Bifid median nerve in patients with carpal tunnel syndrome

Sonographic Measurement of Median Nerve Cross-Sectional Area to Determine Severity of Carpal Tunnel Syndrome: A Cautionary Tale

OBJECTIVES

Evaluate the diagnostic accuracy of median nerve cross-sectional area (CSA) to determine the severity of carpal tunnel syndrome (CTS) vs the presence of CTS across existing electrodiagnostic-based (EDX) classification systems.

METHODS

Retrospective analysis of cross-sectional patient data. Receiver operating characteristic (ROC) analysis was used to determine CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS severity. Identification of CSA cutoff values associated with likelihood ratios capable of achieving conclusive (but at least moderate) shifts in diagnostic probability.

RESULTS

Binary categorizations of CTS (ie, "Normal" vs "Absent") were statistically superior to consolidated categorizations of CTS severity (ie, "Normal," "Mild," "Moderate," or "Severe"). Binary categorizations established consistent CSA cutoff values across all EDX-based classifications examined and achieved conclusive shifts in diagnostic probability based on the following values of distal CSA or delta CSA: <7 or <1 mm2 to rule out and >13 or >7 mm2 to rule in CTS, respectively. Additionally, the following values of distal CSA and delta CSA may be used in certain circumstances because they produce only small shifts in diagnostic probability: ≤10 or ≤3 mm2 to rule out and ≥11 or ≥4 mm2 to rule in CTS, respectively.

CONCLUSIONS

Using median nerve CSA to categorize the severity of CTS is not recommended based on lack of consistent and meaningful shifts in diagnostic probability. Rather, binary categorizations to rule out or rule in CTS based on the proposed CSA cutoff values consistently provided conclusive shifts in diagnostic probability across all EDX-based classifications examined.

Median Nerve Cross-Sectional Area and Carpal Tunnel Syndrome in Specific Populations: Sonographic Analysis of Patients With Type 2 Diabetes or Bifid Anatomy

OBJECTIVES

Evaluate diagnostic accuracy of median nerve cross-sectional area (CSA) to determine severity versus presence of carpal tunnel syndrome (CTS) across existing electrodiagnostic-based (EDX) classification systems in patients with type 2 diabetes or bifid anatomy.

METHODS

Retrospective analysis of cross-sectional patient data. Receiver operating characteristic analysis used to determine median nerve CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS in patients with type 2 diabetes or bifid anatomy. Determine shifts in diagnostic probability based on established cutoff values and associated likelihood ratios. Distal CSA measured at or near carpal tunnel inlet, proximal CSA at level of pronator quadratus muscle, and delta CSA by subtracting proximal from distal.

RESULTS

Binary categorizations of CTS were statistically superior to consolidated categorizations of CTS severity in patients with type 2 diabetes or bifid anatomy. Binary categorizations established reasonably consistent median nerve CSA cutoff values across all EDX-based classifications examined resulting in the following for distal CSA or delta CSA: ≤10 or ≤4 mm2 to rule out and ≥11 or ≥5 mm2 to rule in CTS, respectively. These cutoff values resulted in small shifts in diagnostic probability in patients with type 2 diabetes and small to conclusive shifts in diagnostic probability in patients with bifid anatomy.

CONCLUSIONS

Binary categorizations to rule out or rule in CTS based on the proposed cutoff values provide the most meaningful information about shifts in diagnostic probability across all EDX-based classifications examined. The use of median nerve CSA to categorize severity of CTS is not recommended in patients with type 2 diabetes or bifid anatomy.

An Anatomical Variant of Bilateral Persistent Median Artery and Bifid Median Nerve: A Cadaveric Case Report

An 89-year-old Caucasian male cadaver with prostate cancer demonstrated bilateral persistence of the median artery and bifid median nerve (BMN) during upper limb dissection. The persistent median artery (PMA) originated from the common interosseous artery and coursed alongside the median nerve. Proximal to the carpal tunnel, the median nerve bifurcated into medial and lateral branches. To our knowledge, this is the first documented case of a bilateral PMA and BMN. While the majority of existing literature focuses on a unilateral PMA or unilateral BMN, bilateral occurrences of either variation are rare. This report presents a novel finding by documenting the simultaneous presence of a bilateral PMA and BMN.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Role of high-resolution ultrasound and magnetic resonance neurography in the evaluation of peripheral nerves in the upper extremity

