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.     

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.     

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.     

Role of magnetic resonance imaging in entrapment and compressive neuropathy—what, where, and how to see the peripheral nerves on the musculoskeletal magnetic resonance image: part 2. Upper extremity

The diagnosis of nerve entrapment and compressive neuropathy has been traditionally based on the clinical and electrodiagnostic examinations. As a result of improvements in the magnetic resonance (MR) imaging modality, it plays not only a fundamental role in the detection of space-occupying lesions, but also a compensatory role in clinically and electrodiagnostically inconclusive cases. Although ultrasound has undergone further development in the past decades and shows high resolution capabilities, it has inherent limitations due to its operator dependency. We review the course of normal peripheral nerves, as well as various clinical demonstrations and pathological features of compressed and entrapped nerves in the upper extremities on MR imaging, according to the nerves involved. The common sites of nerve entrapment of the upper extremity are as follows: the brachial plexus of the thoracic outlet; axillary nerve of the quadrilateral space; radial nerve of the radial tunnel; ulnar nerve of the cubital tunnel and Guyon’s canal; median nerve of the pronator syndrome, anterior interosseous nerve syndrome, and carpal tunnel syndrome. Although MR imaging can depict the peripheral nerves in the extremities effectively, radiologists should be familiar with nerve pathways, common sites of nerve compression, and common space-occupying lesions resulting in nerve compression in MR imaging.     

Bifid median nerve in the carpal tunnel: integrated imaging

PURPOSE: Carpal Tunnel Syndrome (CTS) is a neuropathy caused by compression of the median nerve at the level of the wrist, which is caused by different pathologic conditions. In some cases it has been associated with anatomic variations of the median nerve, mainly with the early duplication of the nerve inside the carpal tunnel (III Group of Lanz). The treatment of CTS is mainly surgical consisting in decompression by transection of the transverse carpal ligament, which is better performed by endoscopic release. The aim of our study was to evaluate the possibility to detect this anatomic variant by integrated imaging and assess the value of this information for planning treatment. MATERIAL AND METHODS: We report 6 cases of bifid median nerve examined by Ultrasonography (US) using mechanic sectorial and linear array transducers operating at 10 to 13 MHz, and by MR imaging using 0.2 T equipment. RESULTS: In all cases US transverse scans showed two adjacent oval formations with a structure similar to that of the median nerve. CONCLUSIONS. MR imaging confirmed the sonographic findings in all cases. All patients underwent open surgical treatment by decompression of the median nerve; in all cases an early duplicated median nerve was confirmed.     

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.     

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.     

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.     

Carpal tunnel syndrome caused by tophaceous gout: CT and MR imaging features in 20 patients

OBJECTIVE: The objective of this study is to describe the CT and MR imaging findings of gouty tophi in the wrist and present this entity as a cause of carpal tunnel syndrome. MATERIALS AND METHODS: Retrospective review of the CT (n = 18) and MR imaging (n = 20) studies of the wrist in patients with a documented diagnosis of gout who presented with gout-related carpal tunnel syndrome was performed; images of 24 wrists were collected over a 5-year period. Patient population included 20 men, who ranged in age from 35 to 76 years. All images were reviewed by two musculoskeletal radiologists who reached a consensus opinion. Surgical correlation was available in 12 patients. RESULTS: Tophi were found in the floor of the carpal tunnel (n = 18), carpal bones (n = 17), radiocarpal joint (n = 17), and extensor tendons or tendon sheaths (n = 16) of the wrist. All tophi showed similar signal characteristics (from low to intermediate signal intensity on T1-weighted images with heterogeneous signal intensity on T2-weighted images) with the exception of tophi in the floor of the carpal tunnel (low signal intensity on T2-weighted images). Varying degrees of calcification were noted on CT and MR imaging studies. Gadolinium-enhanced MR studies showed heterogeneous enhancement. CONCLUSION: Gouty tophi should be entertained as a cause of carpal tunnel syndrome in the appropriate patient population. Familiarity with this entity and its imaging characteristics may prove helpful in diagnosis and preoperative planning.     

Anatomic relations between the median nerve and flexor tendons in the carpal tunnel: MR evaluation in normal volunteers

To ascertain the dynamic changes between the median nerve and flexor tendons in the carpal tunnel, MR images of 16 wrists in eight volunteers were studied in flexion, extension, and neutral positions. T1-weighted axial images, 600/20 (TR/TE) were obtained with the wrists straight, extended at 45 degree, and flexed at 45 degree. Each scan was evaluated with regard to positional changes of the median nerve and flexor tendons in the carpal tunnel as well as alterations in nerve shape. In the neutral position, the median nerve was found in one of two standard positions: either anterior to the superficial flexor tendon of the index finger or interposed more posterolaterally between this tendon and the flexor pollicis longus. During extension, the nerve always maintained or assumed an anterior position between the superficial index finger flexor and the flexor retinaculum, while the flexor tendons moved posteriorly. With flexion, the tendons shifted anteriorly toward the retinaculum, and the median nerve was found in one of three positions. It either remained in its anterior position between the superficial index finger flexor and retinaculum or became interposed between the superficial flexor tendons of the index finger and thumb or middle finger and ring finger. Nerve shape varied with its position. Anteriorly positioned nerves were flattened in the anteroposterior plane between the tendon and flexor retinaculum; this was greatest with flexion and least with extension. Interposed nerves were flattened in the mediolateral plane or rounded in configuration. In conclusion, the alignment of the median nerve in the carpal tunnel, its shape, and its relationship to the flexor tendons were variable and dependent on wrist positioning. These findings may explain why certain wrist motions, flexion in particular, predispose a person to carpal tunnel syndrome.     

