Median Nerve's Microcirculation in Carpal Tunnel Syndrome: Superb Microvascular Imaging.

BACKGROUND: The objectivity of physical and electrodiagnostic tests is limited in detecting carpal tunnel syndrome and its recurrence. Predicting the median nerve blood supply using superb microvascular imaging will allow exact diagnosis and a good follow-up system. The aims of this study include using superb microvascular imaging to correlate with electromyographic diagnosis, and to determine the impact of surgery on improvement in superb microvascular imaging. METHODS: Between July of 2019 and January of 2020, 32 wrists of 21 patients were evaluated prospectively. After preoperative electrodiagnostic studies and vascular index measurement with superb microvascular imaging, open carpal tunnel release was performed by a single surgeon, and 3 months later standardized superb microvascular imaging was performed. Preoperative vascular indexes were compared with the mild, moderate, and severe electrodiagnostic study results. Preoperative and postoperative vascular index results were compared. RESULTS: The average of the preoperative and postoperative imaging groups was 2.77 and 1.48, respectively, and there was a statistically significant difference between the two groups (p < 0.05). Although no significant difference was found between preoperative and postoperative vascular index values in patients presenting with mild carpal tunnel syndrome (p > 0.05), there was a significant decrease in vascular index values in patients presenting with moderate and severe carpal tunnel syndrome after surgical decompression. CONCLUSIONS: Superb microvascular imaging is emerging as a groundbreaking, new, and reliable technique. Evaluation of the median nerve blood supply is a reliable method that would be helpful for early diagnosis, planning treatment, determining the severity of carpal tunnel syndrome, and postoperative follow-up. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, IV.

[Acute carpal tunnel syndrome caused by a thrombosis of a persistent median artery: 2 case reports]. / Canal carpien aigu : penser à la thrombose de l'artère persistante du nerf médian !

Carpal tunnel syndrome is a common peripheral neuropathy, usually idiopathic or post-traumatic due to the compression of the median nerve. Numbness and paresthesias in the median nerve distribution are the most common symptoms associated with this condition. Persistent median artery is a rare anatomic variation, thrombosis of this additional artery can be responsible for an acute carpal tunnel syndrome, and patients frequently complain about coldness and acute hand swelling. These unusual features must lead clinicians to think of a vascular cause. The diagnosis can be easily confirmed by using ultrasound doppler, but CT-scan and MRI are sometimes helpful. We describe 2 cases of acute carpal tunnel syndrome due to thrombosed persistent median artery, including a case of thromboangiitis obliterans. These thrombosis might also be due to traumatic causes. No guidelines are currently available to help physicians for the management of carpal tunnel syndrome from thrombosed persistent median artery. Antiplatelet therapy, statin, anticoagulant might be helpful, and surgery has sometimes be reported as effective.

Neural Perforasomes of the Upper Extremity.

BACKGROUND: In the setting of the rapid advancement of integumentary vascular knowledge, the authors hypothesized that the extrinsic blood supply to the major peripheral nerves of the upper extremity could be categorized into discrete neural "perforasomes." METHODS: Total limb perfusion of the arterial system was performed with gelatin-red lead oxide in cadaveric upper limbs. The perforating vessels to the radial, median, and ulnar nerves were identified, confirmed with fluoroscopy, and dissected. Distances to major anatomical landmarks of the upper extremity were measured. Additional cadaveric limbs' nerves were dissected and source arteries were selectively cannulated and injected to assess specific contribution to extrinsic nerve perfusion. The perfusion of each nerve was then calculated among all specimens. RESULTS: The radial, median, and ulnar nerve perforators were mapped. The corresponding neural perforasomes were mapped. The distal portions of the superficial radial nerve and the posterior interosseous nerve demonstrated a lack of staining. Similarly, at the carpal tunnel and at the proximal 25 percent of the median nerve (corresponding to the pronator teres), the nerve lacked vascular staining. At the Guyon canal and the flexor carpi ulnaris, the ulnar nerve demonstrated a lack of vascular staining. CONCLUSIONS: Peripheral nerves can be divided into neural perforasomes with limited overlap. The extrinsic perfusion of peripheral nerves is highly segmental. Absent stains within the nerves correspond to common sites of compression: carpal tunnel and pronator teres for the median nerve, supinator for the posterior interosseous nerve, and the Guyon canal and the flexor carpi ulnaris for the ulnar nerve.