Upper extremity entrapment neuropathies are common conditions in which peripheral nerves are prone to injury at specific anatomical locations, particularly superficial regions or within fibro-osseous tunnels, resulting in pain and potential disability. Although neuropathy is primarily diagnosed clinically by physical examination and electrophysiology, imaging evaluation with ultrasound and magnetic resonance neurography are valuable complementary non-invasive and accurate tools for evaluation and can help define the site and cause of nerve dysfunction which ultimately leads to precise and timely treatment. Ultrasound, which has higher spatial resolution, can quickly and comfortably characterize the peripheral nerves in real time and can evaluate for denervation related muscle atrophy. Magnetic resonance imaging on the other hand provides excellent contrast resolution between the nerves and adjacent tissues, also between pathologic and normal segments of peripheral nerves. It can also assess the degree of muscle denervation and atrophy. As a prerequisite for nerve imaging, radiologists and sonographers should have a thorough knowledge of anatomy of the peripheral nerves and their superficial and deep branches, including variant anatomy, and the motor and sensory territories innervated by each nerve. The purpose of this illustrative article is to review the common neuropathy and nerve entrapment syndromes in the upper extremities focusing on ultrasound and magnetic resonance neurography imaging.

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.

Prevalência de variações anatômicas encontradas em pacientes com síndrome do túnel do carpo submetidos a liberação cirúrgica por via aberta clássica

Objective  To evaluate the prevalence of anatomical variations encountered in patients with carpal tunnel syndrome who underwent carpal tunnel classical open release.

Methods  A total of 115 patients with a high probability of clinical diagnosis for carpal tunnel syndrome and indication for surgical treatment were included. These patients underwent electroneuromyography and ultrasound for diagnostic confirmation. They underwent surgical treatment by carpal tunnel classical open release, in which a complete inventory of the surgical wound was performed in the search and visualization of anatomical variations intra- and extra-carpal tunnel.

Results  The total prevalence of anatomical variations intra- and extra-carpal tunnel found in this study was 63.5% (95% confidence interval [CI]: 54.5–72.4). The prevalence of the carpal transverse muscle was 57.4% (95% CI: 47.8–66.6%), of the bifid median nerve associated with the persistent median artery was 1.7% (95% CI: 0.0–4.2%), and the median bifid nerve associated with the persistent median artery and the transverse carpal muscle was 1.7% (95% CI: 0.0–4.2%).

Conclusion  The most prevalent extra-carpal tunnel anatomical variation was carpal transverse muscle. The most prevalent intra-carpal tunnel anatomical variation was median bifid nerve associated with the persistent median artery. The surgical finding of an extra-carpal tunnel anatomical variation, such as the transverse carpal muscle, may indicate the presence of other associated carpal intra tunnel anatomical variations, such as the bifid median nerve, persistent median artery, and anatomical variations of the recurrent median nerve branch.

Nerve Imaging in the Wrist

Neuropathic symptoms involving the wrist are a common clinical presentation that can be due to a variety of causes. Imaging plays a key role in differentiating distal nerve lesions in the wrist from more proximal nerve abnormalities such as a cervical radiculopathy or brachial plexopathy. Imaging complements electrodiagnostic testing by helping define the specific lesion site and by providing anatomical information to guide surgical planning. This article reviews nerve anatomy, normal and abnormal findings on ultrasonography and magnetic resonance imaging, and common and uncommon causes of neuropathy.

Bifid median nerve as an anatomical risk factor for carpal tunnel syndrome: A meta-analysis

As the median nerve enters the carpal tunnel, it is a single nerve that soon bifurcates into lateral and medial branches into the hand. If the bifurcation is proximal to the carpel tunnel, a bifid median nerve results. Carpal tunnel syndrome is often associated with a bifid median nerve with or without a persistent median artery. Individual keywords and MeSH phrases were searched in the Google Scholar, SCOPUS, and PubMed databases. Full texts were then collected and assessed for suitability. The prevalence of bifid median nerve at the wrist joint in normal and carpal tunnel syndrome wrists (pre-canal part) and the mean difference between groups were recorded. Only human data were used to test the findings. The pooled odds ratio (with minimal heterogeneity) was 1.50 [1.17-1.93, 95% CI]. The bifid median nerve cross-sectional area (CSA) was significantly greater than that of a solitary median nerve in normal wrists. The mean difference in CSA between the two was 1.50 mm² [0.56-2.45 mm² , 95% CI] without heterogeneity (i²  = 0). Sex and laterality distributions scarcely differed between the two types of wrists. Owing to the insufficiency of data, the relationships with mean height and weight were not examined. There was a 50% greater incidence of bifid median nerves in carpal tunnel syndrome patients than in normal subjects. A bifid median nerve increases the mean CSA at the wrist joint by 1.5 mm² . These findings indicate that the bifid median nerve is an anatomical risk factor for carpal tunnel syndrome. This article is protected by copyright. All rights reserved.

