median nerve cross-sectional area (CSA) to determine the severity of carpal tunnel syndrome (CTS) vs the presence of CTS across existing electrodiagnostic-based (EDX) classification systems.

METHODS

Retrospective analysis of cross-sectional patient data. Receiver operating characteristic (ROC) analysis was used to determine CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS severity. Identification of CSA cutoff values associated with likelihood ratios capable of achieving conclusive (but at least moderate) shifts in diagnostic probability.

RESULTS

Binary categorizations of CTS (ie, "Normal" vs "Absent") were statistically superior to consolidated categorizations of CTS severity (ie, "Normal," "Mild," "Moderate," or "Severe"). Binary categorizations established consistent CSA cutoff values across all EDX-based classifications examined and achieved conclusive shifts in diagnostic probability based on the following values of distal CSA or delta CSA: <7 or <1 mm2 to rule out and >13 or >7 mm2 to rule in CTS, respectively. Additionally, the following values of distal CSA and delta CSA may be used in certain circumstances because they produce only small shifts in diagnostic probability: ≤10 or ≤3 mm2 to rule out and ≥11 or ≥4 mm2 to rule in CTS, respectively.

CONCLUSIONS

Using median nerve CSA to categorize the severity of CTS is not recommended based on lack of consistent and meaningful shifts in diagnostic probability. Rather, binary categorizations to rule out or rule in CTS based on the proposed CSA cutoff values consistently provided conclusive shifts in diagnostic probability across all EDX-based classifications examined.

Clinical Results of Carpal Tunnel Release Using Ultrasound Guidance in Over 100 Patients at Two to Six Years

Purpose

The purpose of this study was to determine the clinical results of carpal tunnel release using ultrasound guidance (CTR-US) at a minimum of 2 years postprocedure.

Methods

The study consisted of 102 patients (162 hands) treated with CTR-US by the same physician between June 2017 and October 2020 for whom minimum 2-year follow-up data were available. Questionnaires were sent to gather long-term information, with additional phone calls for clarification if needed. Outcomes included Boston Carpal Tunnel Questionnaire symptom severity (BCTQ-SSS) and functional status (BCTQ-FSS) scores; Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) scores; global satisfaction scores; and subsequent surgeries.

Results

The 102 patients included 68 females and 34 males with a mean age of 56.9 years at the time of surgery. Fifty-five (53.9%) patients had simultaneous bilateral procedures, 42 (41.2%) had unilateral procedures, and 5 (4.9%) had staged bilateral procedures. Significant improvements in BCTQ-SSS, BCTQ-FSS, and QuickDASH scores persisted at a mean final follow-up of 46 months (range 2-6 years). At final follow-up, 91.2% of patients reported satisfaction with the procedure. No outcomes were significantly different between those treated with simultaneous bilateral versus unilateral procedures. No revision surgeries were reported.

Conclusions

CTR-US is a safe and effective procedure that results in significant improvements that persist up to 6 years postprocedure. Long-term results of simultaneous bilateral and unilateral procedures are similar.

Type of study/level of evidence

Therapeutic IV.

Ultrasound and magnetic resonance imaging neurography assessment of diagnostic criteria in patients with carpal tunnel syndrome using electrophysiological tests as gold standard: A prospective study

Objectives

Evaluating peripheral neuropathy mainly relies on physical examination, patient history, and electrophysiological studies. High-resolution ultrasound is a fast, noninvasive modality for dynamic nerve assessment that enables the length of the nerve to be examined. Magnetic resonance imaging is preferred for examining deeper nerves with a high contrast resolution; its use shows excellent benefit in patients with atypical presentation, equivocal diagnosis, suspected secondary causes, and postsurgical relapse. We aimed to assess the measurements and criteria for both ultrasound and magnetic resonance neurography for the diagnosis of carpal tunnel syndrome, based mainly on the three measurements assessed by Buchberger et al.

Methods

This prospective study was conducted to test diagnostic accuracy. Thirty-two patients who presented clinically with, and were diagnosed by electrophysiological tests as having, carpal tunnel syndrome participated. Superficial ultrasound of the wrist joint was performed on all participants, followed by magnetic resonance imaging within 1 week of ultrasonography.

Results

The three main parameters of cross-sectional area measurement, distal nerve flattening, and flexor retinaculum bowing indices showed positive occurrences of 93.7%, 59.4%, and 59.4%, respectively; 90.6% of patients had decreased nerve echotexture. The diagnostic ability of magnetic resonance imaging was decreased when cross-sectional area measurements were used: positive results were achieved in 81.2% of patients, but the positive results showing the distal tunnel nerve increased flattening and bowed flexor retinaculum slightly decreased to 56.2% for each. A high T2 signal of the median nerve was observed in 90.6% of patients. In an agreement analysis, we found a statistically significant difference that supported the use of ultrasound as a primary diagnostic modality for carpal tunnel syndrome. However, magnetic resonance imaging improved tissue characterization and was a good diagnostic modality, with a statistically significant difference, for cases of secondary carpal tunnel syndrome, detection of the underlying entrapping cause, and early abnormality detection in the innervated muscle.

Conclusions

Our results demonstrate that ultrasound examination can be used as the first imaging modality after physician evaluation, with results comparable to those of electrophysiological studies for evaluating carpal tunnel syndrome and determining its cause. Magnetic resonance neurography examination is the second step in detecting secondary causes in cases with suspected early muscle denervation changes that cannot be elicited by ultrasound or in cases with equivocal results.

Clinical Application of Ultrasound-guided Electrode Placement and Detection of Nerve Action Potential

BACKGROUND

 We explore a minimally invasive method (combined ultrasound detection, electrode placement and electrophysiologic nerve examination) to evaluate the early-stage quality of a nerve suture site.

METHODS

 Ten patients with median and/or ulnar nerve injuries who had undergone nerve suture were recruited. Postoperative ultrasound examination found that the nerve injury was sutured. Then, a stimulating electrode and recording electrode were located beside the nerve proximal and distal to the suture site guided by ultrasound. Measurement of nerve action potentials (NAP) were performed with these electrodes, followed by surgical exploration. The pre- and intraoperative electrophysiologic findings were compared, together with amplitude, latency, and wave shape of NAP.

