Median Nerve Injury in Ultrasound-Guided Hydrodissection and Corticosteroid Injections for Carpal Tunnel Syndrome

Purpose Permanent nerve damage after corticosteroid injection has been suggested when symptoms of median nerve injury (MNI) are irreversible. We assess the outcomes of MNI and their association with ultrasonography (US)-guided hydrodissection and the following corticosteroid injection for symptomatic carpal tunnel syndrome (CTS). Methods US-guided hydrodissection and the following corticosteroid injections were administered to 126 CTS patients. Occurrence of MNI, clinical data, and post-hydrodissection findings were evaluated. Post-hydrodissection findings included vascular injury during hydrodissection, altered echogenicity, reduced flattening ratio, and increased cross-sectional area of the MN at the inlet of the carpal tunnel (MN-CSA-Inlet) on ultrasonography after hydrodissection. The relevance of MNI with respect to these clinical data and findings was determined. The outcome was rated using Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) scores. Results Nine patients suffered MNI (incidence, 7.1 %) but improved significantly at follow-up. Clinical data and vascular injury during hydrodissection, altered echogenicity, and reduced flattening ratio after hydrodissection were unrelated to prolonged transient MNI (p > 0.05). MNI was significantly associated with increased CSA (p = 0.005). A CSA increase > 2 mm2 after hydrodissection yielded the greatest performance (0.979) for MNI in the receiver operating characteristic analysis. Decreases in BCTQ scores after injection did not differ significantly between groups with and without MNI (p > 0.05). Conclusion MNI during hydrodissection may be reversible. MNI is indicated by an increase in MN-CSA-inlet immediately after hydrodissection.

OBLIGATORY ALTERATIONS IN THE MORPHOLOGY OF MEDIAN NERVE: A SONOGRAPHIC STUDY IN ASYMPTOMATIC INDIVIDUALS

Introduction: Median nerve is formed in axilla by contributions from medial and lateral cords of brachial plexus. It descends in the arm, forearm and then through carpal tunnel in close conjunction with flexor tendons of forearm. Carpal tunnel syndrome (CTS) is a common entrapment neuropathy. Median nerve cross sectional area (CSA) and ratio of nerve major axis to minor axis (flattening ratio) serve as potential diagnostic criteria for carpal tunnel syndrome. Median nerve cross sectional area and flattening ratio (FR) can be assessed by ultrasonography (US). Aim of the study was to assess median nerve by US and tabulate mean values for CSA and FR in asymptomatic population. This would serve to limit the cut-off values that differentiate asymptomatic nerves from neuropathic nerves. Material & Methods: Study was conducted in the Department of Anatomy, KGMU, Lucknow. Fifty randomly selected asymptomatic volunteers (undergraduate students: 30 males, 20 females) participated in the study. Sonography was performed to evaluate certain morphological dimensions of median nerve. Height, weight and wrist circumference of participants were also noted. Ultrasonography was performed using high frequency linear probe and observations were made at two pre-determined sites. Observations were recorded, tabulated and analyzed. Results: Median nerve was easily observable at both sites. It was round in shape in forearm (Fo), and flattened as it reached the carpal tunnel (Ct). Among all 50 study subjects, at both sites, flattening was more on right side (FRFoRt-1.71; FRCtRt-3.08) than on left side (FRFoLt-1.66; FRCtLt-2.78). In right forearm, nerve was flatter in females (FRFoRt-1.77) as compared to males (FRFoRt-1.68). In left forearm, median nerve was slightly rounder in females (FRFoLt-1.65) as compared to males (FRFoLt-1.67). At the distal wrist crease on right side, increased flattening was observed in females (FRCtRt-3.30) as compared to males (FRCtRt-2.94), whereas on left side, at same site flattening was more in females (males FRCtLt-2.74; females FRCtLt-2.83). Conclusion: Altered FR has both diagnostic as well as prognostic values in carpal tunnel syndrome. The database generated from the study will help in facilitating comparisons between normal, asymptomatic and pathological, asymptomatic individuals.

Feasibility of sagittal T2 mapping of the median nerve in patients with carpal tunnel syndrome

Purpose: To evaluate patients with carpal tunnel syndrome (CTS) by using 3-Tesla magnetic resonance imaging (MRI) sagittal T2 mapping of the median nerve for localization of abnormal regions. Material and Methods: Nine hands of seven patients with CTS and five hands of five healthy volunteers were evaluated using sagittal T2 mapping and axial spoiled gradient-echo (SPGR) images. Three regions of interest (ROIs) at the carpal tunnel (ROI-1 to ROI-3) and one control ROI distal to the carpal tunnel (ROIC) were defined on the median nerve and T2-ratios at ROI-1 to ROI-3 relative to ROI-C were calculated. The flattening ratio (F-ratio; width/height of the median nerve) was also calculated from the axial SPGR images. Results: On sagittal T2 mapping, the medial nerve of normal volunteers showed constant T2 values at all ROIs. In the patients with CTS, there was large variation in T2 among the ROIs and the region of highest T2 value varied among the patients. T2-ratios at ROI-2 and -3 and the F-ratios along all carpal tunnel levels were significantly higher in the patients with CTS than in the normal volunteers. A significant correlation was found between terminal latency and T2-ratio at ROI-2 but not between terminal latency and F-ratio. Conclusion: Sagittal T2 mapping was feasible for the localization of abnormal T2 regions of the median nerve in patients with CTS.

