The terminal segment of the human phrenic nerve as a novel implantation site for diaphragm pacing electrodes: Anatomical and clinical description.

BACKGROUND: Diaphragm pacing allows certain ventilator-dependent patients to achieve weaning from mechanical ventilation. The reference method consists in implanting intrathoracic contact electrodes around the phrenic nerve during video-assisted thoracic surgery, which involves time-consuming phrenic nerve dissection with a risk of nerve damage. Identifying a phrenic segment suitable for dissection-free implantation of electrodes would constitute progress. STUDY DESIGN: This study characterizes a free terminal phrenic segment never fully described before. We conducted a cadaver study (n = 14) and a clinical observational study during thoracic procedures (n = 54). RESULTS: A free terminal phrenic segment was observed on both sides in 100% of cases, "jumping" from the pericardium to the diaphragm and measuring 60 mm [95% confidence interval; 48-63] and 72.5 mm [65-82] (right left, respectively; p = 0.0038; cadaver study). This segment rolled up on itself at end-expiration and became unravelled and elongated with diaphragm descent (clinical study). Three categories of fat pads were defined (type 1: pericardiophrenic bundle free of surrounding fat; type 2: single fatty fringe leaving the phrenic nerve visible until diaphragmatic entry; type 3: multiple fatty fringes masking the site of penetration of the phrenic nerve) that depended on body mass index (p = 0.001, clinical study). Hematoxylin-eosin and toluidine blue staining (cadaver study) showed that all of the phrenic fibers in the distal, pre-branching part of the terminal segment were contained within a single epineurium containing a variable number of fascicles (right: 1 [95%CI 0.65-4.01]; left 5 [3.37-7.63]; p = 0.03). CONCLUSION: Diaphragm pacing through periphrenic electrodes positioned on the terminal phrenic segment should be tested.

Aberrant branches of the subclavian artery and their relationship with the phrenic nerve and the brachial plexus / Ramas aberrantes de la arteria subclavia y su relación con el nervio frénico y el plexo braquial

SUMMARY: Variations in subclavian artery branches are relatively common and may impact surgical procedures and effects. During educational dissection of a male cadaver, we encountered an extremely rare variation of the right subclavian artery branches. The internal thoracic artery, the thyrocervical trunk, and the costocervical trunk arose from the third part of the right subclavian artery. In addition, the phrenic nerve displaced remarkably laterally by the thyrocervical trunk, and the course of the costocervical trunk was between the upper trunk and the middle trunk of the brachial plexus. These variations may pose a potential risk for nerve compression and increase the risk of arterial and nerve puncture. This case report would bring attention to the possibility of other similar cases, and early detection of these variations through diagnostic interventions is helpful to reduce postoperative complications.

RESUMEN: Las variaciones en las ramas de la arteria subclavia son relativamente comunes y pueden afectar los procedimientos y efectos quirúrgicos. Durante la disección educativa de un cadáver masculino, encontramos una variación extremadamente rara de las ramas de la arteria subclavia derecha. La arteria torácica interna, el tronco tirocervical y el tronco costocervical nacían de la tercera parte de la arteria subclavia derecha. Además, el nervio frénico se desplazaba lateralmente por el tronco tirocervical, y el trayecto del tronco costocervical se encontraba entre el tronco superior y el tronco medio del plexo braquial. Estas variaciones pueden suponer un riesgo potencial de compresión nerviosa y aumentar el riesgo de punción arterial y nerviosa. Este reporte de caso llamaría la atención sobre la posibilidad de otros casos similares, y la detección temprana de estas variaciones a través de diagnósticos es útil para reducir las complicaciones postoperatorias.

Laparoscopic fundoplication and new aspects of neural anatomy at the oesophagogastric junction.