RESULTS

 Of the 10 patients, 3 patients were diagnosed with median nerve injury, 2 with ulnar nerve injury, and 5 with the median nerve and ulnar nerve injury. NAP could not be detected pre- and intraoperatively in three median nerves from three patients and in two ulnar nerves from two patients. NAP was detected in 10 nerves from the remaining 5 patients. The pre- and intraoperative NAP results showed consistent results concerning the status of the nerve suture. Wilcoxon's signed-rank test indicated no significant difference in the amplitude and latency detected via sonographically placed electrodes and during surgical exploration. The number of negative-phase waves were equally distributed.

CONCLUSION

 Ultrasound-guided electrode placement and NAP detection can substitute surgery and serve as a minimally invasive approach to evaluate the regeneration of a sutured nerve.

Ultrasound-guided interventions in primary carpal tunnel syndrome: perineural injection to thread carpal tunnel release

Carpal tunnel syndrome (CTS), the most common entrapment neuropathy, is compression of the median nerve deep to transverse carpal ligament at wrist. Ultrasonography and electrophysiological study are complementary in the diagnosis and grading of CTS in appropriate clinical settings. The initial management of patients with CTS is conservative with medical therapy and splinting. However, surgical interventions are indicated in patients in whom medical management has failed. With evolution of the concept of safe zone on ultrasonography and identification of the sonoanatomical landmarks of carpal tunnel in greater detail, Ultrasonography-guided interventions are safer and preferred over surgical management in CTS. The primary ultrasonography-guided interventions include perineural injection, perineural hydrodissection and ultrasonography-guided release of transverse carpal ligament. This review article presents the principles of ultrasonography-guided perineural injection, perineural hydrodissection in CTS, the merits and demerits of injectant used in perineural injection/ hydrodissection, and percutaneous ultrasonography-guided thread release of transverse carpal ligament utilizing the concept of safe zone of the ultrasonography-guided interventions for CTS.

Role of high-resolution ultrasound and magnetic resonance neurography in the evaluation of peripheral nerves in the upper extremity

Upper extremity entrapment neuropathies are common conditions in which peripheral nerves are prone to injury at specific anatomical locations, particularly superficial regions or within fibro-osseous tunnels, resulting in pain and potential disability. Although neuropathy is primarily diagnosed clinically by physical examination and electrophysiology, imaging evaluation with ultrasound and magnetic resonance neurography are valuable complementary non-invasive and accurate tools for evaluation and can help define the site and cause of nerve dysfunction which ultimately leads to precise and timely treatment. Ultrasound, which has higher spatial resolution, can quickly and comfortably characterize the peripheral nerves in real time and can evaluate for denervation related muscle atrophy. Magnetic resonance imaging on the other hand provides excellent contrast resolution between the nerves and adjacent tissues, also between pathologic and normal segments of peripheral nerves. It can also assess the degree of muscle denervation and atrophy. As a prerequisite for nerve imaging, radiologists and sonographers should have a thorough knowledge of anatomy of the peripheral nerves and their superficial and deep branches, including variant anatomy, and the motor and sensory territories innervated by each nerve. The purpose of this illustrative article is to review the common neuropathy and nerve entrapment syndromes in the upper extremities focusing on ultrasound and magnetic resonance neurography imaging.

Diagnostic and Interventional US of the Wrist and Hand: Quadrant-based Approach

Diagnostic and interventional US of the wrist and hand can be challenging due to the small size and superficial location of structures and various disorders that need to be considered. A quadrant-based approach (volar, ulnar, dorsal, and radial) provides a rational method for performing a focused examination and joint positioning during both diagnostic imaging and intervention. Volar wrist disorders primarily involve the median nerve and the digital flexor system comprised of the flexor tendons and pulleys. The ulnar nerve and extensor carpi ulnaris tendon are chiefly responsible for ulnar-sided wrist pain. The differential diagnosis for dorsal-sided symptoms typically involves the extensor tendon compartments and includes distal intersection syndrome, extensor pollicis longus tear, and digital extensor apparatus injury. The soft-tissue ganglion is the most common abnormality in the dorsal wrist, typically associated with wrist ligaments or joint capsule. Radial-sided pain may be secondary to de Quervain tenosynovitis and must be differentiated from the more proximal intersection syndrome. US is an important tool for assessing the ulnar collateral ligament of the first metacarpophalangeal joint of the thumb and differentiating between displaced and nondisplaced tears, thereby influencing management. Despite the complexity of the anatomy and potential pathologic features within the wrist, a focused quadrant-based examination can permit the sonologist to focus on the structures of relevance. In conjunction with a systematic approach, this can aid in precise and efficient diagnostic scanning and intervention of the wrist and hand. ©RSNA, 2023 Supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Anatomical Variants of the Upper Limb Nerves: Clinical and Preoperative Relevance

Profound knowledge of nerve variations is essential for clinical practice. It is crucial for interpreting the large variability of a patient's clinical presentation and the different mechanisms of nerve injury. Awareness of nerve variations facilitates surgical safety and efficacy. Clinically significant anatomical variations can be classified into two main groups: variability in the course of the nerve and variability of structures surrounding the nerve. In this review article we focus on the most common nerve variants of the upper extremity and their clinical relevance.

Application of deep learning algorithms in automatic sonographic localization and segmentation of the median nerve: A systematic review and meta-analysis

OBJECTIVE

High-resolution ultrasound is an emerging tool for diagnosing carpal tunnel syndrome caused by the compression of the median nerve at the wrist. This systematic review and meta-analysis aimed to explore and summarize the performance of deep learning algorithms in the automatic sonographic assessment of the median nerve at the carpal tunnel level.

METHODS

PubMed, Medline, Embase, and Web of Science were searched from the earliest records to May 2022 for studies investigating the utility of deep neural networks in the evaluation of the median nerve in carpal tunnel syndrome. The quality of the included studies was evaluated using the Quality Assessment Tool for Diagnostic Accuracy Studies. The outcome variables included precision, recall, accuracy, F-score, and Dice coefficient.

RESULTS

In total, seven articles were included, comprising 373 participants. The deep learning and related algorithms comprised U-Net, phase-based probabilistic active contour, MaskTrack, ConvLSTM, DeepNerve, DeepSL, ResNet, Feature Pyramid Network, DeepLab, Mask R-CNN, region proposal network, and ROI Align. The pooled values of precision and recall were 0.917 (95 % confidence interval [CI], 0.873-0.961) and 0.940 (95 % CI, 0.892-0.988), respectively. The pooled accuracy and Dice coefficient were 0.924 (95 % CI, 0.840-1.008) and 0.898 (95 % CI, 0.872-0.923), respectively, whereas the summarized F-score was 0.904 (95 % CI, 0.871-0.937).

