Does the ratio of the carpal tunnel inlet and outlet cross-sectional areas in the median nerve reflect carpal tunnel syndrome severity?

Carpal tunnel syndrome

Median neuropathy at the wrist, commonly referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy. It is caused by chronic compression of the median nerve at the wrist within the space-limited carpal tunnel. Risk factors that contribute to the etiology of compression include female gender, obesity, work-related factors, and underlying medical conditions, such as hypothyroidism, pregnancy, and amyloidosis. The diagnosis is made on clinical grounds, although these can be confounded by anatomical variations. Electrodiagnostic studies, which are specific and sensitive in diagnosing CTS, support the diagnosis; however, a subgroup may present with normal results. The advent of imaging techniques, including ultrasound and MRI, further assists the diagnostic process. The management of CTS is divided into the nonsurgical approaches that include hand therapy, splinting and corticosteroid injection, and surgical decompression of the carpal tunnel. Although several surgical techniques have been developed, no one method is more effective than the other. Each of these management approaches are effective at providing symptom relief and are utilized at different severities of the condition. There is, however, a lack of consensus on standardized diagnostic criteria, as well as when and to whom to refer patients for surgery.

Spatial Relationship of the Median Nerve and Transverse Carpal Ligament in Asymptomatic Hands

The spacing between the median nerve and transverse carpal ligament (TCL) within the carpal tunnel can potentially affect the nerve morphology. This study aimed to quantify the spatial relationship between the median nerve and transverse carpal ligament in asymptomatic hands. Twelve subjects were recruited to image the carpal tunnel using robot-assisted ultrasound. The median nerve and TCL were segmented from each image and three-dimensionally reconstructed using kinematic information from the robot. The TCL-median nerve distance, nerve cross-sectional area, circularity, and position were measured along the entirety of the nerve length within the carpal tunnel. Results were averaged at every 5% of nerve length. At the nerve length percentages of 0% (distal), 25%, 50%, 75%, and 100% (proximal), the TCL-median nerve distance (±SD) was 0.7 ± 0.4, 0.7 ± 0.2, 0.5 ± 0.2, 0.5 ± 0.2, and 0.6 ± 0.3 mm, respectively. The corresponding nerve cross-sectional area was 9.4 ± 1.9, 10.6 ± 2.6, 11.2 ± 2.1, 11.2 ± 1.7, and 9.7 ± 1.9 mm2. A one-way analysis of variance showed no significant differences between the respective percentages of nerve length for TCL-median nerve distance (p = 0.219) and cross-sectional area (p = 0.869). Significant (p < 0.0001) but weak correlations were observed between the TCL-median nerve distance with cross-sectional area (r = -0.247) and circularity (r = -0.244). This study shows that the healthy median nerve morphology is consistent along the continuous nerve length within the carpal tunnel, supporting the use of 2D imaging in the evaluation of the healthy nerve.

Ultrasonographic measurement of median nerve and wrist skin thickness in patients with carpal tunnel syndrome: relationship with clinical, electrophysiologic and functionality

The study aimed to investigate the relationship between the proximal and distal cross-sectional area (CSA) of the median nerve and wrist skin thickness measured by ultrasound in patients with carpal tunnel syndrome (CTS), demographics, disease characteristics, electrophysiological measurements, symptom severity, functionality, and symptom severity. 98 patients with electrophysiological diagnoses of CTS in the dominant hand were included in the study. Proximal and distal CSAs of the median nerve and wrist skin thickness were measured ultrasonographically. Demographic and disease characteristics of the patients were recorded. Patients were evaluated with the Historical-Objective scale (Hi- Ob) for clinical staging, the Functional status scale (FSS) for functional status, and the Boston symptom severity scale (BSSS) for symptom severity. Ultrasonographic findings were correlated with demographic and disease characteristics, electrophysiological findings, Hi-Ob scala, Functional status scale (FSS), and Boston symptom severity scale (BSSS). Proximal median nerve CSA median was 11.0 (7.0-14.0) mm2, distal median nerve CSA median was 10.5 (5.0-18.0) mm2, and wrist skin thickness was measured 1.10 (0.6-1.40) mm. Median nerve CSAs were positively correlated with the CTS stage and FSS, negatively correlated with the sensory nerve action potential of the median nerve (SNAP) and the compound muscle action potential of the median nerve (CMAP) ( p<0.05). Wrist skin thickness was positively correlated with disease characteristics, including the presence of paresthesia and loss of dexterity and FSS and BSSS levels. Ultrasonographic measurements in CTS are associated with functionality rather than demographics. Especially the increase in wrist skin thickness leads to an increase in symptom severity.