Spontaneous Compartment Syndrome of the Hand in Systemic Sclerosis.

Compartment syndrome refers to a condition of compromised circulation within a limited space due to increased pressure within that space. The reduced tissue perfusion results in reduced venous drainage, leading to increased interstitial tissue pressure and subsequent compromised arterial flow. Although not as common as compartment syndrome of the leg and forearm, compartment syndrome of the hand is not rare and can lead to devastating sequelae as a result of tissue necrosis. Compartment syndrome of the hand has several etiologies, including trauma, arterial injury, thermal injury, and constrictive bandaging. The cardinal clinical sign is pain that is aggravated by passive stretching of the muscles within the involved compartments. Extremity function is usually restored with expeditious fasciotomy of the involved myofascial compartments, and complications, such as intrinsic muscular dysfunction and Volkmann's ischemic contracture, can usually be prevented. There are no reported cases of compartment syndrome of the hand in patients with systemic sclerosis or Raynaud's phenomenon. Systemic sclerosis is a form of scleroderma that affects the skin and internal organs. The limited cutaneous subset affects the skin of the extremities but is associated with a set of characteristic features that includes calcinosis, Raynaud's phenomenon, esophageal involvement, sclerodactyly, and telangiectasia. This report describes an unusual case of a patient who had spontaneous compartment syndrome of the hand. The patient's concomitant limited cutaneous systemic sclerosis may have played a role in this unusual occurrence. The diagnosis was based on the clinical picture, and the symptoms resolved after surgical decompression.

Ultrasound for diagnosis of carpal tunnel syndrome: comparison of different methods to determine median nerve volume and value of power Doppler sonography.

OBJECTIVE: To compare ultrasound measurement of median nerve cross-sectional area (CSA) at different anatomical landmarks and to assess the value of power Doppler signals within the median nerve for diagnosis of carpal tunnel syndrome (CTS). METHODS: A prospective study of 135 consecutive patients with suspected CTS undergoing two visits within 3 months. A final diagnosis of CTS was established by clinical and electrophysiological findings. CSA was sonographically measured at five different levels at forearm and wrist; and CSA wrist to forearm ratios or differences were calculated. Intraneural power Doppler signals were semiquantitatively graded. Diagnostic values of different ultrasound methods were compared by receiver operating characteristic curves using SPSS. RESULTS: CTS was diagnosed in 111 (45.5%) wrists; 84 (34.4%) had no CTS and 49 (20.1%) were possible CTS cases. Diagnostic values were comparable for all sonographic methods to determine median nerve swelling, with area under the curves ranging from 0.75 to 0.85. Thresholds of 9.8 and 13.8 mm(2) for the largest CSA of the median nerve yielded a sensitivity of 92% and a specificity of 92%. A power Doppler score of 2 or greater had a specificity of 90% for the diagnosis of CTS. Sonographic median nerve volumetry revealed a good reliability with an intraclass correlation coefficient of 0.90 (95% CI 0.79 to 0.95). CONCLUSIONS: Sonographic assessment of median nerve swelling and vascularity allows for a reliable diagnosis of CTS. Determination of CSA at its maximal shape offers an easily reproducible tool for CTS classification in daily clinical practice.

The vascularization of the median nerve in the distal forearm and its potential clinical importance.

PURPOSE: The aims of this anatomical study were to identify any extrinsic blood supply to the median nerve in the distal forearm and to measure the tension required to approximate the severed nerve after and before dissecting it while maintaining its extrinsic blood supply. METHODS: We injected the arterial system of 15 lightly embalmed forearms with red latex to define the vascular anatomy of the median nerve in the distal forearm. We measured the gap resulting from spontaneous retraction of the cut ends of the divided median nerve and the average tension needed to reapproximate the ends before and after resection of the attachments to the nerve on its superficial, deep, and ulnar aspects. RESULTS: A constant branch to the median nerve arises from the radial artery approximately 5 cm proximal to the radial styloid process. The mean gap between the severed nerve ends was 1.2 cm (range, 0.9-1.7 cm). The mean tension required to coapt the nerve ends was 231 g force (range, 200-280 g), reducing to 89 g force (range, 60-110 g) when only its radial attachments, including this vessel, were preserved. CONCLUSIONS: This cadaveric study suggests that it may be possible to advance the median nerve at the wrist while retaining the vascular connection and blood supply from the radial artery, and so maintain the vascularity of the nerve at the common site of nerve repair in the distal forearm. CLINICAL RELEVANCE: This cadaveric study identifies constant arterial feeding branches from the radial artery to the median nerve in the distal forearm, and is a preliminary investigation into the possibility of advancing the median nerve for repair in the distal forearm while maintaining the continuity of this branch.

