Sonography in the diagnosis of carpal tunnel syndrome.

OBJECTIVE: The few papers published on the use of sonography in carpal tunnel syndrome suggest it may be a useful diagnostic test. This study aims to prospectively evaluate the use of sonographic measurements of the median nerve in the diagnosis of carpal tunnel syndrome. SUBJECTS AND METHODS: Patients with documented carpal tunnel syndrome and a group of asymptomatic control subjects were enrolled and underwent high-resolution sonography of the carpal tunnel. A small-footprint linear array transducer was used to scan and measure the median nerve cross-sectional area and the maximum transverse and anteroposterior diameters. Data from the patient group and the control group were compared to establish optimal diagnostic criteria for carpal tunnel syndrome. RESULTS: Sixty-eight carpal tunnel syndrome patients (50 women, 18 men) with 102 affected nerves and 68 nerves in 36 asymptomatic controls (23 women, 13 men) were examined. Qualitative assessment alone was found to be unreliable. All measurements showed significant differences between patients and controls. The most predictive measurement was swelling of the median nerve, which was significantly greater in carpal tunnel syndrome patients compared with controls (mean, 0.13 cm2 versus 0.07 cm2). Thus, quantitative assessment of the median nerve provides an accurate diagnostic test (sensitivity, 82%; specificity, 97%), with an area larger than 0.09 cm2 being highly predictive of carpal tunnel syndrome. CONCLUSION: We confirm that median nerve cross-sectional area measurement correlates well with the presence of carpal tunnel syndrome and is both sensitive and specific for the diagnosis.     

高频超声技术诊断肘管综合征的价值

目的：探讨超声技术诊断肘管综合征（CTS）的准确性。方法：对30例肘管综合征患者的30只手和50例无CTS志愿者的100只手肘部行动态超声检查,测量并比较两组尺神经的上下径、横径及截面积,并用ROC曲线评价超声诊断肘管综合征标准值的准确性。结果：CTS患者的尺神经在内上髁水平的截面积、上下径及左右径明显大于正常对照组,两组比较差异有统计学意义,尺神经的截面积增大对于诊断肘管综合征最有预测价值。以尺神经在内上髁水平的截面积7.5mm2为阈值,诊断敏感度为93%,诊断特异性为91%。结论：超声测量尺神经的截面积是诊断肘管综合征的可靠方法。     

High resolution ultrasonography in the diagnosis of the carpal tunnel syndrome

PURPOSE: Carpal tunnel syndrome (CTS) is a neuropathy caused by compression of the median nerve in the carpal tunnel. Our purpose was to evaluate the role of high-resolution ultrasonography (US), performed with a 10-13 MHz probe, in the detection of morphovolumetric changes of the median nerve to confirm the clinical diagnosis. MATERIALS AND METHODS: Fifty healthy volunteers were examined first by US; subsequently we studied 294 wrists in 186 symptomatic patients, calculating the cross-sectional area of the median nerve at three levels: before the median nerve enters the carpal tunnel, at the carpal tunnel inlet and at the outlet. US was considered diagnostic for CTS when the median nerve area increased at the inlet or flattening was present along the carpal tunnel. RESULTS: Ultrasonography showed pathologic findings in 267 wrists: in 261 cases morphovolumetric changes of the median nerve were found; in six cases anatomic variant of the median nerve was detected. Surgery was performed in 277 cases and all patients became symptom-free. The sensitivity of US was 96.3 % . CONCLUSIONS: Our study confirms that quantitative ultrasonographic assessment is a useful support in confirming the clinical diagnosis of CTS.     

