Proximal Median Nerve Compression: Pronator Syndrome

Lacertus syndrome: recent advances

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

Pronator syndrome and anterior interosseous nerve palsy due to neurolymphomatosis: a case report

Pronator syndrome is a median nerve entrapment neuropathy that can be difficult to diagnose due to its variable presentation and objective findings. Neurolymphomatosis is an uncommon disease in which malignant lymphocytes infiltrate central or peripheral nerve endoneurium and is often missed for prolonged periods prior to diagnosis. We present a rare case of pronator syndrome and anterior interosseous nerve palsy due to neurolymphomatosis that was occult on initial MRI in spite of the presence of a median nerve mass discovered intra-operatively during neurolysis. This case demonstrates the value of ultrasound for the examination of peripheral nerve pathology and illustrates its utility as an adjunct to MRI, in part due to the ability to screen a large region.

Intraosseous Nontraumatic Median Nerve Entrapment at the Elbow: A Case Report

Intraosseous median nerve entrapment at the level of the elbow can occur after a traumatic event such as fracture and/or dislocation of the elbow. It is considered a rare and severe entity. We present a rare case of nontraumatic median nerve entrapment inside the distal humerus. No article about atraumatic intraosseous entrapment was encountered in literature.

The prevalence of double- and multiple crush syndromes in patients surgically treated for peripheral nerve compression in the upper limb

OBJECTIVE

The double crush syndrome describes a condition characterized by multifocal entrapment of a nerve. In the upper limb, the high prevalence of carpal tunnel syndrome makes it a common diagnosis of assumption in the setting of median neuropathy. More proximal compressions may tend to be overlooked, under-diagnosed and under-treated in the population. This study aims to map the prevalence of peripheral upper limb nerve compressions among patients undergoing peripheral nerve decompression.

METHODS

A prospective case series was conducted on 183 patients undergoing peripheral nerve decompression in a private hand surgery clinic. Level(s) of nerve compression in the median, ulnar and radial nerves were determined by history and physical examination. The prevalence of each nerve compression syndrome or combination of syndromes was analyzed.

RESULTS

A total of 320 upper limbs in 183 patients were analyzed. A double crush of the median nerve at the levels of the lacertus fibrosus and carpal tunnel was identified in 78% of upper limbs with median neuropathy, whereas isolated lacertus syndrome and carpal tunnel syndrome were present in only 5% and 17% of affected limbs respectively. Cubital tunnel syndrome affected 12.5% of upper limbs, and 80% of these had concomitant lacertus and carpal tunnel syndromes, compared to only 7.5% with isolated cubital tunnel syndrome.

CONCLUSION

A high prevalence should prompt clinicians towards more routine assessment for double crush syndrome to avoid misdiagnosis, inadequate treatment, recurrence, and revision surgeries.

Intraoperative immediate strength recovery following lacertus fibrosus release in patients with proximal median nerve compression at the elbow

PURPOSE

In the literature, we find that patients with lacertus syndrome (LS), proximal median nerve compression at the elbow, present subjective improvement of thumb, and index flexion strength after lacertus fibrosus (LF) release. The aim of this study is to objectively evaluate the immediate change in intraoperative flexion strength after LF release.

METHOD

We retrospectively reviewed prospectively collected data of a cohort of 24 patients with a double crush syndrome of the median nerve with no response to conservative treatment. All patients had surgery with LF and carpal tunnel release (CTR) under wide-awake local anaesthesia and no tourniquet (WALANT) and were evaluated intraoperatively with a dynamometer immediately before and after LF release. Flexor digitorum profundus of the second finger (FDP2) and Flexor pollicis longus (FPL) were tested in peak strength to failure. The primary outcome was the percentage of change in strength before and after the release in both assessed muscles. CTR was done after evaluating the change in flexor strength.

RESULTS

A percentage of 79.2 women with an average age of 43.3 years. The average strength of FDP2 before LF release was 15.5 pounds (lbs.) (7.0 kg) (SD, 7.2 lbs (3.3 kg)) and 27.1 lbs. (12.2 kg) (SD, 7.1 lbs. (3.2 kg)) after LF release, which corresponds to a 96% (SD, 70%) change in strength (p=0.000). For FPL, the average pre-release strength was 17.7 lbs. (8.0kg) (SD, 4.8 lbs. (2.2 kg)) and 27.4 lbs. (12.4 kg) (SD, 5.2 lbs. (2.4 kg)) post-release, this corresponded to a 65% (SD, 38%) change in strength (p=0.000).