Median nerve changes following steroid injection for carpal tunnel syndrome.

INTRODUCTION: Neuromuscular ultrasound is a painless, radiation-free, high-resolution imaging modality for assessment of the peripheral nervous system. The purpose of this study was to use neuromuscular ultrasound to assess the changes that occur in the median nerve after steroid injection for carpal tunnel syndrome (CTS). METHODS: Ultrasound and nerve conduction studies were performed at baseline and 1 week, 1 month, and 6 months after steroid injection in 19 individuals (29 wrists) with CTS. RESULTS: Significant changes were noted in median nerve cross-sectional area (P < 0.001), mobility (P = 0.001), and vascularity (P = 0.042) at the distal wrist crease after steroid injection, and the nerve cross-sectional area correlated with symptom score and electrodiagnostic parameters. Changes in the ultrasonographic parameters were seen within 1 week of injection. CONCLUSIONS: These findings suggest neuromuscular ultrasound is potentially helpful for the assessment of individuals undergoing treatment for CTS, as typical changes can be expected after successful treatment injection.

Mesenchymal stem cells in a polycaprolactone conduit enhance median-nerve regeneration, prevent decrease of creatine phosphokinase levels in muscle, and improve functional recovery in mice.

Although the majority of peripheral-nerve regeneration studies are carried out on the sciatic nerve, lesions of the upper extremities are more common in humans and usually lead to significant physical disabilities. The present study was driven by the hypothesis that a combination of strategies, namely grafts of mesenchymal stem cells (MSC) and resorbable polycaprolactone (PCL) conduits would improve median-nerve regeneration after transection. Mouse median nerves were transected and sutured to PCL tubes that were filled with either green fluorescent protein (GFP(+)) MSC in DMEM or with DMEM alone. During the post-operative period, animals were tested weekly for flexor digitorum muscle function by means of the grasping test. After 8 weeks, the proximal and middle portions of the PCL tube and the regenerating nerves were harvested and processed for light and electron microscopy. The flexor digitorum muscle was weighed and subjected to biochemical analysis for creatine phosphokinase (CK) levels. Scanning electron microscopy of the PCL tube 8 weeks after implantation showed clear signs of wall disintegration. MSC-treated animals showed significantly larger numbers of myelinated and unmyelinated nerve fibers and blood vessels compared with DMEM-treated animals. The flexor digitorum muscle CK levels were significantly higher in the MSC-treated animals, but muscle weight values did not differ between the groups. Compared with the DMEM-treated group, MSC-treated animals showed, by the grasping test, improved functional performance throughout the period analyzed. Immunofluorescence for S-100 and GFP showed, in a few cases, double-labeled cells, suggesting that transplanted cells may occasionally transdifferentiate into Schwann cells. Our data demonstrate that the polycaprolactone conduit filled with MSC is capable of significantly improving the median-nerve regeneration after a traumatic lesion.

Aberrant course of a communicating branch of the ulnar nerve to the median nerve contributing to hypothenar Hammer syndrome.

This presentation represents a unique anatomic predisposition to the development of hypothenar hammer syndrome (HHS). In this case, a communicating branch of the ulnar nerve to the median common digital nerve of the ring finger was identified crossing volar to the superficial palmar arch. This relationship caused thrombosis of the superficial palmar arch proximal to this crossing nerve branch. The aberrant course of this nerve created a structural anomaly contributing to HHS, which ultimately mandated surgical intervention.

Angiosome territories of the nerves of the upper limbs.

