The ultrasonographic correlates of carpal tunnel syndrome in patients with normal electrodiagnostic tests

Automated segmentation of the median nerve in patients with carpal tunnel syndrome

Machine learning and deep learning are novel methods which are revolutionizing medical imaging. In our study we trained an algorithm with a U-Net shaped network to recognize ultrasound images of the median nerve in the complete distal half of the forearm and to measure the cross-sectional area at the inlet of the carpal tunnel. Images of 25 patient hands with carpal tunnel syndrome (CTS) and 26 healthy controls were recorded on a video loop covering 15 cm of the distal forearm and 2355 images were manually segmented. We found an average Dice score of 0.76 between manual and automated segmentation of the median nerve in its complete course, while the measurement of the cross-sectional area at the carpal tunnel inlet resulted in a 10.9% difference between manually and automated measurements. We regard this technology as a suitable device for verifying the diagnosis of CTS.

Sonographic reference values for median nerve cross-sectional area: A meta-analysis of data from healthy individuals

Objective

Establish median nerve CSA reference values and identify patient-level factors impacting diagnostic thresholds.

Methods

Studies were identified through a robust search of multiple databases, and quality assessment was conducted using a modified version of the National Institute of Health Study Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. A meta-analysis was performed to identify normative values stratified by anatomic location. A meta-regression was conducted to examine heterogeneity effects of age, sex, and laterality.

Results

The meta-analysis included 73 studies; 41 (56.2%) were high quality. The median nerve CSA [95% CI] was 6.46mm2 [6.09-6.84], 8.68mm2 [8.22-9.13], and 8.60mm2 [8.23-8.97] at the proximal forearm, the carpal tunnel inlet, and the proximal carpal tunnel, respectively. Age was positively associated with CSA at the level of proximal carpal tunnel (β=0.03mm2, p=0.047). Men (9.42mm2, [8.06-10.78]) had statistically larger proximal tunnel CSA (p = 0.03) as compared to women (7.71mm2, [7.01-8.42]). No difference was noted in laterality.

Conclusion

A reference value for median nerve CSA in the carpal tunnel is 8.60mm2. Adjustments may be required in pediatrics or older adults. The diagnostic threshold of 10.0mm2 for male patients should be cautiously applied as the upper limit of normative averages surpasses this threshold.

Comparison efficacy of ultrasound-guided needle release plus corticosteroid injection and mini-open surgery in patients with carpal tunnel syndrome

This retrospective study was to compare clinical outcomes of ultrasound-guided needle release with corticosteroid injection vs. mini-open surgery in patients with carpal tunnel syndrome (CTS). From January 2021 to December 2021, 40 patients (40 wrists) with CTS were analyzed in this study. The diagnosis was based on clinical symptoms, electrophysiological imaging, and ultrasound imaging. A total of 20 wrists were treated with ultrasound-guided needle release plus corticosteroid injection (Group A), and the other 20 wrists were treated with mini-open surgery (Group B). We evaluated the Boston carpal tunnel questionnaire, electrophysiological parameters (distal motor latency, sensory conduction velocity, and sensory nerve action potential of the median nerve), and ultrasound parameters (cross-sectional area, flattening ratio, and the thicknesses of transverse carpal ligament) both before and 3 months after treatment. Total treatment cost, duration of treatment, healing time, and complications were also recorded for the two groups. The Boston carpal tunnel questionnaire and electrophysiological and ultrasound outcomes at preoperatively and 3 months postoperatively had a significant difference for each group (each with P < 0.05). There were no complications such as infection, hemorrhage, vascular, nerve, or tendon injuries in both groups. Ultrasound-guided needle release and mini-open surgery are both effective measures in treating CTS patients. Ultrasound-guided needle release plus corticosteroid injection provides smaller incision, less cost, less time of treatment, and faster recovery compared with mini-open surgery. Ultrasound-guided needle release plus corticosteroid injection is better for clinical application.

The cross-sectional morphology of median nerve in carpal tunnel of healthy, adult population: A systematic review and meta-analysis

The cross-section area is a crucial parameter to assess peripheral neuropathy. The ultrasonographic evaluation of cross-section area of median nerve is a low-cost and readily available tool for diagnosis and assessment. However, the intra-nerve dimensional variability and its normative reference value in a healthy subject are missing. The current meta-analysis aims to capture the median nerve cross-section area for healthy subjects and generate a comprehensive ultrasonographic reference data set for each population.

METHODS

The full text of manuscripts were collected after short-listing the abstracts collected from search strategy. A quality assurance tool was used to capture the risk of bias of each study after reviewing the included manuscripts. The pooled estimate of cross-section area was stratified according to anatomical landmarks, sex, and ancestry.

RESULTS

A total of 97 observational studies dealt with 6679 wrists of healthy subjects were included. The pooled estimate of the cross-section area of median nerve at carpal tunnel inlet was 8.54mm² [95% CI: 8.34-8.74mm²]. The same pooled estimate at carpal tunnel outlet was 8.03mm² [95% CI: 7.46-8.60mm²]. Both these pooled estimates have significant correlation with mean age of population. Age and sex were two primary predictors of the cross-section of median nerve. The flattening ratio, circularity, and wrist-forearm ratio of median nerve were also computed.

CONCLUSION

These normative data could serve as a reference for assessing median nerve pathologies, including carpal tunnel syndrome. The ethnic variation of pooled estimate and heterogeneity will guide clinician set up the reference value for diagnostic criteria.

