Anesthetic effect of ultrasound-guided block of the musculocutaneous nerve during endovascular treatment of dysfunctional radiocephalic arteriovenous fistulas.

BACKGROUND: Delivering requisite and minimal anesthesia for endovascular treatment (EVT) of dysfunctional arteriovenous fistulas (AVFs) under the target nerve block can achieve reasonable analgesia. We evaluated the anesthetic efficacy of ultrasound (US)-guided selective block of the musculocutaneous nerve (MCN) during the EVT of runoff venous strictures in the forearm through the radiocephalic (RC)-AVF at the wrist or the anatomical snuff box and analyzed the factors inhibiting the analgesia achieved under the MCN block. METHODS: We enrolled 30 adult patients undergoing hemodialysis who had received 78 EVT sessions in an outpatient clinic mainly for long and/or multiple outflow-venous strictures in the forearm under US-guided blocks of the MCN, which provides sensory innervation to the anterolateral forearm where the cephalic vein courses. We assessed patients' pain during balloon dilations using the Wong-Baker FACES® Pain Rating Scale (WBFRS) and evaluated the factors increasing the pain (WBFRS score ⩾4), including patient characteristics, dilated strictures, additional nerve blocks, and types of balloon catheters. RESULTS: In 25 EVT sessions (32.1%) out of 78 sessions, patients complained of stronger pain (WBFRS score ⩾4), while in the other 53 sessions (67.9%), presented with no pain and slight pain (WBFRS score = 0 or 2). Univariate analysis clarified that dilation of the AVF anastomosis, presence of dilated stenosis >4 cm, and a single block of the MCN or its sensory terminal significantly triggered more pain (p < 0.05). Consequently, multivariate analysis of all the factors with p < 0.1 in the univariate analysis, including multiple dilated stenosis sites, demonstrated that dilation of the AVF anastomosis significantly caused severe pain despite the anesthesia of the MCN block (p < 0.05). CONCLUSION: US-guided selective block of the MCN could be a leading anesthetic option for EVT for multiple long stenoses of the cephalic vein draining through the RC-AVF in the wrist or anatomical snuff box.

Fentanyl sparing effect of ultrasound-guided proximal radial, ulnar, median, and musculocutaneous nerve (RUMM) block for radial and ulnar fracture repair in dogs: a retrospective case-control study.

This study retrospectively evaluated the fentanyl-sparing effect of ultrasound-guided proximal radial, ulnar, median, and musculocutaneous nerve (RUMM) block for radial and ulnar fracture repair in dogs. Fentanyl was prepared for intraoperative analgesia in dogs, although proximal RUMM block was performed using 0.5% or 0.25% bupivacaine before surgery in the block group. Dogs without a nerve block were assigned to the control group. The fentanyl dose in the block group [0.8 (0-1.9) µg/kg/hr] [median (interquartile range)] was significantly lower than in the control group [8.4 (7.2-10) µg/kg/hr]. Surgery was performed without fentanyl in >50% of the dogs (5/7), using 0.5% bupivacaine. Ultrasound-guided proximal RUMM block can be useful as an intraoperative analgesic for radial and ulnar fracture repair in dogs.

Comparing Electrical Stimulation With and Without Ultrasound Guidance for Phenol Neurolysis to the Musculocutaneous Nerve.

BACKGROUND: Ultrasound guidance is increasingly being used for neurolytic procedures that have traditionally been done with electrical stimulation (e-stim) guidance alone. Ultrasound visualization with e-stim-guided neurolysis can potentially allow adjustments in injection protocols that will reduce the volume of neurolytic agent needed to achieve clinical improvement. OBJECTIVE: This study compared e-stim only to e-stim with ultrasound guidance in phenol neurolysis of the musculocutaneous nerve (MCN) for elbow flexor spasticity. We also evaluated the ultrasound appearance of the MCN in this population. DESIGN: Retrospective review. SETTING: University hospital outpatient clinic. PARTICIPANTS: Adults (N = 167) receiving phenol neurolysis to the MCN for treatment of elbow flexor spasticity between 1997 and 2014 and adult control subjects. METHODS: For each phenol injection of the MCN, the method of guidance, volume of phenol injected, technical success, improved range of motion at the elbow postinjection, adverse effects, reason for termination of injections, and details of concomitant botulinum toxin injection were recorded. The ultrasound appearance of the MCN, including nerve cross-sectional area and shape, were recorded and compared between groups. MAIN OUTCOME MEASURES: The volume of phenol injected and MCN cross-sectional area and shape as demonstrated by ultrasound. RESULTS: The addition of ultrasound to e-stim-guided phenol neurolysis was associated with lower doses of phenol when compared to e-stim guidance alone (2.31 mL versus 3.69 mL, P < .001). With subsequent injections, the dose of phenol increased with e-stim guidance (P < .001), but not with e-stim and ultrasound guidance (P = .95). Both methods of guidance had high technical success, improved ROM at elbow postinjection, and low rates of adverse events. In comparing the ultrasound appearance of the MCN in patients with spasticity to that of normal controls, there was no difference in the cross-sectional area of the nerve, but there was more variability in shape. CONCLUSIONS: Combined e-stim and ultrasound guidance during phenol neurolysis to the MCN allows a smaller volume of phenol to be used for equal effect, both at initial and repeat injection. The MCN shape was more variable in individuals with spasticity; this should be recognized so as to successfully locate the nerve to perform neurolysis. LEVEL OF EVIDENCE: IV.

