Cervical variations of the phrenic nerve

The Aberrant Origin of the Suprascapular Artery May Hide Neural Covariants: A Cadaveric Finding

The axillary artery is the continuation of the subclavian artery. Occasionally, some of the subclavian artery's distal branches may atypically originate from the axillary artery, such as the suprascapular artery. The suprascapular artery's distal (low) origin from the axillary artery, instead of the subclavian artery, may also be characterized as an aberrant suprascapular artery. The current cadaveric report describes the coexistence of an aberrant suprascapular artery (of axillary origin), variant course, and termination with atypically formatted nerves originating from the cervical (the phrenic nerve) and the brachial (the long thoracic and the median nerves) plexus. An unusual interconnection between the phrenic and the long thoracic nerves was also described. The aberrant suprascapular artery had an atypical termination below the superior transverse scapular ligament, along with the suprascapular vein and nerve. Except for the atypically formatted phrenic and long thoracic nerves, the aberrant suprascapular artery coexisted with an atypical passage of the anterior ramus of the C6 spinal nerve, through the middle scalene muscle, before the long thoracic nerve formation, and a variant formation of the median nerve. Understanding neurovascular variants is crucial for interventionists and surgeons who work in the supra- and infraclavicular areas. Being aware of the different origins of the brachial plexus branches, in the supraclavicular part, may help reduce the occurrence of iatrogenic axillary injury. Efforts should be made to expand the number of cadaveric studies that investigate the origin, course, interconnection, and branching patterns of these nerves and related covariants, in a systematic way, thus unifying their study and comprehension.

Targeting drug or gene delivery to the phrenic motoneuron pool

Phrenic motoneurons (PhrMNs) innervate diaphragm myofibers. Located in the ventral gray matter (lamina IX), PhrMNs form a column extending from approximately the third to sixth cervical spinal segment. Phrenic motor output and diaphragm activation are impaired in many neuromuscular diseases, and targeted delivery of drugs and/or genetic material to PhrMNs may have therapeutic application. Studies of phrenic motor control and/or neuroplasticity mechanisms also typically require targeting of PhrMNs with drugs, viral vectors, or tracers. The location of the phrenic motoneuron pool, however, poses a challenge. Selective PhrMN targeting is possible with molecules that move retrogradely upon uptake into phrenic axons subsequent to diaphragm or phrenic nerve delivery. However, nonspecific approaches that use intrathecal or intravenous delivery have considerably advanced the understanding of PhrMN control. New opportunities for targeted PhrMN gene expression may be possible with intersectional genetic methods. This article provides an overview of methods for targeting the phrenic motoneuron pool for studies of PhrMNs in health and disease.

Recovery from hemidiaphragmatic paralysis with improved respiratory function following cervical laminoplasty and foraminotomy: illustrative case

BACKGROUND

Hemidiaphragmatic paralysis can occasionally be caused by cervical canal and foraminal stenosis. Rarely is the effect of surgical decompression on hemidiaphragmatic paralyzed patient respiratory function recorded. This report details a case of postoperative respiratory function restoration in a patient with cervical spondylosis-related hemidiaphragmatic paralysis.

OBSERVATIONS

A 77-year-old woman suffered hemidiaphragmatic paralysis caused by cervical canal and foraminal stenosis. The phrenic nerve palsy was thought to be caused by compression of the cervical spinal cord and its nerve root. The patient received a C3 laminectomy, a C4-6 laminoplasty, and a left C3-4 and C4-5 posterior foraminotomy. After surgery, she improved her maximum inspiratory pressure and respiratory function.

LESSONS

Cervical canal and foraminal stenosis may cause hemidiaphragmatic paralysis due to radiculopathy-induced phrenic nerve palsy. Laminoplasty and posterior foraminotomy can restore respiratory dysfunction related to diaphragmatic paralysis by decompressing the ventral horn of the spinal cord and spinal nerve root.

Ultrasound-Guided Phrenic Nerve Block for Lung Nodule Biopsy: Single-Center Initial Experience

RATIONALE AND OBJECTIVES

Biopsy of lung nodules in the lower lung fields can be difficult because of breathing motion. Ipsilateral phrenic nerve block (PNB) before biopsy should make the biopsy safer, easier, and more precisely targeted. We describe the use of ultrasound-guided PNB before lung nodule biopsy, including relevant anatomy and variations, complications, and technique, along with our first 40 cases.

