Magnetic Resonance Imaging–Measured Cross-Sectional Area of the Median Nerve

Characteristics of Patients with Clinical Signs and Symptoms of Carpal Tunnel Syndrome but Negative Diagnostic Testing

Background

Carpal tunnel syndrome (CTS) is a clinical diagnosis involving numerous confirmatory diagnostic tools, including patient questionnaires, ultrasound (US), and electrodiagnostic studies (EDX.) Patients may experience clinical symptoms of CTS with false negative diagnostic testing. The purpose of this study was to identify characteristics of patients with clinical symptoms of CTS with negative diagnostic testing.

Methods

An existing database of 295 hands containing the six-item CTS-6, US of the median nerve, and EDX was queried. Patients with symptoms of carpal tunnel scoring 12.5 or higher on CTS-6 were sorted into those with all positive testing or negative testing.

Results

In 60 patients, 103 hands had both positive US and EDX and a CTS-6 of 12.5 or higher. Twenty-nine hands in 25 patients had a CTS-6 of 12.5 or higher and both negative ultrasound and EDX. There was a significantly younger average age of 43 (P = 0.007) and lower average BMI of 28 (P < 0.0001) of patients in the negative diagnostic study group, compared with the average age of 53, and a body mass index (BMI) of 34 in the positive diagnostic study.

Conclusions

In this series, patients with symptoms of carpal tunnel syndrome and negative diagnostic studies were on average younger and had a lower BMI. These patients may warrant more careful consideration of CTS clinical diagnosis and counseling regarding a higher risk of false-negative confirmatory testing. Further studies are needed to determine possible effects of age and BMI on electrodiagnostic studies and ultrasound testing in CTS.

Association Between Thenar Musculature and Carpal Tunnel Syndrome

Background: Dynamic forces acting on the transverse carpal ligament (TCL) may influence the mechanics of the carpal tunnel (CT), thus affecting the occurrence of CT syndrome (CTS). Previous studies demonstrated an association between muscle overlying the CT and the diagnosis of CTS. Understanding the location of insertion/origin of the thenar musculature will allow mechanical analysis of the forces applied to the TCL during performance of individual tasks. Our purpose was to determine the location of muscle overlying the CT on magnetic resonance imaging (MRI) in CTS and controls. Methods: Case-control study of 21 normal adult wrist MRI scans. MRI measurements were performed on an axial cut at the level of the hook-of-hamate. Median nerve cross-sectional area (CSA), median nerve shape and increased signal intensity within the CT were associated with CTS. The amount and length of muscle crossing the midline and the CT on the same cut was measured and the association with the occurrence of CTS was analysed. Results: We found an inverse relationship between the amount of muscle crossing the midline and the size of the CT, and a direct relationship with occurrence of CTS p less than 0.01, but no differences regarding length of muscle crossing the midline. Conclusions: This study supports an association between the thenar musculature location relative to the CT and the predictors of CTS on MRI. Since the location of muscle origin/insertion is variable, their effect may differ accordingly, therefore, further study is needed to describe the exact location of origin/insertion and its differential dynamic or static effect on the pathogenesis of CTS. Level of Evidence: Level IV (Diagnostic).

Potential Relationships between the Median Nerve Cross-Sectional Area and Physical Characteristics in Unilateral Symptomatic Carpal Tunnel Syndrome Patients

Background: The present study investigated the relationships between the median nerve cross-sectional area (CSA) and physical characteristics in patients with unilateral symptomatic carpal tunnel syndrome (CTS). Methods: Height, weight, body mass index (BMI), disease duration, results of electrodiagnostic testing (EDX), and median nerve CSA at the level of the wrist crease were recorded in 81 patients with CTS who presented with symptoms on only one side. Correlation coefficients between median nerve CSA and physical characteristics, disease duration, and results of EDX were analyzed. Results: Median nerve CSA at the wrist crease (mm2) was significantly larger on the symptomatic side (14.1 ± 3.8) than on the asymptomatic side (11.5 ± 2.9). Median nerve CSA correlated with body weight (correlation coefficient = 0.39) and BMI (correlation coefficient = 0.44) on the asymptomatic side, but not on the symptomatic side. These correlations were slightly stronger in females (correlation coefficient = 0.46) than in males (correlation coefficient = 0.40). No correlations between median nerve CSA and disease duration and the results of EDX were observed in both sides. Conclusions: In patients with unilateral symptomatic CTS, median nerve CSA correlated with BMI only on the asymptomatic side. The present results suggest that the relationship between median nerve CSA and BMI in CTS is significant until symptom onset but may be masked by edema and pseudoneuroma after its onset. A higher BMI is associated with a larger CSA of the median nerve, which may be a risk factor for the development of CTS.

Sex differences in neuromuscular disorders

The prevalence, onset, pathophysiology, and clinical course of many neuromuscular disorders (NMDs) may significantly differ between males and females. Some NMDs are more frequently observed in females, and characterized to show a higher grade of severity during or after the pregnancy. Meanwhile, others tend to have an earlier onset in males and exhibit a more variable progression. Prevalently, sex differences in NMDs have a familiar character given from genetic inheritance. However, they may also influence clinical presentation and disease severity of acquired NMD forms, and are represented by both hormonal and genetic factors. Consequently, to shed light on the distinctive role of biological factors in the different clinical phenotypes, we summarize in this review the sex related differences and their distinctive biological roles emerging from the current literature in both acquired and inherited NMDs.