Longitudinal Median Nerve Ultrasound Changes in Individuals With Spinal Cord Injury and an Age- and Sex-Matched Nondisabled Cohort

Objectives

To assess the natural history for development of carpal tunnel syndrome (CTS) in persons with acute spinal cord injury (SCI) at 1 year postdischarge from initial rehabilitation and to assess baseline median nerve (MN) cross-sectional area (CSA) above/below 10 mm2 correlates with any longitudinal changes in quantitative ultrasound (US) of the MN.

Design

A prospective cohort study of persons with acute SCI evaluated for CTS using quantitative US and compared to a group without SCI (non-SCI).

Setting

Academic medical center.

Participants

N=69 total (N=34 SCI, N=35 non-SCI). The average age in both groups was 28 and the SCI group included 30 males and 2 females and the non-SCI group included 30 males and 3 females.

Interventions

Not applicable.

Main Outcome Measures

The primary outcome was the change in quantitative US parameters of the MN, including CSA and grayscale, from baseline to 1-year follow-up in those with SCI and those without SCI. CTS symptomatology and physical exam sum score and US measures for dominant and nondominant arms were considered secondary outcomes.

Results

The SCI had darker nerves at baseline (P=.036, nondominant), greater CTS symptoms at follow-up (P≤.036, bilateral), and no differences in all change scores (all P≥.056). Individuals with smaller nerves at baseline had larger increases in nerve size (P=.029, nondominant) vs those with larger nerves. Change in CTS symptoms CSA (nondominant) and nerve echogenicity (dominant) were inversely associated with their respective baseline values (all P≤.045).

Conclusions

We observed few differences between the SCI group and the non-SCI control group and between those with smaller vs larger MN. In general, MN pathology changes (CTS symptoms and US variables) over 1 year were more common in the nondominant arm and appear to be a function of MN pathology at enrollment. Individuals with SCI may experience increased CTS symptoms as soon as 1 year after injury.

How to Differentiate Pronator Syndrome from Carpal Tunnel Syndrome: A Comprehensive Clinical Comparison

The diagnostic process that allows pronator syndrome to be differentiated reliably from carpal tunnel syndrome remains a challenge for clinicians, as evidenced by the most common cause of pronator syndrome misdiagnosis: carpal tunnel syndrome. Pronator syndrome can be caused by compression of the median nerve as it passes through the anatomical structures of the forearm, while carpal tunnel syndrome refers to one particular topographic area within which compression occurs, the carpal tunnel. The present narrative review is a complex clinical comparison of the two syndromes with their anatomical backgrounds involving topographical relationships, morphology, clinical picture, differential diagnosis, and therapeutic options. It discusses the most frequently used diagnostic techniques and their correct interpretations. Its main goal is to provide an up-to-date picture of the current understanding of the disease processes and their etiologies, to establish an appropriate diagnosis, and introduce relevant treatment benefiting the patient.

A systematic review: normative reference values of the median nerve cross-sectional area using ultrasonography in healthy individuals

Median nerve cross-sectional area (CSA) was used for screening and diagnosis of neuropathy, but few studies have suggested reference range. Hence, this systematic review was performed to evaluate a normative values of median nerve CSA at various landmarks of upper limb based on ultrasonography. PubMed and Web of science were used to search relevant articles from 2000 to 2020. Forty-one eligible articles (2504 nerves) were included to access median nerve CSA at different landmarks (mid-arm, elbow, mid-forearm, carpal tunnel (CT) inlet and CT outlet). Data was also stratified based on age, sex, ethnicity, geographical location, and method of measurement. Random effects model was used to calculate pooled weighted mean (95% confidence interval (CI), [upper bound, lower bound]) at mid-arm, elbow, mid-forearm, CT inlet and outlet which found to be 8.81 mm², CI [8.10, 9.52]; 8.57 mm² [8.00, 9.14]; 7.07 mm² [6.41, 7.73]; 8.74 mm² [8.45, 9.03] and 9.02 mm² [8.08, 9.95] respectively. Median nerve CSA varies with age, geographical location, and sex at all landmarks. A low (I² < 25%) to considerable heterogeneity (I² > 75%) was observed, indicating the variation among the included studies. These findings show that median nerve CSA is varying not only along its course but also in other sub-variables.

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

BACKGROUND

Power Doppler ultrasonography has been used as an adjunct in the diagnosis of peripheral nerve compression neuropathy. To better characterize its sensitivity and specificity, the authors performed a systematic review of its use in carpal and cubital tunnel syndrome diagnosis.

METHODS

The authors systematically reviewed published literature on the use of power Doppler ultrasound to diagnose peripheral compression neuropathy using Ovid MEDLINE, Embase.com, Scopus, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects, Health Technology Assessment Database, NHS Economic Evaluation Database, World Health Organization International Clinical Trial Repository Platform, and Clinicaltrials.gov. No filters for language, date, or publication type were used.

RESULTS

After reviewing 1538 identified studies, 27 publications were included involving 1751 participants with compression neuropathy (2048 median and 172 ulnar). All but three studies examined patients with carpal tunnel syndrome. Heterogeneity between study design and methodology was a noted limitation. Sensitivity and specificity of power Doppler ultrasound in the diagnosis of carpal tunnel syndrome ranged from 2.2 to 93.4 percent, and 89 to 100 percent, respectively, whereas sensitivity for cubital tunnel syndrome was 15.3 to 78.9 percent. There was variability in power Doppler signal detection based on location, with higher sensitivities at the carpal tunnel inlet and in areas of increased nerve swelling.