Diagnostic Value of Ultrasound for Detecting Carpal Tunnel Syndrome in Patients With Rheumatoid Arthritis: A Three-Arm Cross-Sectional Study

Objective:

This study was conducted to assess the diagnostic value of sonography in detecting carpal tunnel syndrome (CTS) in patients with rheumatoid arthritis (RA) and to compare the results with a normal control group.

Materials and Methods:

In this three-arm cross-sectional study, the sonographically measured median nerve cross-sectional area (MNCSA) was compared in three groups: RA patients with CTS, RA patients without CTS, and normal subjects (no RA, no CTS). A nerve conduction study (NCS) was performed for all enrolled participants, across the three study arms.

Results:

In this study, 38 RA patients (17 in CTS group and 21 in no CTS group) and 19 healthy subjects were recruited. The MNCSAs were 11.86 (±1.87) mm2 in RA patients with CTS, 10.16 (±1.71) mm2 in RA patients without CTS, and 9.42 (±1.46) mm² in healthy control patients. The accuracy of sonography in detecting CTS was 0.79 (95% confidence interval, 0.67–0.91), with a sensitivity and specificity of 88% and 57%, respectively. The MNCSA in CTS group was significantly higher than the control group ( P = .02).

Conclusion:

In this cohort, the sonographic measurement of MNCSA was an accurate and sensitive method for the diagnosis of CTS, especially in its early stages. In addition, in this cohort, RA without CTS did not increase the MNCSA.

Sonographic Diagnosis of Carpal Tunnel Syndrome

Diagnostic ultrasound in the diagnosis of carpal tunnel syndrome is firmly established. Preoperative evaluation is based on quantitative parameters such as measurement of the pathologically enlarged cross-sectional area of the nerve. The value of postoperative ultrasound lies in the visualization of the anatomy and the conclusions that can be drawn from it. It focuses on the semiquantitative sonographic parameters of nerve compression. Nerve lesions and persistent strictures can be visualized and clearly localized. In recurrent disease, the primary focus is to dynamically exclude postoperative scarring, which results in a reduction of nerve gliding.

Variations ignored in routine wrist MRI reports: prevalence of the median nerve anatomical variations and persistent median artery

BACKGROUND

It is vital to know the anatomical variations of the wrist to avoid iatrogenic injuries during carpal tunnel (CT) surgery.

PURPOSE

To determine the anatomical variations of the median nerve (MN) and the prevalence of persistent median artery (PMA) on wrist magnetic resonance imaging (MRI).

MATERIAL AND METHODS

A total of 300 wrists evaluated by MRI during 2013-2015 were retrospectively identified. While branching of the MN distal to the CT is accepted as the normal anatomy, proximal to the tunnel and within the tunnel were considered as variations. The prevalence of PMA was also evaluated. The patients were assigned to groups according to age, gender, and wrist side and compared to determine whether there was any significant difference in terms of these variations. All evaluations were assessed with the shared decision of a musculoskeletal radiologist and a radiology resident.

RESULTS

Of the 300 wrists, 38 (12.7%) and 34 (11.3%) had a bifid MN proximal to the CT and within the CT, respectively. Only one nerve trifurcation was seen within the CT. The MN exhibited branching distal to the CT in 227 (76%) patients. PMA was observed in 44 (14.7%) patients. Of the 44 PMA cases, 28 (63.6%) also had a coexisting MN variation. There was no significant difference in the prevalence of MN variations and PMA in the subgroups (P > 0.05).

CONCLUSION

Nearly one in four patients (24.4%) have MN variations and 14.8% had PMA. Preoperative evaluation of these common anatomical variations with MRI will be protective against postoperative complications of CT surgery.

