Anatomy of the median nerve and its clinical applications

Acupoint injection and electrical stimulation for postoperative nausea and vomiting: A randomized clinical trial

OBJECTIVE

To assess the efficacy and safety of dexamethasone injection into the Neiguan acupoint combined with transcutaneous electrical acupoint stimulation (TEAS) on postoperative nausea and vomiting (PONV) in patients undergoing gynaecological laparoscopic surgery.

STUDY DESIGN

This trial included 160 patients aged between 18 and 65 years who underwent gynaecological laparoscopic surgery. Participants were assigned at random to one of four groups - the acupoint injection (AI) + TEAS group, AI group, TEAS group or control group - in a 1:1:1:1 ratio. The primary outcome was the incidence of PONV within 0-24 h of surgery. Secondary outcomes included the incidence of PONV within 0-12 h and 0-48 h of surgery, Myles score within 0-24 h of surgery, number of rescue antiemetic administrations within 0-48 h of surgery, postoperative recovery-related indicators, patient satisfaction and adverse events.

RESULTS

Of the 160 patients, 38 (23.8 %) experienced PONV within 24 h of surgery. The use of AI + TEAS (17.5 %) and AI (17.5 %) was associated with lower risk of PONV [odds ratio (OR) 0.354, 95 % confidence interval (CI) 0.125-0.997; p = 0.045] compared with the control group (37.5 %). However, no significant difference was observed between the TEAS group (22.5 %) and the control group (OR 0.484, 95 % CI 0.182-1.289; p = 0.143). The AI + TEAS group had significantly fewer patients with a second dose of antiemetics compared with the control group (relative risk 0.125, 95 % CI 0.016-0.945; p = 0.029).

CONCLUSION

Dexamethasone injection into the Neiguan acupoint was effective in reducing the risk of PONV, and reduced the need for rescue antiemetics when combined with TEAS. Both AI and TEAS interventions enhanced patient satisfaction.

Grip Force Modulation on Median Nerve Morphology Changes

Compression on the median nerve can lead to carpal tunnel syndrome (CTS), and median nerve indicators measured from ultrasound images can be used for CTS diagnosis. The aim of this study was to investigate the relationship between grip force modulation and dynamic morphological changes of the median nerve. We used a digital grip dynamometer to measure grip force while simultaneously conducting ultrasound examinations. Ultrasound images were sampled for both the dominant and nondominant hands of all participants (n = 20) during a baseline condition at approximately 0% maximum voluntary force (MVF), during sustained grip force conditions at 25%, 50%, 75%, and 100% MVF, and during the return to a relaxed state (≈0% MVF) directly following each grip force condition. Regardless of hand dominance, grip force level, and grip force modulation, median nerve cross-sectional area (MNCSA) during the grip tasks was smaller relative to the initial baseline condition without grip force. With respect to shape change, the median nerve became more flattened, including increased longitudinal diameter (D1) and decreased vertical diameter (D2), when grip force was relaxed compared to the preceding sustained grip force condition for the dominant hand; however, there were no significant shape changes for the nondominant hand. As morphological changes to tissue result in strain, our results indicate that median nerve injury development may be associated with more hand usage (dominant hand, grip exertion, and grip force modulation), and further suggests the evaluative potential for median nerve dynamics within the carpal tunnel.

Preoperative Physiotherapy Effects on Hand Function and Quality of Life in Carpal Tunnel Syndrome: 3 - & 6 - month randomized controlled trial

INTRODUCTION

Carpal Tunnel Syndrome (CTS) is a prevalent upper limb mononeuropathy that often leads to delayed surgical intervention, resulting in prolonged symptoms and reduced quality of life.

AIM

To describe the effect of a three-session treatment involving nerve mechanical interface mobilization and self-mobilization combined with education in hand function, symptoms, and quality of life of pre-surgical CTS patients at 3 and 6-months follow-ups; 3) A randomized clinical trial was performed in 42 preoperative CTS patients. Patients were randomized into an experimental group, receiving a three-session intervention of education, diacutaneous fibrolysis, and self-mobilization, or a control group receiving standard care. Primary outcomes included the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, while secondary outcomes assessed paresthesia, mechanosensitivity of the median nerve, mechanical threshold with the Semmes Weinstein monofilament, pinch strength, and quality of life, with the short-form-36 & EuroQol-5D.