Ultrasound features of carpal tunnel syndrome: a prospective case-control study

Purpose The purpose of the study was to examine the most adequate cut-off point for median nerve cross-sectional area and additional ultrasound features supporting the diagnosis of carpal tunnel syndrome (CTS). Material and methods Forty wrists from 31 CTS patients and 63 wrists from 37 asymptomatic volunteers were evaluated by ultrasound. All patients were women. The mean age was 49.1 years (range: 29–78) in the symptomatic and 45.1 years (range 24–82) in the asymptomatic group. Median nerve cross-sectional area was obtained using direct (DT) and indirect (IT) techniques. Median nerve echogenicity, mobility, flexor retinaculum measurement and the anteroposterior (AP) carpal tunnel distance were assessed. This study was IRB-approved and all patients gave informed consent prior to examination. Results In CTS the median nerve cross-sectional area was increased compared with the control group. Median nerve cross-sectional area of 10 mm² (DT) and 9 mm² (IT) had high sensitivity (85% and 88.5%, respectively), specificity (92.1% and 82.5%) and accuracy (89.3% and 82.5%) in the diagnosis of CTS. CTS patients had an increased carpal tunnel AP diameter, flexor retinaculum thickening, reduced median nerve mobility and decreased median nerve echogenicity. Conclusion Ultrasound assists in the diagnosis of CTS using the median nerve diameter cut-off point of 10 mm² (DT) and 9 mm² (IT) and several additional findings.     

Carpal tunnel syndrome: diagnosis with high-resolution sonography.

OBJECTIVE. Carpal tunnel syndrome is characterized by typical anatomic changes that can be shown with high-resolution sonography. To determine whether these findings are reliable and can be used to establish the diagnosis, sonograms of patients with the disease were compared with sonograms obtained in patients with normal wrists. Also compared were sonograms and MR images obtained in the patients with carpal tunnel syndrome. SUBJECTS AND METHODS. Twenty wrists in 18 consecutive patients with clinical symptoms of carpal tunnel syndrome and with abnormal nerve conduction studies were examined with real-time sonography and MR imaging. The sonograms and MR images were evaluated quantitatively by two unbiased observers with regard to the size and shape of the median nerve and the palmar bowing of the flexor retinaculum. A t test was used to compare these data with those from previous sonographic studies of 28 normal wrists. Correlation coefficients for the measurements obtained with sonography and with MR were calculated. The relative accuracies of different diagnostic criteria for the diagnosis of carpal tunnel syndrome were assessed by using receiver-operating-characteristic analytical techniques. RESULTS. Characteristic findings on both MR and CT scans of the 20 wrists with carpal tunnel syndrome included swelling of the median nerve in the proximal part of the carpal tunnel in 16 wrists, flattening of the median nerve in the distal part of the carpal tunnel in 13 wrists, and increased palmar bowing of the flexor retinaculum in nine wrists. Comparison with the data of 28 normal wrists proved that these findings were significant (p less than .01 to p less than .001). Receiver-operating-characteristic analysis showed that the discrimination between wrists in normal subjects and in patients with carpal tunnel syndrome achieved with each of the three diagnostic criteria was not significantly different. Measurements of the size and flattening of the median nerve obtained from sonograms were similar to those on MR images, whereas sonography was less accurate for measuring the palmar bowing of the flexor retinaculum. CONCLUSION. We conclude that the results of sonography are reliable, and that the diagnosis of carpal tunnel syndrome can be established on the basis of sonographic findings.     

Median nerve stiffness measurement by shear wave elastography: a potential sonographic method in the diagnosis of carpal tunnel syndrome

Objectives

To measure the median nerve (MN) stiffness by quantitative shear wave elastography (SWE) at the carpal tunnel inlet and to determine whether SWE can be used in the diagnosis of carpal tunnel syndrome (CTS).

Methods

The study included 37 consecutive patients (60 wrists) with a definitive diagnosis of CTS and 18 healthy volunteers (36 wrists). The MN cross-sectional area (CSA) by ultrasound and stiffness by SWE were studied. The difference between CTS patients and controls, and the difference among subgroups based on electrodiagnostic tests were studied by the Student’s t test. Interobserver variability and ROC analysis were performed.

