A prospective study of the anatomic variations of the median nerve in the carpal tunnel in Asians

Thrombosed Persistent Median Artery with Coexisting Bifid Median Nerve in a Robotic Arthroplasty Surgeon: A Case Report

CASE

A 47-year-old orthopaedic surgeon presented with acute volar left wrist pain. He performed over 250 robot-assisted knee arthroplasties each year. Color Doppler evaluation revealed bilateral persistent median arteries and bifid median nerves, with focal occlusive thrombosis of the left median artery. He was advised rest and oral aspirin. He could return to his professional activities after 1 month. He had no recurrence of symptoms at 1 year of follow-up.

CONCLUSION

Orthopaedic surgeons use vibrating hand tools on a daily basis. The possibility of hand-arm vibration syndrome must be considered in the differential diagnosis of wrist pain among orthopaedic surgeons.

Improved visualization of median, ulnar nerves, and small branches in the wrist and palm using contrast-enhanced magnetic resonance neurography

Background

Magnetic resonance imaging of peripheral nerves in the wrist and palm is challenging due to the small size, tortuous course, complex surrounding tissues, and accompanying blood vessels. The occurrence of carpal palmar lesions leads to edema, swelling, and mass effect, which may further interfere with the display and identification of nerves.

Objective

To evaluate whether contrast-enhanced magnetic resonance neurography (ceMRN) improves the visualization of the morphology and pathology of the median, ulnar nerves, and their small branches in the wrist and palm.

Design

An observational study.

Methods

In total 57 subjects, including 36 volunteers and 21 patients with carpal palmar lesions, were enrolled and underwent ceMRN and non-contrast MRN (ncMRN) examination at 3.0 Tesla. The degree of vascular suppression, nerve visualization, diagnostic confidence, and lesion conspicuity was qualitatively assessed by two radiologists. Kappa statistics were obtained for inter-reader agreement. The signal-to-noise ratio, contrast ratio (CR), and contrast-to-noise ratio (CNR) of the median nerve were measured. The subjective ratings and quantitative measurements were compared between ncMRN and ceMRN.

Results

The inter-reader agreement was excellent (k > 0.8) for all qualitative assessments and visualization assessment of each nerve segment. Compared with ncMRN, ceMRN significantly improved vascular suppression in volunteers and patients (both p < 0.001). The ceMRN significantly enhanced nerve visualization of each segment (all p < 0.05) and diagnostic confidence in volunteers and patients (both p < 0.05). The ceMRN improved lesion conspicuity (p = 0.003) in patients. Quantitatively, ceMRN had significantly higher CRs of nerve versus subcutaneous fat, bone marrow, and vessels and CNR of nerve versus vessel than ncMRN (all p < 0.05).

Conclusion

The ceMRN significantly improves the visualization of peripheral nerves and pathology in the wrist and palm by robustly suppressing the signals of fat, bone marrow, and especially vessels in volunteers and patients.

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.

The persistent median artery and its vascular patterns: A meta-analysis of 10,394 subjects

The presence of a persistent median artery (PMA) has been implicated in the development of compression neuropathies and surgical complications. Due to the large variability in the prevalence of the PMA and its subtypes in the literature, more awareness of its anatomy is needed. The aim of our meta-analysis was to find the pooled prevalence of the antebrachial and palmar persistent median arteries. An extensive search through the major databases was performed to identify all articles and references matching our inclusion criteria. The extracted data included methods of investigation, prevalence of the PMA, anatomical subtype (antebrachial, palmar), side, sex, laterality, and ethnicity. A total of 64 studies (n = 10,394 hands) were included in this meta-analysis. An antebrachial pattern was revealed to be more prevalent than a palmar pattern (34.0% vs. 8.6%). A palmar PMA was reported in 2.6% of patients undergoing surgery for carpal tunnel syndrome when compared to cadaveric studies of adult patients in which the prevalence was 8.6%. Both patterns of PMA are prevalent in a considerable portion of the general population. As the estimated prevalence of the PMA was found to be significantly lower in patients undergoing surgery for carpal tunnel syndrome than those reported in cadaveric studies, its etiological contribution to carpal tunnel syndrome is questionable. Surgeons operating on the forearm and carpal tunnel should understand the anatomy and surgical implications of the PMA and its anatomical patterns.

"Million dollar nerve" magnetic resonance neurography: first normal and pathological findings

OBJECTIVES

To evaluate prospectively the feasibility of magnetic resonance neurography (MRN) in identifying the anatomical characteristics of thenar muscular branch (TMB) of the median nerve, also known as the "million dollar nerve," in patients and controls.

METHODS

Thirteen patients affected by carpal tunnel syndrome (CTS) and four healthy controls had their hands scanned on a 3-T MR imaging scanner for TMB visualization. Median nerve anatomical variations were classified into four groups according to Poisel's classification system modified by Lanz. TMB signal intensity and diameter were assessed for the diagnosis of neuropathy.

RESULTS

TMB was successfully identified in all patients and subjects by using MRN. The most suitable pulse sequences to identify and measure nerve diameter were 3D DW-PSIF and T2-FS-TSE. The axial oblique and sagittal oblique planes are complementary in demonstrating its entire course. TMB had mostly an extraligamentous course with radial side origin (93.8%, each). All patients experienced increased T2 signal intensity (p < 0.001) and thickened nerves. Mean TMB diameters were 1.27 ± 0.21 mm (range, 1.02-1.74 mm) and 0.87 ± 0.16 mm (0.73-1.08 mm) (p = 0.008) in the patient and control groups, respectively.

CONCLUSION

MRN is a reliable imaging technique for identification and anatomical characterization of TMB in patients affected by CTS. This innovative imaging workup may therefore be included in the preoperative evaluation of patients scheduled for carpal tunnel release, especially in CTS with TMB involvement or even in isolated TMB neuropathy.