BACKGROUND: In fundoplication, mobilization of the distal oesophagus and proximal stomach is essential to obtain a sufficient tension-free intra-abdominal oesophageal length for creation of an efficient antireflux barrier. Most surgical literature and anatomical illustrations do not describe nerve branches running from the diaphragm to the stomach. After observing small nerve branches at laparoscopic fundoplication, penetrating the left crus of the diaphragm lateral to the hiatus and apparently running into the stomach, an anatomical cadaver study was undertaken to identify the origin and target organ of these nerves. METHODS: Fifty-three human cadavers (23 men, 30 women; age range 35-103 years) were dissected with special attention to the nerves that penetrate the left crus of the diaphragm. The entire course of these nerves was documented with standardized drawings and photos. RESULTS: Small nerve branches penetrating the diaphragm lateral to the left crus of the hiatus were found in 17 (32 per cent) of the 53 cadavers. In 14 of these 17 cadavers, one or two splanchnic nerve branches were identified, and in ten of the 17 the nerve branches were found to be phrenic nerves. In seven of these 17 cadavers, two different nerve branches were found and assigned to both splanchnic and phrenic nerves. CONCLUSION: Nerves penetrating the left crus with splanchnic origin or phrenic origin have been identified. Their function remains unclear and their relationship to postfundoplication symptoms remains to be determined.

ANTECEDENTES: A la hora de realizar una fundoplicatura, la movilización del esófago distal y del estómago proximal es esencial para obtener una longitud de esófago intraabdominal suficiente y sin tensión para crear una barrera antirreflujo eficiente. La mayoría de la literatura quirúrgica y de las ilustraciones anatómicas no describen unas ramas nerviosas que discurren desde el diafragma al estómago. Tras observar pequeñas ramas nerviosas durante la realización de una fundoplicatura laparoscópica que penetran la crura izquierda del diafragma lateral al hiato y que aparentemente discurren hacia el estómago, se llevó a cabo un estudio anatómico en cadáver para identificar el origen y el órgano diana de estos nervios. MÉTODOS: Se diseccionaron 53 cadáveres humanos (23 varones, 30 mujeres, rango de edad: 35-103 años) con especial atención hacia los nervios que penetran la crura izquierda del diafragma. Se documentó el recorrido completo de estos nervios con fotos y dibujos de una forma estandarizada. RESULTADOS: En 17 (32%) de 53 cadáveres se hallaron pequeñas ramas nerviosas que penetraban el diafragma lateral a la crura izquierda del hiato. En 14 cadáveres (de los 17) se identificaron una o dos ramas nerviosas esplácnicas, y en 10 de los 17 cadáveres las ramas nerviosas que se hallaron resultaron ser nervios frénicos. En 7 de estos 17 cadáveres, se hallaron dos ramas nerviosas diferentes y se asignaron a ambos nervios, esplácnicos y frénicos. CONCLUSIÓN: Se han identificado los nervios que penetran la crura izquierda con un origen esplácnico y frénico. Sus funciones están por aclarar, así como su relación con los síntomas que aparecen tras la fundoplicatura.

Phrenic Nerve Palsy and Regional Anesthesia for Shoulder Surgery: Anatomical, Physiologic, and Clinical Considerations.

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.

MRI Reconstructions of Human Phrenic Nerve Anatomy and Computational Modeling of Cryoballoon Ablative Therapy.

The primary goal of this computational modeling study was to better quantify the relative distance of the phrenic nerves to areas where cryoballoon ablations may be applied within the left atria. Phrenic nerve injury can be a significant complication of applied ablative therapies for treatment of drug refractory atrial fibrillation. To date, published reports suggest that such injuries may occur more frequently in cryoballoon ablations than in radiofrequency therapies. Ten human heart-lung blocs were prepared in an end-diastolic state, scanned with MRI, and analyzed using Mimics software as a means to make anatomical measurements. Next, generated computer models of ArticFront cryoballoons (23, 28 mm) were mated with reconstructed pulmonary vein ostias to determine relative distances between the phrenic nerves and projected balloon placements, simulating pulmonary vein isolation. The effects of deep seating balloons were also investigated. Interestingly, the relative anatomical differences in placement of 23 and 28 mm cryoballoons were quite small, e.g., the determined difference between mid spline distance to the phrenic nerves between the two cryoballoon sizes was only 1.7 ± 1.2 mm. Furthermore, the right phrenic nerves were commonly closer to the pulmonary veins than the left, and surprisingly tips of balloons were further from the nerves, yet balloon size choice did not significantly alter calculated distance to the nerves. Such computational modeling is considered as a useful tool for both clinicians and device designers to better understand these associated anatomies that, in turn, may lead to optimization of therapeutic treatments.