Results

The MN stiffness was significantly higher in the CTS group (66.7 kPa) when compared to controls (32.0 kPa) (P?<?0.001), and higher in the severe or extreme severity group (101.4 kPa) than the mild or moderate severity group (55.1 kPa) (P?<?0.001). A 40.4-kPa cut-off value on SWE revealed sensitivity, specificity, PPV, NPV and accuracy of 93.3 %, 88.9 %, 93.3 %, 88.9 % and 91.7 %, respectively. Interobserver agreement was excellent for SWE measurements.

Conclusions

Median nerve stiffness at the carpal tunnel inlet is significantly higher in patients with carpal tunnel syndrome, for whom shear wave elastography appears to be a highly reproducible diagnostic technique.

Key Points

? Clinical examination is important for diagnosis of carpal tunnel syndrome ? Shear wave elastography (SWE) offers new clinical opportunities within diagnostic ultrasound ? SWE is highly reproducible in evaluation of median nerve stiffness ? Median nerve stiffness is significantly increased in carpal tunnel syndrome ? Elastography could become useful in diagnosis of carpal tunnel syndrome     

腕管综合征的MRI诊断

研究腕管综合征（CTS）的MRI特征及应用价值。材料和方法：经临床及手术证实的CTS12例，行MRI检查，以横断面为主。结果：12例CTS的MRI表现为：正中神经进入腕管时肿胀增粗12例，正中神经肿胀率（MNSR）为2．25：1。正中神经腕管内受压变扁12冽，正中神经扁平率（MNFR）为3．4。腕横韧带向掌侧膨隆10例，腕横韧带膨隆率（BR）为15．8％。T2WI像正中神经信号增高12例。结论：MRI对CTS的诊断、治疗方式的选择及疗效观察有重要的价值。     

High-resolution computed tomography of the wrist in patients with carpal tunnel syndrome

High resolution computed tomography (CT) was used to scan the wrists of 19 patients with idiopathic carpal tunnel syndrome. Thirteen normal volunteers were used as controls. Measurements obtained from the CT images included the cross-sectional area of the carpal tunnel, the relative amount of synovium within the carpal tunnel, the attenuation coefficient of the carpal tunnel, and the thickness of the transverse carpal ligament. No significant difference in any of these measurements was found when comparing the wrists of symptomatic patients with controls. High resolution CT of the wrist does not appear to be of value in the preoperative evaluation of patients with idiopathic carpal tunnel syndrome.     

高频超声对腕管综合征断面面积的测量研究

目的:研究高频超声定量测量腕管断面面积与腕管内容物断面面积之比,从而提高超声诊断腕管综合征的敏感性、特异性。方法:对经电生理及临床症状确诊的26例35侧患者组及30例60侧健康志愿者,高频超声测量豌豆骨水平及钩骨钩水平腕横韧带厚度、腕管断面积与腕管内容物断面积之比,采用ROC曲线分析测定各测量指标的诊断阈值,计算敏感度与特异度;并分析腕横韧带厚度与断面积比值之间相关性。结果:豌豆骨水平腕管断面积与腕管内容物断面积比值取最佳截点值2.447时,灵敏度为61.7%,特异度为77.1%。钩骨钩水平腕管断面积与腕管内容物断面积比值取最佳截点值2.177,灵敏度为83.3%,特异度为62.9%。腕横韧带厚度与断面积比值呈负相关性。结论:高频超声测量腕管断面积比值是诊断腕管综合征的一种有价值的新方法。     

Sonographic findings of the median nerve and prevalence of carpal tunnel syndrome in patients with Parkinson's disease