KEY POINTS

• Magnetic resonance neurography allows precise visualization of the thenar muscular branch of the median nerve. • Thenar muscular branch anatomical variations can be correctly identified. • Preoperative scanning can contribute to reducing the risk of iatrogenic injuries during carpal tunnel release, especially in carpal tunnel syndrome with thenar muscular branch involvement or even in isolated thenar muscular branch neuropathy.

Prevalence, variants, and morphometrics of Palmaris Longus tendon: a magnetic resonance imaging study

PURPOSE

The palmaris longus (PL) tendon present a high degree of variations; the commonest is its absence which could reach more than 40% in some populations. The PL tendon is highly relevant in hand reconstructive surgery; however, MRI variations of PL tendon have been exceptionally reported. To this, this study investigated PL tendon variations using MRI in a Lebanese population.

METHODS

This is a retrospective study of distal forearm MRI examinations to evaluate the presence, anatomical variations and morphometric of PL tendon. The outcomes were set as overall frequency, gender-based and side-base frequencies, correlations between prevalence and gender/side, morphological variants, thickness, and width of PL tendon.

RESULTS

The sample comprised 335 patients including a total of 339 MRI scans. The PL was present in 221 wrists (65.2%), and bilaterally in only one (25%) out of the 4 bilateral cases. All PL were located using the Axial T1 views. Univariate and multivariate analyses showed no correlation with side, gender, or Tesla power. The only morphological variation was a reversed PL in 2 cases (0.6%). The mean width was 4.24 ± 1.2 mm. The mean thickness was 2.75 ± 0.6 mm.

CONCLUSION

As far as we know, this is the first study to report the total array of variations of PL tendon using MRI, and its prevalence in a Lebanese population. The mean width of PL tendon calculated with high quality MR imaging was found to be similar to that reported by cadaveric studies.

Branches of ulnar artery in human fetuses: anatomical and morphometric study

PURPOSE

This study was conducted to demonstrate morphological pattern of the ulnar artery and to evaluate morphometrically its anatomical branching pattern in human fetuses.

METHODS

Branching pattern of ulnar artery was evaluated on 121 upper limbs of dissected 63 of formalin-fixed fetus cadavers with gestational age ranging from 17 to 40 weeks. In order to obtain second and third trimester data, according to their gestational age, two groups were determined.

RESULTS

In 79 of all 121 upper limbs (65%) ulnar artery gave anterior and posterior ulnar recurrent arteries as separate branches. In this study frequency of presence of a median artery was 46.28% among total examined 121 upper limbs. Median arteries originated from ulnar artery (3.57%) and from the common interosseous artery (53.57%) and anterior interosseous artery (42.85%). Mean distances of the measured parameters were demonstrated according to the gestational age and differences between group I (second trimester) and group II (third trimester). No statistical difference for groups was observed for gender and between right and left sides.

CONCLUSIONS

Ulnar artery shows predictable patterns during second and third trimester of fetal period and can be suitable access effective alternative for diagnostic and therapeutic coronary interventions. Persistent median artery is important variation and knowledge of its incidence is important for diagnostic difficulties and also during awareness of its injury during surgical approaches.

Carpal Tunnel Syndrome Associated with Bifid Median Nerve and Palmaris Profundus - Case Report and Literature Review

The anatomic variations of the median nerve and of the muscles of the wrist have been widely reported in literature. It is essential for the surgeon to be familiar with these variations in order to avoid accidental injury to the nerve during surgery. We report a rare case of bifid median nerve accompanied by an anomalous tendon of palmaris profundus discovered during the surgical release of carpal tunnel. The transverse carpal ligament was dissected and the anomalous tendon was left in situ because any direct compression over the median nerve was noticed intraoperatively. The patient was evaluated one year postoperatively clinically and radiologically (with MRI). At the follow up the resolution of symptoms was complete and the sleep disturbance was solved. The patient achieved a postoperative QuickDASH score of 9.1 and a Michigan Hand Questionnaire outcome score of 90 points.

Persistent Median Artery as an Unusual Finding in the Carpal Tunnel: Its Contribution to the Blood Supply of the Hand and Clinical Significance

BACKGROUND Knowledge of the variable relation of the persistent median artery (PMA) to the median nerve and its contribution to the formation of the superficial palmar arch is of great clinical significance. This study presents a proposal of specific variables which might be introduced to characterize the PMA in the wrist region. MATERIAL AND METHODS One hundred and twenty-five randomly selected, isolated upper limbs fixed in 10% formalin solution were subjected to anatomical dissection. RESULTS Of the 125 upper limbs, PMA was found in 5 specimens (4% of the total number of limbs). In the carpal tunnel, the artery occupied the anterolateral position (2 cases), the anterior position (2 cases) or the anteromedial position (1 case) in relation to the median nerve. Two types of superficial palmar arches with significant contributions from the PMA were observed in the studied material: complete medio-ulnar arch and an incomplete arch without a connection between the territories of the ulnar and median arteries. The mean ratio of the diameter of the PMA to the diameter of ulnar artery at the level of the wrist was 0.59 (min.=0.38, max=0.83, SD=0.19). CONCLUSIONS Orthopedic and hand surgeons should be aware of the probability of occurrence of the PMA in both planning and conducting surgeries within the wrist region and within the carpal tunnel, as this anomalous vessel might present significant contributions to the arterial blood supply of the hand and might potentially play an important role in the presence of notable clinical symptoms and presentations.

PALMARIS LONGUS ABSENT IN ONE IDENTICAL TWIN: A CASE REPORT

SUMMARY – Palmaris longus is a very variable muscle in the human body, but it is often used as an applicable tendon graft. We report on differences between one pair of identical twins regarding the existence of the palmaris longus, which were detected accidentally during examination of the presence/absence of this muscle in Caucasian population. In one of the twins, the palmaris longus was present at both forearms, while the other twin was lacking this muscle at both forearms. On search of the available literature, we found no articles about distinctions in the presence or absence of the palmaris longus in twins.

