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.

A "Clear" Carpal Tunnel Syndrome Diagnosis on Ultrasound Examination Does Not Predict Improved Outcomes When Compared With a "Borderline" Diagnosis.

BACKGROUND: Nerve conduction studies (NCS) and ultrasound (US) remain imperfect compared with clinical diagnosis and/or diagnostic tools such as carpal tunnel syndrome-6 (CTS-6) for diagnosis of carpal tunne syndrome (CTS). One potential reason for the discrepancy between clinical diagnosis and testing is "borderline" case inclusion. This study aims to compare clinical outcomes after carpal tunnel release (CTR) between "borderline" and "clear" patients with CTS determined by NCS and US. METHODS: This was a retrospective review of patients who underwent CTR. We collected NCS and US measurements of the median nerve cross-sectional area (MNCSA) at the carpal tunnel inlet, and the Boston Carpal Tunnel Questionnaire (BCTQ) scores comprised of the Symptom Severity Scale (SSS) and the Functional Status Scale (FSS). Ultrasound measurements defined patients as having "borderline" (MNCSA < 13 mm2) or "clear" (MNCSA ≥ 13 mm2) CTS. RESULTS: The study included 94 unilateral patients with CTS. "Borderline" CTS was diagnosed in 58 patients (62%), and "clear" CTS was diagnosed in 36 patients (38%). No significant differences in BCTQ scores were found between groups. At greater than 6-month follow-up, the mean FSS was 1.44 and 1.45 for clear and borderline groups, respectively (P = .97) and the mean SSS was 1.47 and 1.51, respectively (P = .84). However, a significant difference between groups when comparing distal motor latency (DML) and distal sensory latency (DSL) existed. The mean DSL was 3.71 and 4.44 for the clear and borderline groups, respectively (P = .02). The mean DML was 4.59 and 5.36 (P = .048). CONCLUSION: Categorizing CTS diagnosis into "borderline" and "clear" based on preoperative US and NCS testing did not correlate with BCTQ changes after CTR. It remains unclear whether the BCTQ is a valid postoperative assessment tool, despite its frequent use in literature.

Reduction in median nerve cross-sectional area at the forearm correlates with axon loss in carpal tunnel syndrome.

OBJECTIVE: To explore the relationship between axon loss and measured cross-sectional areas of the median nerve (MN) in severe carpal tunnel syndrome (CTS). METHODS: In this retrospective study of 158 examined wrists, we compared axon loss to the ultrasound parameters MN cross-sectional area at the wrist (wCSA), MN cross-sectional area at the forearm (fCSA) and wrist-to-forearm ratio (WFR), in patients with moderate to extreme CTS. Axon loss was evaluated by needle electromyography (EMG) of the abductor pollicis brevis muscle (spontaneous activity and reduction of interference pattern). RESULTS: Both the spontaneous activity and interference pattern reduction correlated negatively to fCSA (r = -0.189, p = 0.035; r = -0.210, p = 0.019; respectively). In moderate CTS, both the spontaneous activity and interference pattern reduction correlated positively to WFR (r = 0.231, p = 0.048; r = 0.232, p = 0.047; respectively). The WFR was highest when slight spontaneous activity was detected. Neither wCSA nor WFR correlated with axon loss in severe and extreme CTS. CONCLUSIONS: The fCSA is smaller when axon loss in CTS is more prominent. The WFR is highest when CTS is associated with slight axon loss of the MN. SIGNIFICANCE: CTS might cause retrograde axonal atrophy detected as small fCSA. Prominent axon loss in CTS may reduce the diagnostic value of WFR.

High-resolution ultrasonography in carpal tunnel syndrome: role of ancillary criteria in diagnosis and response to steroid injection.

