Unusual compression neuropathies of the forearm, part II: median nerve

Compressive Neuropathies of the Upper Extremity: Anatomy for the Peripheral Nerve Surgeon

Advance knowledge of anatomy is a prerequisite for the peripheral nerve surgeon. This article serves to provide an outline of anatomic regions where nerve entrapment or compression can occur. Each section is subdivided into anatomic regions where the etiology, indications, and relevant and aberrant anatomy are discussed, as well as common surgical approaches to the problematic anatomic site. The purpose is to provide an overview for the peripheral nerve surgeon and offer a valuable resource to provide a better understanding and optimal care for this patient population.

Non-invasive in vivo study of morphology and mechanical properties of the median nerve

The current literature studied the median nerve (MN) at specific locations during joint motions. As only a few particular parts of the nerve are depicted, the relevant information available is limited. This experiment investigated the morphological and biomechanical properties of the MN. The effects of the shoulder and wrist motions on MN were explored as well. Eight young healthy female individuals were tested with two-dimensional ultrasound and shear wave elastography (SWE). The morphological and biomechanical properties were examined in limb position 1, with the wrist at the neutral position, the elbow extended at 180°, and the shoulder abducted at 60°. In addition, the experiment assessed the differences among the wrist, forearm, elbow, and upper arm with Friedman's test and Bonferroni post hoc analysis. Two groups of limb positions were designed to explore the effects of shoulder movements (shoulder abducted at 90° and 120°) and wrist movements (wrist extended at 45° and flexed at 45°) on the thickness and Young's modulus. Differences among the distributions of five limb positions were tested as well. The ICC3, 1 values for thickness and Young's modulus were 0.976 and 0.996, respectively. There were differences among the MN thicknesses of four arm locations in limb position 1, while Young's modulus was higher at the elbow and wrist than at the forearm and upper arm. Compared to limb position 1, only limb position 4 had an effect on MN thickness at the wrist. Both shoulder and wrist motions affected MN Young's modulus, and the stiffness variations at typical locations all showed a downward trend proximally in all. The distributions of MN thickness and Young's modulus showed fold line patterns but differed at the wrist and the pronator teres. The MN in the wrist is more susceptible to limb positions, and Young's modulus is sensitive to nerve changes and is more promising for the early diagnosis of neuropathy.

Effect of pronator teres muscle botulinum neurotoxin type-A injection on proximal median nerve entrapment

PURPOSE

We aimed to evaluate the effect of botulinum neurotoxin type-A (Btx-A) injection into the pronator teres muscle in proximal median nerve entrapment (PMNE).

METHODS

Intramuscular injection of 30 IU Btx-A into the pronator teres muscle was performed in 12 patients (14 extremities) diagnosed with PMNE. The injection was made under nerve stimulator control. One patient with thoracic outlet syndrome was excluded from the study and not included in the clinical evaluation. Grip and pinch strength, 2-point discrimination, Q-DASH score, and pain on VAS were evaluated and compared before and 6-8 months after injection. The patients were contacted again by phone after the first and fifth years and asked about PMNE symptomatology.

RESULTS

None of the patients had complications. No significant difference in pinch strength was observed following Btx-A injection, but there was significant improvement in grip strength, 2-point discrimination, and Q-DASH and VAS pain scores.

CONCLUSION

The outcomes of our study were promising: Btx-A injection improved symptoms in patients with PMNE.

LEVEL OF EVIDENCE

Level IV.

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.

How to Differentiate Pronator Syndrome from Carpal Tunnel Syndrome: A Comprehensive Clinical Comparison

The diagnostic process that allows pronator syndrome to be differentiated reliably from carpal tunnel syndrome remains a challenge for clinicians, as evidenced by the most common cause of pronator syndrome misdiagnosis: carpal tunnel syndrome. Pronator syndrome can be caused by compression of the median nerve as it passes through the anatomical structures of the forearm, while carpal tunnel syndrome refers to one particular topographic area within which compression occurs, the carpal tunnel. The present narrative review is a complex clinical comparison of the two syndromes with their anatomical backgrounds involving topographical relationships, morphology, clinical picture, differential diagnosis, and therapeutic options. It discusses the most frequently used diagnostic techniques and their correct interpretations. Its main goal is to provide an up-to-date picture of the current understanding of the disease processes and their etiologies, to establish an appropriate diagnosis, and introduce relevant treatment benefiting the patient.