PURPOSE: Parkinson's disease (PD) is a chronic progressive disorder which is characterized by rest tremor, akinesia or bradykinesia and rigidity. Carpal tunnel syndrome (CTS) is caused by compression of median nerve and can occur as a result of repetitive trauma. The aim of this study was to estimate the prevalence of CTS in PD and evaluate the median nerve sonographically. MATERIALS AND METHODS: Fifty-three wrist of 29 patients with PD were included in the study according to Hoehn and Yahr (H&Y) clinical stage and divided into two groups. The first group consisted of 29 wrists of patients with mild PD (H&Y stage I-II). The second group consisted of 24 wrists of patients with severe PD (H&Y stage III-IV). Thirty-six wrists of 20 age-matched patients were used as control group. Both of the patients with PD and control group underwent sonography and electromyography (EMG). Axial sonograms of the median nerve were obtained at the level of distal radioulnar joint (level 1) and at the level of pisiform bone in the carpal tunnel (level 2). At each level, the cross-sectional area of the median nerve and flattening ratio were calculated. RESULTS: There was no significant difference for all parameters, except one parameter, between the patients with PD and control group, and also among mild and severe groups of PD and control group (p>0.05). Interestingly, amplitude of median nerve in the second finger was significantly lower in PD patients than control group within normal limits (p=0.010). Of all wrists of PD patients, 13 (24.4%) have been diagnosed as CTS and 7 (19.4%) control wrists had CTS. Median nerve cross-sectional area of CTS patients were more than 10mm(2) in 6 (46%) wrists of PD patients but in only 1 (14%) control wrist at each level. Although it was not statistically significant, there was higher cross-sectional area at each level in patients with severe PD (level 1: 10.43+/-2.30mm(2), level 2: 10.35+/-3.19mm(2)) than patients with mild PD (level 1: 9.93+/-2.61mm(2), level 2: 9.51+/-2.83mm(2)) and control group (level 1: 9.69+/-3.19mm(2), level 2: 9.07+/-3.61mm(2)). CONCLUSION: PD may pose a risk for the development of CTS due to the repetitive movement of tremor. Although sonography is not an ideal method of diagnosis for CTS, it may take our attention for indicating CTS in patients with PD especially in severe ones.     

Comparison of Magnetic Resonance Imaging and Ultrasonography in Diagnosing and Grading Carpal Tunnel Syndrome: A Prospective Study

ObjectiveTo use anatomic measurements on magnetic resonance imaging (MRI) and ultrasonography (USG) in diagnosing and grading carpal tunnel syndrome (CTS) using nerve conduction studies (NCS) as the gold standard.Material and methodsIn this prospective study, 26 patients with CTS (45 wrists; 22 female and 4 male patients; mean ± SD age of 49.42 + 14.47 years) and 19 age and sex matched healthy volunteers (32 wrists; 15 female and 4 male volunteers, mean ± SD age of 42.52 + 10.85 years) underwent MRI and USG. Cross-sectional area (CA) of median nerve was measured using free hand ROI at four levels: hamate hook (H0), pisiform bone (PI0), 1 cm proximal (PI1) and 2 cm proximal to PI0 (PI2). Relative median nerve signal intensity (MNSI) was calculated as ratio of median nerve signal intensity with hypothenar muscle signal intensity. Flexor retinacular bowing was calculated at hamate hook level. Echogenicity and Power Doppler vascularity of median nerve were assessed on USG. Independent t-test, chi square test and receiver operating characteristic curve analysis were used as appropriate.ResultsOn USG, CA measured at PI0 (95% confidence interval of 0.872-0.987) and retinacular bowing (0.816-0.912), while, on MRI, CA at PI1 (0.874-0.997) were most useful in diagnosing CTS based on the ROC and Zombie plot analysis. Area under curves for CA measurements on USG and MRI were not significantly different. CA at PI1 on MRI (0.752-0.965) was significantly different between minimal to moderate CTS and severe to extreme CTS groups (on NCS).ConclusionCA of median nerve is the most useful parameter to diagnose and grade CTS and USG and MRI are comparable for measurements. Increased retinacular bowing on USG and hypoechogenicity of median nerve increase the diagnostic confidence while MRI helps in picking up important associated conditions.     

MR imaging of the carpal tunnel syndrome

Magnetic resonance (MR) imaging of the carpal tunnel was performed in 23 wrists of 13 patients who were suspected to have carpal tunnel syndrome (CTS). In ten out of 23 wrists, diagnostic images of the carpal tunnel could be obtained. MR images were analysed retrospectively as to swelling of the median nerve, signal intensity of the median nerve on T2 weighted image, and swelling of the tendon sheath. In 8 wrists the median nerve was significantly swollen at the inlet of the carpal tunnel. Four of them showed increased signal intensity of the median nerve on T2 weighed image at the inlet. Swelling of the tendon sheath was demonstrated in two cases. These finding seem to represent edematous change of the median nerve due to compression. Surgical correlation was obtained in two wrists. Since MR imaging is capable of demonstrating pathological changes of the median nerve in CTS, it can be a diagnostic tool in selected cases.     