Bilateral Bifid Median Nerve with Bilateral Carpal Tunnel Syndrome: An Atypical Presentation, a Rare Cause and a Familiar Disease

We report a case of bilateral carpal tunnel syndrome (CTS) with bilateral bifid median nerve (BMN) without a persistent median artery diagnosed by clinical examination, NCV and Ultrasonography. Bilateral BMN to produce bilateral CTS is extremely rare and is contrary to the popular classifications which state that BMN without persistent median artery or its anomalies will not produce CTS. Ultrasonogram is of additional help to identify such aberrations in the median nerve to prevent iatrogenic injuries during carpal tunnel decompression.

Hypercholesterolemia Is Associated with the Subjective Evaluation of Postoperative Outcomes in Patients with Idiopathic Carpal Tunnel Syndrome Who Undergo Surgery: A Multivariate Analysis

BACKGROUND

Carpal tunnel syndrome is a compression neuropathy of the median nerve at the wrist; its symptoms include neuropathic pain and sensory and motor disturbance distributed by the median nerve. Carpal tunnel syndrome and hypercholesterolemia have similar backgrounds, but the effect of these similarities on postoperative outcomes has not been reported. Using multivariate analysis, the authors analyzed the relationship between prognostic factors, including the presence of hypercholesterolemia, and subjective postoperative outcomes of patients with idiopathic carpal tunnel syndrome.

METHODS

Of 168 hands with carpal tunnel syndrome that were treated surgically, 141 that were followed up and assessed 1 year postoperatively or thereafter were included. The mean postoperative follow-up period was 40.8 months. Surgery was performed through a small palmar skin incision under local anesthesia. The outcomes were postoperative symptoms, including pain and numbness, and overall Kelly assessment.

RESULTS

Preoperative numbness and pain resolved and alleviated in 94 of 141 hands and was diminished in 59 of 64 hands. Univariate analysis showed that postoperative numbness and Kelly assessment were significantly associated with hypercholesterolemia. Multivariate analysis showed that postoperative numbness was significantly associated with smoking and hypercholesterolemia, and Kelly assessment was significantly associated with smoking (adjusted OR, 3.3; 95 percent CI, 1.1 to 10; p = 0.04) and hypercholesterolemia (adjusted OR, 2.9; 95 percent CI, 1.4 to 6.3; p = 0.01).

CONCLUSION

Hypercholesterolemia, usually a systemic condition in sites other than the hand, is associated with the subjective evaluation of postoperative symptoms in patients with idiopathic carpal tunnel syndrome.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Normal Palmar Anatomy and Variations That Impact Median Nerve Decompression

Annually, carpal tunnel release is one of the most commonly executed orthopaedic procedures. Despite the frequency of the procedure, complications may occur as a result of anatomic variations. Understanding both normal and variant anatomy, including anomalies in neural, vascular, tendinous, and muscular structures about the carpal tunnel, is fundamental to achieving both safe and efficacious surgery. Reviewing and aggregating this information reveals certain principles that may lead to the safest possible surgical approach. Although it is likely that no true internervous plane or so-called safe zone exists during the approach for carpal tunnel release, the long-ring web space axis does appear to pose the lowest risk to important structures.

Ultrasound imaging of the thenar motor branch of the median nerve: a cadaveric study

INTRODUCTION

Anatomic variations of the median nerve (MN) increase the risk of iatrogenic injury during carpal tunnel release surgery. We investigated whether high-frequency ultrasonography could identify anatomic variations of the MN and its thenar motor branch (MBMN) in the carpal tunnel.

METHODS

For each volar wrist of healthy non-embalmed cadavers, the type of MN variant (Lanz classification), course and orientation of the MBMN, and presence of hypertrophic muscles were scored by 18-MHz ultrasound and then by dissection.

RESULT

MBMN was identified by ultrasound in all 30 wrists (15 subjects). By dissection, type 1, 2 and 3 variants were found in 84%, 3%, and 13% of wrists, respectively. Ultrasound had good agreement with dissection in identifying the variant type (kappa =0.9). With both techniques, extra-, sub-, and transligamentous courses were recorded in 65%, 31%, and 4% of cases, respectively. With both techniques, the bifid nerve, hypertrophic muscles, and bilateral symmetry for variant type were identified in 13.3%, 13.3%, and 86.7% of wrists, respectively. Agreement between ultrasound and dissection was excellent for the MBMN course and orientation (kappa =1).

CONCLUSION

Ultrasound can be used reliably to identify anatomic variations of the MN and MBMN. It could be a useful tool before carpal tunnel release surgery.

KEY POINTS

• Ultrasound can identify variations of the motor branch of the median nerve. • Ultrasound mapping should be used prior to carpal tunnel release surgery. • All sub-, extra-, and transligamentous courses were accurately identified. • Type 3 variants (bifid nerve), hypertrophic muscles, and bilateral symmetry were accurately identified.

Sonographic Findings of the Bifid Median Nerve and Persistent Median Artery in Carpal Tunnel: A Preliminary Study in Chinese Individuals

OBJECTIVE:

The aim of this study was to investigate the prevalence of anatomic variations of the bifid median nerve, persistent median artery and persistent median vein in Chinese individuals and their relationship with carpal tunnel syndrome.

METHODS:

One hundred and sixty median nerves were examined using ultrasonography and colour Doppler ultrasonography. The location, shape, and size of the bifid median nerve, persistent median artery and persistent median vein were recorded. The cross-sectional area of the bifid median nerve (two trunks) was measured at the level of the pisiform.

RESULTS:

Among the 160 wrists examined, a bifid median nerve was observed in 15 (9.4%) wrists, and a persistent median artery was observed in 12 (7.5%) wrists. These two variations either coexisted or were observed independently, and the probability of coexistence (6.3%) was higher than the probability of existing independently (bifid median nerve only 3.1%, persistent median artery only 1.3%). The cross-sectional area of the radial trunk was greater than (13 in 15, 86.7%) the cross-sectional area of the ulnaris trunk. Persistent median vein was observed in 9 wrists (5.6%).

CONCLUSIONS:

The persistent median artery and bifid median nerve tend to coexist, and the persistent median vein sometimes runs parallel to the persistent median artery. Their positional relationship in carpal tunnel is uncertain, and thus, preoperative ultrasound is necessary. These three variations do not present any additional risk for the development of carpal tunnel syndrome.