Evaluation of the relationship between the topographical anatomy in the axillary region of the brachial plexus and the body mass index.

To investigate the topographic anatomy of the median, musculocutaneous, radial and ulnar nerves with respect to the axillary artery and to seek whether these configurations are associated with baseline descriptive data including age, gender, and body-mass index. This cross-sectional trial was carried out on 199 patients (85 women, 114 men; average age: 46.78 ± 15.45 years) in the department of anaesthesiology and reanimation of a tertiary care center. Topographic anatomy of the median, musculocutaneous, radial and ulnar nerves was assessed with ultrasonography. Localization of these nerves with respect to the axillary artery was marked on the map demonstrating 16 zones around the axillary artery. Frequencies of localizations of every nerve in these zones were recorded, and the correlation of these locations with descriptive data including age, gender and BMI was investigated. There was no difference between women and men for the distribution of the median (p = 0.74), ulnar (p = 0.35) and radial (p = 0.64) nerves. However, the musculocutaneous nerve was more commonly located in Zone A13 in men compared to women (p = 0.02). The localization of the median (p = 0.85), ulnar (p = 0.27) and radial (p = 0.88) nerves did not differ remarkably between patients with BMI < 25 kg/m2 and patients with BMI ≥ 25 kg/m2. Notably, the musculocutaneous nerve was more often determined in Zone A10 in cases with BMI ≥ 25 kg/m2 (p = 0.001). Our results imply that the alignment of the musculocutaneous nerve may vary in men and overweight people. This fact must be considered by the anaesthetist before planning the axillary block of brachial plexus. All these informations may enlighten the planning stages of the brachial plexus blockade.

Preoperative ultrasound for runoff-venous decompression of peripheral nerves for arteriovenous access-related pain in the upper limb.

INTRODUCTION: Arteriovenous access (AVA)-related pain treated successfully with runoff-venous decompression of the causative nerve, following ultrasound (US)-assisted preoperative evaluation, has never been reported. CASE PRESENTATION: A 57-year-old man suffering from constant exhausting pains along the outflow cephalic vein of the radiocephalic arteriovenous fistula at the wrist and the antecubital fossa, was treated surgically after the diagnosis of AVA-related pain derived from cephalic vein compression on two peripheral cutaneous nerves, the superficial radial nerve (SRN) and the lateral antebrachial cutaneous nerve (LACN). TECHNIQUE: The SRN and LACN, which ran along and/or provided sensory innervation to the painful regions in the upper limb, were traced using ultrasonography in the short axis and proved to be compressed by and in contact with veins where the pain existed, at the wrist and the antecubital fossa. Once diagnostic US-guided blocks of both were performed and pain disappeared, they were identified as the causative nerves. The cephalic venous decompression surgeries that separated and transposed the veins away from the SRN and the LACN were performed sequentially under pneumatic tourniquet inflation to improve nerve visualization. RESULTS: The pains disappeared after the operations. An adequate length of the runoff cephalic vein was maintained for needle cannulations during hemodialysis. CONCLUSIONS: Outflow venous compression to the peripheral nerves may be a cause of AVA-related pain. US-guided assessments of the nerves may improve the safety and efficiency of venous decompression surgeries to treat AVA-related pains.

The relationship of the musculocutaneous nerve to the brachial plexus evaluated by MRI.

Axillary plexus blocks (AXB) are widely used for upper limb operations. It is recommend that AXB should be performed using a multiple injection technique. Information about the course and position of the musculocutaneous nerve (MCN) is of relevance for AXB performance. The objective of this study was to examine the position of the MCN and its relationship to the axillary sheath using MRI. 54 patients underwent an AXB with 40 ml of local anaesthetic before MRI examination. The course of the MCN and the position where it left the axillary sheath and perforated the coracobrachial muscle (MCN exit point), in relation to the axillary artery and the block needle insertion point in the axillary fold, were recorded. The MCN was seen clearly in 23, partly in 26, and not identified in five patients at the MCN exit point. The mean distance from the insertion point of the block needle in the axillary fold to the MCN exit point was 36.8 mm (SD = 18.9, range: 0-90.5). In 37 patients the MCN exit point was positioned inside the Q1 quadrant (lateral anterior to the axillary artery) and in 11 patients inside the Q2 quadrant (medial anterior to the axillary artery). There is a wide variability as to where the musculocutaneous nerve (MCN) leaves the axillary sheath. Therefore multiple injection techniques, or the use of a proximally directed catheter, should be appropriate to block the MCN.