Cervical and retrosternal approach to the left thoracic cavity using a flexible endoscope.

OBJECTIVES: Mediastinoscopy remains the gold standard for surgical exploration of the mediastinum. The use of this approach to access the left thoracic cavity could be complicated by vascular or neurological lesion. The aim of this experimental work was to describe a new approach to the left thoracic cavity through a cervical incision and retrosternal space using a flexible endoscope as a unique instrument. METHODS: We conducted an experimental work on 12 refrigerated and non-embalmed cadavers. Through a cervical incision, we dissected the retrosternal space to the level of Louis angle and then opened the left mediastinal pleura. We introduced the flexible endoscope through this pleural window into the left thoracic cavity. We defined three distances between the borders of the endoscope entry point, the phrenic nerve and the mammary artery: Distance 1: between the medial edge of the endoscope entrance point and the medial edge of the left mammary artery, Distance 2: between the top of the endoscope entrance point and the penetration of phrenic nerve in the left thoracic cavity and Distance 3: between the lateral edge of the entrance point of the endoscope and the medial edge of the phrenic nerve. To measure these distances, we performed a left postero-lateral thoracotomy. RESULTS: Procedure was successfully executed in 10 of the 12 studied subjects. The mean distances 1, 2 and 3 were 17.1 (range 2-40), 39.5 (17-80) and 19.1 mm (10-40), respectively. The minimal Distance 1 was in two subjects 0.2 and 0.5 mm. CONCLUSIONS: This approach avoids the para-aortic and supra-aortic zone; this access could be less dangerous than already described access techniques. Despite the limits of our work on cadavers, and the two failures in the application of the access, the mean distances we calculated show the potential safety of our approach concerning the phrenic nerve and the mammary artery. An experimental protocol on living animals is currently underway with the aim of confirming the safety of our approach.

Near-infrared fluorescence imaging can help identify the contralateral phrenic nerve during robotic thymectomy.

PURPOSE: Unilateral robotic thymectomy is gaining popularity. Identifying the contralateral phrenic nerve is a key limitation to achieving maximal thymic tissue resection. We evaluated the feasibility and technique of fluorescence imaging on the daVinci-Si robot (Intuitive Surgical Inc, Sunnyvale, CA) to identify the contralateral periocardiophrenic neurovascular bundle (PNB). DESCRIPTION: A unilateral right robotic thymectomy was performed in 10 patients. The thymus and its poles were mobilized. Indocyanine green was injected and fluoresced to identify the left PNB in four different viewing angles to assess the view that consistently positively identified the PNB. EVALUATION: No complications from indocyanine green or injuries to the phrenic nerve occurred. The contralateral PNB was visualized in 80% of patients from a left pleural view, infrequently from a mediastinal view, and never distal to the aortopulmonary window. CONCLUSIONS: During right robotic thymectomy, fluorescence imaging facilitates identification of the contralateral phrenic nerve by fluorescing the pericardiophrenic vessels. It is best visualized from a left pleural view. This technology has the potential to maximize thymic tissue resection with a unilateral approach while reducing operative time and nerve injury.

An anatomical study of the full-length phrenic nerve and its blood supply: clinical implications for endoscopic dissection.