CONCLUSIONS

Power Doppler ultrasound is unreliable as a screening test but appears to increase diagnostic accuracy of ultrasonography in compression neuropathies. It is most beneficial in moderate to severe disease and may be valuable in detecting early cases and in disease surveillance.

Utility of shear wave elastography and high-definition color for diagnosing carpal tunnel syndrome

OBJECTIVE

The diagnostic values of measuring median nerve (MN) stiffness and vascularity with shear wave elastography (SWE) and high-definition (HD) color were investigated in carpal tunnel syndrome (CTS).

METHODS

Seventy patients (123 wrists) with CTS and thirty-five healthy volunteers (70 wrists) were enrolled. Based on nerve conduction studies (NCS), the patients were subdivided into NCS-negative, mild-to-moderate, and severe CTS groups. MN and abductor pollicis brevis (APB) SWE and MN HD color were performed on a longitudinal plane.

RESULTS

The mild-to-moderate and severe CTS groups showed increased MN stiffness at the wrist and MN stiffness ratio (wrist-to forearm) compared with the control (p < 0.001). The NCS-negative CTS group showed increased MN stiffness at the wrist (p = 0.022) and MN stiffness ratio (p = 0.032) compared with the control. The severe CTS group showed increased MN stiffness at the wrist compared with the mild-to-moderate CTS group (p = 0.034). The cutoff-values in diagnosing NCS-confirmed CTS were 50.12 kPa for MN stiffness at the wrist, 1.91 for MN stiffness ratio, and grade 1 for HD color.

CONCLUSIONS

SWE and HD color are good supportive tools in diagnosing and assessing severity in CTS.

SIGNIFICANCE

SWE and HD color demonstrated that MN in CTS was associated with increased stiffness and hypervascularity.

Microvascular blood flow changes of the abductor pollicis brevis muscle during sustained static exercise

A practical assessment of the general health and microvascular function of the palm muscle, abductor pollicis brevis (APB), is important for the diagnosis of different conditions. In this study, we have developed a protocol and a probe to study microvascular blood flow using near-infrared diffuse correlation spectroscopy (DCS) in APB during and after thumb abduction at 55% of maximum voluntary contraction (MVC). Near-infrared time resolved spectroscopy (TRS) was also used to characterize the baseline optical and hemodynamic properties. Thirteen (n=13) subjects were enrolled and subdivided in low MVC (N=6, MVC<2.3 kg) and high MVC (N=7, MVC≥2.3 kg) groups. After ruling out significant changes in the systemic physiology that influence the muscle hemodynamics, we have observed that the high MVC group showed a 56% and 36% decrease in the blood flow during exercise, with respect to baseline, in the long and short source-detector (SD) separations (p=0.031 for both). No statistical differences were shown for the low MVC group (p=1 for short and p=0.15 for long SD). These results suggest that the mechanical occlusion, due to increased intramuscular pressure, exceeded the vasodilation elicited by the higher metabolic demand. Also, blood flow changes during thumb contraction negatively correlated (R=-0.7, p<0.01) with the absolute force applied by each subject. Furthermore, after the exercise, muscular blood flow increased significantly immediately after thumb contractions in both high and low MVC groups, with respect to the recorded values during the exercise (p=0.031). An increase of 251% (200%) was found for the long (short) SD in the low MVC group. The high MVC groups showed a significant 90% increase in blood flow only after 80 s from the start of the protocol. For both low and high MVC groups, blood flow recovered to baseline values within 160 s from starting the exercise. In conclusion, DCS allows the study of the response of a small muscle to static exercise and can be potentially used in multiple clinical conditions scenarios for assessing microvascular health.

Ultrasound assessment of carpal tunnel in rheumatoid arthritis and idiopathic carpal tunnel syndrome

Objectives

To comparatively assess the sonographic spectrum of carpal tunnel syndrome (CTS) in patients with rheumatoid arthritis (RA) and in patients with idiopathic CTS.

Methods

Fifty-seven RA patients and 25 idiopathic CTS patients were consecutively enrolled. The diagnosis of CTS in RA patients was made according to clinical history and examination. The following sonographic findings were assessed at carpal tunnel level: median nerve cross-sectional area (CSA) at the carpal tunnel proximal inlet, finger flexor tendons tenosynovitis, radio-carpal synovitis and intraneural power Doppler (PD) signal.

Results

CTS was diagnosed in 15/57 RA patients (26.3%). Twenty-three RA wrists with CTS, 84 RA wrists without CTS and 34 idiopathic CTS wrists were evaluated. The average CSA of the median nerve was higher in idiopathic CTS than in RA wrists with CTS (17.7 mm² vs 10.6 mm², p < 0.01). A higher rate of inflammation of synovial structures (flexor tendons sheath and/or radio-carpal joint) was found in RA wrists with CTS compared with those without CTS (p = 0.04) and idiopathic CTS (p = 0.02). Intraneural PD signal was more common in CTS (in both RA and idiopathic CTS) wrists compared with wrists without CTS (p < 0.01).

Conclusion

The sonographic spectrum of CTS in RA patients is characterized by an inflammatory pattern, defined by the presence of finger flexor tendons tenosynovitis and/or radio-carpal joint synovitis. Conversely, a marked median nerve swelling is the dominant feature in idiopathic CTS. Intraneural PD signal is a frequent finding in both conditions.

