The significance of muscle echo intensity on ultrasound for focal neuropathy: The median- to ulnar-innervated muscle echo intensity ratio in carpal tunnel syndrome

AbstractCarpal tunnel syndrome (CTS) is a compressive focal neuropathy of the median nerve (NM) at the wrist. We hypothesize that reverse Phalen’s test rather than the previously commonly proposed classic Phalen’s maneuver was a logical maneuver in the diagnosis of CTS from the anatomic, pathophysiological and electrophysiological viewpoint. Dorsal flexion of the hand results in an increase in the flexor retinaculum tension (RFT), extension of the finger long flexor muscle tendons and consequential NM entrapment between the tendons and flexor retinaculum (RF). Thus, the carpal tunnel (CT) volume is reduced, the intra-tunnel pressure is increased, while the RF to NM distance is decreased. On Phalen’s maneuver, the forced palmar hand flexion entails opposite consequences i.e. reduced RFT, relaxation of the finger long flexor muscle tendons, decreased pressure upon NM, slight increase in the CT volume, decreased intra-tunnel pressure and increased RF to NM distance. The hypothesis can be tested by a conductive NM study, preferably at three positions: mid-position (palmar/volar angle 180 degrees); forced dorsal flexion (palmar/volar angle about 270 degrees); and forced palmar (volar) flexion (palmar/volar angle about 90 degrees). Relative to mid-position, “deterioration” of electroneurography (ENG) finding is observed in dorsal flexion, whereas “improvement” of ENG finding is recorded in palmar flexion.

Download Full-text

Quantitative Evaluation of the Echo Intensity of Paraneural Area and Myofascial Structure around Median Nerve in Carpal Tunnel Syndrome

Diagnostics ◽

10.3390/diagnostics10110914 ◽

2020 ◽

Vol 10 (11) ◽

pp. 914

Author(s):

Chenglei Fan ◽

Caterina Fede ◽

Carmelo Pirri ◽

Diego Guidolin ◽

Carlo Biz ◽

...

Keyword(s):

Carpal Tunnel Syndrome ◽

Median Nerve ◽

Carpal Tunnel ◽

Ultrasound Images ◽

Echo Intensity ◽

Rater Reliability ◽

Transversal Displacement ◽

Significant Difference ◽

Tunnel Syndrome ◽

And Control

The aim of this study was to investigate whether the echo intensity (EI) of the paraneural area (PA), the median nerve (MN) at the carpal tunnel, the EI of the myofascial structure (MS) around MN, the ‘PA and MN’ at the mid-forearm, and the MN transversal displacement at both sites differs between persons with carpal tunnel syndrome (CTS) and control subjects. Methods: In total, 16 CTS patients and 16 controls, age- and gender-matched, were recruited. Cross-sectional ultrasound images of MN were obtained to evaluate the EI of the PA, the MN at carpal tunnel, the EI of MS, and the ‘PA and MN’ at the mid-forearm in a natural position, then images were taken after a whole-hand grasp movement, to evaluate MN transversal displacement. Inter-rater and intra-rater reliability in control, and differences in the EI and MN displacement between CTS and control, were analyzed. In addition, the correlations between ultrasound parameters and MN displacement were evaluated. Results: The quantitative EI of PA, MN, EI of MS, ‘PA and MN’ had high inter-rater and intra-rater reliability in the control. The EI of PA, MS and ‘PA and MN’ were significantly higher in CTS subjects (p < 0.01), whilst there was no significant difference in the EI of MN at the carpal tunnel. MN displacement was significantly decreased both at the carpal tunnel and the mid-forearm in CTS subjects (p < 0.01). In addition, there were negative correlations among the EI of PA (rs = −0.484, p = 0.004), EI of MS (rs = −0.479, p = 0.002), EI of ‘PA and MN’ (rs = −0.605, p < 0.001) and MN transversal displacement. Conclusions: The higher EI of PA and MS around MN in CTS may indicate greater fibrosis along the course of MN, reducing fascial adaptability, influencing the synergy and coordination of the MS, and increasing the shear stress between MS and MN, and it may further increase the abnormal pressure on the MN not only at the carpal tunnel, but also at the mid-forearm. These results may partly explain the role of PA and MS in CTS pathogenesis.

Download Full-text

Clinical Update: Assessing Maximum Medical Improvement in Carpal Tunnel Syndrome

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2003.julaug02 ◽

2003 ◽

Vol 8 (4) ◽

pp. 4-5

Author(s):

Christopher R. Brigham ◽

James B. Talmage

Keyword(s):

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Proper Time ◽

Carpal Tunnel Release ◽

Hand Function ◽

Factors Affecting ◽

Early Results ◽

Medical Evaluation ◽

Nerve Recovery ◽

Tunnel Syndrome

Abstract Permanent impairment cannot be assessed until the patient is at maximum medical improvement (MMI), but the proper time to test following carpal tunnel release often is not clear. The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) states: “Factors affecting nerve recovery in compression lesions include nerve fiber pathology, level of injury, duration of injury, and status of end organs,” but age is not prognostic. The AMA Guides clarifies: “High axonotmesis lesions may take 1 to 2 years for maximum recovery, whereas even lesions at the wrist may take 6 to 9 months for maximal recovery of nerve function.” The authors review 3 studies that followed patients’ long-term recovery of hand function after open carpal tunnel release surgery and found that estimates of MMI ranged from 25 weeks to 24 months (for “significant improvement”) to 18 to 24 months. The authors suggest that if the early results of surgery suggest a patient's improvement in the activities of daily living (ADL) and an examination shows few or no symptoms, the result can be assessed early. If major symptoms and ADL problems persist, the examiner should wait at least 6 to 12 months, until symptoms appear to stop improving. A patient with carpal tunnel syndrome who declines a release can be rated for impairment, and, as appropriate, the physician may wish to make a written note of this in the medical evaluation report.

Download Full-text

Clinical Update: Understanding Causation: An Example Using Carpal Tunnel Syndrome

Guides Newsletter ◽

10.1001/amaguidesnewsletters.2007.novdec02 ◽

2007 ◽

Vol 12 (6) ◽

pp. 5-8 ◽

Cited By ~ 3

Author(s):

J. Mark Melhorn

Keyword(s):

Risk Factors ◽

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Legal Responsibility ◽

Medical Evidence ◽

Anatomic Structure ◽

Legal Professionals ◽

Compensation Systems ◽

Tunnel Syndrome ◽

Four Levels

Abstract Medical evidence is drawn from observation, is multifactorial, and relies on the laws of probability rather than a single cause, but, in law, finding causation between a wrongful act and harm is essential to the attribution of legal responsibility. These different perspectives often result in dissatisfaction for litigants, uncertainty for judges, and friction between health care and legal professionals. Carpal tunnel syndrome (CTS) provides an example: Popular notions suggest that CTS results from occupational arm or hand use, but medical factors range from congenital or acquired anatomic structure, age, sex, and body mass index, and perhaps also involving hormonal disorders, diabetes, pregnancy, and others. The law separately considers two separate components of causation: cause in fact (a cause-and-effect relationship exists) and proximate or legal cause (two events are so closely related that liability can be attached to the first event). Workers’ compensation systems are a genuine, no-fault form of insurance, and evaluators should be aware of the relevant thresholds and legal definitions for the jurisdiction in which they provide an opinion. The AMA Guides to the Evaluation of Permanent Impairment contains a large number of specific references and outlines the methodology to evaluate CTS, including both occupational and nonoccupational risk factors and assigning one of four levels of evidence that supports the conclusion.

Download Full-text