CONCLUSION

The deep learning algorithm enables automated localization and segmentation of the median nerve at the carpal tunnel level in ultrasound imaging with acceptable accuracy and precision. Future research is expected to validate the performance of deep learning algorithms in detecting and segmenting the median nerve along its entire length as well as across datasets obtained from various ultrasound manufacturers.

Repeatability, Reproducibility and Sources of Variability in the Assessment of Backscatter Coefficient and Texture Parameters from High-Frequency Ultrasound Acquisitions in Human Median Nerve

Ultrasound (US) is an increasingly prevalent and effective diagnostic modality for neuromuscular imaging. Gray-scale B-mode imaging has been the dominant US approach to evaluating nerves qualitatively or making morphometric measurements of nerves, providing important insights into pathological changes for conditions such as carpal tunnel syndrome. Among more recent ultrasound strategies, high-frequency ultrasound (often defined as >15 MHz for clinical applications), quantitative ultrasound and image textural analysis offer promising enhancements for improved and more objective approaches to nerve imaging. In this study, we evaluated the repeatability and reproducibility of backscatter coefficient (BSC) and imaging texture features extracted by gray-level co-occurrence matrices (GLCMs) in homogeneous tissue-mimicking reference phantoms and in median nerves in the wrists of healthy participants. We also investigated several practical sources of variability in the assessment of quantitative parameters, including influences of operators, and participant-to-participant variability. Overall, BSC- and GLCM-based outcomes are highly repeatable and reproducible after operator training, based on measurement of descriptive statistics, repeatability coefficient (RC) and reproducibility coefficient recommended by Quantitative Imaging Biomarker Alliance (QIBA RDC). GLCM parameters appear more reproducible and repeatable than BSC-based parameters in healthy participants in vivo. However, such variability noted here must be compared with the value ranges and variability of the results in pathological nerves, including median nerves afflicted by trauma, overuse syndromes such as carpal tunnel syndrome and after surgical repair.

Long-term Clinical Results of Carpal Tunnel Release Using Ultrasound Guidance

BACKGROUND

The purpose of this study was to determine the long-term safety and efficacy of carpal tunnel release (CTR) using ultrasound guidance in a group of patients treated by a single physician.

METHODS

The study group consisted of 76 consecutive CTRs performed on 47 patients between June 2017 and April 2019 for whom 1-year follow-up was available. All procedures were performed by the same operator using a single CTR technique. Outcomes included complications; Boston Carpal Tunnel Questionnaire symptom severity (BCTQ-SSS) and functional status (BCTQ-FSS) scores; Quick Disabilities of the Arm, Shoulder, and Hand (QDASH) scores; and a 5-point global satisfaction score (4 = satisfied, 5 = very satisfied).

RESULTS

The 47 patients included 27 females and 20 males (ages 31-91 years). Twenty-five patients (50 hands) had simultaneous bilateral CTRs, 4 patients (8 hands) had staged bilateral CTRs, and 18 patients had unilateral CTRs. No complications occurred. Statistically and clinically significant reductions in BCTQ-SSS, BCTQ-FSS, and QDASH scores occurred by 1 to 2 weeks post-CTR and persisted at 1-year (mean 1-year changes vs. pre-CTR -2.11, -1.70, and -44.99, respectively; P < .001 for all). The mean global satisfaction score at 1-year was 4.63.

CONCLUSIONS

CTR using ultrasound (US) guidance is a safe and effective procedure that produces statistically and clinically significant improvements within 1 to 2 weeks postprocedure that persist to 1 year. Furthermore, simultaneous bilateral CTRs using US guidance are feasible and may be advantageous for patients who are candidates for bilateral CTR.

Point-of-care ultrasound of peripheral nerves in the diagnosis of Hansen's disease neuropathy

Introduction

Hansen's disease (HD) is the most common cause of treatable peripheral neuropathy in the world that may or may not involve skin manifestations, and physical examination based on simplified neurologic evaluation is a subjective and inaccurate procedure. High-resolution ultrasound (HRUS) can be used to evaluate peripheral nerves and is a validated technique of good reproducibility, permitting a detailed and precise examination.

Objectives

We proposed to establish objective criteria for absolute values of the measurement of the CSA of peripheral nerves and their indices of the ΔCSA and ΔTpT in the diagnosis of Hansen's disease neuropathy as compared with healthy voluntaries.

Materials and methods

In municipalities from different regions of Brazil, we randomly selected 234 volunteer Brazilian patients diagnosed with leprosy to be submitted to peripheral nerve echography and compared with 49 healthy Brazilian volunteers.

Results

Hansen Disease assessed by high resolution ultrasound is a primarily neural disease that leads to multiple hypertrophic mononeuropathy characterized by CSA values exceeding normal limits (Med CT = 10.2 mm²; UT = 9.8 mm²; UPT = 9.3 mm²; CFFH = 18.3 mm²; T = 9.6 mm²), and the pattern of asymmetry (ΔCSA>2.5 mm² with RR 13) and focality (ΔTPT > 2.5 mm² with RR 6.4) of this thickening has higher sensitivity (76,1%) and specificity (87,8 %) for its early diagnosis that laboratory tests. Analyzing each subject, the percentage of thickened nerves detected among the total number of nerves assessed was higher among patients with HD than among healthy individuals (p < 0.0001). Individuals with two or more thickened nerves were at 24.1 times higher relative risk (95% CI: 6.74–88.98) of HD.

US for Traumatic Nerve Injury, Entrapment Neuropathy, and Imaging-guided Perineural Injection

US is commonly performed to help diagnose traumatic peripheral nerve injury and entrapment neuropathy, particularly with superficial nerves, where higher spatial resolution provides an advantage over MRI. Other advantages of US include dynamic evaluation, easy contralateral comparison, fewer implant contraindications, less artifact from ferromagnetic debris, and facile needle guidance for perineural injections. The authors review peripheral nerve US for traumatic peripheral nerve injury with an emphasis on injury grading and entrapment neuropathy and describe best-practice techniques for US-guided perineural injections while highlighting specific techniques and indications. Online supplemental material is available for this article. ^©RSNA, 2022.