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.     

Sonography and electrodiagnosis in carpal tunnel syndrome diagnosis, an analysis of the literature

We present a review of the international literature concerning sonography for the diagnosis of carpal tunnel syndrome (CTS). Analysis of the results and comparison with electrodiagnostic data provide a sensible albeit personal view on the relevance of sonography and whether it competes or is complementary to electrodiagnosis (EDX). Although EDX is considered as the gold standard for CTS diagnosis, one author chose surgical results to define CTS. The normal and threshold mean values for sonography are particularly variable from one study to another. The standard deviation (S.D.), when compared to mean values, makes normal and abnormal data overlap considerably and produces many false negatives when the specificity is high, and many false positives when the sensitivity is high. In fact, sonography is non-interpretable in only 10 to 15% of the population, and it affirms the median nerve lesion at the wrist in 55% of cases when EDX does it in more than 90% with common tests. Further more the specificity of sonography leads to a false positive diagnosis in 1 case out of 5 versus 1 out of 40 with EDX. The main conclusion is that there is no competition but rather a complementarity between sonography and EDX: sonography is certainly an efficient imaging technique but cannot replace proper EDX performed for upper limb paresthesiae. Namely, sonography can answer only one out of the 8 questions a complete EDX answer: Are sonographic images compatible with a median nerve lesion at the wrist? The answer to this solely question can be obtain with a partial EDX using a single conduction test (motor or sensitive), then duration and cost will be comparable to sonography but will be both more sensitive and specific. Finally, one must kept in mind that the final aim of all examinations in CTS is to determine the cause(s) of upper limb paresthesiae, not simply if there is a median nerve lesion at wrist or not.     

Musculoskeletal sonography and MR imaging. A role for both imaging methods.

Sonography is currently being applied to many areas of the musculoskeletal system. Although some areas are in the experimental stage, there exist several indications in which sonography can produce results at least equal to what is possible with MR imaging. Examples include evaluation for shoulder and ankle tendon abnormalities; soft tissue infection and joint effusion; soft tissue foreign bodies; soft tissue masses, such as Baker's cyst and wrist ganglion cyst; carpal tunnel syndrome; developmental dysplasia of the hip; and other indications where MR imaging is contraindicated. The role of sonography in evaluation of the musculoskeletal system is evolving. With continued experience and research, newer applications for musculoskeletal sonography will likely become established further defining the roles of sonography and MR imaging in evaluation of the musculoskeletal system.     

Assessment of Median Nerve with MR Neurography by Using Diffusion-Tensor Imaging: Normative and Pathologic Diffusion Values

Purpose: To determine normative diffusion values of the median nerve at several anatomic locations in healthy men and women of variable age and to compare these normative values with those in patients with carpal tunnel syndrome. Materials and Methods: After ethics board approval and written informed consent were obtained, 45 healthy volunteers (30 women, 15 men) and 15 patients (10 women, five men) were studied. Volunteers were divided into three age groups. Magnetic resonance (MR) neurography with diffusion-tensor imaging (DTI) was performed in all study participants at 3.0 T by using a single-shot echo-planar imaging sequence (repetition time msec/echo time msec, 10 123/40; b = 1200 sec/mm(2)). Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the median nerve were determined by two readers at three locations: the levels of the distal radioulnar joint, pisiform bone, and hamate bone. Results: Normative FA and ADC values were calculated for men and women, different age groups, and different anatomic locations. FA and ADC did not differ between men and women (P = .28 and P = .38, respectively). FA decreased and ADC increased when moving from proximal to distal locations (P < .001). FA decreased and ADC increased significantly with age (P < .001). There was a significant difference between healthy volunteers and patients with carpal tunnel syndrome (P < .001 for both FA and ADC). An FA threshold of 0.47 and an ADC threshold of 1.054 × 10(-3) mm(2)/sec might be used in the diagnosis of carpal tunnel syndrome. Conclusion: Normative diffusion values for MR neurography of the median nerve with DTI depend on the anatomic location and age but not on sex. Age-specific FA and ADC threshold values might be used to diagnose carpal tunnel syndrome. ? RSNA, 2012.     

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.     