RESULTS

The cohort were predominantly severe CTS patients with associated comorbidities. Statistical improvements were shown for experimental group compared to control group in DASH at 6-month follow-up (p = 0.035; η2 = 0.12). Paraesthesia intensity, mechanosensitivity, and quality of life were also significantly improved in the experimental group compared to control group at both 3- and 6-months (p < 0.05). The same occurred for pinch strength at 6 months (p < 0.05). No significant differences were found in mechanical threshold (p > 0.05); 5) The treatment effectively improved hand function, symptoms, and quality of life in preoperative CTS patients, offering a viable alternative during delays in surgical procedures. Nerve mechanical interface treatment could not only help mild to severe CTS patients but might be relevant for severe CTS patients with associated comorbidities.

Diagnostic Musculoskeletal Ultrasound in the Evaluation of the Median Nerve

The median nerve is a crucial structure in the forearm and wrist, responsible for motor and sensory functions. Accurate diagnosis of nerve injury is essential for appropriate treatment planning and optimizing patient outcomes. Although magnetic resonance imaging (MRI) and nerve conduction studies (NCS) are the gold standard for nerve assessment, diagnostic musculoskeletal (MSK) ultrasound offers a portable, real-time, and cost-effective alternative that is gaining traction in rehabilitation and sports medicine settings. MSK ultrasound has emerged as a valuable, non-invasive imaging modality for evaluating median nerve pathology, including carpal tunnel syndrome (CTS), nerve entrapment, and traumatic nerve injuries. This article reviews the utility of MSK ultrasound in evaluating the median nerve injury, including its anatomy, common injury patterns, sonographic techniques, and clinical implications for professional rehabilitation. By integrating MSK ultrasound into clinical practice, providers can improve the accuracy of diagnosis, monitor healing progression, and guide rehabilitation strategies for optimal patient outcomes.

The Median Nerve Displays Adaptive Characteristics When Exposed to Repeated Pinch Grip Efforts of Varying Rates of Force Development: An Ultrasonic Investigation

OBJECTIVES

Repeated gripping with high grip forces and high rates of grip force development are risk factors for carpal tunnel syndrome. As the nerve's adaptive ability is crucial to prevent disease progression, we investigated how these risk factors influence median nerve deformation and displacement over the time course of a repeated pinch grip task.

METHODS

Seventeen healthy participants performed a repeated grip task against a load cell while their carpal tunnel was scanned with ultrasound. The grip task involved pulp-pinching three consecutive times from 0 to 40% maximal voluntary exertion (MVE), performed at three different rates of force development (RFD): 40% MVE/1 second; 2 seconds; and 5 seconds. Ultrasound images were analyzed at 10% MVE intervals. Nerve circularity, width, height, and cross-sectional area were measured to assess deformation. Median nerve displacement was assessed by its change in position relative to the flexor digitorum superficialis tendon of the third digit (FD) in both radioulnar and palmodorsal axes.

RESULTS

Linear mixed modeling indicated that median nerve deformation increased, becoming more circular, with each repeated pulp-pinch (P < .01) and with grip force magnitude (P < .01). However, a faster RFD decreased nerve deformation (P < .01). Furthermore, the nerve displaced ulnarly during pulp-pinching, with greater displacement during the fastest (ie, 40% MVE/1 second) RFD (P < .01).

CONCLUSIONS

The median nerve deformed and displaced in response to pulp-pinching; however, faster rates of force development hindered this adaptive response. This likely reflects the viscoelastic properties of the healthy nerve and subsynovial connective tissue, highlighting the importance of tissue compliance in preventing nerve compression.

Ultrasound of the Median Nerve: A Pictorial Review. Normal Ultrasound Findings and Variations

This is the first of a two-part article in which we focus on the Ultrasound (US) appearance of the normal median nerve (MN) and its main branches. The detailed anatomy and US anatomy of the MN course are presented with high-resolution images obtained with the latest-generation US machines and transducers. Variations are discussed to avoid misinterpretation of normal findings.