Nerve Imaging in the Wrist

Neuropathic symptoms involving the wrist are a common clinical presentation that can be due to a variety of causes. Imaging plays a key role in differentiating distal nerve lesions in the wrist from more proximal nerve abnormalities such as a cervical radiculopathy or brachial plexopathy. Imaging complements electrodiagnostic testing by helping define the specific lesion site and by providing anatomical information to guide surgical planning. This article reviews nerve anatomy, normal and abnormal findings on ultrasonography and magnetic resonance imaging, and common and uncommon causes of neuropathy.

Bifid median nerve as an anatomical risk factor for carpal tunnel syndrome: A meta-analysis

As the median nerve enters the carpal tunnel, it is a single nerve that soon bifurcates into lateral and medial branches into the hand. If the bifurcation is proximal to the carpel tunnel, a bifid median nerve results. Carpal tunnel syndrome is often associated with a bifid median nerve with or without a persistent median artery. Individual keywords and MeSH phrases were searched in the Google Scholar, SCOPUS, and PubMed databases. Full texts were then collected and assessed for suitability. The prevalence of bifid median nerve at the wrist joint in normal and carpal tunnel syndrome wrists (pre-canal part) and the mean difference between groups were recorded. Only human data were used to test the findings. The pooled odds ratio (with minimal heterogeneity) was 1.50 [1.17-1.93, 95% CI]. The bifid median nerve cross-sectional area (CSA) was significantly greater than that of a solitary median nerve in normal wrists. The mean difference in CSA between the two was 1.50 mm² [0.56-2.45 mm² , 95% CI] without heterogeneity (i²  = 0). Sex and laterality distributions scarcely differed between the two types of wrists. Owing to the insufficiency of data, the relationships with mean height and weight were not examined. There was a 50% greater incidence of bifid median nerves in carpal tunnel syndrome patients than in normal subjects. A bifid median nerve increases the mean CSA at the wrist joint by 1.5 mm² . These findings indicate that the bifid median nerve is an anatomical risk factor for carpal tunnel syndrome. This article is protected by copyright. All rights reserved.

Sonographic Diagnosis of Carpal Tunnel Syndrome

Diagnostic ultrasound in the diagnosis of carpal tunnel syndrome is firmly established. Preoperative evaluation is based on quantitative parameters such as measurement of the pathologically enlarged cross-sectional area of the nerve. The value of postoperative ultrasound lies in the visualization of the anatomy and the conclusions that can be drawn from it. It focuses on the semiquantitative sonographic parameters of nerve compression. Nerve lesions and persistent strictures can be visualized and clearly localized. In recurrent disease, the primary focus is to dynamically exclude postoperative scarring, which results in a reduction of nerve gliding.

The EFSUMB Guidelines and Recommendations for Musculoskeletal Ultrasound - Part I: Extraarticular Pathologies

The first part of the guidelines and recommendations for musculoskeletal ultrasound, produced under the auspices of the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), provides information about the use of musculoskeletal ultrasound for assessing extraarticular structures (muscles, tendons, entheses, ligaments, bones, bursae, fasciae, nerves, skin, subcutaneous tissues, and nails) and their pathologies. Clinical applications, practical points, limitations, and artifacts are described and discussed for every structure. After an extensive literature review, the recommendations have been developed according to the Oxford Centre for Evidence-based Medicine and GRADE criteria and the consensus level was established through a Delphi process. The document is intended to guide clinical users in their daily practice.

MRI Evaluation of Various Elbow, Forearm, and Wrist Neuropathies: A Pictorial Review

Upper extremity entrapment neuropathies are common and can cause pain, sensory loss, and muscle weakness leading to functional disability. We conducted a retrospective review from January 2007 until March 2020 of the magnetic resonance imaging (MRI) features of intrinsic and extrinsic causes of wrist, forearm, and elbow neuropathies of 637 patients who received a diagnosis of neuropathy by means of clinical and electrodiagnostic testing. We discuss cases with varying intrinsic and extrinsic nerve pathologies, including postoperative examples, affecting the median, radial, and ulnar nerve.Our collection of cases demonstrates a diversity of intrinsic and extrinsic causative factors. Intrinsic pathologies include neuritis as well as tumors arising from the nerve. Extrinsic causes resulting in nerve entrapment include masses, acute and chronic posttraumatic cases, anatomical variants, inflammatory and crystal deposition, calcium pyrophosphate deposition disease, and dialysis-related amyloidosis. Finally, we review postsurgical cases, such as carpal tunnel release and ulnar nerve transposition.Although upper extremity neuropathies tend to have a typical clinical presentation, imaging, particularly MRI, plays a vital role in evaluating the etiology and severity of each neuropathy and ultimately helps guide clinical management.

Hand and Wrist Neuropathies: High-resolution Ultrasonography and MR Neurography

High-resolution ultrasonography (US) and magnetic resonance neurography (MRN) have followed parallel paths for peripheral nerve imaging with little comparison of the two modalities. They seem equally effective to study a variety of neuropathies affecting large and small nerves in the wrist and hand. This article outlines the technical considerations of US and MRN and discusses normal and abnormal imaging appearances of hand and wrist nerves from etiologies such as entrapment, injury, tumor, and proximal and diffuse neuropathy, with specific case illustrations.

Electrodiagnostic, Sonographic, and Clinical Features of Carpal Tunnel Syndrome with Bifid Median Nerve

Purpose

A bifid median nerve (BMN) is not a rare variant. This study aimed to investigate the features of carpal tunnel syndrome (CTS) accompanied by BMN.

Patients and Methods

In this retrospective study, we defined a BMN group as CTS with BMN and a non-bifid median nerve (NMN) group as CTS without BMN. All hands were assigned to four severity grades according to the findings of electrodiagnosis (EDx): very mild, mild, moderate, and severe. The cross-sectional area (CSA) of the median nerve, palmar bowing of the flexor retinaculum, and persistent median artery (PMA) were assessed by ultrasonography. Numerical pain rating scale (NRS) and symptom duration were assessed as clinical variables.

Results

Sixty-four hands (57 patients) and 442 hands (341 patients) were enrolled in the BMN and the NMN groups, respectively. BMN was prevalent in 12.6% of all CTS hands. The distribution of EDx severity grade was milder in the BMN group than in the NMN group (P<0.001). The CSA of the BMN group was 16.2±4.1 mm², slightly larger than 15.1±4.2 mm² in the NMN group (P=0.056). The BMN group showed higher NRS than the NMN group (5.5±1.5 and 4.4±1.7, respectively; P<0.001). In the subgroup analysis, NRS was significantly higher in the BMN group than in the NMN group at all EDx severity grades. In the BMN group, the PMA group showed greater EDx severity (P=0.037) and higher NRS (6.0 and 5.0, respectively; P=0.012) than the non-PMA group. The radial side branch's CSA was larger than that of the ulnar side branch (10.0 mm² and 6.0 mm², respectively; P<0.001).