Anterior Interosseous Nerve Syndrome

Anterior interosseous nerve syndrome (AINS) is a rare form of peripheral neuropathy which involves disruption of the anterior interosseous nerve. The pathophysiology of AINS remains unclear. AINS typically initially presents with forearm pain and may gradually progress to palsy of the deep muscles of the anterior forearm. Diagnosis of AINS requires thorough patient history and physical exam. EMG is the preferred diagnostic study and classically reveals abnormal activity and prolonged latency periods within the evoked action potentials of the FPL and PQ. Due to the self-limiting nature of AINS, there is general agreement that conservative and symptomatic management should be explored for up to 6 months as first line therapy, which usually includes analgesics and nonsteroidal anti-inflammatory drugs, contracture prevention, hand therapy, and hand splinting. Surgical options such as internal neurolysis and minimally invasive endoscopic decompression may be explored if functional recovery from conservative management is limited.

Isolated Proximal Median Neuropathy after Aortic Dissection Repair: Case Report

Surgery-related isolated proximal median neuropathy is a rare complication. Brachial plexus injury is a possible complication after major cardiac surgery; however, isolated mononeuropathy is less frequently documented. We present an unusual case of isolated proximal median neuropathy after aortic dissection repair surgery in a 39-year-old man. Electrodiagnostic study and ultrasound examinations helped in localizing the lesion to the axillary region. Serial follow-ups showed improvement in electrodiagnostic parameters, which were compatible with clinical symptoms. Partial recovery was achieved at the seventh month follow-up. This case report aimed to increase awareness of nerve stretching during open heart surgery and demonstrate the diagnosis and clinical follow-up by concomitant use of electrodiagnostic and nerve ultrasound studies.

Percutaneous Ultrasound-Guided Release of the Lacertus Fibrosus for Median Nerve Entrapment at the Elbow

PURPOSE

The aim of this technical note is to present a microinvasive percutaneous ultrasound-guided release of the lacertus fibrosus of the biceps brachii for pronator syndrome, i.e., entrapment of the median nerve at the elbow.

METHODS

Fifteen consecutive patients were included. Patients showed isolated pronator syndrome including pain plus reduced strength of specific median nerve innervated muscles. The release was performed in a non-operating interventional room under wide-awake local anesthesia no tourniquet (WALANT). It was conducted superficial to the pronator teres with in-plane ultrasound guidance. The recovery of strength was first assessed peroperatively, and then systematic visits at postoperative weeks 1 and 4 included assessments of both strength and pain.

RESULTS

Procedures were comfortably completed with no immediate surgical or anesthetic complication. Muscle strength returned immediately and persisted at postoperative visits. Visual analog scores for pain reduced from 6.2 to 2.5 and 0.6 at weeks 1 and 4, respectively. All working patients were able to perform in their professional activities at week 1. The millimetric skin incision healed with no hypertrophic scar tissue. A small hematoma occurred at week 1 and resorbed spontaneously. No other delayed complication was observed. The procedure appeared effective with improved invasiveness compared to existing techniques. Real-time monitoring with ultrasound may improve the safety. The technique could be regarded as a new ultrasound-guided alternative to surgery.

CONCLUSION

Performed superficial to the pronator teres muscle under WALANT anesthesia, the microinvasive percutaneous ultrasound-guided release of the lacertus fibrosus may be an effective treatment of pronator syndrome.

Is Carpal Tunnel Release an Effective Treatment for Patients with Suspected Concurrent Carpal Tunnel and Pronator Syndrome?

Background: Some patients with a confirmed diagnosis of carpal tunnel syndrome (CTS) on clinical examination and electrodiagnostic testing (EDX) may also have one or more clinical features of pronator syndrome (PS). However, the EDX is negative for PS. We label these patients as suspected concurrent carpal tunnel and pronator syndrome (CCPS). We suspect that this is a presentation of reverse double crush syndrome that occurs when a symptomatic distal compression neuropathy converts an asymptomatic proximal compression into a symptomatic one. We believe both compressions can be relieved by decompressing the median nerve only at the wrist. The aim of our study is to determine whether carpal tunnel release (CTR) is an effective treatment for patients suffering from CCPS. Methods: This is a prospective, cohort study of the outcomes of CTR in two matched groups with 37 patients in each group. Group A included patients with suspected CCPS and group B included patients with isolated CTS. All patients were evaluated pre-operatively and 1 year after surgery using the Boston Carpal Tunnel Questionnaire (BCTQ). At one year, patients were also assessed for residual symptoms and positive provocative tests. Results: A significant improvement in the symptom and functional severity scales (SSS and FSS) of the BCTQ was noted in both groups. The degree of improvement in SSS was similar in both groups; however, group A showed a greater improvement in FSS. This could be attributed to higher pre-operative values in some items of FSS in group A. No patients in either group had residual symptoms severe enough to necessitate further treatment. Conclusion: The outcomes of CTR are similar in patients with isolated CTS and suspected CCPS and a CTR may be sufficient to address symptoms of CTS and PS in patients with CCPS. Level of Evidence: Level II (Therapeutic).