Key Points • Carpal tunnel syndrome (CTS) associated with rheumatoid arthritis (RA) and idiopathic CTS have distinct ultrasound patterns. • The most characteristic sonographic features of CTS in RA patients are those indicative of synovial tissue inflammation at carpal tunnel level. Conversely, marked median nerve swelling is the dominant finding in idiopathic CTS. • Intraneural power Doppler signal is a frequent finding in both conditions. • In patients with CTS, differently from electrophysiology, US can provide clues prompting a rheumatology referral in case of prominent inflammatory findings at carpal tunnel level.

Gray Scale Histogram Analysis of Carpal Tunnel Syndrome with Ultrasonography

PURPOSE

In this study, we aim to evaluate the diagnostic value of echogenicity ratio with histogram analyses.

MATERIALS & METHODS

This retrospective study was performed on 22 patients with 44 hands. The patients had clinical presentations consistent with CTS, in at one hand. Quantitative ultrasound scanning and image capture were completed using a diagnostic sonography machine. For gray scale histogram analysis, image J software was used.

RESULTS

Mean flexor tendons histogram analysis echogenicity/Mean median nerve histogram analysis echogenicity was significantly high for 1,7 cutoff value.

CONCLUSION

Mean FTE/MNE ratio may be a useful sonographic parameter for CTS.

Value of Grayscale and Power Doppler High-Resolution Ultrasound in Assessment of Patients with Clinically Suspected Carpal Tunnel Syndrome

OBJECTIVES

To determine the value of grayscale and power Doppler ultrasound (PDUS) in the evaluation of carpal tunnel syndrome (CTS) in clinically suspected patients.

METHODS

Eighty-seven wrists of 61 patients with clinically suspected CTS and 57 wrists of 30 healthy control participants were included in our study. Median nerve (MN) cross-sectional area (CSA) measurements were performed at the tunnel inlet level (wCSA) and proximal pronator quadratus muscle level (fCSA). Two parameters were calculated: CSA absolute difference (ΔCSA), which was the difference between the two measurements; and CSA ratio (RCSA), calculated by dividing wCSA over fCSA. The MN at the wrist level was evaluated for hypervascularity with PDUS.

RESULTS

The mean wCSA, R-CSA, and ΔCSA values were significantly higher in patients (17 mm² , 2.45, and 9.9 mm² , respectively) than in control participants (8 mm² , 1.29, and 1.65 mm² ; (P < .0001). At their corresponding cutoff values, the wCSA yielded higher sensitivity (95%) and lower specificity (88%) compared to the RCSA and ΔCSA (89% and 93% sensitivity and 93% and 89% specificity). Power Doppler US was the most specific US parameter (100%) but the least sensitive (76%). A multivariate logistic regression model including the wCSA, RCSA, and PDUS yielded 97% diagnostic accuracy at their optimal cutoffs, which increased to 99% after eliminating age and body mass index confounding effects.

CONCLUSIONS

The combination of MN swelling measurements and PDUS increases the diagnostic accuracy of US in patients with clinically suspected CTS.

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.

Median nerve ultrasound in carpal tunnel syndrome with normal electrodiagnostic tests

INTRODUCTION

To evaluate the ultrasound findings of the median nerve in patients with clinical assigned carpal tunnel syndrome but normal nerve conduction studies.

METHODS

This prospective, cross-sectional study involved 41 patients (51 hands) with clinically assigned CTS and normal nerve conduction studies and 20 healthy controls (30 hands). Ultrasonography was performed in all participants, and cross-sectional area (CSA), hypoechogenicity, and mobility of the median nerve were evaluated. All patients were assessed with Boston Carpal Tunnel Questionnaire (BCTQ).

RESULTS

CSA of the median nerve in the wrist was significantly higher in the patient group when compared to the control group. Echogenicity and mobility were significantly decreased in the patient group. Ultrasound abnormalities were positively correlated with clinical features. A significant correlation was observed among sensory loss, provocative tests, body mass index, BCTQ, and high CSA.

CONCLUSION

US can help the clinicians with the diagnosis of carpal tunnel syndrome in patients with clinical symptoms but negative nerve conduction study results.

Upper limb neurodynamic test 1 in patients with clinical diagnosis of carpal tunnel syndrome: A diagnostic accuracy study

STUDY DESIGN

Diagnostic accuracy.

INTRODUCTION

Upper limb neurodynamic test 1 (ULNT1) is used to evaluate the mechanical sensitivity especially in the peripheral nerves of the upper limbs. The reproduction of typical symptoms in the affected hand improves the estimation of the probability of carpal tunnel syndrome (CTS). However the test has not been evaluated sufficiently to determine its real usefulness. In the present study the diagnostic accuracy of ULNT1 as a clinical test for CTS was determined.

METHODS

We used the ULNT1 as the index test and nerve conduction as the reference standard. 120 subjects, (240 hands), with a medical diagnosis of CTS were evaluated. The study population was a consecutive series of participants. Sensitivity, specificity, positive and negative predictive values, accuracy, and positive likelihood ratio were calculated.

RESULTS

ULNT1 was found to have a sensitivity of 93 % and a specificity of 6.67 %. The positive likelihood ratio was 1.04 and the negative likelihood ratio was 1.00. The positive predictive value was 86.9 % and the negative predictive value was 12.5%.