Conclusion

CTS with BMN presented more severe symptoms and relatively milder EDx severity. When assessing the severity of CTS with BMN, the clinical symptoms should primarily be considered, as well as we should complementarily evaluate the EDx and ultrasonography.

Carpal tunnel syndrome caused by the entrapment of a bifid Lanz IIIA Type anatomical variant of median nerve: A case report and systematic literature review

Background:

Carpal tunnel syndrome (CTS) is the most common entrapment peripheral neuropathy. Median nerve may present several anatomical variations such as a high division or bifid median nerve (BMN). A thorough knowledge of the normal anatomy and variations of the median nerve at the wrist are fundamental to reduce complications during carpal tunnel release.

Case Description:

A 63-year-old man with CTS underwent preoperative ultrasound that showed the entrapment of the median nerve and disclosed a BMN Lanz IIIA Type anatomical variation at the carpal tunnel. During the surgery, the anatomical variant of a BMN at the wrist has been visualized. Both nervous rami entirely occupied the carpal canal and this may have predisposed to the development of the entrapment syndrome. Nor persistent median artery, or other associated abnormalities, have been identified. At the 6 months follow-up control, the patient referred a good surgical recovery with complete resolution of the preoperative symptoms of the median nerve entrapment.

Conclusion:

A rare case of Lanz IIIA BMN Type at the wrist has been encountered in a patient with a CTS and a systematic review and practical considerations have been presented with the aim of raising awareness to the neurosurgical community of a such rare variant that could be encountered during carpal tunnel release procedures. CTS may be caused by the entrapment of a BMN Lanz IIIA Type anatomical variant of median nerve. Preoperative US would help to identify such patients to reduce risk of iatrogenic injuries.

Assessing Diagnostic and Severity Grading Accuracy of Ultrasound Measurements for Carpal Tunnel Syndrome Compared to Electrodiagnostics

BACKGROUND

The combined sensory index (CSI) is the most sensitive electrodiagnostic criteria for carpal tunnel syndrome (CTS), and the CSI and Bland criteria have been shown to predict surgical treatment outcomes. The proposed ultrasound measurements have not been assessed against the CSI for diagnostic accuracy and grading of CTS severity.

OBJECTIVE

To investigate the use of ultrasound evaluations for both diagnosis and assessment of severity grading of CTS in comparison to electrodiagnostic assessment.

DESIGN

All patients underwent an electrodiagnostic evaluation using the CSI and Bland severity grading. Each patient underwent an ultrasound evaluation including cross-sectional area (CSA), the change in CSA from the forearm to the tunnel (∆CSA), and the wrist-forearm ratio (WFR). These measurements were assessed for diagnostic and severity grading accuracy using the CSI as the gold standard.

SETTING

Tertiary academic center.

PARTICIPANTS

All patients referred for electrodiagnostic evaluation for CTS were eligible for the study. Only those with idiopathic CTS were included and those with prior CTS treatment were also excluded. Ninety-five patients were included in the study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The primary study outcome measure was concordance between CSI diagnosis and severity categories and the ultrasound measurements. Both outcomes were also assessed using Bland criteria.

RESULTS

Optimal cut-points for diagnosis of CTS were found to be CSA ≥12 mm² , ∆CSA ≥4 mm² , WFR ≥1.4. Using these cut-points, C-statistics comparing diagnosis of CTS using ultrasound measurements versus using the CSI ranged from 0.893-0.966. When looking at CSI severity grading compared to ∆CSA, however, the C-statistics were 0.640-0.661 with substantial overlap between severity groups.

CONCLUSIONS

Although ultrasound measurements had high diagnostic accuracy for CTS based on the CSI criteria, ultrasound measurements were unable to adequately distinguish between CSI severity groups among patients with CTS.

Back to the roots of rheumatology - Imaging of regional pain syndromes

Musculoskeletal regional pain syndromes (RPS) often lead to patient referrals in general and rheumatological practice. Detailed history taking and clinical examination can, in most cases, reveal the cause for pain and direct the subsequent management of the conditions. Yet, when in doubt, imaging methods, such as ultrasound (US) may support the clinical assessment. This paper reviews the underlying pathologies of some of the most frequently encountered RPS and the role of musculoskeletal US imaging for their diagnosis and treatment. If available, data on diagnostic accuracy and comparisons with gold standards are reported. The article stresses the importance of anatomical and sonoanatomical knowledge for the proper interpretation of the US images, points out the advantages and disadvantages of this imaging tool, and suggests the future research agenda.

Clinico-radiological review of peripheral entrapment neuropathies - Part 1 upper limb

PURPOSE

This article aims to review the pertinent anatomy, etiopathogenesis, current clinical and radiological concepts and principles of management in case of upper limb entrapment neuropathies.

METHODS

The review is based on critical analysis of the existing literature as well as our experience in dealing with entrapment neuropathies.

RESULTS

Entrapment neuropathies of the upper limb peripheral nerves are common conditions that are often misdiagnosed because of their varying clinical presentations and lack of standardized diagnostic methods. Clinical assessment and electrodiagnostic studies have been the mainstay; however, imaging techniques have provided newer insights into the pathophysiology of these entities, leading to a paradigm shift in their diagnosis and management. The current best practice protocols for entrapment syndromes are constantly evolving with increasing emphasis on the role high-resolution ultrasound and magnetic resonance imaging. Many imaging criteria are described and we have tried to present the most validated measurements for diagnosing entrapment neuropathies.

CONCLUSION

It is imperative for a clinical radiologist to be familiar with the etiopathogenesis and clinical features of these conditions, in addition to being thorough with the anatomy and the latest imaging strategies.

Unusual Triad of Bifid Median Nerve, Persistent Median Artery, and Aberrant Muscle Causing Carpal Tunnel Syndrome: A Case Report

CASE

A 15-year-old boy presented with intermittent pain, in the left nondominant hand, for the past 3 years. He recently developed numbness in the radial 3 and a half digits. Ultrasonography revealed a bifid median nerve (BMN) with a persistent median artery (PMA). An open carpal tunnel release was performed, which revealed an accessory lumbrical muscle in addition to the BMN and a PMA.