Outcome of Surgical Treated Isolated Pronator Teres Syndromes-A Retrospective Cohort Study and Complete Review of the Literature

PURPOSE

This study aims to elucidate the occurrence of postoperative carpal tunnel syndrome (CTS), the functional outcome of patients with primary pronator teres syndrome (PTS), and review complete literature regarding this topic.

MATERIAL AND METHODS

A retrospective chart review was conducted in patients with PTS at a single center. In all patients, a numeric Visual Analog Scale (VAS) score, Pinch-Test, Jamar hand dynamometer test (JAMAR), and the Disabilities of the Arm Shoulder and Hand (DASH) score were analyzed preoperatively and at final follow-up to assess outcome. Additionally, a complete review of the literature was performed, including all data dealing with pronator teres syndrome.

RESULTS

Ten female and two male patients were included with a mean age of 49 years. Significant improvement in DASH and numeric VAS was detected at latest postoperative follow-up. In three patients, clinical signs of CTS pathology were detected during the follow-up period. One patient needed to be treated surgically, and in the other two patients, a conservative management was possible. In one patient (8%), a PTS recurrence was detected. All patients presented satisfied at latest follow-up.

CONCLUSION

In one-fourth of our patients, a CTS occurred during the follow-up period. Therefore, focusing on double-crush syndrome in unclear or mixed symptoms is necessary to avoid multiple operations. Furthermore, it seems that assessment with NCV is not enough for diagnosing PTS; therefore, further research is needed to clarify this problem.

Isolated Anterior Interosseous Neuropathy Affecting Only the Flexor Digitorum Profundus to the Index Finger After Shoulder Arthroscopy: A Case Report and Review of the Literature

ABSTRACT

Anterior interosseous nerve neuropathy is an uncommon neuropathy with multiple potential etiologies. We present a rare case of anterior interosseous nerve neuropathy affecting only the flexor digitorum profundus to the index finger and occurring after shoulder arthroscopy. This unique presentation used a combination of both electrodiagnostic testing and neuromuscular ultrasound to obtain an accurate diagnosis and highlights the importance of these complementary tests in the evaluation of nerve disorders. To our knowledge, anterior interosseous nerve neuropathy after shoulder arthroscopy affecting only the flexor digitorum profundus to the index finger has not been previously described in the literature.

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

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

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

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

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

Electrodiagnostic Assessment of Uncommon Mononeuropathies

Carpal tunnel syndrome, ulnar neuropathy at the elbow, and peroneal neuropathy are the most common mononeuropathies; however, other individual nerves may also be injured by various processes. These uncommon mononeuropathies may be less readily diagnosed owing to unfamiliarity with the presentations and vague symptoms. Electrodiagnostic studies are essential in the evaluation of uncommon mononeuropathies and can assist in localization and prognostication. However, they can also be challenging; stimulation at the proximal sites is difficult and well-validated reference values are not available. This article reviews the electrodiagnostic assessment of several uncommon upper and lower extremities mononeuropathies.

Compression Neuropathies of the Upper Extremity: A Review

Compressive neuropathies of the forearm are common and involve structures innervated by the median, ulnar, and radial nerves. A thorough patient history, occupational history, and physical examination can aid diagnosis. Electromyography, X-ray, and Magnetic Resonance Imaging may prove useful in select syndromes. Generally, first line therapy of all compressive neuropathies consists of activity modification, rest, splinting, and non-steroidal anti-inflammatory drugs. Many patients experience improvement with conservative measures. For those lacking adequate response, steroid injections may improve symptoms. Surgical release is the last line therapy and has varied outcomes depending on the compression. Carpal Tunnel syndrome (CTS) is the most common, followed by ulnar tunnel syndrome. Open and endoscopic CTS release appear to have similar outcomes. Endoscopic release appears to incur decreased cost baring a low rate of complications, although this is debated in the literature. Additional syndromes of median nerve compression include pronator syndrome (PS), anterior interosseous syndrome, and ligament of Struthers syndrome. Ulnar nerve compressive neuropathies include cubital tunnel syndrome and Guyon’s canal. Radial nerve compressive neuropathies include radial tunnel syndrome and Wartenberg’s syndrome. The goal of this review is to provide all clinicians with guidance on diagnosis and treatment of commonly encountered compressive neuropathies of the forearm.

[Anatomical aspects regarding the endoscopic release of the nervus interosseus anterior]

BACKGROUND

Decompression of the anterior interosseous nerve can be performed in an open operative exploration or endoscopically. Using an endoscopic decompression superficial anatomical landmarks serve as reference point. The aim of the study was to determine the location of the distribution of the median nerve in relation to the elbow joint in order to facilitate preparation during endoscopic decompression.