BACKGROUND: The use of free vascularized nerve grafts requires intimate knowledge of the blood supply of peripheral nerves. The authors aimed to demonstrate radiographically the topography of the upper limb nerves with their blood supply, and to examine them as an application of the angiosome concept. An angiosome is a three-dimensional block of composite tissue supplied by a single source artery. METHODS: This anatomical study involved the meticulous dissection of four fresh upper limb specimens injected intraarterially with a gelatin-lead oxide mixture. The nerves were tagged circumferentially with copper wire and radiographs were taken of the nerves with their arterial blood supply. The median, ulnar, radial, musculocutaneous, and axillary nerves were examined. RESULTS: The authors showed that the nerves of the upper limb were supplied segmentally by source vessels, which reinforced the angiosome concept. The suitability of each nerve for harvest in free vascularized nerve transfer was assessed according to its pattern of blood supply. CONCLUSIONS: The authors' work has a wide range of clinical applications and provides an anatomical basis for neurovascular and neurocutaneous flaps and free vascularized nerve grafting.

Occurrence and fate of palmar type of median artery.

BACKGROUND: The median artery represents a persistent part of the embryonic arterial axis of the upper extremity. It appears mainly as two types: an antebrachial type and a palmar type. The palmar type is of major clinical significance. METHOD: This study was undertaken to investigate the incidence and fate of the palmar type of the median artery in 19 cadavers. The occurrence was 15.8% and of this two incidences (5.2%) were on the right side and four (10.6%) were on the left side. On the right side, the artery originated from the ulnar and joined with the superficial palmar arch or anterior interosseous artery and communicated with the radial artery. CONCLUSIONS: This study concludes that palmar type of median artery is found at a higher incidence than the antebrachial type and that it may be involved in the pronator teres syndrome, carpal tunnel syndrome and anterior interosseous syndrome.

Responses of human sensory and motor axons to the release of ischaemia and to hyperpolarizing currents.

This study compared directly the post-ischaemic behaviour of sensory and motor axons in the human median nerve, focusing on the excitability changes produced by ischaemia and its release and by continuous polarizing DC. The decrease in threshold during ischaemia for 13 min was greater, the post-ischaemic increase in threshold was more rapid, and the return to the pre-ischaemic excitability took longer in sensory axons. However, a transient depolarizing threshold shift developed in sensory axons a few minutes after release of ischaemia. This pattern could not be reproduced by polarizing currents designed to mimic the probable pump-induced changes in membrane potential, even though the applied currents produced greater changes in threshold. Hyperpolarizing currents of equivalent intensity produced a greater increase in threshold for motor axons than sensory axons and, in studies of threshold electrotonus using graded hyperpolarizing DC, accommodation was greater in sensory than motor axons. The post-ischaemic changes in threshold were not uniform for axons of different threshold, whether sensory or motor, the threshold increase was usually less prominent for low-threshold axons. A transient post-ischaemic depolarization could be produced in motor axons with ischaemia of 20 min duration. Greater ischaemic and post-ischaemic changes in threshold for sensory axons could reflect greater dependence on the electrogenic Na+-K+ pump to maintain resting membrane potential and/or greater extracellular K+ accumulation in ischaemic sensory axons. Inward K+ currents due to extracellular K+ accumulation would then be more likely to trigger a depolarizing shift in membrane potential, the degree of K+ accumulation and pump activity being dependent on the duration of ischaemia. In sensory axons the greater tendency to accommodate to hyperpolarizing stimuli presumably contributes to shaping their post-ischaemic behaviour but is probably insufficient to explain why their behaviour differs from that of motor axons.

Measurement of median nerve blood flow during carpal tunnel release with laser Doppler flowmetry.

Eight consecutive median nerves in eight patients with clinical carpal tunnel syndrome were prospectively examined by non-contact laser Doppler flowmetry before and after undergoing carpal tunnel release. Before performing carpal tunnel release, the difference in the median nerve blood flow between the values at the distal and proximal portions to the transverse carpal ligament was statistically significant (p = 0.021). After carpal tunnel release, the median nerve blood flow both distal and proximal to the transverse carpal ligament increased by 1.5 and 1.3 times, respectively, compared to the flow prior to carpal tunnel release, however, only the difference at the distal portion to the transverse carpal ligament was statistically significant (p = 0.015). In this study, we directly measured the median nerve blood flow using non-contact laser Doppler flowmetry and thus demonstrated a significant difference in the median nerve blood flow between the values at the distal and proximal portions to the transverse carpal ligament before carpal tunnel release and a significant increase in the nerve blood flow only at the distal portion to the transverse carpal ligament after surgery. This technique is thus considered to be an easy and reproducible way to intraoperatively evaluate the nerve blood flow in real time during the release of entrapment neuropathies.