OBJECTIVES: (1) Development and validation of a composite ultrasound score (cUSS) for the diagnosis of carpal tunnel syndrome (CTS). (2) To predict treatment response after local corticosteroid injection. METHODS: Wrists of CTS patients and controls were evaluated with high-resolution ultrasound and cross-sectional area of median nerve at carpal tunnel inlet (CSAp) and outlet (CSAd) and bowing of flexor retinaculum (FRB), flexor tenosynovitis, and intraneural vascularity and echogenicity changes were noted. Patients were prospectively followed after ultrasound-guided corticosteroid injection. RESULTS: We studied 479 wrists of 141 patients and 99 controls. Optimal cut-offs for diagnosing CTS were 9.5 mm2 and 10.5 mm2, respectively, for CSAp and CSAd. A cUSS consisting of the following parameters was developed: age, CSAp, CSAd, FRB, and flexor tenosynovitis and echogenicity changes. External validation of cUSS yielded sensitivity, specificity, and diagnostic accuracy of 91.7%, 87.1%, and 89.8%, respectively. Treatment responses from 88 injections (median duration of follow-up of 6 months) were available with satisfactory initial responses in 69.32% (61/88) and relapses in 30.86% (25/81). Median time to relapse was 2 months. Initial response was predicted by FRB (odds ratio (OR): 5.43, 95% confidence interval (CI): 1.45-20.3, p = 0.012). Relapse was predicted by age (hazard ratio (HR) 1.168, 95% CI: 1.076-1.268, p = 0.0002), male gender (HR: 8.1.02, 95% CI: 2.394-27.422, p = 0.0007), FRB, (HR: 46.982, 95% CI: 5.048-437.293, p = 0.0008), and higher body mass index (HR: 0.238, 95% CI: 0.064-0.892, p = 0.0332). CONCLUSIONS: The developed cUSS has a diagnostic accuracy of 88% for diagnosing CTS. Ultrasound parameters could predict both initial treatment response and relapse. KEY POINTS: • Anatomical ultrasound parameters in addition to nerve cross-sectional area is important for diagnosis of CTS. • A composite US score for diagnosis of CTS was developed with accuracy 88.6%. • Bowing of flexor retinaculum predicts short and long term response to local steroid injection.

Ultrasound (US) Changes in the Median Nerve Cross-Sectional Area After Microinvasive US-Guided Carpal Tunnel Release.

OBJECTIVE: To document changes in the median nerve cross-sectional area (CSA) in the proximal carpal tunnel region after ultrasound (US)-guided carpal tunnel release (CTR). METHODS: Prospective data were collected on 23 consecutive patients (37 wrists) treated with US-guided CTR by the primary author using the same office-based microinvasive technique. Ultrasound was used to measure the largest CSA of the median nerve in the proximal carpal tunnel region both preoperatively and postoperatively. The primary outcome measure was the change in the preoperative versus 6- to 10-week postoperative median nerve CSA. RESULTS: The mean CSA of the median nerve decreased from 16.08 to 12.75 mm2 at 6 to 10 weeks after US-guided CTR (P < .001). During the same period, the mean Boston Carpal Tunnel Questionnaire (BCTQ) symptom score decreased from 3.23 to 1.67 (P < .001), and mean BCTQ functional score decreased from 2.49 to 1.47 (P < .001), both exceeding minimal clinically important differences. Although the primary end point was the median nerve CSA at 6 to 10 weeks, statistically significant reductions in the median nerve CSA, as well as BCTQ scores, were also observed as early as 2 to 4 weeks after US-guided CTR (median nerve CSA, 12.40 mm2 ; BCTQ symptom score, 2.00; BCTQ functional score, 1.75; all P ≤ .03). CONCLUSIONS: To our knowledge, this investigation was the largest to date examining changes in the proximal median nerve CSA after US-guided CTR. Statistically significant reductions in the proximal median nerve CSA were observed within 6 to 10 weeks after ultrasound-guided CTR. These reductions were similar to those previously reported for open and endoscopic CTR and validate the ability of US-guided CTR to relieve median nerve compression.

Ultrasonography Findings in Severe Carpal Tunnel Syndrome.

Background: Increasing severity of carpal tunnel syndrome (CTS), as graded by nerve conduction studies (NCS), has been demonstrated to predict the speed and completeness of recovery after carpal tunnel release (CTR). The purpose of this study is to compare the cross-sectional area (CSA) of the median nerve in patients with severe and nonsevere CTS as defined by NCS. Methods: Ultrasound CSA measurements were taken at the carpal tunnel inlet at the level of the pisiform bone by a hand fellowship-trained orthopedic surgeon. Severe CTS on NCS was defined as no response for the distal motor latency (DML) and/or distal sensory latency (DSL). Results: A total of 274 wrists were enrolled in the study. The median age was 51 years (range: 18-90 years), and 72.6% of wrists were from female patients. CSA of median nerve and age were comparatively the best predictors of severity using a linear regression model and receiver operator curves. Using cutoff of 12 mm2 for severe CTS, the sensitivity and specificity are 37.5% and 81.9%, respectively. Conclusions: Ultrasound can be used to grade severity in younger patients (<65 years) with a CTS-6 score of >12.