Review Article "Spotlight on Ultrasonography in the Diagnosis of Peripheral Nerve Disease: The Evidence to Date"

Neuromuscular ultrasound is rapidly becoming incorporated into clinical practice as a standard tool in the assessment of peripheral nerve diseases. Ultrasound complements clinical phenotyping and electrodiagnostic evaluation, providing critical structural anatomical information to enhance diagnosis and identify structural pathology. This review article examines the evidence supporting neuromuscular ultrasound in the diagnosis of compressive mononeuropathies, traumatic nerve injury, generalised peripheral neuropathy and motor neuron disease. Extending the sonographic evaluation of nerves beyond simple morphological measurements has the potential to improve diagnostics in peripheral neuropathy, as well as advancing the understanding of pathological mechanisms, which in turn will promote precise therapies and improve therapeutic outcomes.

Hand surgeons and amyloidosis specialists warning: transthyretin-associated amyloidosis with bifid median nerve as a cause of bilateral carpal tunnel syndrome. A case report and literature review

INTRODUCTION

Approximately 75% of patients with carpal tunnel syndrome (CTS) are diagnosed as idiopathic. Despite this, the presence of an underlying cause such as an anatomical variant or a systemic disease must always be suspected, especially in cases of bilateral presentation without an obvious cause, recurrence or complications. The anatomical variant known as the bifid median nerve (BMN) is a very rare abnormality that can occasionally lead to CTS. On the other hands, transthyretin-associated amyloidosis (ATTR) is one of the possible causes of bilateral CTS. We report a case where these two very rare pathologies converge as the cause of bilateral CTS and a review of the literature.

CASE REPORT

We report a 71-year-old male with prior history of lumbar canal stenosis, bilateral trigger finger, rupture of the supraspinatus muscle tendon and of the long portion of the right biceps brachial. He also had 8-year-old bilateral CTS that recurred after CTS surgery. He was surgically re-intervened and was diagnosed incidentally with BMN and an ultrasound of the other hands also showed BMN. Because of all the prior musculoskeletal history, a biopsy of the transverse carpal ligament was taken showing ATTR deposits that led to the diagnosis of cardiac ATTR wild type.

CONCLUSIONS

This case highlights the natural history of the multiple musculoskeletal manifestations related to ATTR and the importance of performing intraoperative biopsies in patients with CTS surgery as this can lead to early diagnosis of cardiac ATTR.

Electrodiagnostic, Sonographic, and Clinical Features of Carpal Tunnel Syndrome with Bifid Median Nerve

Purpose

A bifid median nerve (BMN) is not a rare variant. This study aimed to investigate the features of carpal tunnel syndrome (CTS) accompanied by BMN.

Patients and Methods

In this retrospective study, we defined a BMN group as CTS with BMN and a non-bifid median nerve (NMN) group as CTS without BMN. All hands were assigned to four severity grades according to the findings of electrodiagnosis (EDx): very mild, mild, moderate, and severe. The cross-sectional area (CSA) of the median nerve, palmar bowing of the flexor retinaculum, and persistent median artery (PMA) were assessed by ultrasonography. Numerical pain rating scale (NRS) and symptom duration were assessed as clinical variables.

Results

Sixty-four hands (57 patients) and 442 hands (341 patients) were enrolled in the BMN and the NMN groups, respectively. BMN was prevalent in 12.6% of all CTS hands. The distribution of EDx severity grade was milder in the BMN group than in the NMN group (P<0.001). The CSA of the BMN group was 16.2±4.1 mm², slightly larger than 15.1±4.2 mm² in the NMN group (P=0.056). The BMN group showed higher NRS than the NMN group (5.5±1.5 and 4.4±1.7, respectively; P<0.001). In the subgroup analysis, NRS was significantly higher in the BMN group than in the NMN group at all EDx severity grades. In the BMN group, the PMA group showed greater EDx severity (P=0.037) and higher NRS (6.0 and 5.0, respectively; P=0.012) than the non-PMA group. The radial side branch's CSA was larger than that of the ulnar side branch (10.0 mm² and 6.0 mm², respectively; P<0.001).

Conclusion

CTS with BMN presented more severe symptoms and relatively milder EDx severity. When assessing the severity of CTS with BMN, the clinical symptoms should primarily be considered, as well as we should complementarily evaluate the EDx and ultrasonography.