MATERIALS AND METHODS

The median nerve and the anterior interosseous nerve were dissected in 31 human specimens with regard to the elbow joint. The superficial anatomical landmark was the intercondyle line between the medial and lateral epicondyles. The distance between the origination of the anterior interosseous nerve of the median nerve was measured in relation to the intercondyle line.

RESULTS

The anatomical preparation was done using 62 adult cadaveric upper extremities. 11 specimens were formalin fixed and 20 specimens were fresh frozen cadaveric upper extremities. The average of the intercondyle distance was 7.2 cm ± 0.5 (min. 5.8; max. 7.8). The anterior interosseous nerve originated from the median nerve in average 39 mm ± 18 (min. 8; max. 80) distal to the intercondyle line. In 12 cases the distance was within the first 2 cm. There was only a correlation between the length of the upper arm and the nerve junction.

CONCLUSION

The anterior interosseous nerve originated from the median nerve in average 4 cm distal to the intercondyle line. Although there was a distribution under 2 cm in around 20 % of the cases. This is very important with regard to the endoscopically technique and should be considered.

[Lesions of the anterior interosseous nerve: differentiating between compression neuropathy and neuritis]

BACKGROUND

In cases of anterior interosseous nerve (AIN) syndrome, it is often difficult to differentiate between compression neuropathy and neuritis.

MATERIAL AND METHODS

This review analyses the clinical aspects of the neuritic AIN syndrome and the different diagnostic tools for securing the diagnosis and differentiating the condition from compression neuropathy. Based on these data, the current therapeutic options are proposed.

RESULTS

The AIN syndrome often results from neuritis of the AIN fascicles within the trunk of the median nerve. The differentiation between neuritis and compression neuropathy of the AIN is based on dedicated neurophysiological examinations as well as nerve sonography and MRI neurography. Although conservative treatment is the gold standard, microsurgical interventions have become more important in recent years.

CONCLUSION

A dedicated diagnostic workup of the AIN syndrome is paramount for optimal treatment. Conservative treatment remains the standard to date. However, if torsions and constrictions of nerve fascicles are detected, intrafascicular neurolysis should be considered, as current research shows the potential for an improved outcome in such cases.

Proximal Median Nerve Compression: Pronator Syndrome

Pronator syndrome (PS) is a compressive neuropathy of the median nerve in the proximal forearm, with symptoms that often overlap with carpal tunnel syndrome (CTS). Because electrodiagnostic studies are often negative in PS, making the correct diagnosis can be challenging. All patients should be initially managed with nonsurgical treatment, but surgical intervention has been shown to result in satisfactory outcomes. Several surgical techniques have been described, with most outcomes data based on retrospective case series. It is essential for clinicians to have a thorough understanding of median nerve anatomy, possible sites of compression, and characteristic clinical findings of PS to provide a reliable diagnosis and treat their patients.

Role of fasciae around the median nerve in pathogenesis of carpal tunnel syndrome: microscopic and ultrasound study

This study investigated the connections between the median nerve paraneural sheath and myofascial structures near it, from both macroscopic and microscopic points of view. Four samples of median nerve and surrounding tissues were excised from nine non-embalmed upper limbs for microscopic analysis. Ultrasound images were analysed in 21 healthy subjects and 16 carpal tunnel syndrome patients to evaluate median nerve transversal displacement during finger motion at carpal tunnel and forearm levels. An anatomical continuity between epimysium and paraneural sheath and a reduction of paraneural fat tissue from proximal to distal was found in all samples. Median nerve displacements at both levels were significantly reduced in carpal tunnel syndrome subjects (P < 0.001). It was observed that the median nerve is not an isolated structure but is entirely connected to myofascial structures. Therefore, unbalanced tension of epimysial fasciae can affect the paraneural sheath, limiting nerve displacement, and consequently this must be included in carpal tunnel syndrome pathogenesis.

Prediction Model for Choosing Needle Length to Minimize Risk of Median Nerve Puncture With Dry Needling of the Pronator Teres

OBJECTIVE

The aim of this study was to relate forearm anthropometric measures to ultrasound pronator teres depth to determine the necessary needle length to prevent median nerve (MN) injury during pronator teres dry needling.

METHODS

We conducted a study employing a diagnostic accuracy prediction model (NCT03308279) at a Spanish university center. The study recruited 65 participants to predict the depth of the MN (measured with ultrasound) in the pronator teres using a decision tree algorithm to reduce the risk of MN puncture using 2 needle lengths (13 mm or 25 mm). The decision tree was developed by automatically selecting a cutoff for body mass index, forearm length and circumference, and pronator teres thickness.