MATERIALS AND METHODS

We retrospectively reviewed patients who underwent PNB before computed tomography (CT)- or ultrasound-guided lung nodule biopsy from April 2015 through March 2020. Patient demographics, CT fluoroscopy time, radiation dose, complications, diagnostic yield, and effectiveness of PNB were recorded. Effectiveness of PNB was based on direct observation of diaphragmatic motion. Control group data for biopsies during the same time frame were collected and matched with nodules ≤1 cm from the PNB group.

RESULTS

Among 40 patients identified, no complications occurred related to the PNB. Mean (SD) nodule size was 12.4 (6.2) mm. True-positive results were obtained in 39 patients (98%), with 1 false-negative after an ineffective PNB. PNB was effective in 70%. When CT fluoroscopy was used for the biopsy, radiation dose was significantly lower after an effective PNB than an ineffective PNB (p < .001). Effective PNB was significantly more common with injection of ≥4 mL of local anesthetic (p = .01). Comparison with 19 matched controls showed significantly fewer instances of pneumothorax (p = .02) and greater diagnostic success (p = .03) for the PNB group.

CONCLUSION

Ultrasound-guided PNB is safe and effective and can improve outcomes when used before lung nodule biopsy.

The phrenic neuromuscular system

The phrenic neuromuscular system consists of the phrenic motor nucleus in the mid-cervical spinal cord, the phrenic nerve, and the diaphragm muscle. This motor system helps sustain breathing throughout life, while also contributing to posture, coughing, swallowing, and speaking. The phrenic nerve contains primarily efferent phrenic axons and afferent axons from diaphragm sensory receptors but is also a conduit for autonomic fibers. On a breath-by-breath basis, rhythmic (inspiratory) depolarization of phrenic motoneurons occurs due to excitatory bulbospinal synaptic pathways. Further, a complex propriospinal network innervates phrenic motoneurons and may serve to coordinate postural, locomotor, and respiratory movements. The phrenic neuromuscular system is impacted in a wide range of neuromuscular diseases and injuries. Contemporary research is focused on understanding how neuromuscular plasticity occurs in the phrenic neuromuscular system and using this information to optimize treatments and rehabilitation strategies to improve breathing and related behaviors.

Effects of Cervical Spine Mobilization on Respiratory Function and Cervical Angles of Stroke Patients: A Pilot Study

The forward head posture (FHP) of stroke patients has a negative impact on respiratory function. Cervical spine mobilization is a manual therapy technique that used to prevent and treat FHP and respiratory function. This pilot study investigated whether cervical spine mobilization can effectively improve outcomes following FHP and respiratory function of stroke patients. Twenty-four patients participated in our assessor-blinded randomized controlled trial. All the participants received neurodevelopmental treatments (gait training and trunk rehabilitation). The experimental group additionally received 15-min sessions of cervical spine mobilization three times per week for 4 weeks. The control group received cervical spine sham mobilization during the same period. For the cervical angles, the cranial vertebral angle (CVA) and cranial rotation angle (CRA) were measured. A respiratory function test was performed to measure the forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), peak expiratory flow (PEF), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and chest circumferences (upper and lower chest sizes). Except for MIP, there was no significant difference between the experimental group and the control group. The CVA and CRA were significantly increased in the experimental group only. Cervical spine mobilization improved cervical angles and inspiratory function of the stroke patients in this study. However, a comparative study with a larger number of patients is needed to confirm this finding from our pilot study, which had a small sample size.

[C5-6 nerve root block technique for postoperative analgesia of shoulder arthroscope: a randomized controlled trial]

OBJECTIVE

To compare the effects of ultrasound-guided interscalene brachial plexus block and C5-6 nerve root block for analgesia after shoulder arthroscopy.