Sonographic Visualization of Thenar Motor Branch of the Median Nerve: A Cadaveric Validation Study

BACKGROUND

The thenar motor branch (TMB) of the median nerve may be affected in carpal tunnel syndrome and can be injured during carpal tunnel surgery. Although ultrasound has been used to identify small nerves throughout the body, the sonographic evaluation of the TMB has not been investigated formally.

OBJECTIVE

To document the ability of ultrasound to visualize the TMB of the median nerve in an unembalmed cadaveric model.

DESIGN

Prospective laboratory investigation.

SETTING

Procedural skills laboratory at a tertiary medical center.

METHODS

On the basis of anatomical descriptions, dissection and clinical experience, a technique was developed to sonographically identify the presumed TMB of the median nerve at the distal carpal tunnel. A single, experienced examiner then identified the presumed TMB in 10 unembalmed, cadaveric upper limb specimens (4 right, 6 left) obtained from 9 donors (4 male, 5 female) ages 76-85 years with body mass indices of 18.2-29.5 kg/m² with both 12-3 MHZ and 16-7 MHz linear array transducers. The same examiner then injected 0.2-0.3 mL of diluted colored latex into and around the presumed TMB using direct ultrasound guidance. At a minimum of 24 hours postinjection, specimens were dissected under loupe magnification to determine the location of the latex injectate.

MAIN OUTCOME MEASURE

The location of latex injectate relative to the anatomically identified TMB.

RESULTS

A vertical, linear, hypoechogenic region was sonographically identified arising from the median nerve at the distal carpal tunnel in all 10 specimens and was hypothesized to represent the vertical segment of the TMB. Both transducers allowed identification of the TMB, although localization was subjectively facilitated by the higher frequency transducer. All 10 sonographically guided injections placed latex into and around the TMB of the median nerve, confirming that ultrasound had accurately identified the TMB.

CONCLUSIONS

Sonographic evaluation of the TMB of the median nerve is technically feasible and should be considered when clinically indicated. Further research and clinical experience is necessary to define the role of sonographic TMB imaging in the evaluation and management of patients with carpal tunnel syndrome.

LEVEL OF EVIDENCE

IV.

The Prevalence of Anatomical Variations of the Median Nerve in the Carpal Tunnel: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVE

The course and branches of the median nerve (MN) in the wrist vary widely among the population. Due to significant differences in the reported prevalence of such variations, extensive knowledge on the anatomy of the MN is essential to avoid iatrogenic nerve injury. Our aim was to determine the prevalence rates of anatomical variations of the MN in the carpal tunnel and the most common course patterns and variations in its thenar motor branch (TMB).

STUDY DESIGN

A systematic search of all major databases was performed to identify articles that studied the prevalence of MN variations in the carpal tunnel and the TMB. No date or language restrictions were set. Extracted data was classified according to Lanz's classification system: variations in the course of the single TMB--extraligamentous, subligamentous, and transligamentous (type 1); accessory branches of the MN at the distal carpal tunnel (type 2); high division of the MN (type 3); and the MN and its accessory branches proximal to the carpal tunnel (type 4). Pooled prevalence rates were calculated using MetaXL 2.0.

RESULTS

Thirty-one studies (n = 3918 hands) were included in the meta-analysis. The pooled prevalence rates of the extraligamentous, subligamentous, and transligamentous courses were 75.2% (95%CI:55.4%-84.7%), 13.5% (95%CI:3.6%-25.7%), and 11.3% (95%CI:2.4%-23.0%), respectively. The prevalence of Lanz group 2, 3, and 4 were 4.6% (95%CI:1.6%-9.1%), 2.6% (95%CI:0.1%-2.8%), and 2.3% (95%CI:0.3%-5.6%), respectively. Ulnar side of branching of the TMB was found in 2.1% (95%CI:0.9%-3.6%) of hands. The prevalence of hypertrophic thenar muscles over the transverse carpal ligament was 18.2% (95%CI:6.8%-33.0%). A transligamentous course of the TMB was more commonly found in hands with hypertrophic thenar muscles (23.4%, 95%CI:5.0%-43.4%) compared to those without hypertrophic musculature (1.7%, 95%CI:0%-100%). In four studies (n = 423 hands), identical bilateral course of the TMB was found in 72.3% (95%CI:58.4%-84.4%) of patients.

CONCLUSIONS

Anatomical variations in the course of the TMB and the MN in the carpal tunnel are common in the population. Thus, we recommend an ulnar side approach to carpal tunnel release, with a careful layer by layer dissection, to avoid iatrogenic damage to the TMB.

Bifid median nerve in carpal tunnel syndrome: do we need to know?

INTRODUCTION

We tested the hypothesis that a bifid median nerve predisposes to development of carpal tunnel syndrome (CTS) and investigated differences in electrophysiological findings and outcome.

METHODS

A total of 259 consecutive patients with clinically defined CTS were included and investigated clinically, electrophysiologically, and ultrasonographically. Fifty-four healthy asymptomatic volunteers were investigated ultrasonographically.

RESULTS

The prevalence of bifid median nerves is equal in patients with CTS and controls. Electrophysiological and ultrasonographic abnormalities are more pronounced in patients with non-bifid median nerves. Some outcome data are better in patients with non-bifid median nerves, but others do not show significant differences.

CONCLUSIONS

A bifid median nerve is not an independent risk factor for development of CTS. Some of our data suggest outcome after surgical decompression to be different, but others do not. The surgical technique in these patients may therefore have to be reevaluated.

Cadaveric study of anatomical variations of the median nerve and persistent median artery at wrist

Background:

Awareness of anatomical variations of the median nerve at wrist is important in repair of traumatic injuries and treatments of compression syndrome because in these situations precise dissection of the nerve is mandatory and such variations are not infrequent.

Materials and Methods:

In this study, 52 hands of 52 fresh cadavers were dissected and median nerve anatomy along with the presence of persistent median artery (PMA) was noted.