CONCLUSION

The surgeon should be aware of the possible coexistence of 3 anomalous structures while performing carpal tunnel release in a young patient.

Repetitive Strain Injuries of the Upper Extremity: Imaging of Tendon Pathology and Compressive Neuropathies

Repetitive strain injuries (RSIs) encompass a broad clinicopathologic spectrum which includes discrete patterns of tissue injury involving tendons, bursae and nerves although an element of subjective symptomatology may be contributory. Upper extremity RSIs include De Quervain's tenosynovitis, intersection syndromes, epicondylitis, ulnar, and median neuritis as well as other compressive neuropathies. It is estimated that RSIs cost the US economy over $60 billion annually and while detailed clinical examination remains the diagnostic mainstay, imaging can aid in diagnosis, guide management and reduce costs.

Sonography before and after carpal tunnel release: video article

Carpal tunnel release for compression of the median nerve at the wrist is a common procedure, often resulting in good clinical outcomes. There are, however, many anatomical variations in and around the carpal tunnel and it is important to be aware of these during carpal tunnel release. After surgery, recurrent carpal tunnel syndrome is uncommon, but difficult to diagnose and treat. Ultrasonography is often necessary for the evaluation of the anatomical variations before carpal tunnel release and to evaluate the most common complications after carpal tunnel release.

Carpal tunnel sonography

Carpal tunnel syndrome (CTS) is the most frequent entrapment neuropathy of peripheral nerves, with an incidence of 1-3 patients in 1000. CTS typically occurs between 45 and 60 years of age, and it is more frequent in women than in men. The main cause of CTS is chronic compression of the median nerve and ischemic suffering secondary to increased pressure in the carpal tunnel. There are many possible causes of CTS, which can be differentiated into idiopathic causes, which include most cases, and secondary causes. Classical CTS diagnosis is based on the patient's clinical examination and electrophysiological tests, such as electromyography and nerve conduction studies. The latter are helpful for determining the site of nerve compression, assessing its severity, monitoring the course of the disease after therapy, and excluding other causes of median nerve pain, such as cervical radiculopathies, brachial plexopathies, polyneuropathy, or other forms of mononeuropathies. However, clinical examination and electrophysiological tests are not able to differentiate idiopathic forms from secondary forms of CTS, and discrepancies are possible between clinical examination and electrophysiological tests (false negatives). Ultrasound examination is able to recognize most of the secondary forms of CTS. It can evaluate the morphological alterations of the nerve and correlate them with the severity of nerve suffering in all cases, even idiopathic ones, with a sensitivity and specificity equal to those of electrophysiological tests. It can also highlight some anatomical predisposing variants or conditions that may represent contraindications to minimally invasive treatments. Ultrasound examination also plays a fundamental role in evaluating patients with an unfavorable outcome after surgical treatment.

Clinical Results of Ultrasound-Guided Carpal Tunnel Release Performed by a Primary Care Sports Medicine Physician

OBJECTIVES

The purpose of this study was to determine the safety and efficacy of ultrasound-guided carpal tunnel release (USCTR) in a consecutive group of patients treated by a single primary care sports medicine physician.

METHODS

The study group consisted of 35 USCTRs performed on 22 consecutive patients for whom clinical outcomes were available before USCTR and at 1 to 2 weeks, 1 month, and 3 months after USCTR. All procedures were performed by the same operator using a single USCTR technique. Outcomes included complications, Quick Disabilities of the Arm, Shoulder, and Hand scores, Boston Carpal Tunnel Questionnaire symptom severity and functional status scores, and a 5-point global satisfaction score.

RESULTS

The 22 patients included 13 female and 9 male patients (ages 31-82 years). Eleven patients (22 wrists) had bilateral simultaneous USCTRs; 2 patients (4 wrists) had staged bilateral USCTRs; and 9 patients had unilateral USCTRs. No complications occurred in any patient. Statistically and clinically significant reductions in Quick Disabilities of the Arm, Shoulder, and Hand scores and Boston Carpal Tunnel Questionnaire symptom severity and functional status scores occurred by 1 to 2 weeks after USCTR (mean 1- to 2-week changes, -29.23, -1.74, and -1.18, respectively), and further improvements occurred during the 3-month follow-up period (mean 3-month changes, -51.11, -2.29, and -1.91; P < .0001 for all values versus before USCTR). Mean global satisfaction scores at 1 to 2 weeks and 3 months were 4.63 and 4.66.

CONCLUSIONS

Ultrasound-guided CTR is a safe and effective procedure that can be performed by an experienced primary care sports medicine physician and typically results in significant improvements within the first 2 weeks after the procedure. Furthermore, bilateral simultaneous USCTRs are feasible and may provide significant advantages for patients who are candidates for bilateral CTRs.

Macrophages as Drug Delivery Carriers for Acoustic Phase-Change Droplets

The major challenges in treating malignant tumors are transport of therapeutic agents to hypoxic regions and real-time assessment of successful drug release via medical imaging modalities. In this study, we propose the use of macrophages (RAW 264.7 cells) as carriers of drug-loaded phase-change droplets to penetrate ischemic or hypoxic regions within tumors. The droplets consist of perfluoropentane, lipid and the chemotherapeutic drug doxorubicin (DOX, DOX-droplets). The efficiency of DOX-droplet uptake, migration mobility and viability of DOX-droplet-loaded macrophages (DLMs) were measured using a transmembrane cell migration assay, the alamarBlue assay and flow cytometric analysis, respectively. Our results indicate the feasibility of utilizing macrophages as DOX-droplet carriers (DOX payload of DOX-droplets: 459.3 ± 35.8 µg/mL, efficiency of cell uptake DOX-droplets: 88.8 ± 3.5%). The migration mobility (total number of migrated microphages) of DLMs decreased to 32.3% compared with that of healthy macrophages, but the DLMs provided contrast-enhanced ultrasound imaging (1.7-fold enhancement) and anti-tumor effect (70.9% cell viability) after acoustic droplet vaporization, suggesting the potential theranostic applications of DLMs. Future work will assess the tumor penetration ability of DLMs, mechanical effect of droplet vaporization on in vivo anti-tumor therapy and the release of the carried drug by ultrasound-triggered vaporization.