DISCUSSION

Acute or relatively mild CTS cases may not be accurately identified through nerve conduction tests. The findings of this study coincide with other studies in the finding that ULNT1 has a significant diagnostic and clinical screening value for CTS in people at-risk, or with upper limb symptoms.

CONCLUSION(S)

This research suggests the use of ULNT1 as a screening test for CTS, followed by tests that are more specific.

LEVEL OF EVIDENCE

III-2.

Diagnostic Accuracy of Ultrasound Parameters in Carpal Tunnel Syndrome: Additional Criteria for Diagnosis

OBJECTIVES

To determine the diagnostic capacity of ultrasound (US) in detecting carpal tunnel syndrome (CTS).

METHODS

Volunteer adults with and without CTS symptoms were recruited from offices in metropolitan Manila, where employees' work was hand/wrist intensive. Carpal tunnel syndrome was independently diagnosed by a reference standard (positive findings on a physical examination and nerve conduction studies). Blinded US measurements were taken of the median nerve (cross-sectional area, hypervascularity, wrist-to-forearm ratio, wrist-forearm difference, swelling ratio, flattening ratio, and palmar bowing of the flexor retinaculum) at the carpal tunnel inlet and carpal tunnel outlet (CTO).

RESULTS

A total of 117 eligible consenting participants (234 hands) were included, with 54 hands (23.1%) with a diagnosis of CTS. There were no anthropometric differences between arms with and without CTS. Men and women older than 33 years were 5 times more likely to report CTS than younger people. A CTO wrist-forearm difference of greater than 0.03 cm had the strongest association with CTS (odds ratio, 4.7; 95% confidence interval, 1.4-15.9), with an area under the curve of 0.58 (sensitivity, 94.4%; specificity, 21.7%). The area under the curve increased to 0.59 when the next strongest measurement (CTO hypervascularity of 1+: odds ratio, 3.8; 95% confidence interval, 1.8-8.1) was included (sensitivity, 98.1%; specificity, 27.7%). Adding further US parameters did not improve the diagnostic capacity of US for CTS. Diagnostic capacity was independent of age and the duration of CTS symptoms.

CONCLUSIONS

Combining US findings for the CTO wrist-forearm difference and hypervascularity provides a sensitive, alternative diagnostic tool for CTS.

Medical Ultrasound in the Evaluation of the Carpal Tunnel: A Critical Review

The use of medical ultrasound as an imaging modality in the evaluation of the carpal tunnel syndrome has been growing. Technical progress and the introduction of new, high-quality devices and ultra-high frequency transducers with smaller dimensions have led to a better quality of acquired images and the development of new examination methodologies. The sonographic method has a number of advantages: available, non-invasive, cheaper, and allows an easier and faster evaluation and diagnosis of carpal tunnel syndrome, along with the possibility to assess various parameters of the median nerve, including its size, blood flow, and mobility. In addition, medical ultrasound may be used to detect anatomical variations and space-occupying lesions in the carpal tunnel to monitor the therapeutic response in patients suffering from carpal tunnel syndrome and to evaluate median nerve injuries. Herein, we present a review of the pertinent literature with regard to the diagnostic potential of medical ultrasound in the evaluation of pathological changes in the carpal tunnel.

[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.

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.

Treatment outcome in patients with clinically defined carpal tunnel syndrome but normal electrodiagnostic test results: a randomized controlled trial

Little is known about treatment effect of carpal tunnel release in patients with clinically defined carpal tunnel syndrome (CTS), but normal electrodiagnostic test results (EDX). The aim of this study was to determine whether this category of patients will benefit from surgical treatment. 57 patients with clinically defined CTS and normal EDX were randomized for surgical treatment (n = 39) or non-surgical treatment (n = 18). A six-point scale for perceived improvement as well as the Boston Carpal Tunnel Questionnaire was completed at baseline and at follow-up after 6 months. A significant improvement of complaints was reported by 70.0% of the surgically treated patients and 39.4% reported full recovery 6 months after surgery. Furthermore, both Functional Status Score and Symptom Severity Score improved significantly more in the surgically treated group (p = 0.036 and p < 0.001, respectively). This study demonstrates that most patients with clinically defined CTS and normal EDX results will benefit from carpal tunnel release. Therefore, this group of CTS patients must not a priori be refrained from surgery.

Nerve ultrasound in clinical management of carpal tunnel syndrome in mucopolysaccharidosis

AIM

Mucopolysaccharidoses (MPS) are a group of diseases with an almost 100% lifetime incidence of carpal tunnel syndrome (CTS) in MPSsubtypes I, II, and VI. We compared nerve ultrasound with clinical signs and electrophysiology in a clinical setting to screen for CTSin MPS.

METHOD

Twenty-four patients (13 male, 11 female, mean age of 7y 11mo [SD8y 5mo], range 6mo-29y) were screened for CTS. Eight of these patients were re-examined post-operatively. Clinical signs, distal motor latency, compound muscle action potential, sensory nerve action potential amplitude and velocity, as well as echogenicity and the cross-sectional area (CSA) of the median nerve at the wrist and forearm determined with ultrasound were assessed and the wrist to forearm ratio (WFR) calculated. Eighteen healthy participants formed a comparison group, who were also investigated with nerve ultrasound.

RESULTS

In 26% of the patients' hands, clinical signs of CTSwere present; 77% fulfilled electrophysiological and 92% nerve ultrasound criteria for CTS. Post-operatively, electrophysiology improved significantly, whereas ultrasound results were unchanged. In the comparison group, age and height correlated with the CSA, but not with WFR.