Dynamic MR imaging of carpal tunnel syndrome

 Objective. To evaluate the diagnostic value of the MR imaging syndrome before and after performance of provocative exercises in patients with dynamic carpal tunnel syndrome. Design. Fat-suppressed proton-density and T2-weighted spin-echo images of the wrist were obtained prior to and after provocative, standardized exercises. Images were interpreted in masked fashion with regard to six MR criteria of carpal tunnel syndrome: (a) bowing of the transverse ligament, (b) and (c) deformation of the median nerve at the pisiform and hamate levels respectively, (d) signal abnormality of the median nerve, (e) presence of fluid in the wrist joints and/or carpal tunnel, and (f) presence of synovial swelling. Patients. Twenty-one wrists in 20 patients with subjective complaints of carpal tunnel syndrome and equivocal or negative clinical findings and negative electrodiagnostic examinations were included (age range 21–61 years, mean 37 years, 2 men and 18 women). The diagnosis of dynamic carpal tunnel syndrome was made and confirmed by surgery in 18 of the 21 symptomatic wrists. The control group consisted of 15 asymptomatic wrists in volunteers (age range 22–60 years, mean 35 years, 8 men and 7 women). Results and conclusions. Sensitivities and specificities of the six MR criteria were 90.5–100%, and 6.7–86.7%, respectively, both before and after exercise. Likelihood ratios proved statistically significant differences between the symptomatic and asymptomatic wrists (P<0.0001–0.0002) for the prevalence of all MR criteria with the exception of fluid within the carpal joints and/or carpal tunnel. Changes of the MR appearance after exercise had a low sensitivity (4.8–71.4%) but high specificity (86.7–100%) for dynamic carpal tunnel syndrome. In conclusion, MR imaging contributes to the diagnosis of carpal tunnel syndrome when clinical signs are confusing and electrodiagnostic studies are negative. Dynamic examinations improve specificity of MR imaging for such diagnosis.     

Carpal tunnel: MR imaging. Part II. Carpal tunnel syndrome

The magnetic resonance (MR) images of 14 wrists of patients with carpal tunnel syndrome (CTS) were studied. Four general findings visible regardless of the cause of CTS included swelling of the median nerve, best evaluated at the level of the pisiform bone; flattening of the median nerve, most reliably judged at the hamate level; palmar bowing of the flexor retinaculum, best visualized at the level of the hamate bone; and increased signal intensity of the median nerve on T2-weighted images. Findings related to cause were tendon sheath edema in traumatic tenosynovitis, synovial hypertrophy in rheumatoid tenosynovitis, a ganglion cyst, and excessive amount of fat within the carpal tunnel, a persistent median artery, and a large adductor pollicis muscle. Knowledge of these findings may permit more rational choice of treatment. In four cases in which symptoms persisted after surgery, findings valuable in explaining or predicting the failure included incomplete incision of the flexor retinaculum, excessive fat within the carpal tunnel, persistent neuritis of the median nerve, and development of neuromas.     

Quantitative MR imaging of carpal tunnel syndrome.

