Baroreflex failure syndrome after bilateral excision of carotid body tumors: an underestimated problem

Carotid baroreceptor dysfunction after carotid body tumour resections

OBJECTIVE

Carotid body tumours (CBTs) and baroreceptor failure (BRF) are two distinct but interrelated conditions, affecting the carotid body and its regulatory mechanisms. We aim to describe and quantify BRF after unilateral and bilateral CBT resections.

METHODS

Prospective cohort study. We included all patients with unilateral or bilateral CBT undergoing resection from April 2021 to January 2023. Demographics and CBTs characteristics were analysed; baroreceptor sensitivity assessment was conducted using the Composite Autonomic Severity Score (CASS). Statistical analyses were performed using R. Significance level was set at a 2-tailed α = 0.05.

RESULTS

A total of 30 patients with CBT underwent surgical resection, twenty-three were included in the study (18 unilateral and 5 bilateral CBTs). All 23 (100 %) were females, median age of 60 years. Regarding patients with unilateral CBT; preoperatively, 13 had BRF, the most common dysfunction subtype was mixed. Postoperatively, the most common dysfunction subtype was sympathetic failure. With regards to bilateral CBTs; 2 patients did not have autonomic dysfunction preoperatively. After bilateral surgical resection one patient remained without autonomic dysfunction; however, all other patients persisted with BRF.

CONCLUSION

BRF was present in 13 patients with unilateral CBT and 3 patients with bilateral tumours preoperatively; most will remain with BRF and will only change the characteristics postoperatively. No associations were found between type, severity of BRF and Shamblin classification or laterality. It is paramount that research in this area continues as many features are yet unknown regarding CBT pathogenesis, hence, BRF may be present yet not affect significantly quality of life.

Fifteen Years of Experience with Surgical Management of Bilateral Non-familial Carotid Body Tumors

BACKGROUND

Bilateral carotid body tumors (CBTs) clinical manifestation is infrequent. We conducted this work to describe our experience in the surgical treatment of bilateral CBT and to analyze our results.

METHODS

A retrospective, observational study. We analyzed the totality of bilateral CBT resections that had been performed in our institution from January 2008 to September 2023. Data was obtained from medical records and anonymized, ethics approval was obtained from our institution committee. As the number of observations was less than those required by the central limit theorem our sample was considered nonparametric. Statistical analysis was performed on Stata 17.

RESULTS

We evaluated 16 patients with a total of 32 CBT; surgical resection was performed in 28 cases (87.50%). Median age of the patients was 60 years (interquartile range [IQR] 46-64). Regarding the Shamblin classification, 9 CBTs (32.14%) were classified as Shamblin I, 11 (39.29%) as Shamblin II, and 8 (28.57%) as Shamblin III. The median Distance to the Base of the Skull (DTBOS) was 3.5 cm (IQR 2.7-5.1), and the median tumor volume was 11.25 cc (IQR 3.4-18.7). The median bleeding volume was 300 ml (IQR 200-500), and the median surgical time was 190 min (IQR 145-240). All surgeries were performed using the Retrocarotid Dissection technique. We documented 9 (32.14%) cases of nerve injuries, all of which were transitory. In the median regression a statistically significant association was found between DTBOS, Shamblin classification and tumor volume with intraoperative bleeding and length of stay.

CONCLUSIONS

Surgical treatment remains safe and should be considered the gold standard for accurate histologic diagnosis. DTBOS and tumor volume, in addition to Shamblin classification, must be considered in preoperative planning to predict bleeding and hospital stay.

Physiological and clinical impact in the carotid baroreceptor function following the surgical management of bilateral carotid body tumors

OBJECTIVE

The bilateral presentation of Carotid Body Tumors (CBT) is rare; the surgical resection of these masses remains the mainstay management due to the malignant potential. We aim to describe, classify, and quantify baroreceptor failure (BRF) after the surgical management of patients with bilateral CBT to better understand the clinical consequences.

METHODS

Retrospective review of patients that underwent bilateral CBT resection to assess the changes in baroreceptor function. We describe the clinical events associated to BRF after surgery, baseline patient's demographics, characteristics, comorbidities. Additionally, clinical and a quantitative evaluation of baroreceptor sensitivity were conducted using the Composite Autonomic Severity Score (CASS).