INTERPRETATION

Nerve ultrasound is a useful and painless primary screening tool for CTSin MPS.

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.

Detection of Intraneural Median Nerve Microvascularity Using Contrast-Enhanced Sonography: A Pilot Study

OBJECTIVES

Demonstrating vascularity within the human median nerve may be difficult using power Doppler sonography. To this end, a pilot study documenting contrast-enhanced vascularity of the median nerve was conducted.

METHODS

Patients undergoing contrast-enhanced transthoracic echocardiography were recruited for this study (n = 24). During echocardiography, a simultaneous contrast-enhanced sonographic examination of the median nerve was conducted. The study and study protocol were built from preclinical evidence. Image analysis was based on the power Doppler pixel intensity within a defined region of interest to obtain quantitative data representing the average pixel intensity, maximum pixel intensity, and power Doppler pixel dot count. Semiquantitative data representing the power Doppler dot count grading were also obtained.

RESULTS

Spearman correlations between analytical methods showed strong positive, statistically significant (P< .05) correlations between the average pixel intensity and maximum pixel intensity and between the power Doppler dot count and dot count grading. Statistically significant increases in the average pixel intensity and power Doppler dot count were seen at all but 1 time point throughout the contrast-enhanced sonographic examination when compared to precontrast administration. Statistically significant increases in the maximum pixel intensity were seen at all but 4 time points.

CONCLUSIONS

These pilot results represent early evidence that contrast-enhanced sonography can be used to image median nerve vascularity. In this convenience sample, median nerve contrast-enhanced sonographic data collection was feasible, safe, and consistent.

Electrosonodiagnosis in Carpal Tunnel Syndrome: A Proposed Diagnostic Algorithm Based on an Analytic Literature Review

BACKGROUND

Suspected carpal tunnel syndrome (CTS) remains the most common clinical scenario prompting referral for electrodiagnostic (EDx) studies to identify objective correlates of reported subjective symptoms and clinical examination findings. Despite much debate and a rapidly expanding literature, identification of an optimal algorithm for diagnosing focal median mononeuropathy at the wrist (FMMW) associated with CTS signs and symptoms remains elusive. The introduction and rapid dissemination of peripheral nerve ultrasound imaging (PN-USI) of the median nerve has raised new questions regarding the relative value of structural information from PN-USI versus physiological information from EDx in the diagnosis of FMMW, as well as the significance of various clinical signs and symptoms suggestive of CTS. The means by which PN-USI and EDx may be optimally deployed and integrated in the process of diagnosing FMMW remains to be clearly delineated.

OBJECTIVE

To complete an analytical literature review to guide the formulation of a clinical diagnostic algorithm (CDA) integrating the use of PN-USI and EDx for the optimal detection of FMMW in the context of making a clinical diagnosis of CTS.

DATA SOURCES

A structured literature review was performed on the MEDLINE medical literature database accessed through PubMed.

ANALYSIS

Papers with particular relevance and connection to the goal of formulating the CDA were selected from the identified studies. Studies specifically examining the correlations between systematically documented clinical symptomatology, EDx findings, and PN-USI findings were reviewed for consistent outcomes that could be incorporated into a CDA to guide the integration of these two complementary technologies in the diagnostic process.

LIMITATIONS

The formulation of the algorithm was limited to measures with established validity that can be readily obtained by means of widely accepted protocols using standard EDx and ultrasound equipment. The formulated algorithm assumes a consistent association between pathophysiology and anatomical deformation of the median nerve, which may not occur in certain situations. It may also not be as accurately applied to patients with CTS with significant comorbid neuromuscular conditions.

CONCLUSIONS

An algorithm has been developed and presented, and illustrated as a flow chart, based on findings reported in the relevant reviewed literature in which PN-USI is proposed as a painless and rapidly performed screening test for FMMW to be completed before subjecting a patient to a systematic EDx testing process.

Diagnosis of Severe Carpal Tunnel Syndrome Using Nerve Conduction Study and Ultrasonography

This study investigated the correlation between nerve conduction study and ultrasonographic findings for assessment of the usefulness of ultrasonography in determining carpal tunnel syndrome severity. Hands of adults with carpal tunnel syndrome were assessed using ultrasound and nerve conduction studies and grouped according to median nerve cross-sectional area (CSA). There were significant differences (p < 0.01) in mean median nerve CSA between controls, patients with median sensory nerve conduction velocity ≤40 m/s and patients with absent sensory nerve action potential and between controls, patients with median nerve distal motor latency ≥4.5 ms and patients with absent compound muscle action potentials of the abductor pollicis brevis. This is the first report to define median nerve CSA cutoff values (18 mm(2)) for determining carpal tunnel syndrome severity in patients with absent compound muscle action potentials of the abductor pollicis brevis. Median nerve CSA values below the cutoff values should prompt clinicians to consider other disorders, such as cervical compressive myelopathy.

Comparative study between physical examination, electroneuromyography and ultrasonography in diagnosing carpal tunnel syndrome

OBJECTIVE

To evaluate the sensitivity of electromyography and ultrasonography in diagnosing carpal tunnel syndrome (CTS), in comparison with physical examination, which is considered to be the gold standard.

METHODS

In this cross-sectional study, the medical files of 56 patients with 70 hands affected by CTS who were attended between March 2010 and June 2012 were reviewed. The study included patients with a clinical diagnosis of CTS. The sensitivity of the complementary examinations was analyzed and compared with physical examination.