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.

Magnetic Resonance Neurography: Improved Diagnosis of Peripheral Neuropathies

Peripheral neuropathies account for the most frequent disorders seen by neurologists, and causes are manifold. The traditional diagnostic gold-standard consists of clinical neurologic examinations supplemented by nerve conduction studies. Due to well-known limitations of standard diagnostics and atypical clinical presentations, establishing the correct diagnosis can be challenging but is critical for appropriate therapies. Magnetic resonance neurography (MRN) is a relatively novel technique that was developed for the high-resolution imaging of the peripheral nervous system. In focal neuropathies, whether traumatic or due to nerve entrapment, MRN has improved the diagnostic accuracy by directly visualizing underlying nerve lesions and providing information on the exact lesion localization, extension, and spatial distribution, thereby assisting surgical planning. Notably, the differentiation between distally located, complete cross-sectional nerve lesions, and more proximally located lesions involving only certain fascicles within a nerve can hold difficulties that MRN can overcome, when basic technical requirements to achieve sufficient spatial resolution are implemented. Typical MRN-specific pitfalls are essential to understand in order to prevent overdiagnosing neuropathies. Heavily T2-weighted sequences with fat saturation are the most established sequences for MRN. Newer techniques, such as T2-relaxometry, magnetization transfer contrast imaging, and diffusion tensor imaging, allow the quantification of nerve lesions and have become increasingly important, especially when evaluating diffuse, non-focal neuropathies. Innovative studies in hereditary, metabolic or inflammatory polyneuropathies, and motor neuron diseases have contributed to a better understanding of the underlying pathomechanism. New imaging biomarkers might be used for an earlier diagnosis and monitoring of structural nerve injury under causative treatments in the future.

[Imaging of the hand : What should be considered regarding the nerves?]

BACKGROUND

Peripheral nerve disorders of the hand and wrist are most commonly caused by entrapment neuropathies, while traumatic nerve injuries and neoplasms are less common.

OBJECTIVES

The indication for additional imaging methods and different imaging options, especially in patients with atypical symptoms or remaining unclear etiology of symptoms after completion of standard diagnostics, are presented.

MATERIALS AND METHODS

The imaging methods magnetic resonance (MR) neurography and neurosonography are introduced, and typical findings as well as diagnostic pitfalls are presented.

RESULTS

The diagnostic gold standard, which comprises a past medical history, neurologic examination and electrophysiology, can often establish the diagnosis. Imaging methods, especially MR neurography and neurosonography, are gaining increasing importance in the diagnostic workup of atypical neuropathies, as well as in the determination of the exact lesion location and spatial lesion extension, especially for surgical planning. Recent technical advances allow high-resolution depiction of small distal terminal nerve branches.

CONCLUSIONS

MR neurography allows for the high-resolution depiction of peripheral nerves of the hand and wrist. It can confirm the diagnosis of neuropathy, identify the exact lesion location, and rule out any differential diagnoses. Neurosonography is a time- and cost-efficient alternative diagnostic method.

Role of High Frequency Ultrasound in Diagnosing Carpal Tunnel Syndrome as Compared with Conventional Nerve Conduction Studies

Objective:

Our aim was to evaluate High Frequency Ultrasonography as a tool for diagnosis in patients withcarpal tunnel syndrome in comparison with electrophysiological study.

Methods:

Thirty- one patients [56 hands] with CTS and twenty-five asymptomatic controls [50 hands] were assessed and underwent ultrasonography of the wrists and electrophysiological testing. Data from the patient and the control groups was compared for both the investigations to determine the CTS and the grade of severity.