For surgeries aimed at the dissection of full-length phrenic nerve, a full appreciation of its trajectory, blood supply and correlation with adjacent anatomical structures is necessary, especially for endoscopic manipulations. A fresh cadaver study was conducted with the purpose of avoiding surgical complications and ensuring further efficacy and efficiency of endoscopic manipulations. Ten fresh adult cadavers were dissected. Special attention was paid to the topography of the origin, the trajectory of the phrenic nerve, and its anatomic communication with the surrounding vessels and organs. In the second side of the cadavers, thoracic endoscopic manipulations and observations were also performed. The full length of the phrenic nerve was 24.6 ± 1.7 and 30.6 ± 1.8 cm on the right and left side, respectively; the blood supply of the phrenic nerve in the thoracic cavity came exclusively from the pericardiacophrenic artery; the distance between the origin of the pericardiacophrenic artery and that of the internal thoracic artery ranged from 0.5 to 5.2 cm on the right side, and from 1.4 to 5.6 cm on the left; most of the pericardiacophrenic veins intermingled with small vessels of pericardium and pleura, forming a venous network and joining the innominate vein. Endoscopic dissection of the thoracic phrenic nerve together with the accompanying pericardiacophrenic artery can be performed. Extreme attention should be paid during surgery to a section of about 6 cm in length of the artery originating from the internal thoracic artery, while the accompanying veins do not require to be spared.

Morphometric analysis of the phrenic nerve in male and female Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR)

Ventilatory differences between rat strains and genders have been described but the morphology of the phrenic nerve has not been investigated in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. A descriptive and morphometric study of the phrenic nerves of male (N = 8) and female (N = 9) SHR, and male (N = 5) and female (N = 6) WKY is presented. After arterial pressure and heart rate recordings, the phrenic nerves of 20-week-old animals were prepared for epoxy resin embedding and light microscopy. Morphometric analysis performed with the aid of computer software that took into consideration the fascicle area and diameter, as well as myelinated fiber profile and Schwann cell nucleus number per area. Phrenic nerves were generally larger in males than in females on both strains but larger in WKY compared to SHR for both genders. Myelinated fiber numbers (male SHR = 228 ± 13; female SHR = 258 ± 4; male WKY = 382 ± 23; female WKY = 442 ± 11 for proximal right segments) and density (N/mm²; male SHR = 7048 ± 537; female SHR = 10355 ± 359; male WKY = 9457 ± 1437; female WKY = 14351 ± 1448) for proximal right segments) were significantly larger in females of both groups and remarkably larger in WKY than SHR for both genders. Strain and gender differences in phrenic nerve myelinated fiber number are described for the first time in this experimental model of hypertension, indicating the need for thorough functional studies of this nerve in male and female SHR.

Surface anatomy and surface landmarks for thoracic surgery: Part II.

Surface anatomy is an integral part of a thoracic surgeon's armamentarium to assist with the diagnosis, staging, and treatment of thoracic pathology. As reviewed in this article, the surface landmarks of the lungs, heart, great vessels, and mediastinum are critical for appropriate patient care and should be learned in conjunction with classic anatomy.

Anatomy of the pleura: reflection lines and recesses.

Knowledge of the anatomy of the lines of pleural reflection, triangular ligaments, and pleural recesses is important to thoracic surgeons because their anatomic areas are used daily for radiographic interpretation as well as for the performance of procedures such as chest tube insertion, thoracentesis, and pericardiocentesis. Their knowledge is also important for thoracic surgeons doing surgical procedures such as parietal pleurectomies, extrapleural mobilization and resection of the lungs, and pleuroneumonectomies for destroyed lungs or malignant pleural neoplasms.

Nerves of the mediastinum.

Knowledge of the anatomy of the mediastinal nerves is essential for the evaluation and surgical treatment of most thoracic neoplasms. Thorough knowledge of the normal anatomy of the mediastinal nerves and of their variants cannot be overestimated because nerve trauma during nerve anatomy is also important because mediastinal or lung tumors can locally infiltrate those nerves either directly or through nodal metastases, making them generally unresectable.