Median nerve entrapment neuropathy: a review on the pronator syndrome

Pronator syndrome is a compression neuropathy of the median nerve within the anatomical structures of the elbow and forearm. It presents with neuropathic pain, numbness, and weakness of the forearm and hand, which are often exacerbated by repetitive pronation-supination movements. Patient presentation may mimic the signs and symptoms of carpal tunnel syndrome. Diagnosis requires comprehensive clinical assessment, employing provocative examination along with electrophysiological and imaging studies for accurate evaluation. Treatment strategies encompass conservative measures such as activity modification and physical therapy, whereas surgical intervention may be warranted in severe cases that are refractory to conservative treatment. By reviewing the current literature within the spectrum of median nerve entrapment neuropathies, this review aimed to enhance and summarize the current understanding by consolidating the existing knowledge for improved patient outcomes.

Imaging of elbow entrapment neuropathies

Entrapment neuropathies at the elbow are common in clinical practice and require an accurate diagnosis for effective management. Understanding the imaging characteristics of these conditions is essential for confirming diagnoses and identifying underlying causes. Ultrasound serves as the primary imaging modality for evaluating nerve structure and movement, while MRI is superior for detecting muscle denervation. Plain radiography and CT play a minor role and can be used for the evaluation of bony structures and calcifications/ossifications. Comprehensive knowledge of anatomical landmarks, nerve pathways, and compression sites is crucial for clinicians to accurately interpret imaging and guide appropriate treatment strategies for entrapments of ulnar, median, and radial nerves, and their branches. CRITICAL RELEVANCE STATEMENT: Accurate imaging and anatomical knowledge are essential for diagnosing elbow entrapment neuropathies. Ultrasound is the preferred modality for assessing nerve structure and motion, while MRI excels in detecting muscle denervation and guiding effective management of ulnar, median, and radial nerve entrapments. KEY POINTS: Ultrasound is the primary modality for assessing nerve structure and stability. Findings include nerve structural loss, isoechogenicity, thickening, and hyper-vascularization. MRI provides a comprehensive evaluation of the elbow and accurate muscle assessment. Imaging allows the identification of compressive causes, including anatomical variants, masses, or osseous anomalies. Awareness of anatomical landmarks, nerve pathways, and compression sites is essential.

Pronator Teres Syndrome - Case Report with Imaging Tests Diagnosis

Pronator teres syndrome is characterized by compression of the median nerve, leading to dysfunction of the affected limb. Median nerve entrapment causes paresthesia, changes in sensitivity, and loss of strength in the fingers, in addition to causing loss of hand dexterity. The diagnosis of pronator teres syndrome is complicated, due to its similarity with other neuropathies of the median nerve. So, it is important to emphasize the need for a physical examination together with imaging tests, especially ultrasound, for its correct diagnosis. We report the case of a 28-year-old woman who complained of tingling for ten years in the proximal third of the left forearm at rest that worsens on exertion and weakness if not moving. On physical examination, she has no limitation of movement but refers to a feeling of weakness and numbness in his forearm. Ultrasonography demonstrates compression of the median nerve between the ulnar and humeral heads of the pronator teres muscle, a finding confirmed by magnetic resonance imaging and electroneuromyography. The patient was treated with physiotherapy presenting improvement of symptoms after 45 days.

Prevalence and Risk Factors Associated With Carpal Tunnel Syndrome Among Sudanese Females: A Cross-Sectional Study

BACKGROUND

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy resulting from compression of the median nerve. This condition is more common in females than in males. The earlier the diagnosis, the better the prognosis and treatment outcomes.

MATERIAL AND METHODS

This is a cross-sectional hospital-based study conducted at Soba Teaching Hospital in obstetrics and gynecology outpatient clinic in Khartoum in the period from February 2022 to March 2022. A simple random sampling was applied, and an interview was conducted using a four-part questionnaire. The first part was based on socio-demographic data, the second was lifestyle, and the third and fourth were based on the Boston Carpal Tunnel Questionnaire (BCTQ). The data were analyzed using the statistical package for social sciences (SPSS) software, version 23 (IBM Corp., Armonk, NY) to find the correlation between the various variables.

RESULTS

A total of 113 women participated in the study (response rate=100%). The prevalence of CTS was found to be 5%. No significant association was found between lifestyle and medical history, e.g., obesity and oral contraceptives and CTS were p=0.167, 0.841 respectively. Conversely, there was a significant association between age and residency, with p=0.005 and 0.049, respectively.

CONCLUSIONS

The prevalence of CTS is increasing in Sudan. Therefore, it is essential to thoroughly assess patients for any symptoms related to hand pain by asking detailed questions during consultations. In addition, further studies covering more states are needed to better understand the regional variation in CTS prevalence.