[Diagnostic nerve ultrasonography]

CLINICAL/METHODICAL ISSUE

For the diagnostics of nerve lesions an imaging method is necessary to visualize peripheral nerves and their surrounding structures for an etiological classification.

STANDARD RADIOLOGICAL METHODS

Clinical neurological and electrophysiological investigations provide functional information about nerve lesions. The information provided by a standard magnetic resonance imaging (MRI) examination is inadequate for peripheral nerve diagnostics; however, MRI neurography is suitable but on the other hand a resource and time-consuming method.

METHODICAL INNOVATIONS

Using ultrasonography for peripheral nerve diagnostics.

PERFORMANCE

With ultrasonography reliable diagnostics of entrapment neuropathies and traumatic nerve lesions are possible. The use of ultrasonography for neuropathies shows that a differentiation between different forms is possible.

ACHIEVEMENTS

Nerve ultrasonography is an established diagnostic tool. In addition to the clinical examination and clinical electrophysiology, structural information can be obtained, which results in a clear improvement in the diagnostics. Ultrasonography has become an integral part of the diagnostic work-up of peripheral nerve lesions in neurophysiological departments.

PRACTICAL RECOMMENDATIONS

Nerve ultrasonography is recommended for the diagnostic work-up of peripheral nerve lesions in addition to clinical and electrophysiological investigations. It should be used in the clinical work-up of entrapment neuropathies, traumatic nerve lesions and spacy-occupying lesions of nerves.

Occurrence of bifid median nerve in healthy and carpal tunnel syndrome patients

We investigated the possible association between median nerve morphology and carpal tunnel size, hand side and nerve conduction measurements. The study included a patient group (n = 58; 44 women) with idiopathic carpal tunnel syndrome (CTS) in 100 hands and a control group of healthy volunteers (n = 56, 112 hands; 44 women). The following data were recorded: (1) median and ulnar motor and sensory nerve conduction parameters (2) ultrasonographic dimensions of the carpal tunnel inlet area (CTA_in) and inlet area of the median nerve. The prevalence of bifid median nerve was 19% in the CTS hands and 13.3% in the control group. Bilateral bifid nerve was detected in 7 subjects and unilateral in 23, with no side or sex preponderance. The median nerve area was larger in the participants with single than those with bifid median nerve. No correlation was found between CTA_in and median nerve area for single or bifid nerves in controls or patients. It was concluded that bifid median nerve was not a rare variation. We could not, however, support its etiological relation to CTS. Ultrasonographic examination of the carpal tunnel region supplementing neurophysiology provided a reliable means to detect median nerve size and morphology.

CLINICAL TRIAL REGISTRATION NUMBER

84; 5/3/15.

The Median Nerve at the Carpal Tunnel … and Elsewhere

The median nerve (MN) may be affected by various peripheral neuropathies, each of which may be categorized according to its cause, as either an extrinsic (due to an entrapment or a nerve compression) or an intrinsic (including neurogenic tumors) neuropathy. Entrapment neuropathies are characterized by alterations of the nerve function that are caused by mechanical or dynamic compression. It occurs because of anatomic constraints at specific locations including sites where the nerve courses through fibro-osseous or fibromuscular tunnels or penetrates a muscle. For the diagnosis of peripheral neuropathies, physicians traditionally relied primarily on clinical findings and electrodiagnostic testing with electromyography. However, if further doubt exists, clinicians may ask for an additional imaging evaluation.

Exploratory use of ultrasound to determine whether demyelination following carpal tunnel syndrome co-exists with axonal degeneration

Carpal tunnel syndrome (CTS) accompanied by secondary axonal degeneration cannot be clearly discriminated using the current cross-validated ultrasound severity classification system. This study aimed at exploring cut-off values of ultrasound parameters, including wrist cross-sectional area (W-CSA), wrist perimeter (W-P), ratio of cross-sectional area (R-CSA) and perimeter (R-P), changes of CSA and P from wrist to one third distal forearm (ΔCSA&ΔP) for differentiation. Seventy-three patients (13 male and 60 female) were assigned into group A (demyelination only, n = 40) and group B (demyelination with secondary axonal degeneration, n = 33) based on the outcomes of nerve conduction studies (NCS). Receiver Operative Characteristics (ROC) curves were plotted to obtain sensitivity, specificity, and accuracy of cut-off values for all the ultrasound parameters. The overall identified cut-off values (W-CSA 12.0 mm², W-P 16.27 mm, R-CSA 1.85, R-P 1.48, ΔCSA 6.98 mm², ΔP 5.77 mm) had good sensitivity (77.1–88.6%), fair specificity (40–62.2%) and fair-to-good accuracy (0.676–0.758). There were also significant differences in demographics (age and severity gradation, P < 0.001), NCS findings (wrist motor latency and conduction velocity, P < 0.0001; wrist motor amplitude, P < 0.05; distal sensory latency, P < 0.05; sensory amplitude, P < 0.001) and ultrasound measurements (W-CSA, W-P, R-CSA, R-P, ΔCSA&ΔP, P < 0.05) between groups. These findings suggest that ultrasound can be potentially used to differentiate demyelinating CTS with secondary axonal degeneration and provide better treatment guidance.

Review of Ultrasonography in the Diagnosis of Carpal Tunnel Syndrome and a Proposed Scanning Protocol

Carpal tunnel syndrome is the most common peripheral compressive neuropathy. Ultrasonography (US) is an emerging technology that can be used in the diagnosis of carpal tunnel syndrome. Although the cross-sectional area is the most studied and validated measurement for carpal tunnel syndrome, there is no standardized neuromuscular US scanning protocol. We review the most studied neuromuscular US characteristics and protocols in the evaluation of carpal tunnel syndrome and propose a standardized protocol for evaluating carpal tunnel syndrome with neuromuscular US based on current literature.

Cross-sectional area of the median nerve is increased in primary autoimmune hypothyroidism and decreases upon treatment with thyroxine

BACKGROUND

The purpose of this study was to assess changes in the cross-sectional area (CSA) of nervus medianus by ultrasound in newly diagnosed primary hypothyroid patients after thyroxine replacement treatment.

PATIENTS AND METHODS

The cohort comprised 30 patients with newly diagnosed primary autoimmune hypothyroidism. These were subsequently compared with 30 controls, matched for sex, BMI and age. Ultrasound evaluation, including measurement of CSA at the level of the pisiform bone or tunnel inlet was performed at baseline and after 3months. A CSA threshold of more than 10mm(2) was considered pathological.