Results:

A total of 26 hands (50%) had the deviation from the standard text book anatomy of the median nerve. There was early division of the median nerve into the medial and lateral branches in 11.53% hands. There was early branching of the 2^nd common digital nerve in 9.6% hands. The transligamentous motor branch to the thenar muscle was most prevalent (42.3% hands). The single motor branch to the thenar muscles was found in the majority of hands (84.6%). The PMA was present in 11.53% hands and it was associated with variations in the median nerve anatomy in all cases.

Conclusions:

This study shows a high percentage of deviation from standard anatomy as well as a high percentage of transligamentous thenar muscle motor branch. The presence of PMA was associated with variations in the median nerve anatomy in all cases. Therefore if PMA is present there are very high chances of associated median nerve anomalies.

Prevalence of bifid median nerves and persistent median arteries and their association with carpal tunnel syndrome in a sample of Latino poultry processors and other manual workers

INTRODUCTION

The prevalence of bifid median nerves and persistent median arteries, their co-occurrence, and their relationship to carpal tunnel syndrome (CTS) are only understood partially.

METHODS

We screened 1026 wrists of 513 Latino manual laborers in North Carolina for bifid median nerves and persistent median arteries using electrodiagnosis and ultrasound.

RESULTS

A total of 8.6% of wrists had a bifid median nerve, and 3.7% of wrists had a persistent median artery independent of subgroup ethnicity, age, gender, or type of work. An association with definite carpal tunnel syndrome was not found. The presence of either anatomic variant was associated with a high likelihood of co-occurrence of another variant in the same or the contralateral wrist.

CONCLUSIONS

The occurrence of median anatomic variants can be determined in field studies using ultrasound. Persistent median arteries and bifid median nerves tend to co-occur but do not put manual laborers at additional risk of developing CTS.

Clinical prevalence of palmaris longus agenesis: a systematic review and meta-analysis

We report a systematic review and a proportion meta-analysis of prevalence studies evaluating the prevalence of palmaris longus agenesis (PLA) in the literature. The overall PLA rate was defined to be the primary outcome. Secondary outcomes were rates of PLA in relation to ethnicity, laterality, side, gender, age, and hand dominance. We identified 26 articles which met the inclusion criteria. Meta-analyses showed an overall PLA pooled rate of 20.25%, higher than the commonly reported overall rate of 15%. Our results also showed significantly lower pooled rates in Africans (11.3%) and East Asians (4.5%) when compared to Arab Middle Eastern population (41.7%). A subgroup analysis of the African group showed a pooled rate of 2.71%, the lowest, in the East and South East African population. The pooled rate was 26.3% among Caucasians, 26.16% among South and Southeast Asians and 34.13% among Turkish. In discordance with the literature, PLA was statistically more predominant on the right side. No significant differences in PLA rates were found for laterality, gender, the combination of gender and side or the combination of gender and laterality. The lowest rate of PLA found in East and South East African populations might be indicative of the subsequent phylogenetic degeneration of the palmaris longus muscle in modern humans after the "Out of Africa" migration.

Different frequency of the absence of the palmaris longus according to assessment methods in a Korean population

The palmaris longus (PL) is a slender, spindle-shaped weak flexor of the wrist. Congenital absence of the PL is estimated to occur in 15% among individuals worldwide. However, the frequency of its absence varies considerably among different population groups and with different detection techniques. In the present study, the presence of the PL tendon was examined in a Korean population (n=269) using three clinical tests, namely the Traditional Test, Mishra's Test II, and the Gangata Test. We classified subjects into six types based on whether inspection or palpation was required to determine the presence of the PL and flexor carpi radialis. The most reliable test was determined using Kendall's coefficient of concordance. Our results showed that the PL tendon was absent in 4.1% of the subjects in our study, and bilateral and unilateral absences were 2.2% and 1.8%, respectively. Statistical analysis revealed that these tests had similar reliability for assessing the PL tendon, and the Traditional Test showed the highest effectiveness, at 93%. Therefore the Traditional Test was found to be the most effective for revealing the PL in this Korean population.

A cadaveric study of needle insertion at PC6 in eight wrists of four subjects and an understanding of the anatomy

The anatomical structures vulnerable to acupuncture around the PC6 acupuncture point were investigated. Needles were inserted in PC6 of eight wrists from four cadavers to a depth of 2 cm, the forearms were dissected and the adjacent structures around the path of the needles were observed. The needles passed between the tendons of the palmaris longus and flexor carpi radialis muscles and then penetrated the flexor digitorum superficialis, flexor digitorum profundus and pronator quadratus muscles. The inserted needles were located adjacent to the median nerve. To minimise the risk of unintended injury by acupuncture, it is recommended that needles should not be inserted deeply at the PC6 acupuncture point. An understanding of the anatomical variations of the median nerve and the persistent median artery in the forearm is of clinical importance when performing acupuncture procedures.

Thenar motor neuropathy electrophysiological study of 28 cases

PURPOSE

To report an electrophysiological study on thenar motor neuropathy of the median nerve.

METHODS

Twenty-eight consecutive patients (mean age, 48.8 years; 17 men) with dominant hand thenar muscle weakness without sensory symptoms were enrolled in this study. Electromyography of hand and forearm muscles and neurography of median, ulnar, radial, and palmar nerves, including distal motor latency recording from the second interosseous-lumbrical muscles, were performed.

RESULTS

Complete denervation of the abductor pollicis brevis muscle was observed in one case and delayed median abductor pollicis brevis-distal motor latency was observed in the others. Other neurographic findings were normal.

CONCLUSIONS

Thenar motor neuropathy may have different pathogeneses. It may be considered a variant of carpal tunnel syndrome involving the motor branch only or more likely due to chronic direct compression of the branch, because it preferentially affects males, dominant hand, and persons doing manual work. In both cases, anatomic origin and variations in the course of the branch may favor thenar motor neuropathy.