The Role of Imaging for Disorders of Peripheral Nerve

Peripheral nerve imaging is a helpful and sometimes essential adjunct to clinical history, physical examination, and electrodiagnostic studies. Advances in imaging technology have allowed the visualization of nerve structures and their surrounding tissues. The clinical applications of ultrasound and magnetic resonance imaging (MRI) in the evaluation of peripheral nerve disorders are growing exponentially. This article reviews basics of ultrasound and MRI as they relate to nerve imaging, reviews advantages and limitations of each imaging modality, reviews the applications of ultrasound and MRI in disorders of peripheral nerve, and discusses emerging advances in the field.

Carpal tunnel syndrome caused by the entrapment of a bifid Lanz IIIA Type anatomical variant of median nerve: A case report and systematic literature review

Background:

Carpal tunnel syndrome (CTS) is the most common entrapment peripheral neuropathy. Median nerve may present several anatomical variations such as a high division or bifid median nerve (BMN). A thorough knowledge of the normal anatomy and variations of the median nerve at the wrist are fundamental to reduce complications during carpal tunnel release.

Case Description:

A 63-year-old man with CTS underwent preoperative ultrasound that showed the entrapment of the median nerve and disclosed a BMN Lanz IIIA Type anatomical variation at the carpal tunnel. During the surgery, the anatomical variant of a BMN at the wrist has been visualized. Both nervous rami entirely occupied the carpal canal and this may have predisposed to the development of the entrapment syndrome. Nor persistent median artery, or other associated abnormalities, have been identified. At the 6 months follow-up control, the patient referred a good surgical recovery with complete resolution of the preoperative symptoms of the median nerve entrapment.

Conclusion:

A rare case of Lanz IIIA BMN Type at the wrist has been encountered in a patient with a CTS and a systematic review and practical considerations have been presented with the aim of raising awareness to the neurosurgical community of a such rare variant that could be encountered during carpal tunnel release procedures. CTS may be caused by the entrapment of a BMN Lanz IIIA Type anatomical variant of median nerve. Preoperative US would help to identify such patients to reduce risk of iatrogenic injuries.

Neuromuscular ultrasound findings in carpal tunnel syndrome with symptoms mainly in the nondominant hand

BACKGROUND

Carpal tunnel syndrome (CTS) may be associated with structural lesions or anatomical variations at the wrist, especially in patients whose symptoms are more severe in, or limited to, the nondominant hand. The aims of this study were to identify the type and frequency of structural abnormalities and anatomical variations, and to demonstrate the contribution of ultrasound in this subgroup of CTS patients.

METHODS

A retrospective chart review was performed on all patients referred to the electromyography laboratory who fulfilled the diagnostic criteria for CTS and who underwent neuromuscular ultrasound.

RESULTS

Of 114 CTS patients with symptoms mainly in nondominant hand, 51 (44.7%) had structural abnormalities or anatomical variations detected by ultrasound. In multivariable analysis, symptoms mainly in the nondominant hand and a body mass index (BMI) <30 kg/m² were the only independent variables significantly associated with structural findings, odds ratios 2.3 (P < .001) and 1.9 (P = .006), respectively.

CONCLUSIONS

Neuromuscular ultrasound, in addition to electrodiagnostic studies, should be considered in all CTS patients with symptoms more severe in nondominant hand as a significant number have abnormal structural abnormalities or anatomical variations that may be causative or change the therapeutic approach.

Techniques for Peripheral Nerve Stimulator Implantation of the Upper Extremity

OBJECTIVE

To present a technical note on how to perform upper extremity peripheral nerve stimulators for three major nerves: median, ulnar, and radial.

DESIGN

Literature review and expert opinion.

SETTING

Single academic center.

RESULTS

Peripheral nerve stimulation has recently become popular with the development and availability of peripheral nerve stimulators with an external pulse generator. Here, we describe ultrasound anatomy and technical details for peripheral nerve stimulation in the upper extremity for three major nerves: median, ulnar, and radial.