CONCLUSIONS

Peak strength to failure in FDP2 and FPL has an immediate significant recovery after LF surgical release in patients with Lacertus syndrome.

LEVEL OF EVIDENCE

IV, retrospective study.

Management of Failed Carpal and Cubital Tunnel Release: An Evidence-Based Guide to Success

Carpal tunnel and cubital tunnel syndromes are the most common compressive neuropathies of the upper extremity with surgical treatment having high success rates for both conditions. Although uncommon, persistent or recurrent carpal and cubital tunnel syndrome presents a challenge for patients and providers. Diagnosis of persistence versus recurrence of the pathology is key in establishing an appropriate treatment plan to provide the best possible patient outcomes. After an established diagnosis, a wide array of treatment options exist which varies based on previous procedures performed. This review discusses relevant anatomy, etiology, and clinical presentations of persistent and recurrent carpal and cubital tunnel syndromes. The range of treatment options is presented based on history and diagnostic findings. Treatment options span from revision of nerve decompression to the use of soft tissue rearrangement procedures. Some specific treatment options discussed include simple revision nerve decompression, external neurolysis, soft tissue rearrangement, such as the hypothenar fat flap or various transposition techniques, and the use of nerve wraps. Included is an evidence-based management guide for diagnosis and treatment of persistent versus recurrent carpal and cubital tunnel syndromes.

Lacertus syndrome: a ten year analysis of two hundred and seventy five minimally invasive surgical decompressions of median nerve entrapment at the elbow

PURPOSE

This study aims to assess the clinical presentation and surgical outcomes of lacertus syndrome (LS) and concomitant median nerve entrapments.

METHODS

A retrospective study of prospectively collected data was conducted on patients undergoing lacertus release (LR) from June 2012 to June 2021. Available DASH (Disability of the Arm Shoulder Hand questionnaire) scores and post-operative Visual Analogue Scale (VAS) of pain, numbness, subjective satisfaction with surgical outcome, and intra-operative return of strength were analyzed.

RESULTS

Two-hundred-seventy-five surgical cases were identified of which 205 cases (74.5%) underwent isolated LR, and 69 cases (25.1%) concomitant lacertus and carpal tunnel release. The three most common presenting symptoms in LS patients were loss of hand strength (95.6%), loss of hand endurance/fatigue (73.3%), and forearm pain (35.4%). Numbness in the median nerve territory of the hand was found in all patients with combined LS and carpal tunnel syndrome. Quick-DASH significantly improved (pre-operative 34.4 (range 2.3-84.1) to post-operative 12.4 (range 0-62.5), p < 0.0001) as did work and activity DASH (p < 0.0001). The postoperative VAS scores were pain VAS 1.9 and numbness VAS 1.8. Eighty-eight percent of patients reported good/excellent satisfaction with the surgical outcome. Intra-operative return of strength was verified in 99.2% of cases.

CONCLUSION

LS is a common median nerve compression syndrome typically presenting with loss of hand strength and hand endurance/fatigue. Minimally invasive LR immediately restores hand strength, significantly improves DASH scores, and yields positive outcomes regarding VAS pain, numbness, and subjective satisfaction with surgery in patients with proximal median nerve entrapment at a minimum six month follow-up.

A Rare Case of Traumatic Acute Pronator Syndrome in the Setting of Anticoagulation Therapy

Pronator syndrome (PS) is a rare type of peripheral compression neuropathy in which the median nerve becomes entrapped as it passes through the pronator teres muscle at the proximal forearm. We report an unusual case of acute PS in a 78-year-old patient on warfarin who presented after traumatic forearm injury with forearm swelling, pain, and paresthesias. After emergent nerve decompression and hematoma evacuation, the patient regained near complete recovery of median nerve function six months after diagnosis and treatment.