Prevalence of the palmaris longus in relation to the hand dominance

PURPOSE

The incidence of left-handedness in the general population is between 8 and 15%. There is a presumption that the prevalence of palmaris longus muscle differ between right-handed and left-handed people. This prospective study was conducted to determine the prevalence of the palmaris longus in relation to the hand dominance.

METHODS

The study included 542 subjects (216 male and 326 female). They were initially tested to hand dominance and after that they were asked to do the standard test (Schaeffer's test) for the assessment of the palmaris longus tendon. If the tendon was not visualized or palpable, four additional tests (Thompson's test, Mishra's tests I and II, Pushpakumar's "two-finger sign" method) were done to confirm its absence.

RESULTS

Right hand dominance was recorded in 452 (83.4%) subjects while the left hand dominance was recorded in 90 (16.6%) subjects. In right-handed subjects, palmaris longus tendon was absent on the right side in 24 (5.3%) and on the left side in 50 (11.1%) cases. In left-handed subjects, it was absent on the right side in 18 (20%) and on the left side in 2 (2.2%) cases. These differences were statistically significant. Bilateral absence of palmaris longus tendon was similar in both examined groups (25.1% in the overall series, 24.3% in right-handed subjects, 28.9% in left-handed subjects).

CONCLUSIONS

The results of our study show that a right-sided absence was more common in left-handed persons while the left-sided absence was more common in right-handed persons. Unilateral tendon absence was more common on the non-dominant hand.

Prevalence of the palmaris longus through clinical evaluation

PURPOSE

Most standard textbooks of hand surgery report on the rate of palmaris longus muscle absence of 15%. The aim of the study was to determine the absence of palmaris longus and to correlate it with age, sex and body side.

METHODS

The study included 800 subjects (400 male and 400 female). They were initially asked to do the standard test for the assessment of the palmaris longus tendon. If the tendon was not visualized or palpable, four additional tests were done to confirm its absence.

RESULTS

Unilateral absence of the palmaris longus was recorded in 173 (21.6%) and bilateral in 127 (15.9%) study subjects. According to body side, right-sided absence of palmaris longus was found in 69 (8.6%) and left-sided in 104 (13%) subjects, yielding a statistically significant difference. Bilateral absence was slightly more common in men. The prevalence of palmaris longus absence on the right and left side was similar in men, whereas in women it was significantly more common on the left side. Differences between the three age groups (young, middle-aged and old) were not significant; however, the middle-aged and young groups showed a lower rate of palmaris longus presence as compared to old-age group.

CONCLUSIONS

It has been suggested that this tendon is rapidly disappearing in humans. The results of our study show a relatively high incidence of tendon absence and pointed to more pronounced loss of the muscle on the left side.

The bifid median nerve re-visited

This report presents a venous malformation arising from the persistent median vessels associated with a bifid median nerve. The literature on bifid median nerve is reviewed and a classification of its associated abnormalities is offered.

Carpal tunnel syndrome: electrophysiological grading and surgical results by minimum incision open carpal tunnel release

The safety and effectiveness of the minimum incision technique were assessed in 138 hands of 108 consecutive patients with carpal tunnel syndrome treated from April 1, 1997 to March 31, 2006. Clinical and electrophysiological examinations were conducted before and after surgical decompression. All hands were divided into early, mild, moderate, and severe groups based on preoperative electrophysiological severity. We examined the surgical outcomes of the affected hands in each group. Nocturnal or daytime dysesthesia, which had been present in 132 (96%) of the 138 hands preoperatively, was completely relieved in 124 (94%) of the 132 hands. Complete relief was achieved in 7 (100%) of the 7 hands in the early group, 68 (99%) of the 69 hands in the mild group, and 45 (94%) of the 48 hands in the moderate group. Complete relief was achieved only in 4 (50%) of the 8 hands in the severe group, and 3 (38%) of the 8 hands did not show any improvement. No painful or hypertrophic scar formation was observed in this series. Only 2 patients complained of postoperative scar discomfort after more than 12 months, which completely disappeared by 14 months after surgery. Minimum incision open carpal tunnel release is a safe and reliable procedure with a high rate of functional improvement and patient satisfaction. Postoperative results were satisfactory regardless of the degree of preoperative electrophysiological severity if preoperative sensory nerve action potentials were detected.

Bifid median nerve in patients with carpal tunnel syndrome

OBJECTIVE

The aim of this study was to investigate the frequency of the anatomic variation of a bifid median nerve in patients with carpal tunnel syndrome (CTS) and to determine the size criteria for sonography.

METHODS

On axial sonograms of 320 hands of 170 patients with CTS and 240 hands of 120 unaffected individuals, the median nerve was evaluated morphologically for a bifid median nerve, and the cross-sectional area was measured at 3 levels (radial-ulnar junction, pisiform, and hook of the hamate). Electrophysiologic studies were performed in addition to clinical and sonographic evaluations in all patients, controls with a bifid median nerve, and controls with a cross-sectional area of greater than 0.09 cm(2).

RESULTS

A bifid median nerve was seen in 32 (19%) of 170 patients and 11 (9%) of 120 controls. It occurred relatively frequently in patients with CTS (P < .01). The cross-sectional area of the bifid median nerve was relatively higher than that of the nonbifid median nerve in controls at 2 of the 3 levels (P < .001; P = .226; P < .01). The cutoff values for the cross-sectional area at the level of the pisiform were 0.11 cm(2) (sensitivity, 90%; specificity, 99%; P < .001) for patients with a bifid median nerve and 0.10 cm(2) (sensitivity, 98%; specificity, 81%; P < .001) for patients with a nonbifid median nerve.

CONCLUSIONS

A bifid median nerve occurs relatively frequently in patients with CTS. It may facilitate compression of the median nerve in the carpal tunnel because of its relatively higher cross-sectional area compared with a nonbifid median nerve. The size criterion for CTS in patients with a bifid median nerve is slightly higher than in those with a nonbifid median nerve.