OBJECTIVE: Previous MR imaging studies have produced evidence of changes to structures within the wrist believed to be associated with carpal tunnel syndrome. In an attempt to resolve the conflicting and inconclusive results of these studies, we report here the results of an MR imaging study at a field strength of 3.0 T, which is higher than that previously reported. SUBJECTS AND METHODS: Patients with carpal tunnel syndrome and control groups of asymptomatic subjects were studied using MR imaging. We evaluated electrophysiologically the median nerve function of the affected wrists of all patients. A gradient-recalled echo pulse sequence was used to study 13 3-mm-thick slices within the wrist of each patient or asymptomatic subject. Spatial resolution was approximately 0.3 x 0.3 mm2. The median nerve and other structures associated with the carpal tunnel, which were clearly shown on the MR images, were analyzed to yield structural data. RESULTS: Analysis revealed that the cross-sectional area of the nerve within and proximal to the carpal tunnel was approximately 50% larger in patients with carpal tunnel syndrome than in asymptomatic subjects. We found no significant difference in the area of the nerve within the carpal tunnel compartment compared with the area of the nerve proximal to the carpal tunnel either in patients or in asymptomatic subjects. Also, flattening of the nerve on entering the carpal tunnel was not significantly different in patients than in asymptomatic subjects. In patients an increase in the palmar bowing of the flexor retinaculum was found only at the level of the hamate compared with that found in asymptomatic subjects. The cross-sectional area of the carpal tunnel was of a similar size in patients and in asymptomatic subjects. Comparison of electrodiagnostic results indicated no correlations between the MR parameters and electrophysiologic dysfunction of the median nerve for patients. CONCLUSION: The only statistically significant differences found between patients with carpal tunnel syndrome and asymptomatic subjects were that the median nerve was approximately 50% larger within and proximal to the carpal tunnel in patients with carpal tunnel syndrome and palmar bowing of the flexor retinaculum occurred in patients only at the level of the hamate.     

Diagnostic criteria of carpal tunnel syndrome using high-resolution ultrasonography: correlation with nerve conduction studies

The aim of this work was to evaluate the diagnostic performance of grey-scale, color Doppler, and dynamic ultrasound (US) for diagnosing carpal tunnel syndrome (CTS) using the medical diagnostic test called nerve conduction study (NCS) as the reference standard, and to correlate the increase in median nerve (MN) cross-sectional area (CSA) with severity of CTS. Fifty-one patients (95 wrists) with clinical symptoms of idiopathic CTS were recruited. The CSA and flattening ratio of the MN were measured at the distal radio-ulnar joint, pisiform, and hamate levels; bowing of the flexor retinaculum was determined at the hamate level. The hypervascularity of the MN was evaluated. The transverse sliding of the MN was observed dynamically and recorded as being either normal or restricted/absent. Another 15 healthy volunteers (30 wrists) were recruited as controls. Interoperator reliability was established for all criteria. CTS was confirmed in 75 wrists (75/95: 79 %; 14 minimal, 21 mild, 23 moderate, 17 severe). CSA at the pisiform level was found to be the most reliable and accurate grey-scale criterion to diagnose CTS (optimum threshold: 9.8 mm²). There was a good correlation between the severity of NCS and CSA (r?=?0.78, p?相似文献   

Gray scale and color Doppler sonography in the diagnosis of carpal tunnel syndrome

Purpose

To determine the diagnostic accuracy of gray scale and color Doppler sonography in the diagnosis of patients with carpal tunnel syndrome.

Patients and methods

A total of 53 wrists in 41 consecutive patients with clinical suspicion of carpal tunnel syndrome, referred from the Department of Physical medicine, Rheumatology & Rehabilitation were examined with ultrasonography using a 12 MHz linear array transducer. The presence of median nerve edema, swelling, and bowing of the flexor retinaculum was evaluated by gray scale sonography, while intraneural hypervascularity was evaluated by color Doppler sonography. Sensitivity and specificity were calculated for each sonographic feature and compared with electrodiagnostic test (EDT) results.

Results

Electrodiagnostic tests confirmed carpal tunnel syndrome in 48 wrists. A median nerve cross sectional area (CSA) of 11 mm² was calculated as a definition of median nerve swelling. In comparison with electrodiagnostic tests, median nerve swelling showed the highest accuracy (89%) among the gray scale sonographic criteria, and the presence of median nerve hypervascularization showed the highest accuracy (94%) among all sonographic criteria. Median nerve edema and bowing of the flexor retinaculum showed accuracies of 81% and 77% respectively.