RESULTS

CSA was increased in patients compared with controls (9.8±0.7mm(2) vs 7.2±1.1mm(2); P<0.001). Thyroxin substitution increased fT4 levels (baseline, 11.0±0.6pmol/L vs 15.5±0.4pmol/L; P<0.001) and decreased TSH (baseline, 23.9±6.0mIU/L vs 2.7±0.2mIU/L; P<0.001). Thyroxine treatment decreased CSA to 8.4mm(2)±0.3mm(2) (P=0.033). Before treatment, four patients experienced distal paresthesia in the median nerve distribution area. Increased CSA pathognomonic for carpal tunnel syndrome found in two symptomatic patients normalized after 3months. No clinical symptoms were observed after 3months. A positive correlation was found between TSH and CSA (R=0.155, P=0.05) before treatment.

CONCLUSION

Our study demonstrates that increase in median nerve CSA caused by primary autoimmune hypothyroidism can be fully reversible after achieving target levels of TSH and fT4.

Sonography of Common Peripheral Nerve Disorders With Clinical Correlation

Sonography is now considered an effective method to evaluate peripheral nerves. Low cost, high resolution, the ability to image an entire limb in a short time, and dynamic assessment are several of the positive attributes of sonography. This article will review the normal appearance of peripheral nerves as shown with sonography. In addition, the most common applications for sonography of the peripheral nerves will be reviewed, which include entrapment neuropathies, intraneural ganglion cyst, nerve trauma, and peripheral nerve sheath tumors. Clinical information related to nerve disorders is also included, as it provides valuable information that can be obtained during sonographic examinations, increasing diagnostic accuracy.

Entrapment and traumatic neuropathies of the elbow and hand: An imaging approach

Ultrasound and magnetic resonance imaging currently offer a detailed analysis of the peripheral nerves. Compressive and traumatic nerve injuries are the two main indications for imaging investigation of nerves with several publications describing the indications, technique and diagnostic capabilities of imaging signs. Investigation of entrapment neuropathies has three main goals, which are to confirm neuronal distress, search for the cause of nerve compression and exclude a differential diagnosis on the entire nerve. For traumatic nerve injuries, imaging, predominantly ultrasound, occasionally provides essential information for management including the type of nerve lesion, its exact site and local extension.

The Prevalence of Anatomical Variations of the Median Nerve in the Carpal Tunnel: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVE

The course and branches of the median nerve (MN) in the wrist vary widely among the population. Due to significant differences in the reported prevalence of such variations, extensive knowledge on the anatomy of the MN is essential to avoid iatrogenic nerve injury. Our aim was to determine the prevalence rates of anatomical variations of the MN in the carpal tunnel and the most common course patterns and variations in its thenar motor branch (TMB).

STUDY DESIGN

A systematic search of all major databases was performed to identify articles that studied the prevalence of MN variations in the carpal tunnel and the TMB. No date or language restrictions were set. Extracted data was classified according to Lanz's classification system: variations in the course of the single TMB--extraligamentous, subligamentous, and transligamentous (type 1); accessory branches of the MN at the distal carpal tunnel (type 2); high division of the MN (type 3); and the MN and its accessory branches proximal to the carpal tunnel (type 4). Pooled prevalence rates were calculated using MetaXL 2.0.

RESULTS

Thirty-one studies (n = 3918 hands) were included in the meta-analysis. The pooled prevalence rates of the extraligamentous, subligamentous, and transligamentous courses were 75.2% (95%CI:55.4%-84.7%), 13.5% (95%CI:3.6%-25.7%), and 11.3% (95%CI:2.4%-23.0%), respectively. The prevalence of Lanz group 2, 3, and 4 were 4.6% (95%CI:1.6%-9.1%), 2.6% (95%CI:0.1%-2.8%), and 2.3% (95%CI:0.3%-5.6%), respectively. Ulnar side of branching of the TMB was found in 2.1% (95%CI:0.9%-3.6%) of hands. The prevalence of hypertrophic thenar muscles over the transverse carpal ligament was 18.2% (95%CI:6.8%-33.0%). A transligamentous course of the TMB was more commonly found in hands with hypertrophic thenar muscles (23.4%, 95%CI:5.0%-43.4%) compared to those without hypertrophic musculature (1.7%, 95%CI:0%-100%). In four studies (n = 423 hands), identical bilateral course of the TMB was found in 72.3% (95%CI:58.4%-84.4%) of patients.

CONCLUSIONS

Anatomical variations in the course of the TMB and the MN in the carpal tunnel are common in the population. Thus, we recommend an ulnar side approach to carpal tunnel release, with a careful layer by layer dissection, to avoid iatrogenic damage to the TMB.

Carpal tunnel syndrome assessment with ultrasonography: value of inlet-to-outlet median nerve area ratio in patients versus healthy volunteers

Objective

To evaluate the diagnostic value of the Inlet-to-outlet median nerve area ratio (IOR) in patients with clinically and electrophysiologically confirmed carpal tunnel syndrome (CTS).

Methods

Forty-six wrists in 46 consecutive patients with clinical and electrodiagnostic evidence of CTS and forty-four wrists in 44 healthy volunteers were examined with ultrasonography. The cross-sectional area (CSA) of the median nerve was measured at the carpal tunnel inlet (the level of scaphoid-pisiform) and outlet (the level of the hook of the hamate), and the IOR was calculated for each wrist. Ultrasonography and electrodiagnostic tests were performed under blinded conditions. Electrodiagnostic testing combined with clinical symptoms were considered to be the gold standard test. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic value between the inlet CSA and IOR.

Results

The study population included 16 men and 30 women (mean age, 45.3 years; range, 18–83 years). The control population included 18 men and 26 women (mean age, 50.4 years; range, 18–79 years). The mean inlet CSA was 8.7 mm² in healthy controls and 14.6mm² in CTS group (P<0.001). The mean IOR in healthy volunteers (1.0) was smaller than that in patients (1.6, P<0.001). Receiver operating characteristic analysis revealed a diagnostic advantage to using the IOR rather than the inlet CSA (P<0.01). An IOR cutoff value of ≥ 1.3 would yield 93% specificity and 91% sensitivity in the diagnosis of CTS.

Conclusion

The IOR of median nerve area promises to be an effective means in the diagnosis of CTS. A large-scale, randomized controlled trial is required to determine how and when this parameter will be used.