METHODS

In the study, 40 patients of ASA I-II were selected for elective general anesthesia to repair the shoulder ligament rupture in Peking University Third Hospital, who were randomly divided into two groups, respectively for the intermuscular brachial plexus block group (group I) and C5-6 nerve root block group (group C), n=20. The forty patients underwent ultrasound-guided brachial plexus block or C5-6 nerve root block before general anesthesia. Group I: 0.2% ropivacaine 10 mL was injected into brachial plexus intermuscular approach; Group C: 0.2% ropivacaine 10 mL was injected around the nerve roots of C5 and C6, and the ultrasound images showed that the liquid wrapped nerve roots. The time of sensory and motor block after puncture, operation time, the time of postoperative analgesia, numerical rating scale (NRS) scores at 1, 6, 12, and 24 h postoperatively and the finger movements were recorded. The adverse drug reactions and the patient satisfaction were recorded. The primary end point was the study of shoulder rest and movement pain in the patients with postoperative nerve blockage; the secondary end point was the patient's limb movements and thepatient satisfaction.

RESULTS

The duration of analgesia was (571.50±70.11) min in group I and (615.60±112.15) min in group C, and there was no difference between the two groups (P>0.05). The static and dynamic NRS scores at 1, 6, and 12 h in group C were lower than those in group I (P<0.05). There was no difference in static and dynamic NRS scores between the two groups during 24 hours (P>0.05). There was a significant difference in grade of muscle strength between group C [5(4,5)] and group I [4(2,4)] in the patients with nerve block hind limb (P<0.01), and there were significant differences between the two groups' sensation in the radial nerve group C [1(0,2)] and group I [2(1,2)], the median nerve group C [0(0,2)] and group I [2(1,2)], and the ulnar nerves group C [0(0,1)] and group I [1(1,2)] (P<0.01). There was no statistical difference between the two groups in the sencation of the shoulder, group C 2(1,2) and group I 2(1,2) , P>0.05. Compared with group I 8(6,9), group C 9(8,10) was a significant difference in satisfaction (P<0.01).

CONCLUSION

Interscalene brachial plexus block and C5-6 nerve root block could satisfy the needs of analgesia after shoulder arthroscopy, but C5-6 nerve root blockage does not limit the limb activity, the numbness is less, and the patient's satisfaction is higher.

Variant communication of phrenic nerve in neck

PURPOSE

Variations of the phrenic nerve gain importance in the context of subclavian vein cannulation, implanted venous access portals and supraclavicular nerve block for regional anaesthesia. Some of the variations of phrenic nerve are very common and may have implications even while performing very simple and routine procedures.

METHODS

During routine dissection in the Department of Anatomy, an anatomical variation was observed in the course of the phrenic nerve in an adult male cadaver.

RESULTS

On the right side, phrenic nerve in its early course in the neck, close to its origin was giving a communicating branch to the upper trunk of the brachial plexus. Further course of the phrenic nerve was typical. On the left side, no such communication between phrenic nerve and brachial plexus was observed.

CONCLUSIONS

A thorough knowledge of the anatomical variations and standard anatomy of phrenic nerve is a necessity for the safe and efficient practice of regional anaesthesia.

The human phrenic nerve serves as a morphological conduit for autonomic nerves and innervates the caval body of the diaphragm

Communicating fibres between the phrenic nerve and sympathetic nervous system may exist, but have not been characterized histologically and immunohistochemically, even though increased sympathetic activity due to phrenic nerve stimulation for central sleep apnoea may entail morbidity and mortality. We, therefore, conducted a histological study of the phrenic nerve to establish the presence of catecholaminergic fibres throughout their course. The entire phrenic nerves of 35 formalin-fixed human cadavers were analysed morphometrically and immunohistochemically. Furthermore, the right abdominal phrenic nerve was serially sectioned and reconstructed. The phrenic nerve contained 3 ± 2 fascicles in the neck that merged to form a single fascicle in the thorax and split again into 3 ± 3 fascicles above the diaphragm. All phrenic nerves contained catecholaminergic fibres, which were distributed homogenously or present as distinct areas within a fascicle or as separate fascicles. The phrenicoabdominal branch of the right phrenic nerve is a branch of the celiac plexus and, therefore, better termed the “phrenic branch of the celiac plexus”. The wall of the inferior caval vein in the diaphragm contained longitudinal strands of myocardium and atrial natriuretic peptide-positive paraganglia (“caval bodies”) that where innervated by the right phrenic nerve.