An overview of hand postures and aging on morphological changes of the median nerve.

BACKGROUND: High-resolution ultrasound is being widely used in carpal tunnel examination to understand morphological and biomechanical characteristics of the median nerve and surrounding anatomy structures. MAIN BODY: Healthy young and elderly men were recruited. The median nerve at proximal wrist region was examined by ultrasound imaging technique. A total of seven wrist angle was examined. Generally, the median nerve cross-sectional area of the elderly group is significantly larger than the young group. SHORT CONCLUSION: Wrist posture in greater flexion or extension caused a larger decrease in the median nerve cross-sectional area across both groups.

Deformation of the median nerve at different finger postures and wrist angles.

BACKGROUND: The objective of this study was to evaluate the changes of the median nerve cross-sectional area (MNCSA) and diameters of the median nerve at different finger postures and wrist angles. METHODS: Twenty-five healthy male participants were recruited in this study. The median nerve at wrist crease was examined at six finger postures, and repeated with the wrist in 30° flexion, neutral (0°), and 30° extension. The six finger postures are relaxed, straight finger, hook, full fist, tabletop, and straight fist. RESULTS: The main effects of both finger postures and wrist angles are significant (p < 0.05) on changes of the MNCSA. Different finger tendon gliding postures cause a change in the MNCSA. Furthermore, wrist flexion and extension cause higher deformation of the MNCSA at different finger postures. DISCUSSION: The median nerve parameters such as MNCSA and diameter were altered by a change in wrist angle and finger posture. The results may help to understand the direct biomechanical stresses on the median nerve by different wrist-finger activities.

Effects of grip force on median nerve deformation at different wrist angles.

The present study investigated the effects of grip on changes in the median nerve cross-sectional area (MNCSA) and median nerve diameter in the radial-ulnar direction (D1) and dorsal-palmar direction (D2) at three wrist angles. Twenty-nine healthy participants (19 men [mean age, 24.2 ± 1.6 years]; 10 women [mean age, 24.0 ± 1.6 years]) were recruited. The median nerve was examined at the proximal carpal tunnel region in three grip conditions, namely finger relaxation, unclenched fist, and clenched fist. Ultrasound examinations were performed in the neutral wrist position (0°), at 30°wrist flexion, and at 30°wrist extension for both wrists. The grip condition and wrist angle showed significant main effects (p < 0.01) on the changes in the MNCSA, D1, and D2. Furthermore, significant interactions (p < 0.01) were found between the grip condition and wrist angle for the MNCSA, D1, and D2. In the neutral wrist position (0°), significant reductions in the MNCSA, D1, and D2 were observed when finger relaxation changed to unclenched fist and clenched fist conditions. Clenched fist condition caused the highest deformations in the median nerve measurements (MNCSA, approximately -25%; D1, -13%; D2, -12%). The MNCSA was significantly lower at 30°wrist flexion and 30°wrist extension than in the neutral wrist position (0°) at unclenched fist and clenched fist conditions. Notably, clenched fist condition at 30°wrist flexion showed the highest reduction of the MNCSA (-29%). In addition, 30°wrist flexion resulted in a lower D1 at clenched fist condition. In contrast, 30°wrist extension resulted in a lower D2 at both unclenched fist and clenched fist conditions. Our results suggest that unclenched fist and clenched fist conditions cause reductions in the MNCSA, D1, and D2. More importantly, unclenched fist and clenched fist conditions at 30°wrist flexion and 30°wrist extension can lead to further deformation of the median nerve.

Median nerve behavior at different wrist positions among older males.

The effect of wrist flexion-extension on the median nerve appearance, namely the cross-sectional area (MNCSA) and the longitudinal (D1) and vertical (D2) diameters, was investigated among older adults (N = 34). Ultrasound examination was conducted to examine the median nerve at different wrist angles (neutral; and 15°, 30°, and 45° extension and flexion), in both the dominant and nondominant hand. Median nerve behavior were significantly associated with wrist angle changes. The MNCSA at wrist flexion and extension were significantly smaller (P < .001) compared with the neutral position in both the dominant and nondominant hand. The D1 and D2 were significantly reduced at flexion (P < .001) and extension (P < .001), respectively, in both the dominant and nondominant hand. Our results suggest that a larger flexion-extension angle causes higher compression stress on the median nerve, leading to increased deformation of the MNCSA, D1, and D2 among older adults.