Anconeus and pronation: a palpatory and ultrasonographic study

PURPOSE

Depending on its axis, pronation varies from the radius rotation around the steady ulna to the reciprocal adduction of the radius and abduction of the ulna. While there is no question that pronator teres is a central pronation agonist, anconeus's role is not settled. The current investigation comparing palpation and ultrasonography in these two muscles during pronation along the axis capitulum-second digit evolved from a serendipitous finding in a clinical anatomy seminar.

METHODS

Single-hand palpation and two-transducer ultrasonography over anconeus and pronator teres were used on ten normal subjects to investigate their contraction during pronation around the capitulum-second digit axis. These studies were done independently and blind to the results of the other. The statistical analysis between palpation and ultrasonography was performed with Cohen's kappa coefficient and the χ2 test.

RESULTS

On palpation, on resisted full pronation, anconeus contracted in 8/10 subjects and pronator teres in 10/10 subjects. Without resistance, the corresponding ratios were 5/10 and 9/10. On two-transducer ultrasonography, the comparable ratios were 7/10 and 10/10, and 3/10 and 10/10. A fair concordance (Cohen's kappa = 0.21) between palpation and ultrasonography in detecting the simultaneous status of anconeus and pronator teres during resisted full pronation. Anatomic dissection illustrated the elements involved.

CONCLUSIONS

Plain palpation confirmed by ultrasonography showed the simultaneous contraction of anconeus and pronator teres during resisted pronation in most of the studied subjects. The study suggests that palpation can be helpful in directly studying muscle activity during movement.

Lacertus syndrome: recent advances

Lacertus syndrome consists in proximal median nerve entrapment with median nerve compression at the lacertus fibrosus, causing hand weakness and fatigue, forearm pain and occasional numbness. Recent advances emphasized the importance of clinical examination, due to limitations in electromyographic diagnosis and delayed diagnosis. The Hagert clinical triad, lacertus notch sign, lacertus antagonist test and taping help accurate diagnosis. Non-operative treatment should be tried; and surgical techniques, whether open or ultrasound-guided under WALANT (wide-awake, local anesthesia, no tourniquet) show promising outcomes. Improved awareness, accurate diagnosis and innovative treatments enhance patient care for this challenging condition.

Risk of carpal tunnel syndrome among patients with osteoarthritis: a US population-based study

BACKGROUND

Carpal tunnel syndrome (CTS), an entrapment neuropathy caused by pressure of the median nerve, is a progressive condition that can lead to a decreased quality of life. Studies suggest an association between CTS and arthritis; however, previous studies examining osteoarthritis (OA) and CTS are limited in number, scope and study design. This study estimated the incidence and risk of CTS among patients with OA, both overall and by specific joints, in a large population-based cohort in the United States.

METHODS

Patients from the Optum claims database aged ≥ 45 years and diagnosed with OA between January 1, 2018, and December 31, 2022, were eligible for the OA cohort. The non-OA cohort included those without a diagnosis of OA at the index date and no history of OA for 12 months pre-index. Baseline characteristics were balanced using propensity score matching. The risk of CTS in the OA and non-OA cohort were evaluated using incidence rates and adjusted hazard ratios that were estimated using Cox regression.

RESULTS

After applying the inclusion/exclusion criteria, 3,610,240 of the 6,023,384 adults with a diagnosis of OA remained in the OA cohort. After propensity-score matching, each cohort included 1,033,439 individuals. The incidence rates for CTS per 1000 person-years were 7.35 (95% confidence interval [CI] 7.21-7.49) in the OA cohort and 1.44 (95% CI 1.38-1.50) in the non-OA cohort. The risk of developing CTS in patients with OA was ~ 4 times that of patients without (hazard ratio = 3.80; 95% CI 3.54-4.07). This increased risk was found across all OA joint types, with OA of the hand/wrist having the highest risk for CTS. Additionally, multiple OA joints presented a higher risk compared with a single affected joint.

CONCLUSIONS

OA increases the risk of CTS, but this is not limited to patients with hand/wrist OA, suggesting a systemic impact of OA on CTS. While the risk appears highest for patients with hand/wrist OA, patients with more distant affected joints like knee or hip also have an increased risk of CTS.