Conduction block in vasculitic neuropathy.

Vasculitis involving peripheral nerves usually presents as an acute asymmetrical axonal neuropathy. We report a 67-year-old man with a symmetrical subacute neuropathy in which nerve conduction studies showed prominent conduction block, a finding indicative of demyelination. Sural nerve biopsy showed a vasculitic neuropathy with invasion of blood vessel walls by inflammatory cells and a mixture of nerve fiber loss and demyelination. The demyelination in this case was presumably a consequence of subinfarctive nerve ischemia.

A comparison of immediate and delayed nerve repair using autologous freeze-thawed muscle grafts in a large animal model. The simple injury.

Freeze-thawed muscle grafts (FTMG) have been suggested as an alternative to nerve grafts in reconstruction of peripheral nerve defects. This study compares the results of immediate and delayed nerve repair with freeze-thawed muscle graft in a large animal model. Under general anaesthesia, ten adult sheep underwent excision of 3 cm of the right median nerve. Five had immediate nerve reconstruction with FTMGs (Group A) and five were repaired after 4 weeks (Group B). At 6 months, both the right (repaired) and left ("control") median nerves of each sheep were assessed. Nerve blood flow distal to the graft in both groups of repaired nerves was approximately 60% of that in their respective control nerves. Peak nerve conduction velocities were significantly slower in the repaired nerves. The mean fibre diameters of the immediate and delayed repairs were 5.06 and 3.90 mu respectively compared to a control mean of 8.58 mu. G-ratios confirmed that the repaired nerves in both groups were well myelinated. The authors conclude that the FTMG can be used in delayed as well as immediate nerve reconstruction with minimal impairment of final results.

Brachial plexus stretching injuries: microcirculation of the brachial plexus.

This study was undertaken to investigate the pathogenesis of brachial plexus stretching injuries at an intensity level not severe enough to cause avulsion injury. While we performed traction on 64 forelegs of 32 rats, we evaluated changes in the blood flow in the extrinsic and intrinsic microvascular systems of the brachial plexus. While we laterally stretched the brachial plexus during 80 degree shoulder abduction, we measured the blood flow at the bifurcation of the brachial plexus and at the median nerve with the hydrogen washout technique. During weak traction the blood flow decreased markedly in the extrinsic system, causing an imbalance in the two systems. In the median nerve, however, no such imbalance occurred. On histologic examination the axon and myelin in the brachial plexus and the median nerve showed no morphologic change. However, in parts of the brachial plexus we noted hypertrophic connective tissue or granulomatous inflammation in tissue surrounding the extrinsic system. The extrinsic system's apparent susceptibility to injury by acute traction may be a factor in the pathogenesis of the brachial plexus stretching injuries.

Acute carpal tunnel syndrome secondary to thrombosis of a persistent median artery

An ususual case of thrombosis of a persistent median artery as a cause of acute carpal tunnel syndrome is reported. The sudden onset of numbness in the median nerve distribution and pain in the fingers were main symptoms. The embryonic development of the median nerve vascular supply and the reported incidence of persistent median artery are reported

Vascular filling and protein extravasation in three varieties of vascularized venous nerve grafts.

The purpose of this study was to compare the microcirculation perfusion and plasma-protein extravasation in varieties of venous nerve grafts. Venous nerve grafts were created from the left median nerve and brachial vein of the rabbit. The vein was interposed between (a) brachial artery to brachial artery (AVA); or (b) brachial artery to proximal cephalic vein (AVV); or (c) brachial vein to brachial vein (VVV). A standard, vascularized, nerve graft was created in the opposite limb, to serve as a control, and the untouched sciatic nerve served as a second control. Microcirculation perfusion and permeability of endoneurial vessels were evaluated using intravenously-injected albumin labelled with Evans blue dye (EBA) as a fluorescent tracer within 1 hr after surgery. Six hours after surgery, the nerves were removed and evaluated for tracer content and distribution. Extravasation of EBA was extensive in both AVA and AVV forms of the venous nerve graft, suggesting good perfusion but showing significant protein leakage and edema. VVV, on the other hand, had only slight extravasation, comparable to untouched sciatic nerves. Although the number of vessels filled with blood in the VVV was 69 percent of the vascularized nerve graft, the lack of marked extravasation may make it the venous nerve graft of choice.