Anatomy of the normal diaphragm.

The thoracic diaphragm is a dome-shaped septum, composed of muscle surrounding a central tendon, which separates the thoracic and abdominal cavities. The function of the diaphragm is to expand the chest cavity during inspiration and to promote occlusion of the gastroesophageal junction. This article provides an overview of the normal anatomy of the diaphragm.

[Anatomic research on the transposition of accessory nerve to phrenic nerve].

OBJECTIVE: To comprehend the anatomic characteristics and correlations between the accessory nerve and the phrenic nerve in the adult corpses. METHODS: The bilateral accessory nerves, phrenic nerves, and their branches of 20 adult corpses (38 sides) were underwent exposure. The morphologic data of the accessory nerves and the phrenic nerves above clavicle were measured. In addition, the minimal and maximal distances from several points on the accessory nerve to the full length of the phrenic nerve above clavicle were measured. Then, the number of motor nerve fibers on different locations of the nerves utilizing the method of immunohistochemistry were counted and compared. RESULT: The accessory nerves after sending out the sternocleido-mastoid muscular branches were similar in the morphologic data with the phrenic nerves. Meanwhile, the accessory nerve had a coiled appearance within this geometrical area. The possibly minimal distance between the accessory nerve and phrenic nerve was (3.19 ± 1.23) cm, and the possibly maximal distance between the starting point of accessory nerve and the end of the phrenic nerve above clavicle was (8.71 ± 0.75) cm. CONCLUSIONS: The accessory nerve and the phrenic nerve are similar in the anatomic evidences and the number of motor nerve fibers. And the length of accessory nerve is sufficiently long to connect with phrenic nerve as needed. It is possible to suture them without strain directly.

Phrenic nerve transfer in the restoration of elbow flexion in brachial plexus avulsion injuries: how effective and safe is it?

OBJECTIVE: Phrenic nerve transfer has been used for treating lesions of the brachial plexus since 1970. Although, today, surgeons are more experienced with the technique, there are still widespread concerns about its effects on pulmonary function. This study was undertaken to evaluate the effectiveness and safety of this procedure. METHODS: Fourteen patients with complete palsy of the upper limb were submitted to phrenic nerve transfer as part of a strategy for surgical reconstruction of their plexuses. Two patients were lost to follow-up, and 2 patients were followed for less than 2 years. Of the remaining 10 patients, 9 (90%) were male. The lesions affected both sides equally. The mean age of the patients was 24.8 years (range, 14-43 years), and the mean interval from injury to surgery was 6 months (range, 3-9 months). The phrenic nerve was always transferred to the musculocutaneous nerve, and a nerve graft (mean length, 8 cm; range, 4.5-12 cm) was necessary in all cases. RESULTS: There was no major complication related to the surgery. Seven patients (70%) recovered functional level biceps strength (Medical Research Council grade >or=3). All of the patients exhibited a transient decrease in pulmonary function tests, but without clinical respiratory problems. CONCLUSION: On the basis of our small series and data from the literature, we conclude that phrenic nerve transfer in well-selected patients is a safe and effective procedure for recovering biceps function.

Immunohistochemical study of the phrenic ganglion.

Peripheral nerve 'pseudoganglia' are described in the literature with little focus on histology. The phrenic ganglia, which are located on the inferior surface of the diaphragm and are associated with the phrenic nerves, have been described by some authors as potentially sympathetic ganglia although this, to the authors' knowledge, has not been proven. The purpose of the present study was to elucidate further the true autonomic nature of this collection of nerve cell bodies. In eight fresh adult cadavers < 6 h after death, the left and right phrenic ganglia were harvested and subjected to immunochemistry. All phrenic ganglia were vasoactive intestinal polypeptide negative but tyrosine hydroxylase positive. These findings indicate that the phrenic ganglia are sympathetic ganglia with most likely a vasomotor function.

Successful use of "cryo-mapping" to avoid phrenic nerve damage during ostial superior vena caval ablation despite nerve proximity.