Minimally invasive surgical technique for unstable supracondylar humerus fractures in children (Gartland type III or IV)

Background

Achieving and maintaining anatomical reduction during the treatment of pediatric humerus fractures, classified as Gartland type III or IV, presents a clinical challenge. Herein, we present a minimally invasive surgical approach using a novel and simple K-wire push technique that aids in achieving and maintaining anatomical reduction.

Methods

We reviewed data of children receiving treatment for supracondylar fractures of the humerus at our hospital between January 2016 and December 2020. Patients were divided into two groups based on the method of treatment: Group 1 was treated with the K-wire push technique, and Group 2 was treated with the standard technique as described by Rockwood and Wilkins. The medical records and radiographic images were reviewed. In total, 91 patients with Gartland types III and IV fractures were included, with 37 and 54 patients in Groups 1 and 2, respectively.

Results

The postoperative reduction radiographic parameters and Flynn scores at final follow-up were not significantly different between the two groups.

Conclusion

The minimally invasive K-wire push technique for unstable supracondylar fractures in children is a safe and effective alternative for improving reduction. Using this technique, complications can be minimized, and the requirement for open reduction can be reduced.

Other median neuropathies

Median mononeuropathy is common, with carpal tunnel syndrome the most frequently encountered acquired mononeuropathy in clinical practice. However, other disorders of the median nerve and many known anatomical variants can lead to misdiagnosis and unexpected surgical complications if their presence is not correctly identified. A number of inherited and acquired disorders can affect the median nerve proximal to the wrist, alone or accompanied by other affected peripheral nerves. Recognizing other disorders that can masquerade as median mononeuropathies can avoid misdiagnosis and misguided management. This chapter explores median nerve anatomical variants, disorders, and lesions, emphasizing the need for careful examination and electrodiagnostic study in the localization of median neuropathy.

A revised electrodiagnosis-based severity classification for carpal tunnel syndrome

BACKGROUND

An electrodiagnostic evaluation is conducted to diagnose carpal tunnel syndrome (CTS) and evaluate its severity.

OBJECTIVE

This study proposes a revised approach for classifying the severity of electrophysiological findings for patients with CTS.

METHODS

This retrospective cross-sectional study included patients with CTS confirmed through electrodiagnostic evaluations. Based on the Stevens' classification, the patients were divided into three groups (mild/moderate/severe). A new intermediate group was defined to identify patients with normal motor nerve conduction studies and abnormal electromyographic results. CTS pain was evaluated using a numeric rate scale. Physical examinations and sonographic evaluation were performed to detect anatomical abnormalities.

RESULTS

Overall, 1,069 CTS hands of 850 CTS patients were included. The mean age was 57.9 ± 10.8 years, and 336 (39.5%) were men. There were 522 (48.8%) mild cases; 281 (26.3%) moderate cases; and 266 (24.9%) severe cases. In the severe group, 49 cases were reclassified into the intermediate group. The median cross-sectional area in the intermediate group significantly differed from that in the severe group. However, the pain score significantly differed from that of the moderate group.

CONCLUSION

The intermediate CTS group showed clinical features that were intermediate to those of the moderate and severe CTS groups.

Anatomical considerations of US-guided carpal tunnel release in daily clinical practice

Carpal tunnel syndrome is the most frequent compression neuropathy with an incidence of one to three subjects per thousand. As specific anatomical variations might lead to unintended damage during surgical interventions, we present a review to elucidate the anatomical variability of the carpal tunnel region with important considerations for daily clinical practice: several variants of the median nerve branches in and around the transverse carpal ligament are typical and must - similarly to the variant courses of the median artery, which may be found eccentric ulnar to the median nerve - be taken into account in any interventional therapy at the carpal tunnel. Unintended interference in these structures might lead to heavy arterial bleeding and, in consequence, even underperfusion of segments of the median nerve or, if neural structures such as variant nerve branches are impaired or even cut, severe pain-syndromes with a profound impact on the quality of life. This knowledge is thus crucial for outcome- and safety-optimization of different surgical procedures at the volar aspect of the wrist and surgical therapy of the carpal tunnel syndrome e.g., US-guided carpal tunnel release, as injury might result in dysfunction and/or pain on wrist motion or direct impact in the region concerned. For most variations, anatomical and surgical descriptions vary, as official classifications are still lacking.