CONCLUSIONS

Upper extremity peripheral nerve stimulation can be considered as an option for refractory neuropathic upper extremity pain.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

Incidental bifid median nerve with a wandering ulnar division separated by the third flexor digitorum superficialis muscle: importance of ultrasound evaluation

Ultrasound evaluation of the median nerve is commonly performed in patients with suspected carpal tunnel syndrome. Radiologists should be familiar with variant anatomy of the median nerve to assist clinicians in the management of these patients, particularly when surgery is being considered. A 63-year-old female was being evaluated for a ganglion cyst and was incidentally found to have a bifid median nerve with wandering ulnar division which coursed superficial to the third digit flexor digitorum superficialis (FDS) muscle belly. The patient did not have any symptoms of carpal tunnel syndrome so surgery has not been performed; however this case highlights the importance of ultrasound evaluation to avoid potential perioperative complications.

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.

Neuromuscular ultrasound in clinical practice: A review

Neuromuscular ultrasound (NMUS) is becoming a standard element in the evaluation of peripheral nerve and muscle disease. When obtained simultaneously to electrodiagnostic studies, it provides dynamic, structural information that can refine a diagnosis or identify a structural etiology. NMUS can improve patient care for those with mononeuropathies, polyneuropathy, motor neuron disease and muscle disorders. In this article, we present a practical guide to the basics of NMUS and its clinical application. Basic ultrasound physics, scanning techniques and clinical applications are reviewed, along with current challenges.

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.

Occurrence of bifid median nerve in healthy and carpal tunnel syndrome patients

We investigated the possible association between median nerve morphology and carpal tunnel size, hand side and nerve conduction measurements. The study included a patient group (n = 58; 44 women) with idiopathic carpal tunnel syndrome (CTS) in 100 hands and a control group of healthy volunteers (n = 56, 112 hands; 44 women). The following data were recorded: (1) median and ulnar motor and sensory nerve conduction parameters (2) ultrasonographic dimensions of the carpal tunnel inlet area (CTA_in) and inlet area of the median nerve. The prevalence of bifid median nerve was 19% in the CTS hands and 13.3% in the control group. Bilateral bifid nerve was detected in 7 subjects and unilateral in 23, with no side or sex preponderance. The median nerve area was larger in the participants with single than those with bifid median nerve. No correlation was found between CTA_in and median nerve area for single or bifid nerves in controls or patients. It was concluded that bifid median nerve was not a rare variation. We could not, however, support its etiological relation to CTS. Ultrasonographic examination of the carpal tunnel region supplementing neurophysiology provided a reliable means to detect median nerve size and morphology.

CLINICAL TRIAL REGISTRATION NUMBER

84; 5/3/15.

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.

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.

Determination of Electrophysiologically Moderate and Severe Carpal Tunnel Syndrome: Ultrasonographic Measurement of Median Nerve at the Wrist

OBJECTIVE

To establish the cutoff value of cross-sectional area (CSA) of the median nerve at the wrist, for determination of electrophysiologically moderate and severe carpal tunnel syndrome (CTS).

METHODS

The prospective study was conducted among patients suspected of having CTS. A total of 106 patients (185 symptomatic wrists) received nerve conduction study (NCS) and ultrasonography. To establish a cutoff value, various diagnostic properties were calculated across a range of the CSA.

RESULTS

A mean±standard deviation of CSA of the median nerve of normal and mild, moderate and severe CTS was 9.4±2.1, 12.0±2.7, 13.8±4.7, and 15.4±4.1 mm², respectively. The positive relationship between CTS severities and CSA was observed (rs=0.56). A 14 mm² CSA had sufficient power to rule in moderate and severe CTS, with a specificity of 91.4% and sensitivity of 42.3%. In addition, it showed a post-test probability (positive predictive value) of 86.3% as against a pre-test probability of 56.2%.

CONCLUSION

Patients who had ≥14 mm² of median nerve CSA had very high probability of moderate to severe CTS.

Iatrogenic Injuries of the Palmar Branch of the Median Nerve Following Volar Plate Fixation of the Distal Radius

Background: Our aims were to identify iatrogenous injuries to the palmar branch of the median nerve sustained during volar plate fixation of the distal radius, make the clinician aware of this relatively uncommon complication of distal radius fixation, to emphasise common threads in symptomatology and to propose an algorithm for evaluation and management.

Methods: Retrospectively interrogating our database over a 5 year period, the case records, neurophysiology records, operative records, therapy records were reviewed. The data was analysed with regard to the grade of surgeon performing the procedure, the site of injury, complexity of the fracture, delay to surgery, implant choice and outcome of the treatment. Variations in nerve anatomy were documented during revision surgery and common themes in symptomatology and clinical presentation were identified.