RESULTS

For forearm circumferences ≤27.5 cm, the predictive value for the 13-mm needle was 92%. For forearm circumferences >27.5 cm and forearm lengths ≤26.75 cm, the predictive value for the 25-mm needle was 100%.

CONCLUSION

Based upon the findings of this study, we suggest that needle length should be selected according to forearm anthropometric measures to prevent MN injury during pronator teres dry needling.

Common Entrapment Neuropathies

PURPOSE OF REVIEW

This article addresses relevant peripheral neuroanatomy, clinical presentations, and diagnostic findings in common entrapment neuropathies involving the median, ulnar, radial, and fibular (peroneal) nerves.

RECENT FINDINGS

Entrapment neuropathies are a common issue in general neurology practice. Early diagnosis and effective management of entrapment mononeuropathies are essential in preserving limb function and maintaining patient quality of life. Median neuropathy at the wrist (carpal tunnel syndrome), ulnar neuropathy at the elbow, radial neuropathy at the spiral groove, and fibular neuropathy at the fibular head are among the most frequently encountered entrapment mononeuropathies. Electrodiagnostic studies and peripheral nerve ultrasound are employed to help confirm the clinical diagnosis of nerve compression or entrapment and to provide precise localization for nerve injury. Peripheral nerve ultrasound demonstrates nerve enlargement at or near sites of compression.

SUMMARY

Entrapment neuropathies are commonly encountered in clinical practice. Accurate diagnosis and effective management require knowledge of peripheral neuroanatomy and recognition of key clinical symptoms and findings. Clinical diagnoses may be confirmed by diagnostic testing with electrodiagnostic studies and peripheral nerve ultrasound.

Bilateral anterior interosseous nerve syndrome with 6-year interval

Flexor pollicis longus paralysis related to idiopathic anterior interosseous nerve syndrome is well known, but few reports exist on bilateral disease. A 24-year-old man with no personal or family history of neurological disease developed isolated total loss of active flexion of the right thumb's interphalangeal joint after undergoing a wrist arthroscopy. Surgical exploration 5 weeks after onset showed flexor pollicis longus tendon to be intact; anterior interosseous nerve decompression was done with no abnormalities found. Because of persistent paralysis, electromyography was performed showing findings consistent with anterior interosseous nerve syndrome. After 7 months without recovery, the patient underwent tendon transfer. After 6 years, the patient presented with left-sided isolated flexor pollicis longus paralysis and electromyography indicated anterior interosseous nerve syndrome. Examination 9 months after onset showed persistent complete flexor pollicis longus paralysis but by 15 months spontaneous complete recovery had occurred. Anterior interosseous nerve syndrome can occur bilaterally and is likely to resolve completely without intervention but recovery may take longer than a year.

The Median Nerve at the Carpal Tunnel … and Elsewhere

The median nerve (MN) may be affected by various peripheral neuropathies, each of which may be categorized according to its cause, as either an extrinsic (due to an entrapment or a nerve compression) or an intrinsic (including neurogenic tumors) neuropathy. Entrapment neuropathies are characterized by alterations of the nerve function that are caused by mechanical or dynamic compression. It occurs because of anatomic constraints at specific locations including sites where the nerve courses through fibro-osseous or fibromuscular tunnels or penetrates a muscle. For the diagnosis of peripheral neuropathies, physicians traditionally relied primarily on clinical findings and electrodiagnostic testing with electromyography. However, if further doubt exists, clinicians may ask for an additional imaging evaluation.

ARCADE OF FLEXOR DIGITORUM SUPERFICIALIS MUSCLE: ANATOMICAL STUDY AND CLINICAL IMPLICATIONS

Objective:

The arcade of the flexor digitorum superficialis muscle (FDS) is an anatomical structure which has not yet been widely studied and is a site of nerve compression. The aim of this study was to analyze the arcade of the FDS muscle and its relations with the median and anterior interosseous nerves through anatomic dissections.

Method:

Fifty arms from 25 adult cadavers (21 males and 4 females) were dissected; 18 were previously preserved in formalin and glycerin and 7 fresh specimens were dissected in the Laboratory of Anatomy.

Results:

The arcade of the superficial flexor muscle was identified in all dissected limbs. The radial and humeral heads were present in all specimens, and the ulnar head in 16 (32%). We identified two varieties of the arcade structure: a fibrous arcade in 32 specimens (64%), and a muscular arcade in 11 specimens (22%). In 4 specimens (8%) the arcade was very fine and so transparent that the nerve could be seen within the arcade. In 3 forearms the arcade was considered irregular because of discontinuity between the fibers that comprised this structure.

Conclusion:

The fibrous arcade of the FDS muscle may be a potential cause of nerve compression of the median and interosseous anterior nerves. Level of Evidence IV; Case series.