The thenar motor branch during carpal tunnel decompression: "the expert opinion"

INTRODUCTION

Iatrogenic injury to the thenar motor branch (TMB) of the median nerve is a rare but serious complication of carpal tunnel decompression (CTD). Variability in the anatomical course of the branch is well documented in the literature. We aimed to explore and document "expert experience and attitude" to the TMB during CTD.

MATERIALS AND METHODS

All members of the British Society for Surgery of the Hand (220) were sent a short postal questionnaire, in which 153 questionnaires (70%) were returned.

RESULTS

The open technique was routinely used by 97% of the surgeons, 70% replied that either very rarely or never formally explored the TMB during CTD and 71% of surgeons saw the TMB lying superficially in less than 5% of cases. Among surgeons, 49 had never encountered an iatrogenic injury while only 14 had seen more than 5 cases in their careers. Finally, 71% of surgeons agreed that formal exploration of the nerve is not necessary during uncomplicated cases.

DISCUSSION

The "consensus" view suggests that formal demonstration of the thenar branch of the median nerve during CTD is unnecessary. The incidence of iatrogenic injuries seen was low. A number of useful strategies to avoid iatrogenic injuries are suggested.

Anomalous median nerve position dorsal to the flexor tendons in a patient with spastic hemiplegia and wrist pain: case report

We report an anomalous dorsally positioned median nerve within the carpal tunnel in a 25-year-old spastic hemiplegic man associated with chronic wrist pain.

Treatment of carpal tunnel syndrome by low-level laser versus open carpal tunnel release

Carpal tunnel syndrome (CTS) is an entrapment neuropathy of the median nerve at the wrist. It is one of the most common peripheral nerve disorders. The cause of idiopathic CTS remains unclear. The diagnosis of CTS is still mainly clinical. Open carpal tunnel release is the standard treatment. The present study was conducted to evaluate the effectiveness of low level laser treatment (LLLT) for CTS in comparison to the standard open carpal tunnel release surgery. Out of 54 patients, 60 symptomatic hands complaining of CTS were divided into two equal groups. Group A, was subjected to LLLT by Helium Neon (He-Ne) laser (632.8 nm), whereas group B was treated by the open approach for carpal tunnel release. The patients were evaluated clinically and by nerve conduction studies (NCSs) about 6 months after the treatment. LLLT showed overall significant results but at a lower level in relation to surgery. LLLT showed significant outcomes in all parameters of subjective complaints (p < or = 0.01) except for muscle weakness. Moreover, LLLT showed significant results in all parameters of objective findings (p < or = 0.01) except for thenar atrophy. However, NCSs expressed the same statistical significance (p < or = 0.01) after the treatment by both modalities. LLLT has proven to be an effective and noninvasive treatment modality for CTS especially for early and mild-to-moderate cases when pain is the main presenting symptom. However, surgery could be preserved for advanced and chronic cases. Refinement of laser tools and introduction of other wavelengths could make LLLT for CTS treatment a field for further investigations.

Carpal tunnel syndrome

PURPOSE OF REVIEW

Carpal tunnel syndrome, though generally successfully treated by surgical decompression, still results in significant morbidity. The causes remain unclear and there is uncertainty about appropriate investigations for diagnosis and assessment of severity. The best nonsurgical treatment is yet to be fully elucidated. Recent work has begun to cast some light on these uncertainties.

RECENT FINDINGS

The pathology of idiopathic carpal tunnel syndrome is a noninflammatory fibrosis of the subsynovial connective tissue surrounding the flexor tendons. Biochemical studies of surgical specimens suggest that a variety of regulatory molecules may be inducing fibrous and vascular proliferation and that this may be a response to mechanical stresses. Ultrasound imaging has begun to demonstrate its ability to accurately image the carpal canal contents and the diagnostic value of measurements of median nerve cross-sectional area showing expansion of the nerve is becoming established. The sensitivity and specificity of such measurements may be comparable to those of nerve conduction studies, though their prognostic value remains unknown. Nonsurgical treatment with steroid injection may be a more effective treatment than previously recognized, and is under used.

SUMMARY

Suspected carpal tunnel syndrome should be investigated first with nerve conduction studies but consideration should be given to the use of magnetic resonance imaging or ultrasound imaging when diagnostic uncertainty remains, or there is a suspicion of a space occupying lesion in the carpal canal, especially if endoscopic surgery is contemplated. Treatment by local steroid injection should be considered a valid alternative treatment, at least for milder cases.

Topographic localization of the motor branch of the median nerve

PURPOSE

To redefine the localization of the thenar branch (TB) of the median nerve in relation to the surface landmarks that are in routine use.

METHODS

The study was performed in 37 hands of 34 patients who had carpal tunnel release. All of the patients were women and the mean age was 50 years (range, 35-67 y). A radiologic marking technique was used to determine the localization of the TB, the middle finger radial side line, and Kaplan's cardinal line. The TB was marked by circumscribing with a soft radiopaque yarn and the surface landmark lines were shown by taping a K-wire to the hand for each line. An image-intensifier-printed image was obtained for each case and the distances between the markers of the TB and the wires were measured.

RESULTS

The TB had a mean ulnar offset of 12.6 mm (range, 4.0-19.7 mm) from the middle finger radial side line and was located 4.4 mm (range, 0-9.5 mm) proximal to the cardinal line.

CONCLUSIONS

During carpal tunnel release surgery the surgeon must pay more attention to the localization of the TB of the median nerve because it was found to be 12.6 mm more ulnar than the location described in the literature.

Ramification pattern of the thenar branch of the median nerve entering the thenar fascia and the distribution of the terminal branches in the thenar musculature: Anatomic cadaver study in 144 hands

Knowledge of the anatomy of the median nerve is important in surgery of the palmar aspect of the hand. The purpose of our study was to investigate the ramification pattern of the thenar branch before entering the thenar fascia and the distribution of the terminal branches in the thenar musculature. The observations were carried out on 144 hands of 74 dissecting room cadavers. According to the number of the thenar branches entering the thenar fascia we classified our specimens into four types. In 121 hands (84%, Group I) the thenar branch piercing the thenar fascia was a single trunk. In 19 hands (13.2%, Group II) two branches; in three (2.1%; Group III), three branches; and in one hand (0.7%; Group IV), four branches were identified entering the thenar fascia. Accessory thenar nerve was found in 8.3% of hands. The further division of each branch to its terminal branches was investigated in detail. Our results show that the more the number of thenar branches entering the thenar fascia, the less the terminal branching. Because more than one branch was seen in 16% of the specimens, meticulous dissection is required for preventing injury of the thenar branches before entering the thenar fascia.