Variation of the yarn cross-section in fabric

The aim of this study is to investigate the cross-sectional shape and size variation of the yarn in fabric depending on the structural parameters of fabric. For this reason, the dimensions of the yarns that are in the different regions of the weave unit have been determined by achieving the cross-sectional images of the fabrics, which were woven with different weave types and at different weft settings. The variation in the cross-section of the yarn has been evaluated by using the flattening ratio. Consequently, it has been observed that the structural factors which determine the geometry of the fabric, such as weave type and setting, affect the cross-sectional properties of the yarn along the yarn path.

Sonographic Findings of Median Nerve and Prevalence of Carpal Tunnel Syndrome in Computer Mouse Users

The purpose of this study was to evaluate the median nerve sonographically and estimate the prevalence of carpal tunnel syndrome (CTS) in computer mouse users. Forty-nine right wrists of 49 employees who had used a computer mouse were included in the study. Thirty-three right wrists of 33 non-mouse user employees were studied as a control group. Both the mouse user and non-mouse user employees underwent sonography and electromyography (EMG). Axial sonograms of the median nerve were obtained proximally, in the middle and distally in the carpal tunnel. At each level, flattening ratio and the cross-sectional area of the median nerve were calculated. We found no significant difference in any parameters between mouse users and control group ( p>0.05). However, when we compared mouse users according to the presence of pain, there was a significant increase in the cross-sectional area of the median nerve proximally in the mouse users having pain ( p<0.05). Of all mouse users, eight (16.3%) were diagnosed as sensory CTS, four (8.2%) as motor CTS by EMG. We also found that four (50%) CTS patients had a proximal cross-sectional area of median nerve exceeding 10 mm2 and five (62.5%) had a distal flattening ratio over three. Prolonged use of a mouse may pose an occupational risk for employees. Sonography can serve as an initial step in symptomatic patients for diagnosis of CTS.

Systematic error analysis of demagnetization and implications for magnetic interpretation

Demagnetization can affect the interpretation of magnetic data significantly. However, little attempt has been made to understand its effects by analyzing systematically the differences between demagnetization‐ corrected and uncorrected magnetic properties. A systematic error analysis is made in this paper using a 2-D elliptic cylinder model. Generally, demagnetization changes the effective susceptibility and remanence or the effective magnetization in both magnitude and direction. Error analyses show that demagnetization causes the magnitude of effective magnetization of a magnetic body to be less than its intrinsic magnetization. This implies that a theoretical anomaly computed without accounting for demagnetization will overestimate the amplitude of the anomaly associated with the body. The decrease in magnetization magnitude depends on the intrinsic magnetic susceptibility of a body as well as on the body’s geometry (flattening ratio) and its relative orientation (magnetic dip) in the geomagnetic field. The magnitude of the effective magnetization, relative to the intrinsic magnetization, decreases with increasing intrinsic magnetic susceptibility. This factor dominates the body’s effective magnetization. When intrinsic magnetic susceptibility is less than 0.1 SI, the demagnetization effects are generally insignificant and may be ignored in magnetic anomaly modeling. The magnetic dip and flattening ratio only cause minor fluctuations in the effective magnetization. Demagnetization also changes the direction of the effective magnetization vector by making it approach the plane of flattening of any flattened body. The difference between the inclinations of the effective and intrinsic magnetization changes the horizontal positions of extreme values of an anomaly, which may affect the precision of magnetic interpretations. Generally, the inclination difference is significant for magnetic dips of 30° to 70° and increases with increasing susceptibility and decreasing flattening ratio. In particular, for large flat‐lying magnetic geological units located at middle magnetic latitudes (30° to 70°), significant magnetic inclination deflections are expected because of demagnetization effects. Theoretical, experimental, and practical examples of magnetic interpretation are presented to illustrate these demagnetization effects.

Effect of Particle-Substrate Materials Combinations on Morphology of Plasma Sprayed Splats

The structure and morphology of plasma sprayed splats are experimentally investigated using different droplet materials and substrate materials. Droplet materials include aluminum, copper, nickel and refractory metals such as molybdenum and tungsten, and substrate materials include aluminum, stainless steel, and molybdenum plates. The results show that the splashing occurs during the splatting of a completely molten droplet. Most splats formed by droplets molten completely are only central part of the ideal disk type ones, which are defined as the annulus-ringed disk-like splat. It is found that the morphology of such annulus-ringed disk-like splat is greatly influenced by the combination of droplet and substrate materials depending on whether substrate melting occurs. With the combinations of droplet and substrate materials which are of similar thermal properties the splashing of central area of splat tends to occur to present a honeycomb structure at the center of splat. When droplet impacting can cause melting of substrate annulus-ringed splat prefers to present a split type. The flattening ratio of an annulus-ringed disk splat is typically less than 2.