Shoulder position influences the location of the musculocutaneous nerve in the axillary fossa.

In the axillary fossa, the musculocutaneous nerve (MC) is generally distant from the axillary artery and from the other brachial plexus nerves. In that way, MC requires a specific block. We observed that the location of MC is influenced by the position of the patient's arm and shoulder. Abduction of the shoulder significantly reduced the distance between the MC and the axillary artery. This change in the location of the MC is probably due to the moving of the nerve because of muscle rearrangements and the ability to achieve better proximity of the probe in the axillary fossae.

Ultrasound-Guided Musculocutaneous Nerve Block in Postherpetic Neuralgia.

Postherpetic neuralgia is a common and challenging complication of herpes zoster infection, particularly in older people. In recent decades, first-line treatments, including oral or topical medication, have become well established. However, few studies have reported the efficacy of interventional procedures for the treatment of postherpetic neuralgia. Here, the authors present a case of intractable postherpetic neuralgia treated with musculocutaneous peripheral nerve block under ultrasound guidance. Symptoms remained controlled at 1 mo follow-up. Ultrasound can be readily applied to improve the accuracy and efficiency of peripheral nerve block as it is currently widely used to evaluate the musculoskeletal system in clinical settings.

Sonographic tracking of the upper limb peripheral nerves: a pictorial essay and video demonstration.

Ultrasound has been the most useful imaging tool for musculoskeletal disorders whereby peripheral nerve lesions constitute a substantial portion. High-resolution ultrasound enables elaboration of peripheral nerve morphology and reciprocal anatomy. However, limited literature is available for delineating standard positions and tracking skills. The present article incorporates a series of ultrasound images and videos to demonstrate how to scan the suprascapular, axillary, musculocutaneous, median, ulnar, and radial nerves. Overall, the authors aim to demonstrate the relevant nerve tracking techniques as regards the upper extremity.

Ultrasound imaging of the musculocutaneous nerve of infants, preschool children, and school children.

The purpose of this imaging study was to investigate whether the musculocutaneous nerve could be visualized ultrasonographically in childhood and to assess how its visualization changes with age. Forty-two children participated in this prospective imaging study. The musculocutaneous nerve was sought both proximally (near the axillary artery) and distally (within the coracobrachialis muscle) by use of an linear ultrasound probe. Location of the musculocutaneous nerve was good (93 %) for all the children, both proximally and distally. For school-aged children, distal visualization of the musculocutaneous nerve reached 100 %. The musculocutaneous nerve is detectable in childhood by use of ultrasonography; success of detection was high for all the age groups examined.

Sonography of the lateral antebrachial cutaneous nerve with magnetic resonance imaging and anatomic correlation.

OBJECTIVES: Abnormalities of the lateral antebrachial cutaneous nerve (LABCN) are associated with antecubital elbow conditions, such as distal biceps brachii tendon tears and traumatic cephalic vein phlebotomy. These can lead to lateral forearm, elbow, and wrist symptoms that can mimic other disease processes. The purpose of this study was to characterize the sonographic appearance of the LABCN using cadaveric dissection and retrospective analysis of sonographic examinations of symptomatic patients with magnetic resonance imaging correlation. METHODS: For the first part of this study, a cadaveric elbow specimen was examined, and sonography was performed after dissection to identify the LABCN. Subsequently, 26 elbows in 13 patients with LABCN abnormalities were identified with sonography and retrospectively evaluated to characterize the appearance of the LABCN in both symptomatic and asymptomatic elbows. RESULTS: The symptomatic LABCNs showed fusiform enlargement, increased echogenicity, and loss of the normal fascicular echo texture. The mean cross-sectional area of the symptomatic nerves was 12.0 mm(2) (range, 6.1-17.2 mm(2)), with a maximum thickness of 3.5 mm (range, 2.3-5.9 mm), compared to 3.3 mm(2) (range, 1.9-5.2 mm(2)), with a maximum thickness of 1.3 mm (range, 0.9-2.2 mm), in the contralateral normal elbows. CONCLUSIONS: The close proximity of the LABCN to the distal biceps tendon and the cephalic vein makes it vulnerable to compression and injury in the setting of distal biceps tendon tears and traumatic phlebotomy, which may cause nerve enlargement and increased echogenicity. Awareness of the location and appearance of the LABCN on sonography is important for determining potential causes of lateral elbow and forearm pain.