Pilot Cadaveric Study of Anatomical Variations of the Median Nerve at the Wrist in the Lithuanian Population

INTRODUCTION

 Carpal tunnel syndrome (CTS) is known as one of the most common neurological disorders in the human body. Nowadays, the prevalence in the general population ranges between 1% and 5%. Due to its high prevalence and increasing incidence of carpal tunnel surgery, the anatomical variations of the median nerve at the wrist are important to know to avoid iatrogenic injury of the nerve.

PURPOSE

The objective of this study was to evaluate the anatomical variation of the median nerve at the level of the wrist in the Lithuanian population with a focus on its thenar motor branch based on the classifications of Lanz.

MATERIAL AND METHODS

A cadaveric study was performed, and 30 wrists of 15 adult Lithuanian cadavers ranging from 70 to 89 years of age were dissected and examined. Eight female and seven male cadavers were included in the study. Any anatomical finding was documented, and the results were compared with the classification of Lanz as well as with the data found in the literature.

RESULTS

All hands showed different patterns in comparison to the standard anatomical variation Lanz type 0. The most common result was dedicated to Lanz group 4A. Nineteen out of 30 hands (63%, p<0.01) had an accessory branch proximal to the carpal tunnel, while one of these hands showed a third thenar motor branch. Five hands (16%) were dedicated to Lanz group 2 with an accessory branch distal to the carpal tunnel. One hand (3%) showed a variation close to Lanz group 2, but in this case, the thenar motor branch had its origin under the flexor retinaculum instead of proximal to it. Two hands each (6%) were classified by Lanz groups 1B and 3A. Additionally, one variation showed a pattern of a combination of Lanz types 3A and 3B. The bifid median nerve had a connecting branch in between which started distal to the flexor retinaculum. Two anatomical variations (6%) were not described by the classification of Lanz.

Anatomical Variants of the Upper Limb Nerves: Clinical and Preoperative Relevance

Profound knowledge of nerve variations is essential for clinical practice. It is crucial for interpreting the large variability of a patient's clinical presentation and the different mechanisms of nerve injury. Awareness of nerve variations facilitates surgical safety and efficacy. Clinically significant anatomical variations can be classified into two main groups: variability in the course of the nerve and variability of structures surrounding the nerve. In this review article we focus on the most common nerve variants of the upper extremity and their clinical relevance.

Unusual Anatomic Location of the Median Nerve Within the Pronator Teres Muscle: A Case Report

CASE

A 57-year-old man presented with pain and paresthesia in both hands and was diagnosed with pronator teres syndrome. Surgical decompression of the left elbow and forearm revealed the median nerve in an unusual anatomic location, specifically running within the pronator teres muscle.

CONCLUSION

Anatomic anomalies of the pronator teres muscle and the path of the median nerve have been described. However, there are no reports of the median nerve entering and traveling within the pronator teres. Surgeons should be aware of this anomaly to avoid potential iatrogenic injury when performing an anterior surgical approach to the elbow and proximal forearm.

The effect of median nerve mobilization on two point discrimination

[Purpose] Two-point discrimination (TPD) is expressed as the minimum distance at which two mechanical stimuli applied simultaneously to the skin can be perceived as two separate points. The aim of this study was to investigate the effect of median nerve mobilization on TPD in healthy adults. [Participants and Methods] This study included 120 healthy adults. Participants were randomized according to their gender into the Neural Mobilization Group (NMG) and Control Group (CG). Demographic data of the participants (gender, age, height, weight, BMI, smoking) were recorded and TPD measurement was performed with baseline aesthesiometer on the palm with distal phalanges of the thumb, index and middle finger on the right-left hand. After the baseline TPD test, participants in the NMG performed Median Nerve Mobilization for 14 days. Measurements were taken before and after training. [Results] A statistically significant difference was found in all other measurements in both groups, except for the right and left palm TPD measurements in the control group. [Conclusion] It is thought that it would be beneficial to investigate the healing effects of the neural mobilization applications, which include all parts of the nerve line in disease conditions.

Application of shear wave elastography and median nerve cross-section area in the diagnosis and staging of carpal tunnel syndrome: a case-control study

Purpose

Imaging is gaining a more prominent role in the diagnosis of carpal tunnel syndrome (CTS), especially ultrasonography. Shear wave elastography (SWE) is a novel qualitative method to study mechanical changes in tissue. In this study, we aim to assess the role of SWE in diagnosing and staining of the disease.