RESULTS

Nocturnal symptoms were found in 96.4%, thenar atrophy in 62.5% and abnormal sense of touch in 50%. The sensitivities found were: ultrasonography, 67.1% (95% CI: 55.7%-78.6%); an association of physical examination tests, 95.7% (95% CI: 90.0%-100%); and electromyography, 98.6% (95% CI: 95.7%-100%). The presence of atrophy, abnormalities of the sense of touch and longer-duration symptoms increased the sensitivity of ultrasonography and physical examination.

CONCLUSION

The sensitivity of ultrasonography for CTS was lower than that of electromyography and physical examination.

Carpal tunnel syndrome severity staging using sonographic and clinical measures

INTRODUCTION

Ultrasonography may be valuable in staging carpal tunnel syndrome severity, especially by combining multiple measures. This study aimed to develop a preliminary severity staging model using multiple sonographic and clinical measures.

METHODS

Measures were obtained in 104 participants. Multiple categorization structures for each variable were correlated to diagnostic severity based on nerve conduction. Goodness-of-fit was evaluated for models using iterative combinations of highly correlated variables. Using the best-fit model, a preliminary scoring system was developed, and frequency of misclassification was calculated.

RESULTS

The severity staging model with best fit (rho 0.90) included patient-reported symptoms, functional deficits, provocative testing, nerve cross-sectional area, and nerve longitudinal appearance. An 8-point scoring scale classified severity accurately for 79.8% of participants.

CONCLUSIONS

This severity staging model is a novel approach to carpal tunnel syndrome evaluation. Including more sensitive measures of nerve vascularity, nerve excursion, or other emerging techniques may refine this preliminary model.

Ultrasound assessment of the median nerve: a biomarker that can help in setting a treat to target approach tailored for carpal tunnel syndrome patients

Ultrasonography (US) is a valuable tool for confirming the diagnosis of carpal tunnel syndrome (CTS) as it enables the detection of changes in the median nerve shape and rule out anatomic variants as well as space-occupying lesions such as ganglion cysts or tenosynovitis. This work was carried out aiming at: 1. Ultrasonography assessment of the median nerve and its neurovascular blood-flow in CTS patients before and after management. 2. Verify the possibility of using baseline US parameters as a biomarker to predict likely outcomes and frame a treatment plan for CTS patients. 233 CTS subjects diagnosed based on clinical and electrophysiological (NCS) testing were included in this work. US measures at the tunnel inlet included: cross sectional area, flattening ratio and neural Power Doppler (PD) signals. Patients who had severe NCS outcomes or neurological deficit were referred for open surgical decompression; the remaining patients were given the choice of either conservative or surgical management. The main outcome variable was improvement >70% in CTS symptoms. Assessments were carried out at baseline, 1-week, 1-month and 6-months post treatment. Results revealed an inverse relation between the neural vasculature and CTS severity defined by NCS (r = - 0.648). In CTS cases treated conservatively, the US measures started to improve within 1-week, whereas in the surgically treated cohort there was an initial phase of post-operative nerve measures increase, before settling at 1-month time of follow-up. The risk of poor outcomes was significantly higher (RR 3.3) in patients with high median nerve flattening ratio. This risk was most marked in the cohort with nerve flattening associated with longer duration of illness (RR 4.3) and low PD signal (RR 4.1). The results revealed that in addition to the diagnostic value of US in CTS, the detection of increased median nerve neuro-vasculature has a good prognostic value as an indicator of early median nerve affection.

The role of ultrasound in the diagnosis and management of carpal tunnel syndrome: a new paradigm

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, affecting 9% of women, and it is responsible for significant morbidity and occupational absence. Clinical assessment is used for initial diagnosis and nerve conduction (NC) studies are currently the principal test used to confirm the diagnosis. Sensitivity of NC studies is >85% and specificity is >95%. There is now good evidence that US can be used as an alternative to NC studies to diagnose CTS. US can assess the anatomy of the median nerve and also identify pathology of the surrounding structures that may compress the nerve. Median nerve enlargement (cross-sectional area ≥10 mm(2) at the level of the pisiform bone or tunnel inlet) is the most commonly used parameter to diagnose CTS on US, and sensitivity has been reported to be as high as 97.9% using this parameter. US may also be used to guide therapeutic corticosteroid injection into the carpal tunnel--thus avoiding median nerve injury--and to objectively monitor the response to treatment. There is now sufficient evidence to propose a new paradigm for the diagnosis of CTS that incorporates US. US is proposed as the initial diagnostic test in CTS based on similar sensitivity and specificity to NC studies but higher patient acceptability, lower cost and additional capability to assess carpal tunnel anatomy and guide injection.

Longitudinal Analysis of Median Nerve Perfusion Using Spectral Doppler in a Working Animal Model

Carpal tunnel syndrome (CTS) is a form of median mononeuropathy (MMN) of the wrist that has become the most common nerve entrapment syndrome of the upper limbs. During the acute phase of CTS, the median nerve becomes hyperemic and enlarged as it begins to be compressed by the transverse carpal ligament; however, continual compression ultimately leads to median nerve ischemia. The objective of this study was to longitudinally quantify the amount of perfusion of the median nerve using spectral Doppler in a working animal model, as the cohort prospectively increased their risk of MMN through a repetitive pinching task. The results of the study provided low-level evidence that the use of spectral Doppler to accurately detect longitudinal changes in vascularity within the median nerve may be diagnostically inadequate. As the subjects in the study moved through the working and nonworking stages of study, spectral Doppler alone proved to lack the level of sensitivity needed to detect physiologic changes within the nerve. This outcome, although inconclusive when it comes to detecting changes in median nerve vascularity, does suggest the need for this method to be analyzed in conjunction with other sonographic features and provocative testing.