Results:

There was a high degree of correlation between the conduction abnormalities of the median nerve as detected by electrodiagnostic tests, historic and objective scale [Hi-Ob] and the measurement of the cross-sectional area of the nerve by US (P < 0.05). A cut-off point of 0.88 mm² for the mean cross-sectional area of the median nerve was found to be the upper limit for normal values. Compared to Ultrasonography which found one hand negative, six hands (10%) were negative on the electrophysiological tests. Using critical CSA value of 1.0 mm² in these CTS cases by US with sensitivity and specificity of 100% and 88%. Based on the results of this study, ultrasonography of wrist is another useful tool along with nerve conduction studies as per sensitivity and specificity patterns found in our study in diagnosis of carpal tunnel syndrome.

Conclusion:

High-frequency US examination of the median nerve and measurement of its cross-sectional area can be strongly considered as useful diagnostic diagnostic modality for the evaluation of CTS along with nerve conduction studies. In addition to its high diagnostic accuracy it is able to define the cause of nerve compression, aids treatment planning and provides a reliable method to follow response to therapy.

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.

Sonoelastic response of median nerve to rehabilitation in carpal tunnel syndrome

Aim of the study

To evaluate the sonoelastic response of the median nerve in patients with carpal tunnel syndrome following conservative rehabilitation with splint plus exercise regimens.

Materials and methods

A total of thirty-five patients diagnosed with mild carpal tunnel syndrome and treated with splint plus exercise therapy; hand resting splint all day for 3 weeks and then only at nights along with nerve gliding exercises in 10 repetitions 3 times a day. The median nerve was evaluated clinically prior to the treatment and at week 6 of therapy using physical examination, electrodiagnostic neurophysiology tests and radiological imaging; Boston Scores, electromyogram, ultrasonography and sonoelastography.

Results

Following the 6-week treatment protocol on 35 subjects with mild carpal tunnel syndrome, sonoelastography showed significantly softer median nerve, while the traditional parameters based on Boston Scores and cross-sectional area based on ultrasonography remained nearly unresponsive. Such early indication of biomechanical changes in the nerve may be of clinical importance if it can offer a prognostic value of the applied treatment, while tissue softening suggests the alleviation of nerve compression.

Conclusions

Sonoelasticity of the median nerve can serve as a reliable marker for assessing therapeutic changes in median nerve stiffness and potentially the outcome early on in mild carpal tunnel syndrome.

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.

Acupotomy for patients with carpal tunnel syndrome: A systematic review protocol

BACKGROUND

This systematic review program is designed to provide an assessment of the effectiveness and safety of needle-knife therapy for the treatment of carpal tunnel syndrome (CTS).

METHODS

A cumulative search till October 2018 will be conducted in the following 8 databases: PubMed, EMBASE, Cochrane Controlled Trials Register, MEDLINE, China National Knowledge Infrastructure, China Biomedical Literature Database, VIP Database, and Wanfang Database, with no language or Publication status restrictions. All randomized controlled trials (RCT) for carpal tunnel syndrome will be considered eligible. The primary outcomes will include changes in the Boston carpal tunnel questionnaire (BCTQ) and visual analogue score (VAS), as well as safety and adverse events. Study inclusion, data extraction, and quality assessment will be done independently by 2 reviewers. If no substantial heterogeneity is detected, a meta-analysis will be performed. Continuous results will be expressed as mean differences or standard average differences, while binary data will be expressed as relative risks. The deviation risk and data synthesis will be assessed using the Review Manager software.

RESULTS

This study will provide a high-quality synthesis of BCTQ and VAS to assess the effectiveness and safety of acupotomy for carpal tunnel syndrome patients.

CONCLUSION

This systematic review will provide evidence to judge whether acupotomy is an effective intervention for patients with carpal tunnel syndrome.

PROSPERO REGISTRATION NUMBER

CRD42018108787.