Anatomical variations of the pronator teres muscle in a Central European population and its clinical significance

The pronator teres (PT) muscle is a forearm flexor with radial and ulnar heads. It is innervated by the median nerve (MN), which passes between these heads. Nerve entrapment, known as “PT syndrome”, may occur in this passage. Anatomical variations in this region may be potential risk factors of this pathology. Therefore, the aim of the study was to determine the relationship between morphologic variations of the PT and the MN. In 50 isolated, formalin-fixed upper limbs, the cubital region and the forearm were dissected. The following measurements were taken: origin of the PT muscle heads, the length of these heads, the length of the forearm, diameter of the MN and the number of its muscular branches to the pronator teres muscle. The forearms with the humeral head originating from the medial humeral epicondyle and medial intermuscular septum (72%) were significantly shorter (p = 0.0088) than those where the humeral head originated only from the medial humeral epicondyle. Moreover, in these specimens, the MN was significantly thinner (p = 0.003). The ulnar head was present in 43 limbs (86%). The MN passed between the heads of the PT muscle (74%) or under the muscle (26%). In the majority of cases, it provided two motor branches (66%). There is an association between the morphologic variation of the PT muscle heads and the course and branching pattern of the MN. Both are related to differences in forearm length. This may have an impact on the risk of PT syndrome and the performance of MN electrostimulation.

Morphology and morphometry of the ulnar head of the pronator teres muscle in relation to median nerve compression at the proximal forearm

INTRODUCTION

The pronator syndrome is a rare compression neuropathy of the median nerve. Ulnar head of the pronator teres muscle may cause compression at proximal forearm.

HYPOTHESIS

Detailed morphologic and morphometric studies on the anatomy of the ulnar head of pronator teres is scarce.

MATERIAL AND METHODS

We dissected 112 forearms of fresh cadavers. We evaluated the morphology and morphometry of the ulnar head of pronator teres muscle.

RESULTS

The average ulnar head width was 16.3±8.2mm. The median nerve passed anterior to the ulnar head at a distance of 50.4±10.7mm from the interepicondylar line. We classified the morphology of the ulnar head into 5 types. In type 1, the ulnar head was fibromuscular in 60 forearms (53.6%). In type 2, it was muscular in 23 forearms (20.5%). In type 3, it was just a fibrotic band in 18 forearms (16.1%). In type 4, it was absent in 9 forearms (8%). In type 5, the ulnar head had two arches in 2 forearms (1.8%). In 80 forearms (71.5%: types 1, 3, and 5), the ulnar head was either fibromuscular or a fibrotic band.

DISCUSSION

Although the pronator syndrome is a rare compression syndrome, the ulnar head of pronator teres is reported as the major cause of entrapment in the majority of the cases. The location of the compression of the median nerve in relation to the ulnar head of pronator teres muscle and the morphology of the ulnar head is important for open or minimally-invasive surgical treatment.

TYPE OF STUDY

Sectional study.

LEVEL OF EVIDENCE

Basic science study.

Pronator Syndrome Due to Schwannoma

This report presents a rare case of pronator syndrome due to median nerve compression by Schwannoma. The tumour was derived from the median nerve and was located between the two heads of origin of the pronator teres muscle in the left antecubital fossa. The patient was completely cured after excision of the tumour.

Median nerve compression at the fibrous arch of the flexor digitorum superficialis: an anatomic study of the pronator syndrome

BACKGROUND

Flexor digitorum superficialis (FDS) arch is a site of compression in pronator syndrome yet little is known about its anatomic structure. The purpose of the study is to delineate the surgical anatomy of the FDS arch along with its relationship to the anterior interosseous nerve (AIN) takeoff.

METHODS

Thirty-eight cadavers were dissected using a modified Henry's approach. The FDS arch was identified, and its distance to the antebrachial crease and medial and lateral epicondyle were measured. The FDS arch was divided in a sequential fashion until adequate decompression of the median nerve was achieved. The total length of the release was measured. The takeoff of the AIN was identified in relation to the FDS arch.

RESULTS

Two types of the FDS arch were discovered, a distinct fibrous arch and an indistinct fibrous arch with vertical fibers blending into overlying fascia. Only 42 % of specimens had a distinct FDS arch averaging 1.69 cm in length. The majority of specimens had an indistinct arch, and of those, 77 % had overlying muscle, requiring an average release of 2.6 cm. The AIN branched at or distal to the FDS arch in 74 % of specimens, and only 8 % was found to have an ulnar-sided origin off the median nerve.

CONCLUSIONS

A longer surgical release is needed with indistinct FDS arches. Overlying muscle during dissection may be indicative of an indistinct arch. Dissection along the ulnar side of the median nerve can possibly decrease the chance of injury to the AIN during decompression.