Results: Seven patients with an iatrogenic injury involving the palmar branch of the median nerve associated with volar plate fixation of the distal radius were assessed. The male: female ratio was 1:6 and the mean age of patients was 47.8 years (33-74 years). The initial operative fixation was undertaken by a consultant orthopaedic surgeon at a mean of 7.8 (1-17) days from injury. The mean time from fracture fixation surgery to referral to the peripheral nerve injury service was 8.9 (2-36) months. Six patients presented with pain on attempted wrist extension. Five patients had parasthesia, hyperaesthesia or dysaesthesia in the distribution of the PCBMN. Anaesthesia or hypoaesthesia was present in three patients. Two patients presented with symptoms of complex regional pain syndrome (CRPS) Type 2.

Conclusions: Revising relevant anatomy and possible variations as well as careful placements of retractors in the region of the median nerve could bring down these injuries. We propose an algorithm for their management.

A comprehensive review of motor innervation of the hand: variations and clinical significance

PURPOSE

The objective of the present review is to assemble the recognized anatomical variations, classifications, and clinical evidence with regard to innervation of the hand and discuss the clinical significance of these variations.

METHODS

The material for this review was obtained by exploring PubMed and Google Scholar (search terms: hand innervation, variations of ulnar nerve, variations of median nerve, variations of radial nerve) as well as from standard anatomy texts. This initial search returned approximately 300 articles, which was reduced by abstract or title review. Reviewing the reference lists of significant papers uncovered further studies missed in the initial search. A few standard anatomy texts were also consulted for normal anatomy.

RESULTS

The median and ulnar nerves frequently display a number of significant deviations from the traditionally taught branching patterns. The traditionally taught innervation of the hand is also found to be highly variable. This is especially evident with regard to the motor innervation of thenar muscles. These variations may be explained by the often under-recognized anastomoses that exist in the hand, such as the motor Riche-Cannieu Anastomosis. Some of these variations are associated significant clinical consequences.

CONCLUSIONS

The median and ulnar nerves display many anatomical variations, often with significant clinical implications. Awareness about these variations is clinically important when interpreting clinical examination findings, electrophysiological and radiological investigation as well as during management of patients in terms of surgical and anesthetic procedures.

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.

Bifid median nerve in a patient with carpal tunnel syndrome: A case report and literature review

A middle-aged man with Carpal tunnel syndrome without any known predisposing risk factors is presented. Ultrasonography demonstrated two structures within the left carpal tunnel with similar echo pattern as median nerve, thus confirming an anatomical variation in the median nerve, described in the literature as bifid median nerve. The knowledge of the existence of bifid median nerve is an important factor in planning surgical decompression of median nerve to avoid nerve and persistent median artery injuries and/or potential relapse if decompression of both branches is not carried out. In addition, this knowledge is important in deciding whether to inject above the bifurcation or into the epineurial of individual nerve trunks in the setting of planned symptomatic corticosteroid injections. In conclusion, bifid median nerve is an anatomic variant that may contribute to carpal tunnel syndrome and can be demonstrated ultrasonographically. It is important to be aware of this anomaly when planning carpal tunnel release surgery and symptomatic corticosteroid injections.

Bifid Median Nerve--A Case Report

A wide variety of anatomic variations of the median nerve at wrist have been reported and the awareness of these variations are essential for the surgeon treating carpal tunnel pathologies to avoid inadvertent injury to the nerve during surgery. We report a rare case of bifid median nerve accompanied by a persistent median artery found incidentally in a patient who underwent flexor tendon reconstruction for subcutaneous tendon rupture. The current literature regarding the anomaly is reviewed and surgically relevant aspects are discussed.

Entrapment and traumatic neuropathies of the elbow and hand: An imaging approach

Ultrasound and magnetic resonance imaging currently offer a detailed analysis of the peripheral nerves. Compressive and traumatic nerve injuries are the two main indications for imaging investigation of nerves with several publications describing the indications, technique and diagnostic capabilities of imaging signs. Investigation of entrapment neuropathies has three main goals, which are to confirm neuronal distress, search for the cause of nerve compression and exclude a differential diagnosis on the entire nerve. For traumatic nerve injuries, imaging, predominantly ultrasound, occasionally provides essential information for management including the type of nerve lesion, its exact site and local extension.

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.