Conclusion

Median nerve intraneural hypervascularity detected by color Doppler sonography is more accurate in detection of median nerve involvement than gray scale sonography criteria in patients with suspected carpal tunnel syndrome.     

Carpal tunnel syndrome: usefulness of sonography

The aim of this study was to evaluate sonographic signs described for carpal tunnel syndrome (CTS). Sixty-four wrists from 40 patients with CTS confirmed by electromyography, and 42 wrists from 24 healthy individuals, were examined using sonography. Cross-sectional area, flattening ratio in proximal, middle and distal segments of the carpal median nerve and bowing of the flexor retinaculum were measured. The accuracies of the sonographic diagnostic criteria for CTS were assessed using receiver-operating-characteristic (ROC) analytical techniques. A significant swelling of the median nerve was observed at the proximal (p < 0.001), middle (p < 0.0001) and distal (p < 0.0001) segments and a significant bowing of the flexor retinaculum in CTS patients with respect to healthy subjects. No significant differences were found in the mean value of flattening ratio between the groups. The sensitivity, specificity, positive predictive value, and the negative predictive value were 73.4, 57.1, 72.3 and 58.5 %, respectively, in the proximal and middle segments; 75, 57.1, 72.7 and 60 % in the distal segment for areas greater than 11 mm²; and 81.3, 64.3, 77.6 and 69.2 % for the bowing of the flexor retinaculum greater than 2.5 mm. All sonographic criteria were found in 34 CTS patients (53.1 %) and none in 3 patients. Sonography may be useful in the diagnosis of CTS. The most reliable sign was increased bowing of the flexor retinaculum and cross-sectional area of median nerve with specificity close to 60 %. Received: 29 September 1999; Revised: 11 February 2000; Accepted: 2 May 2000     

Grey-scale sonography and sonoelastography for diagnosing carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is a common peripheral entrapment neuropathy of the median nerve at wrist level, and is thought to be caused by compression of the median nerve in the carpal tunnel. There is no standard quantitative reference for the diagnosis of CTS. Grey-scale sonography and sonoelastography (SEL) have been used as diagnostic tools. The most commonly agreed findings in grey-scale sonography for the diagnosis of CTS is enlargement of the median nerve cross-sectional area (CSA). Several authors have assessed additional parameters. “Delta CSA” is the difference between the proximal median nerve CSA at the pronator quadratus and the maximal CSA within the carpal tunnel. The “CSA ratio” is the ratio of CSA in the carpal tunnel to the CSA at the mid forearm. These additional parameters showed better diagnostic accuracy than CSA measurement alone. Recently, a number of studies have investigated the elasticity of the median nerve using SEL, and have shown that this also has diagnostic value, as it was significantly stiffer in CTS patients compared to healthy volunteers. In this review, we summarize the usefulness of grey-scale sonography and SEL in diagnosing CTS.     

MR imaging of the carpal tunnel: normal anatomy and preliminary findings in the carpal tunnel syndrome

MR imaging was performed through the carpal tunnel in 18 wrists of nine normal volunteers and compared with cryomicrotome sections from cadaver wrists. MR reliably imaged the flexor retinaculum and carpal bones and thus defined the borders of the carpal tunnel. In all cases the median nerve was seen as an ovoid structure of moderate signal intensity and was easily distinguished from the flexor tendons of the hands running in the carpal tunnel. The tendons were separated from each other by their tendon sheaths, and this allowed for identification of the various tendons. Anatomic variations encountered in the normal volunteers included anomalous positioning of the origin of the lumbrical muscles within the carpal tunnel in two, persistent median arteries in two, and interposition of the median nerve between the flexor pollicis longus and the superficial flexor tendon to the index finger in one. Preliminary observations in 10 wrists of patients with carpal tunnel syndrome include segmental and diffuse swelling of the median nerve in six, distortion of the nerve in one, and thickening of the tendon sheaths in one. We conclude that MR imaging accurately and reliably displays the normal anatomy of the carpal tunnel and can detect morphologic changes in patients with carpal tunnel syndrome.