Use of Multiple Ultrasonographic Parameters in Confirmation of Carpal Tunnel Syndrome

OBJECTIVES

Ultrasonography (US) of the median nerve has been increasingly studied and used for confirmation of carpal tunnel syndrome (CTS). However, a consensus on the choice of parameters to be evaluated is still not established. The aim of this diagnostic accuracy study was to assess the diagnostic value of multiple parameters individually, as well as in different combinations of variable complexity, and to find an optimal approach for US-based confirmation of a CTS diagnosis.

METHODS

All participants completed clinical and electrophysiologic evaluations, and their hands were scanned with a 5-13-MHz linear US transducer. Eighty-six patients with CTS (135 symptomatic hands) and 50 control participants (93 asymptomatic hands) were analyzed. The median nerve was recorded transversely at the forearm, at the carpal tunnel inlet, in the mid tunnel, and at the carpal tunnel outlet. For determining the parameters' diagnostic value, sensitivities, specificities, and area under the curve (AUC) values were calculated.

RESULTS

The inlet cross-sectional area, inlet circumference, and outlet cross-sectional area of the median nerve had the highest AUCs (0.962, 0.920, and 0.913, respectively), sensitivities (87.4%, 80.0%, and 74.1%), and specificities (94.6%, 91.4%, and 92.5%) among single-measurement parameters. An analysis of 2-level parameters (wrist-to-forearm-ratio, inlet-to-outlet-ratio, outlet-to-forearm-ratio, and inlet-outlet mean) yielded the highest AUC (0.974) for the mean cross-sectional area of the median nerve [(inlet + outlet cross-sectional area)/2], with high sensitivity (93.5%) and specificity (91.1%). A compound regression-based index yielded a marginally higher AUC (0.989) than the previously mentioned parameters.

CONCLUSIONS

Results of the study show that the mean cross-sectional area and inlet cross-sectional area may be valid and easy-to-acquire parameters for routine clinical use in confirming CTS.

Inter-Rater and Intra-Rater Reliability of Sonographic Median Nerve and Wrist Measurements

Background:

Electrophysiologic studies have been considered the “gold standard” in diagnosing carpal tunnel syndrome (CTS); however, reports of false-negative results, as well as discomfort for the patient during the procedure has paved the use of ultrasound, being a painless and cost-efficient tool, as an alternative means for its diagnosis. Various ultrasound parameters assessing the median nerve and wrist dimensions have been described, but description of landmarks to assess these in a reliable manner has been lacking.

Methodology:

A systematic search of different databases yielded data regarding ultrasound parameters for CTS diagnosis, the landmarks used, and presence of reliability testing. Based on this, three sonologists discussed the external and sonographic landmarks that will be used in measuring the median nerve measurements, bowing of the flexor retinaculum and the carpal tunnel dimensions. A pilot test with two consecutive healthy participants using the discussed ultrasound parameters was carried out, and results were subjected to inter- and intra-rater reliability testing. Modifications were accordingly made on the acquisition of ultrasound image using external landmarks. The reliability testing proper was done with ten consecutive healthy participants.

Results:

Based on the systematic review and the pilot study, external landmarks were used to locate the median nerve in the forearm, carpal tunnel inlet and outlet. For the forearm measurement, it was taken 10 cm proximal from the distal palmar crease. The distal palmar crease was the external landmark used for the carpal tunnel inlet, while for the carpal tunnel outlet; it was measured 1 cm distal to the distal palmar crease. Instead of using the inner edge of the hook of hamate and trapezium, the apices of these bones were used as the landmarks in measuring the carpal tunnel outlet dimensions. There was excellent intra-rater reliability (mid-forearm, carpal tunnel inlet and outlet) except for the following: cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet and outlet; and bowing of the flexor retinaculum. All the parameters had an excellent inter-rater reliability measured at the three levels (intraclass correlation [ICC]: Of 0.77–0.99) except for CSA of the median nerve at the levels of the forearm (fair-to-good with ICC of 0.71) and the carpal tunnel inlet (fair-to-good reliability of ICC: 0.43).

Conclusion:

There was an improved inter- and intra-rater reliability when external landmarks were used instead of sonographic landmarks.

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.