[Ultrasound-guided axillary block: anatomical variations of terminal branches of the brachial plexus in relation to the brachial artery]. / Bloqueo axilar ecoguiado: variaciones anatómicas de la disposición de los 4 nervios terminales del plexo braquial en relación con la arteria humeral.

OBJECTIVES: To describe the distribution of the terminal branches of the brachial plexus at the axillary level and define distribution patterns after ultrasound evaluation. MATERIAL AND METHOD: Fifty volunteers underwent ultrasound bilateral axillary brachial plexus scanning exploration. Nerve distribution around the humeral artery was described and the distance between each nerve and the center of the artery was measured. The distance and relationship between the ulnar nerve and the humeral vein were also recorded. RESULTS: The median nerve was located in the anterolateral quadrant (-29±40°) and at a mean distance of 2.1±0.9mm from the artery (85%). The ulnar nerve was found at 53±26° and at 4.2±2.1mm from the artery in the anteromedial quadrant (90%), anterolateral to the vein in 46% of cases, and deep to it in 54%. The radial nerve was at 122±38° and at 3.3±1.7mm from the artery in the posteromedial quadrant (86%). The musculocutaneous nerve was found at -103±22° and 9.3±5.6mm from the artery in the posterolateral quadrant (90%) and in the anterolateral quadrant (-55±16°) at 4.8±2.7mm (10%). There were no differences regarding laterality, gender or overweight patients. CONCLUSIONS: Our results allow defining four different anatomical patterns, two based in the position of the musculocutaneous nerve and two based on the disposition of the ulnar nerve with respect to the humeral vein. These patterns were not related to laterality, gender or body weight.

Ultrasound guided alcohol neurolysis of musculocutaneous nerve to relieve elbow spasticity in hemiparetic stroke patients.

Proper management of elbow spasticity is important in stroke rehabilitation. We investigated the effect and safety of ultrasound guided alcohol neurolysis of the MC nerve for controlling elbow flexor spasticity in hemiparetic stroke patients. Ten hemiparetic stroke patients with severe elbow spasticity were recruited for this study. We identified the MC nerve using ultrasound and performed neurolysis with 35% ethyl alcohol. The severity of spasticity was assessed using the modified Ashworth scale (MAS) score and associated reaction (AR) of elbow flexor. During the 2 months follow-up period, both MAS score and AR were reduced in all 10 patients. Before treatment, the mean MAS score was 3.4 ± 0.5, and this improved to 0.1 ± 0.3 immediately post-neurolysis, 1.8 ± 1.0 at one month and 1.9 ± 0.8 at two months (p < 0.001). The mean change of AR of the affected elbow was significantly decreased, from 75.2 ± 30.0° before neurolysis to 24.8 ± 21.3° immediately post-neurolysis, 35.5 ± 24.7° at 1 month and 40.8 ± 25.1° at 2 months (p < 0.001). Ultrasound guided MC nerve block is an effective and safe procedure for relieving localized spasticity of the elbow flexor.

Skin temperature measured by infrared thermography after specific ultrasound-guided blocking of the musculocutaneous, radial, ulnar, and median nerves in the upper extremity.

BACKGROUND: Sympathetic block causes vasodilatation and increases in skin temperature (T(s)). However, the T(s) response after specific nerve blocking is unknown. In this study, we hypothesized that T(s) would increase after specific blocking of the nerve innervating that area. METHODS: Forty-six patients undergoing hand surgery were included. We performed ultrasound-guided, specific nerve blocking of either the musculocutaneous, radial, ulnar, or median nerve in each patient and analysed T(s) in the forearm and hand at 2 min intervals in the following 22 min by the use of infrared thermography. Areas of interest corresponding to the cutaneous innervation area of each of the four nerves were defined and the mean T(s) in each area was analysed. RESULTS: Specific blocking of the ulnar and median nerves caused a substantial increase in mean (sd) T(s) in the areas innervated by these nerves [5.2 (3.2)°C and 5.1 (2.5)°C, respectively; both P<0.0001]. The increase was even larger at the fingertips. Median nerve blocking also increased T(s) in the area of the hand innervated by the radial nerve (P<0.0001). However, T(s) did not increase in any area after either musculocutaneous or radial nerve blocking. CONCLUSIONS: Specific blocking of the ulnar and median nerve causes substantial increases in T(s) in specific areas of the hand. In contrast, the specific blocking of the musculocutaneous or radial nerve does not increase T(s). Further studies are needed to clarify if these findings can be used to objectively evaluate brachial plexus block success.