Experience With Proximal Median Nerve Entrapment by the Lacertus Fibrosus

BACKGROUND

Unconscious bias of the clinician favors the diagnosis of carpal tunnel syndrome (CTS) in patients with median paresthesia. We hypothesized that more patients in this cohort would be diagnosed with proximal median nerve entrapment (PMNE) by strengthening our cognitive awareness of this alternative diagnosis. We also hypothesized that patients with PMNE may be successfully treated with surgical release of the lacertus fibrosus (LF).

METHODS

In this retrospective study, cases of median nerve decompression at the carpal tunnel and in the proximal forearm for the 2-year periods before and after adopting strategies to mitigate cognitive bias for CTS were enumerated. Patients diagnosed with PMNE and treated by LF release under local anesthesia were evaluated to determine surgical outcome at minimum 2-year follow-up. Primary outcome measures were changes in preoperative median paresthesia and proximal median-innervated muscle strength.

RESULTS

There was a statistically significant increase in PMNE cases identified after our heightened surveillance was initiated (z = 3.433, P < .001). In 10 of 12 cases, the patient had previous ipsilateral open carpal tunnel release (CTR) but experienced recurrent median paresthesia. In 8 cases evaluated an average of 5 years after LF release, there was improvement in median paresthesia and resolution of median-innervated muscle weakness.

CONCLUSIONS

Owing to cognitive bias, some patients with PMNE may be misdiagnosed with CTS. All patients with median paresthesia, particularly those with persistent or recurrent symptoms after CTR, should be assessed for PMNE. Surgical release limited to the LF may be an effective treatment for PMNE.

Effect of lacertus fibrosus release on perineural pressure of the median nerve at the elbow: a cadaveric study

PURPOSE

The lacertus fibrosus (or bicipital aponeurosis) is a potential site of proximal median neuropathy at the elbow. Lacertus syndrome with motor and/or sensory symptoms has been addressed with a minimally invasive surgical lacertus release. This study evaluates if a lacertus release alters the maximal perineural pressure (Pmax) of the median nerve at the level of the lacertus fibrosus during elbow flexion.

METHODS

Seven upper limbs from four fresh cadavers were included. Perineural pressure of the median nerve at the level of the lacertus fibrosus was measured continuously during automated elbow flexions by the biceps brachii muscle.

RESULTS

The mean Pmax before the lacertus release was significantly different than the mean Pmax after the lacertus release (669.15 mmHg vs 77.01 mmHg, p = 0.0180). The mean Pmax after the lacertus release decreased with an average 81.41%.

CONCLUSION

A simple surgical release of the lacertus fibrosus significantly decreases the maximal perineural pressure of the median nerve at the level of the lacertus fibrosus during elbow flexion.

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.

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.

Revision of Carpal Tunnel Surgery

Carpal tunnel release is one of the most commonly performed upper extremity procedures. The majority of patients experience significant improvement or resolution of their symptoms. However, a small but important subset of patients will experience the failure of their initial surgery. These patients can be grouped into persistent, recurrent, and new symptom categories. The approach to these patients starts with a thorough clinical examination and is supplemented with electrodiagnostic studies. The step-wise surgical management of revision carpal tunnel surgery consists of the proximal exploration of the median nerve, Guyon’s release with neurolysis, the rerelease of the transverse retinaculum, evaluation of the nerve injury, treatment of secondary sites of compression, and potential ancillary procedures. The approach and management of failed carpal tunnel release are reviewed in this article.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

A cadaveric descriptive study.

METHODS

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

RESULTS

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

CONCLUSION

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

Revision Peripheral Nerve Surgery of the Upper Extremity

Peripheral nerve injuries of the upper extremity can result from a wide array of etiologies, with the two most common being compression neuropathy and traumatic injuries. These types of injuries are common and can be psychologically, functionally, and financially devastating to the patient. A detailed preoperative evaluation is imperative for appropriate management. Traumatic injuries can typically be treated with local burial techniques, targeted muscle reinnervation, and regenerative peripheral nerve interfaces. Median nerve compression is frequently managed with complete release of the antebrachial fascia/transverse carpal ligament and/or use of flap coverage such as the hypothenar fat pad flap and local muscle flaps. Ulnar nerve compression is commonly managed via submuscular transposition, subcutaneous transposition, neurolysis, and nerve wrapping. In this review, we discuss the preoperative evaluation, surgical techniques, and advantages and disadvantages of each treatment modality for patients with compressive and traumatic upper extremity nerve injuries.