Clinical surveillance of carpal tunnel syndrome in two areas of the United Kingdom, 1991-2001

OBJECTIVE

To study the demographic characteristics of patients with carpal tunnel syndrome and changes in incidence over time.

METHODS

Prospective collection of neurophysiological and clinical data on all patients presenting to the subregional department of clinical neurophysiology in Canterbury, UK, from 1992 to 2001 and to the electromyography clinic in St Luke's Hospital, Huddersfield, UK, from 1991 to 1993.

RESULTS

6245 new cases of neurophysiologically confirmed carpal tunnel syndrome were identified in Canterbury and 590 in Huddersfield. The average annual incidences (per 100,000) were 139.4 for women and 67.2 for men in East Kent, and 83.2 for women and 48.0 for men in Huddersfield. Corrected to the WHO European standard population these rates were 120.5 for women and 60.0 for men in East Kent, and 61.5 for women and 35.0 for men in Huddersfield. Between 1992 and 2001 there was an increase in the number of confirmed cases in East Kent but a decrease in their average severity. The age distributions were bimodal with a peak in the 50-54 age group and a second peak between 75 and 84 years. Over half the cases were bilateral. The disorder was consistently worse in the elderly, and more severe in men than in women in all age groups.

CONCLUSIONS

The age distributions of unselected cases of carpal tunnel syndrome in both clinics differ markedly from that usually portrayed in surgical series. There was a significant increase in cases diagnosed between 1992 and 2001 in Canterbury, probably the result of increased ascertainment of milder cases. Median nerve impairment is more severe in the elderly and in men at all ages.

Surface landmarks to locate the thenar branch of the median nerve: an anatomical study

The thenar branch of the median nerve can be injured during carpal tunnel release. The purpose of this study was to identify surface landmarks to consistently predict the location of the thenar branch of the median nerve. Surface landmarks were marked and incised in 28 cadaveric hands. The incisions were made along the longitudinal line of the third web space and the horizontal cardinal line from the hamate hook to the ulnar border of the thumb. The origin of the thenar branch was determined in relation to these longitudinal and horizontal vectors. The origin of the thenar nerve branch was consistently observed in the radial proximal quadrant formed by the aforementioned longitudinal and horizontal vectors. The thenar branch origin was observed to be an average of 8.6 +/- 1.9 mm radial to the longitudinal axis along the third web space. The origin of the thenar branch was observed to be an average of 6.3 +/- 2.0 mm proximal to the horizontal axis between the hamate hook and the ulnar border of the thumb. The thenar branch was observed precisely at the intersection of the longitudinal vector from the second web space to the scaphoid tubercle and the horizontal vector from the hamate hook to the radial edge of the proximal metacarpophalangeal crease in all 28 cadaveric hands. On the basis of these 28 cadaveric dissections, the location of the thenar branch of the median nerve can be predicted by the intersection of the longitudinal vector from the second web space to the scaphoid tubercle and the horizontal vector from the hamate hook to the radial aspect of the metacarpophalangeal crease.

Surgical release of the carpal tunnel

A thorough understanding of the normal anatomy and possible anomalies that may exist is important for the surgeon managing median nerve compression at the wrist. Given the high incidence of anatomic variability occurring in and around the carpal canal, open decompression of the median nerve is the preferred surgical technique for treating carpal tunnel syndrome. This approach provides complete visualization of the region, enabling the surgeon to decompress the nerve thoroughly, identify and treat anatomic abnormalities, and protect important neurovascular structures. Open carpal tunnel release is a safe and reliable operation with a high rate of functional improvement and patient satisfaction.

The outcome of the nonoperated contralateral hand in carpal tunnel syndrome

It is not well known how the nonoperated contralateral hand behaves in bilateral carpal tunnel syndrome (CTS). The postoperative clinical course of the nonoperated contralateral hand in unilateral CTS is not well documented either. Of 324 CTS patients, the authors studied 37 who had carpal tunnel release on one hand only to evaluate the postoperative outcome of the nonoperated contralateral hand. The other 287 patients had operations on both hands. Seven patients were excluded because of missing data or because they could not be contacted. All 324 patients were subject to clinical and electrodiagnostic studies on both hands. The patients were divided into three groups. Group I was composed of patients who had bilateral CTS, diagnosed clinically and electrophysiologically, but who had surgery done only on the hand with the most pronounced symptoms. The patients in group II showed symptoms of CTS in one hand only. However, the opposite hand was diagnosed with subclinical CTS: Electrodiagnostic studies showed involvement of the median nerve, but without symptoms. Group III was composed of true unilateral CTS patients, diagnosed by symptoms and electrodiagnostic study. The results of the electrodiagnosis were categorized according to the severity of median nerve damage (mild, moderate, severe). The outcome and postoperative clinical course of the nonoperated contralateral hand were evaluated by electromyography and telephone survey. This method of survey was used because of the vast spread of patients throughout the country. Within 1 year, all 30 operated hands showed significant improvement, 20 of which belonged to group I. Regarding progress of the nonoperated contralateral hand, 10 patients showed improvement of one grade whereas 5 patients showed three grades of improvement. In another 5 patients there was no change whatsoever. In addition, from groups II and III there were 5 patients who showed no change in the nonoperated hand. The postoperative electromyographic findings of the nonoperated contralateral hand was not commensurate with the symptoms. However, regardless of electromyographic results, the nonoperated contralateral hand showed significant improvement (p < 0.0001). Patients with unilateral CTS did not experience any symptom development in the nonoperated contralateral hand.