Material and methods

A total of 124 wrists were included in the study. Seventy wrists had CTS, and 54 were included as the control group. All of the wrists with CTS had staging done with nerve conduction study. All patients underwent ultrasonography by an expert radiologist and had the SWE and cross-section of the median nerve determined. These values were compared among the 2 groups and different stages of CTS. The receiver operating characteristic curve was utilized to assess the diagnostic role of each of the variables.

Results

Cross-section area (CSA) and SWE were significantly different between the 2 groups (p = 0.0001). CSA was also significantly different among various stages of CTS. SWE was not significantly different among moderate and severe stages of CTS. Both of the variables had a good ability to distinguish mild CTS from healthy wrists (p = 0.0001).

Conclusion

SWE can be used in diagnosing CTS and in the staging of the disease.

Anatomy of the nerves, vessels, and muscular compartments of the forearm, as revealed by high-resolution ultrasound. Part 1: overall structure and forearm compartments

In recent decades, high-resolution ultrasound (HRUS) has revolutionized the morphological and structural evaluation of peripheral nerves and muscles, revealing details of the internal structure of the neural fascicles and muscle architecture. Applications range from diagnostics to interventional procedures. The anatomy of the forearm region is complex, with several muscles and an extensive network of vessels and nerves. To guarantee the success of the evaluation by HRUS, knowledge of the normal anatomy of the region is essential. The aim of these two companion articles is to present the normal anatomy of the nerves and compartments of the forearm, as revealed by HRUS, as well as the relationships between the main vessels and nerves of the region. Part 1 aims to review the overall structure of nerves, muscles and tendons, as seen on HRUS, and that of the forearm compartments. We present a practical approach, with general guidelines and tips on how best to perform the study. Part 2 is a pictorial essay about compartment vascularization and cutaneous innervation. Knowledge of the normal anatomy of the forearm improves the technical quality of the examinations, contributing to better diagnoses, as well as improving the performance and safety of interventional procedures.

Ultrasonographic evaluation of the median nerve: normal and variant anatomy and appearance

The median nerve is a mixed sensory and motor nerve that innervates part of the flexor muscles in the anterior compartment of the forearm and muscles in the lateral part of the hand; palmar cutaneous and digital cutaneous nerves branch from the median nerve, which provides sensory innervation to the skin on the radial side of the palm. Also, the median nerve is an object of interest because neuropathy of the median nerve at the level of the carpal tunnel is the most common entrapment neuropathy which increases dramatically in patients with diabetes. Neuromuscular ultrasound provides extensive diagnostic information and has proved itself as a useful complementary test to electrodiagnostic examinations in cases involving median nerve neuropathy. It often happens that the cause of nerve entrapment and neuropathy are variants of several anatomical structures along the course of the median nerve. It is important to be aware and report such anatomical variations of the median nerve in order to avoid damaging the nerve during surgical treatment. Despite the frequently documented abnormalities in the pathway of the brachial plexus and the median nerve, the anatomical variations are unusual to see and are rarely reported. Moreover, there are variations that do not fit under any of the classifications described in the literature.

The Myth of Median Nerve in Forearm and Its Role in Double Crush Syndrome: A Cadaveric Study

Purpose: This study aims to histologically compare the median nerve in the arm, forearm, and wrist, to help understand how cervical radiculopathy in a double crush phenomenon causes distal nerve dysfunction at the carpal tunnel and median nerve with concurrent absence of symptoms at the forearm.

Methods: The study was performed on 12 fresh cadaveric upper limbs free from any injury or operation. Male cadavers in the age range of 35–40 years were used. The dissection of the median nerve and the histological examination of the specimens from the arm, forearm, and wrist were conducted to evaluate variations in the epineurium thickness (μm), perineurium thickness (μm), number of fascicles per nerve trunk, area percent of myelin covering, and area percent of neurolemmal sheath.

Results: Morphometric and statistical results of the cadaveric median nerve trunk revealed that the mean epineurium and perineurium thickness measured in H&E-stained sections in the forearm were significantly greater than those in the arm and wrist specimens. Further, the mean percent area of the myelin covering in the forearm was significantly lower than that in the arm and wrist specimens in the sections stained with osmium oxide (p < 0.001). There were, however, no significant differences in the neurolemmal sheath among the arm, forearm, and wrist specimens in the silver-stained sections.