Diffusion tensor imaging and tractography of the median nerve in carpal tunnel syndrome: preliminary results

The purpose was to demonstrate the feasibility of in vivo diffusion tensor imaging (DTI) and tractography of the human median nerve with a 1.5-T MR scanner and to assess potential differences in diffusion between healthy volunteers and patients suffering from carpal tunnel syndrome. The median nerve was examined in 13 patients and 13 healthy volunteers with MR DTI and tractography using a 1.5-T MRI scanner with a dedicated wrist coil. T1-weighted images were performed for anatomical correlation. Mean fractional anisotropy (FA) and mean apparent diffusion coefficient (ADC) values were quantified in the median nerve on tractography images. In all subjects, the nerve orientation and course could be detected with tractography. Mean FA values were significantly lower in patients (p=0.03). However, no statistically significant differences were found for mean ADC values. In vivo assessment of the median nerve in the carpal tunnel using DTI with tractography on a 1.5-T MRI scanner is possible. Microstructural parameters can be easily obtained from tractography images. A significant decrease of mean FA values was found in patients suffering from chronic compression of the median nerve. Further investigations are necessary to determine if mean FA values may be correlated with the severity of nerve entrapment.     

Magnetic resonance neurography of median neuropathies proximal to the carpal tunnel

This review provides magnetic resonance neurography (MRN) imaging appearances of median neuropathy proximal to the carpal tunnel. Carpal tunnel syndrome (CTS) and its imaging have been extensively described in the literature; however, there is a relative paucity of information on the MR imaging appearances of different pathologies of the median nerve proximal to the carpal tunnel.     

Clinical, electrophysiological and MRI correlations in carpal tunnel syndrome]

Even though diagnosis of carpal tunnel syndrome is mainly based on clinical findings, other examinations are often useful for confirmation and management. The most useful of these examinations is EMG. However, EMG may be inconclusive and MRI may then be helpful. The indications for MRI in patients with carpal tunnel syndrome will be reviewed. METHOD: 20 patients with a total of 33 clinically suspected cases of carpal tunnel syndrome (CTS) underwent EMG and MRI evaluation. Clinical and EMG findings identified three groups of patients based on degree of deficit: mild, moderate, and severe. The following structures were evaluated at MRI: median nerve, retinaculum, retrotendinous fat, flexor tendons, thenar space, and muscles and bones of the wrist. Surgery was performed for 19 wrists. RESULTS: Only retinacular bowing and increased T2W signal intensity within the median nerve were significantly related to the diagnosis of CTS (sensitivity of 70% and 57% respectively). Retinacular bowing indicates increased "pressure" within the compartment (mechanical compression of the nerve) and increased T2W signal of the median nerve indicates nerve suffering. These findings correlated well with more severe cases based on clinical and EMG findings. CONCLUSION: In cases where there is discordance between clinical and EMG findings, MRI is helpful to identify patients who would benefit from surgical intervention.     

The effect of long-distance bicycling on ulnar and median nerves: an electrophysiologic evaluation of cyclist palsy

BACKGROUND: Distal ulnar neuropathies have been identified in cyclists because of prolonged grip pressures on handlebars. The so-called cyclist palsy has been postulated to be an entrapment neuropathy of the ulnar nerve in the Guyon canal of the wrist. Previous studies utilizing nerve conduction studies have typically been either case reports or small case series. HYPOTHESIS: Electrophysiologic changes will be present in the ulnar and median nerves after a long-distance multiday cycling event. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 28 adult hands from 14 subjects underwent median and ulnar motor and sensory nerve conductions, which were performed on both hands before and after a 6-day, 420-mile bike tour. A ride questionnaire was also administered after the ride, evaluating the experience level of the cyclist, equipment issues, hand position, and symptoms during the ride. RESULTS: Distal motor latencies of the deep branch of the ulnar nerve to the first dorsal interosseous were significantly prolonged after the long-distance cycling event. The median motor and sensory studies as well as the ulnar sensory and motor studies of the abductor digiti minimi did not change significantly. Electrophysiologic and symptomatic worsening of carpal tunnel syndrome was observed in 3 hands, with the onset of carpal tunnel syndrome in 1 hand after the ride. CONCLUSION: Long-distance cycling may promote physiologic changes in the deep branch of the ulnar nerve and exacerbate symptoms of carpal tunnel syndrome.     

Epithelioid sarcoma of the median nerve mimicking a peripheral nerve sheath tumour

We describe a case of epithelioid sarcoma of the median nerve in a 57-year-old woman presenting with symptoms and signs of carpal tunnel syndrome for 2 years. The clinical examination was suggestive of a wrist ganglion compressing the median nerve. Magnetic resonance imaging (MRI) showed a 5 cm x 3 cm mass involving the median nerve in the carpal tunnel and appearances mimicked a benign peripheral nerve sheath tumour. This report illustrates a rare tumour presenting in a rare location and emphasizes the atypical clinical and MRI features that should alert the radiologist to the possibility of a rare sarcoma mimicking a benign peripheral nerve sheath tumour.