Supracondylar process syndrome: case report and literature review

The supracondylar process is a congenital bone projection on the distal anteromedial humerus often associated with a ligament of Struthers, a fibrous connection between the process and medial epicondyle. It is largely asymptomatic and only on rare occasions presents with neurovascular compression resulting in a supracondylar process syndrome. This case report describes a 28-year-old woman with supracondylar process syndrome, and our management. The topic is further explored with a literature review of 43 reported cases. Analysis of the case reports indicates that isolated median nerve injuries are the most common. Other presentations such as fractures, vascular compromise, and ulnar nerve involvement are less frequent.

Median nerve neuropraxia by a large false brachial artery aneurysm

Peripheral nerve compression is a rare complication of an iatrogenic false brachial artery aneurysm. We present a 72-year-old patient with median nerve compression due to a false brachial artery aneurysm after removal of an arterial catheter. Surgical exclusion of the false aneurysm was performed in order to release traction of the median nerve. At 3-month assessment, moderate hand recovery in function and sensibility was noted. In the case of neuropraxia of the upper extremity, following a history of hospital stay and arterial lining or catheterization, compression due to pseudoaneurysm should be considered a probable cause directly at presentation. Early recognition and treatment is essential to avoid permanent neurological deficit.

Evaluation and treatment of upper extremity nerve entrapment syndromes

Nerve entrapment syndromes in the upper extremity are being recognized with increasing frequency. Prompt and correct diagnosis of these injuries is important. This article is a review of the common entrapment nerve injuries seen in the upper extremity. Each of these clinical syndromes is discussed independently, reviewing the anatomy, compression sites, patient presentation (history and examination), the role of additional diagnostic studies, and management.

Uncommon upper extremity compression neuropathies

Hand surgeons routinely treat carpal and cubital tunnel syndromes, which are the most common upper extremity nerve compression syndromes. However, more infrequent nerve compression syndromes of the upper extremity may be encountered. Because they are unusual, the diagnosis of these nerve compression syndromes is often missed or delayed. This article reviews the causes, proposed treatments, and surgical outcomes for syndromes involving compression of the posterior interosseous nerve, the superficial branch of the radial nerve, the ulnar nerve at the wrist, and the median nerve proximal to the wrist.

Endoscopically assisted nerve decompression of rare nerve compression syndromes at the upper extremity

BACKGROUND

Besides carpal tunnel and cubital tunnel syndrome, other nerve compression or constriction syndromes exist at the upper extremity. This study was performed to evaluate and summarize our initial experience with endoscopically assisted decompression.

MATERIALS AND METHODS

Between January 2011 and March 2012, six patients were endoscopically operated for rare compression or hour-glass-like constriction syndrome. This included eight decompressions: four proximal radial nerve decompressions, and two combined proximal median nerve and anterior interosseus nerve decompressions. Surgical technique and functional outcomes are presented.

RESULTS

There were no intraoperative complications in the series. Endoscopy allowed both identifying and removing all the compressive structures. In one case, the proximal radial neuropathy developed for 10 years without therapy and a massive hour-glass nerve constriction was observed intraoperatively which led us to perform a concurrent complementary tendon transfer to improve fingers and thumb extension. Excellent results were achieved according to the modified Roles and Maudsley classification in five out of six cases. All but one patient considered the results excellent. The poorest responder developed a CRPS II and refused post-operative physiotherapy.

CONCLUSION

Endoscopically assisted decompression in rare compression syndrome of the upper extremity is highly appreciated by patients and provides excellent functional results. This minimally invasive surgical technique will likely be further described in future clinical studies.

Posterior interosseous neuropathy: electrodiagnostic evaluation

Electrodiagnostic studies are used to anatomically localize nerve injuries. These tests help differentiate between cervical radiculopathies, brachial plexopathies, and peripheral nerve injuries. They also help to identify or rule out other underlying neurological diseases and disorders. In this case report, a 22-year-old male swimmer presented with left finger extensor weakness following pull-up exercises. Left wrist extension remained intact. Electrodiagnostic testing revealed a severe but incomplete posterior interosseous neuropathy. Magnetic resonance imaging confirmed inflammation of the nerve in the forearm. Posterior interosseous neuropathy is an uncommon but well-studied condition. Typically, this condition presents with weakness in finger and thumb extension with preserved wrist extension as the extensor carpi radialis longus is innervated proximal to the site of nerve compression in most cases. It is important to understand the anatomic course and distribution of the radial nerve in order to make an accurate diagnosis. Once the anatomy is understood, electrodiagnostic testing may be used to identify the location of nerve injury and exclude other disorders.