BACKGROUND: The SVC may require ablation to treat atrial fibrillation. Phrenic nerve proximity identified with pacing maneuvers may preclude ablation. METHODS: We tested a new method using "cryo-mapping" to ablate despite nerve proximity. RESULTS: Of 833 patients undergoing ablation, 110 (12%) had arrhythmogenic substrate at the SVC/RA junction. Of these 110 patients, 66 (60%) had consistent diaphragmatic stimulation when pacing at 10 mA at the prospective site of ablation. Of these 66 patients, 7 had continued arrhythmogenicity despite attempts to modify this substrate. For these 7 patients, we paced 4 cm into the SVC where consistent phrenic nerve stimulation was obtained, and cryoablation at -30 degrees C was performed at sites requiring ablation. In 6 of 7 patients (86%), with continued diaphragmatic capture, cryoablation at -70/-80 degrees C was then performed. In 1 of 7 patients (14%), diaphragmatic stimulation ceased at -30 degrees C, and energy delivery stopped. In the 6 patients in whom cryoablation was completed, the arrhythmogenic substrate was successfully ablated without phrenic nerve injury. CONCLUSIONS: A novel "cryo-mapping" technique during phrenic nerve pacing can be used to successfully ablate arrhythmogenic substrate at the SVC/RA junction despite phrenic nerve proximity.

Incidence of accessory phrenic nerve and its clinical significance: a cadaveric study.

UNLABELLED: The description of accessory phrenic nerve (APN) in the standard textbooks and available literature is vague and sometimes limited to few lines. The incidence of APN varies a great deal from 17.6 % to 80.9 % in the available literature. The aim of the present study was to calculate the incidence and variation of APN in Indian population. MATERIAL AND METHODS: Forty five adult formalin-fixed cadavers (35 male, 10 female; 90 sides) used for gross anatomy dissection for undergraduates; during the 2 year period 2006-2007 were considered. Findings were recorded at different stages of the dissection. RESULTS: Out of 90 body sides studied, the APN was present in 48 sides (53.3 %). In 17 of the above sides the APN was confined to the cervical region (Cervical type) and in 31 sides the APN entered the thorax (Thoracic type), all anterior to the subclavian vein (SV). In eleven specimens the APN was found bilaterally. CONCLUSION: The incidence of APN, with its course and relation to the various structures in cervical and thoracic region will help the surgeons while performing internal thoracic artery (ITA) grafting and other radical neck surgery.

Surgical anatomy of innervation of the gallbladder in humans and Suncus murinus with special reference to morphological understanding of gallstone formation after gastrectomy.

AIM: To clarify the innervation of human gallbladder, with special reference to morphological understanding of gallstone formation after gastrectomy. METHODS: The liver, gallbladder and surrounding structures were immersed in a 10 mg/L solution of alizarin red S in ethanol to stain the peripheral nerves in cadavers (n=10). Innervation in the areas was completely dissected under a binocular microscope. Similarly, innervation in the same areas of 10 Suncus murinus (S. murinus) was examined employing whole mount immunohistochemistry. RESULTS: Innervation of the gallbladder occurred predominantly through two routes. One was from the anterior hepatic plexus, the innervation occurred along the cystic arteries and duct. Invariably this route passed through the hepatoduodenal ligament. The other route was from the posterior hepatic plexus, the innervation occurred along the cystic duct ventrally. This route also passed through the hepatoduodenal ligament dorsally. Similar results were obtained in S. murinus. CONCLUSION: The route from the anterior hepatic plexus via the cystic artery and/or duct is crucial for preserving gallbladder innervation. Lymph node dissection specifically in the hepatoduodenal ligament may affect the incidence of gallstones after gastrectomy. Furthermore, the route from the posterior hepatic plexus via the common bile duct and the cystic duct to the gallbladder should not be disregarded. Preservation of the plexus may attenuate the incidence of gallstone formation after gastrectomy.