Conclusion: The histological differences explained the high concomitant occurrence of carpal tunnel syndrome (CTS) and cervical radiculopathy and the concurrent absence of symptoms at the forearm. Hence, we suggest cautious evaluation of patients with upper limb symptoms, since the management of these conditions requires a different approach.

Restoration of thumb opposition (opponensplasty)

The authors review the therapeutic principles that must be applied when restoring the thumb opposition surgically. Among the many surgical techniques, five are featured: transfer of the flexor digitorum superficialis of the third or fourth finger, transfer of the extensor indicis proprius, transfer of the palmaris longus, translocation of the flexor palmaris longus tendon, transfer of the extensor pollicis longus. After summarizing the procedures, they emphasize the practical points that must be respected. This surgery, which cannot restore sensitivity, requires a precise assessment of the patient's wishes and information on what can be really expected.

Safety of Dry Needling of the Pronator Teres Muscle in Cadavers: A Potential Treatment for Pronator Syndrome

BACKGROUND

Entrapment of the median nerve at the pronator teres muscle can contribute to symptoms in the forearm and wrist. The pronator teres is also involved in patterns of spasticity observed in people who had suffered a stroke. Research on treatment efficacy with dry needling is scarce.

OBJECTIVE

To determine if a solid filiform needle safely penetrates the pronator teres muscle during the clinical application of dry needling.

DESIGN

A cadaveric descriptive study.

METHODS

Needle insertion of the pronator teres was conducted in ten cryopreserved forearms with a 30*0.32 mm filiform needle. With the forearm supinated, the needle was inserted 3 cm distal to the mid-point between the biceps tendon insertion and the medial epicondyle. The needle was advanced in a cranial and medial direction to a depth clinically judged to be in the pronator teres muscle. Safety was assessed by measuring the distance from the needle to the surrounding neurovascular bundles.

RESULTS

Accurate needle penetration of the pronator teres was observed in 100% of the specimens (mean needle penetration: 16.7 ± 4.3 mm, 95%CI 13.6 to 19.7 mm). No neurovascular bundles were pierced in any of the specimen's forearms. The distances from the tip of the needle to the surrounding neurovascular bundles were 16.4 ± 3.9 mm (95%CI 13.6 to 19.2 mm) to the ulnar nerve (A), 9.0 ± 2.2 mm (95%CI 7.3 to 19.5 mm) to the median nerve (B), and 12.8 ± 4.0 mm (95%CI 10.0 to 15.7 mm) to brachial artery (C).

CONCLUSION

The results from this cadaveric study support the assumption that needling of the pronator teres using described anatomical landmarks can be accurately and safely conducted by an experienced clinician.

Variant Median Nerve Anatomy: Ultrasound Evidence of a Pseudoconduction Block

INTRODUCTION

A conduction block at a noncompressible site warrants further investigation.

METHODS AND MATERIALS

A 36-year-old woman with a history of Hodgkin lymphoma and chemotherapy-induced polyneuropathy developed bilateral hand numbness and paresthesias. Workup revealed bilateral carpal tunnel syndrome and an apparent superimposed conduction block of the median nerve in the forearm. Given the history of cancer, there was concern for an infiltrative or an immune-mediated process.

RESULTS

Neuromuscular ultrasound demonstrated that the median nerve descended the upper extremity along an atypical path, deep along the posteromedial aspect of the upper arm, and relatively medially in the forearm. Ultrasound-directed nerve stimulation revealed there was no conduction block. This anatomical variant has been rarely described and has not been reported previously to mimic conduction block or been documented via ultrasound.

CONCLUSIONS

This case demonstrates that neuromuscular ultrasound may supplement the electrodiagnostic study and limit confounding technical factors because of rare anatomic variation.

Ultrasound Findings in Less Frequent Causes of Carpal Tunnel Syndrome

The most common etiology of carpal tunnel syndrome (CTS) is idiopathic. However, secondary causes of CTS should be considered when symptoms are unilateral, or electrodiagnostic studies are discrepant with the clinical presentation. Imaging of the carpal tunnel should be performed when secondary causes of CTS are suspected. An ultrasound evaluation of the carpal tunnel can assess for pathologic changes of the median nerve, detect secondary causes of CTS, and aid in surgical planning.