Provocation tests in doppler ultrasonography for carpal tunnel syndrome

INTRODUCTION

Doppler ultrasonography (DU) has recently been shown to be useful in imaging carpal tunnel syndrome (CTS). In this study, we aim to characterize the changes seen after exercise and electrical stimulation.

METHODS

Five patients with CTS were recruited with 5 age-matched subjects. DU was used to visualize the median nerve, flexor tendon, and bone at base line and after 1 minute of: (a) median nerve motor stimulation, (b) median nerve sensory stimulation, (c) abductor pollicis brevis contraction, and (d) adductor digiti minimi contraction.

RESULTS

Blood flow in the median nerve was greater after APB exercise. Furthermore, blood flow in the median nerve was greater in cases than controls after APB exercise. At baseline, blood flow in the flexor tendon was greater in cases than controls.

CONCLUSIONS

While limited by sample size, this study demonstrates that exercise of median innervated muscles may be useful in enhancing diagnostic utility of DU for CTS.

Relationship between intraneural vascular flow measured with sonography and carpal tunnel syndrome diagnosis based on electrodiagnostic testing

OBJECTIVES

The purpose of this study was to document and analyze intraneural vascular flow within the median nerve using power and spectral Doppler sonography and to determine the relationship of this vascular flow with diagnosis of carpal tunnel syndrome based on electrodiagnostic testing.

METHODS

Power and spectral Doppler sonograms in the median nerve were prospectively collected in 47 symptomatic and 44 asymptomatic subjects. Doppler studies were conducted with a 12-MHz linear transducer. Strict inclusion criteria were established for postexamination assessment of waveforms; routine quality assurance was completed; electrodiagnostic tests were conducted on the same day as sonographic measurements; and the skin temperature was controlled. Included waveforms were categorized by location and averaged by individual for comparative analysis to electrodiagnostic testing.

RESULTS

A total of 416 waveforms were collected, and 245 were retained for statistical analysis based on strict inclusion criteria. The mean spectral peak velocity among all waveforms was 4.42 (SD, 2.15) cm/s. At the level of the pisiform, the most consistent data point, mean peak systole, was 3.75 cm/s in symptomatic patients versus 4.26 cm/s in asymptomatic controls. Statistical trending showed an initial increase in the mean spectral peak velocity in symptomatic but diagnostically negative cases, with decreasing velocity as diagnostic categories progressed from mild to severe.

CONCLUSIONS

An inverse relationship may exist between intraneural vascular flow in the median nerve and an increasing severity of carpal tunnel syndrome based on nerve conduction results. Randomized controlled trials are needed to determine whether spectral Doppler sonography can provide an additive benefit for diagnosing the severity of carpal tunnel syndrome.

Ultrasonographic median nerve cross-section areas measured by 8-point "inching test" for idiopathic carpal tunnel syndrome: a correlation of nerve conduction study severity and duration of clinical symptoms

BACKGROUND

Incremental palmar stimulation of the median nerve sensory conduction at the wrist, the "inching test", provides an assessment with reference to segments proximal and distal to the entrapment. This study used high-resolution ultrasonography (US) to measure the median nerve's cross-section areas (CSAs) like the "inching test" and to correlate with the nerve conduction study (NCS) severity and duration of carpal tunnel syndrome (CTS).

METHODS

Two hundred and twelve (212) "CTS-hands" from 135 CTS patients and 50 asymptomatic hands ("A-hands") from 25 control individuals were enrolled. The median nerve CSAs were measured at the 8-point marked as i4, i3, i2, i1, w, o1, o2, and 03 in inching test. The NCS severities were classified into six groups based on motor and sensory responses (i.e., negative, minimal, mild, moderate, severe, and extreme). Results of US studies were compared in terms of NCS severity and duration of clinical CTS symptoms.

RESULTS

There was significantly larger CSA of the NCS negative group of "CTS-hands" than of "A-hands". The cut-off values of the CSAs of the NCS negative CTS group were 12.5 mm2, 11.5 mm2 and 10.1 mm2 at the inlet, wrist crease, and outlet, respectively. Of the 212 "CTS-hands", 32 were NCS negative while 40 had minimal, 43 mild, 85 moderate, 10 severe, and two extreme NCS severities. The CSAs of "CTS-hands" positively correlated with different NCS severities and with the duration of CTS symptoms. By duration of clinical symptoms, 12 of the 212 "CTS-hands" were in the 1 month group; 82 in >1 month and ≤ 12 months group, and 118 in >12 months group. In "inching test", segments i4-i3 and i3-i2 were the most common "positive-site". The corresponding CSAs measured at i4 and i3, but not at i2, were significantly larger than those measured at points that were not "positive-site".

CONCLUSIONS

Using the 8-point measurement of the median nerve CSA from inlet to outlet similar to the "inching test" has positive correlations with NCS severity and duration of CTS clinical symptoms, and can provide more information on anatomic changes. Combined NCS and US studies using the 8-point measurement may have a higher positive rate than NCS alone for diagnosing CTS.