High resolution imaging of tunnels by magnetic resonance neurography

Peripheral nerves often traverse confined fibro-osseous and fibro-muscular tunnels in the extremities, where they are particularly vulnerable to entrapment and compressive neuropathy. This gives rise to various tunnel syndromes, characterized by distinct patterns of muscular weakness and sensory deficits. This article focuses on several upper and lower extremity tunnels, in which direct visualization of the normal and abnormal nerve in question is possible with high resolution 3T MR neurography (MRN). MRN can also serve as a useful adjunct to clinical and electrophysiologic exams by discriminating adhesive lesions (perineural scar) from compressive lesions (such as tumor, ganglion, hypertrophic callous, or anomalous muscles) responsible for symptoms, thereby guiding appropriate treatment.

MR imaging mapping of skeletal muscle denervation in entrapment and compressive neuropathies

The diagnoses of entrapment and compressive neuropathies have been based on the findings from clinical examinations and electrophysiologic tests, such as electromyography and nerve conduction studies. The use of magnetic resonance (MR) imaging for the diagnosis of entrapment or compressive neuropathies is increasing because MR imaging is particularly useful for discerning potential causes and for identifying associated muscle denervation. However, it is sometimes difficult to localize nerve entrapment or demonstrate nerve compression lesions with MR imaging. Nevertheless, even in these cases, MR imaging may show denervation-associated changes in specific muscles innervated by the affected nerves. The analysis of denervated muscle distributions by using MR imaging, with a knowledge of nerve innervation patterns, would be helpful for determining the nerves involved and the levels of nerve entrapment or compression. In this context, the mapping of skeletal muscle denervation with MR imaging has a supplementary or even a primary role in the diagnosis of entrapment and compressive neuropathies.

Compressive neuropathy in the upper limb

Entrampment neuropathy or compression neuropathy is a fairly common problem in the upper limb. Carpal tunnel syndrome is the commonest, followed by Cubital tunnel compression or Ulnar Neuropathy at Elbow. There are rarer entities like supinator syndrome and pronator syndrome affecting the Radial and Median nerves respectively. This article seeks to review comprehensively the pathophysiology, Anatomy and treatment of these conditions in a way that is intended for the practicing Hand Surgeon as well as postgraduates in training. It is generally a rewarding exercise to treat these conditions because they generally do well after corrective surgery. Diagnostic guidelines, treatment protocols and surgical technique has been discussed.

What's new in the diagnosis and treatment of peripheral nerve entrapment neuropathies

Entrapment neuropathies can be common conditions with the potential to cause significant disability. Correct diagnosis is essential for proper management. This article is a review of recent developments related to diagnosis and treatment of various common and uncommon nerve entrapment disorders. When combined with classical peripheral nerve examination techniques, innovations in imaging modalities have led to more reliable diagnoses. Moreover, innovations in conservative and surgical techniques have been controversial as to their effects on patient outcome, but randomized controlled trials have provided important information regarding common operative techniques. Treatment strategies for painful peripheral neuropathies are also reviewed.

Anterior interosseous nerve syndrome: retrospective analysis of 14 patients

INTRODUCTION

The anterior interosseous nerve (AIN) is a only motor nerve innervating the deep muscles of the forearm. Its compression is rare. We present a retrospective analysis of 14 patients with an AIN syndrome with a variety of clinical manifestations who underwent operative and conservative treatment.

PATIENTS AND METHODS

Fourteen patients (six female, eight male, mean age 48 ± 9 years) were included. In six patients, the right limb was affected, and in eight patients the left limb. Conservative treatment was started for every patient. If no signs of recovery appeared within 3 months, operative exploration was performed. Final assessment was performed between 2 and 9 years after the onset of paralysis (mean duration of follow-up 46 ± 11 months). Patients were examined clinically for return of power, range of motion, pinch and grip strengths. Also the disability of the arm, shoulder, and hand (DASH) score was calculated.

RESULTS

Seven of our 14 patients had incomplete AIN palsy with isolated total loss of function of flexor pollicis longus (FPL), five of FPL and flexor digitorum profundus (FDP)1 simultaneously, and two of FDP1. Weakness of FDP2 could be seen in four patients. Pronator teres was paralysed in two patients. Pain in the forearm was present in nine patients. Four patients had predisposing factors. Eight patients treated conservatively exhibited spontaneous recovery from their paralysis during 3-12 months after the onset. In six patients, the AIN was explored 12 weeks after the initial symptoms and released from compressing structures. Thirteen patients showed good limb function. In one patient with poor result a tendon transfer was necessary. The DASH score of patients treated conservatively and operatively presented no significant difference.

CONCLUSION

AIN syndrome can have different clinical manifestations. If no signs of spontaneous recovery appear within 12 weeks, operative treatment should be performed.