Hemidiaphragmatic paralysis: A case report

Hemidiaphragmatic paralysis is initially recognised as postoperative respiratory distress. The subsequent sequential management of the patient following arthroscopic shoulder surgery under interscalene block is described. Ultrasound-guided technique is considered to be the safest for interscalene block. Reducing the volume of anaesthetic used reduces its spread to the phrenic nerve and thus reduces the incidence of hemidiaphragmatic paralysis. Furthermore, a reduction in anaesthetic volume has equivalent analgesic efficacy.

Anatomy and physiology of phrenic afferent neurons

Large-diameter myelinated phrenic afferents discharge in phase with diaphragm contraction, and smaller diameter fibers discharge across the respiratory cycle. In this article, we review the phrenic afferent literature and highlight areas in need of further study. We conclude that 1) activation of both myelinated and nonmyelinated phrenic sensory afferents can influence respiratory motor output on a breath-by-breath basis; 2) the relative impact of phrenic afferents substantially increases with diaphragm work and fatigue; 3) activation of phrenic afferents has a powerful impact on sympathetic motor outflow, and 4) phrenic afferents contribute to diaphragm somatosensation and the conscious perception of breathing. Much remains to be learned regarding the spinal and supraspinal distribution and synaptic contacts of myelinated and nonmyelinated phrenic afferents. Similarly, very little is known regarding the potential role of phrenic afferent neurons in triggering or modulating expression of respiratory neuroplasticity.

Phrenic Nerve Palsy and Regional Anesthesia for Shoulder Surgery

Regional anesthesia has an established role in providing perioperative analgesia for shoulder surgery. However, phrenic nerve palsy is a significant complication that potentially limits the use of regional anesthesia, particularly in high-risk patients. The authors describe the anatomical, physiologic, and clinical principles relevant to phrenic nerve palsy in this context. They also present a comprehensive review of the strategies for reducing phrenic nerve palsy and its clinical impact while ensuring adequate analgesia for shoulder surgery. The most important of these include limiting local anesthetic dose and injection volume and performing the injection further away from the C5–C6 nerve roots. Targeting peripheral nerves supplying the shoulder, such as the suprascapular and axillary nerves, may be an effective alternative to brachial plexus blockade in selected patients. The optimal regional anesthetic approach in shoulder surgery should be tailored to individual patients based on comorbidities, type of surgery, and the principles described in this article.

New technique targeting the C5 nerve root proximal to the traditional interscalene sonoanatomical approach is analgesic for outpatient arthroscopic shoulder surgery

STUDY OBJECTIVE

Regional anesthesia and analgesia for shoulder surgery is most commonly performed via interscalene nerve block. We developed an ultrasound-guided technique that specifically targets the C5 nerve root proximal to the traditional interscalene block and assessed its efficacy for shoulder analgesia.

DESIGN

Prospective case series.

SETTING

Vanderbilt Bone and Joint Surgery Center.

PATIENTS

Patients undergoing shoulder arthroscopy at an ambulatory surgery center.

INTERVENTIONS

Thirty-five outpatient shoulder arthroscopy patients underwent an analgesic nerve block using a new technique where ultrasound visualization of the C5 nerve root served as the primary target at a level proximal to the traditional interscalene approach. The block was performed with 15mL of 0.5% plain ropivicaine.

MEASUREMENTS

Post anesthesia care unit pain scores, opioid consumption, hand strength, and duration of block were recorded. Cadaver dissection after injection with methylene blue confirmed that the primary target under ultrasound visualization was the C5 nerve root.

MAIN RESULTS

Pain scores revealed 97% patients had 0/10 pain at arrival to PACU, with 91% having a pain score of 3/10 or less at discharge from PACU. Medical Research Council (MRC) hand strength mean (SD) score was 4.17 (0.92) on a scale of 1-5. The mean (SD) duration of the block was 13.9 (3.5) hours.

CONCLUSIONS

A new technique for ultrasound-guided blockade at the level of the C5 nerve root proximal to the level of the traditional interscalene block is efficacious for shoulder post-operative pain control.

Phrenic Nerve Injury After Radiofrequency Denervation of the Cervical Medial Branches

Radiofrequency denervation of the cervical medial branches is a possible treatment for chronic cervical facet pain syndrome when conservative management has failed. According to the literature, complications after radiofrequency denervation of the cervical medial branches are rare. We report a case of possible phrenic nerve injury after ipsilateral radiofrequency denervation of the cervical medial branches following a posterolateral approach.