RESULTS

From 1986 to 2020, a total 146 CBT resections were performed in 132 patients in our institution. Tumors were removed bilaterally in staged procedures in seven patients with a mean age of 61 years (Standard Deviation 11), six (85%) were females, and there was no family history of paragangliomas. The clinical presentation were palpable masses in 5 (71%), and odynophagia in 2 (29%) cases; malignant histopathology following surgery was found in one case. BRF occurred in one patient after unilateral CBT resection, consisting of bradycardia and a 40 s asystole that was not previously associated to BR sensitivity. Three (43%) patients presented BRF in the immediate postoperative period of the contralateral CBT excision, consisting of volatile hypertensive crisis in two cases, and supraventricular tachycardia in one. All the patients developed (100%) chronic baroreceptor sensitivity symptoms consisting in syncope, vertigo and fatigue in 4 (57%), tachycardia in 2 (28%), and orthostatic headache in one (14%). Autonomic testing showed mixed sympathetic and parasympathetic failure in five (71%), severe sympathetic failure in 1 (14%), and parasympathetic dysfunction in one patient (14%).

CONCLUSIONS

Postoperative autonomic assessment confirmed BRF in all studied patients that underwent staged bilateral CBT resection with mixed, sympathetic, and parasympathetic dysfunction. Further studies are necessary to evaluate the incidence and physiological mechanisms of these sequelae to anticipate possible complications and offer the appropriate perioperative management.

A Global Bibliometric Analysis of the Top 100 Most Cited Articles on Carotid Body Tumors

The carotid body, situated at the common carotid artery bifurcation, comprises specialized glomus cells responsible for sensing blood oxygen, carbon dioxide, pH, and temperature changes, crucial for regulating breathing and maintaining oxygen homeostasis. Carotid body tumors (CBTs), arising from these cells, are rare, representing only 0.5% of head and neck tumors, often presenting as benign, slow-growing, vascularized masses. In February 2023, this bibliometric analysis was conducted, which involved screening 1733 articles from the Web of Science database. The screening process was based on citation count, and articles were selected for inclusion based on specific criteria that focused on CBTs located within the carotid bifurcation. Rigorous selection involved independent screening and data extraction by four authors. The top 100 articles, published between 1948 and 2019, totaled 6623 citations and were authored by 98 unique first authors from 22 countries and 77 institutions, spanning 42 journals. Treatment articles were the predominant category, comprising 49% of the literature. This analysis offers insights into publication trends, identifies literature gaps, and outlines areas of research focus, providing a valuable resource to guide future studies on CBTs.

Baroreflex Failure After Anterior Cervical Discectomy and Fusion: A Case Report

CASE

A 58-year-old man underwent anterior cervical discectomy and fusion (ACDF) for the treatment of cervical spondylotic myelopathy. Immediately after surgery, the patient experienced elevated blood pressure with a fall in oxygen saturation which prevented extubation. He required admission to the critical care unit and was diagnosed with baroreflex failure syndrome (BFS). He was managed with a 4-drug medical regimen and stabilized by the second postoperative day.

CONCLUSION

BFS should be considered in the setting of sudden sharp elevation in blood pressure after ACDF. Early diagnosis and initiation of appropriate pharmacotherapy may reduce patient morbidity and mortality.

Operative management of symptomatic, metachronous carotid body tumors involving the skull base and its neurological sequelae

A 44-year-old morbidly obese woman with a history of right carotid body tumor (CBT) resection presented with a symptomatic, nonfunctional, left Shamblin-III CBT. Abutment of the skull base precluded distal internal carotid artery control for arterial reconstruction, favoring parent vessel sacrifice after an asymptomatic provocative test. She underwent CBT resection with anticipated sacrifice of cranial nerves X and XII and the common carotid artery and its branches, developing baroreceptor failure syndrome and sequelae of cranial nerve sacrifice. When facing a symptomatic, metachronous CBT abutting the skull base, upfront operative intervention with adjuvant radiation for residual tumor optimizes curative resection.

Destructive Effects of Acidic Blood on the Intestines: Experimental Study

Objective

This study aimed to investigate the destructive effects of acidic blood on the intestinal structures, which has been reported as the most hazardous biochemical result of vagosympathetic autonomic imbalances in intensive care unit patients with subarachnoid hemorrhage (SAH).

Materials and Methods

In total, 27 hybrid rabbits were used; 5 rabbits were used as a control group, 7 as the SHAM group into whom 1 cc saline was injected into the cisterna magna, and the remaining 15 were used as the study group. These animals received 1 cc of autologous arterial blood injection into the cisterna magna to create the SAH group. Blood pH values were recorded before, during, and after the experimental procedures. Computed tomography was performed to examine the intestinal morphology. Normal and degenerated epithelial cell densities of the intestine were estimated by stereological methods. The relationship between pH values and intestinal tissue changes was analyzed statistically using the Mann-Whitney U test.

Results

The mean blood pH values were 7.364±0.042 in the control group, 7.326±0.059 in the SHAM group, and 7.23±0.021 in the study group. Intestinal epithelial cell injury, desquamation of villus, and cell loss were observed. It is observed that the number of degenerated epithelial cells, fragmented villi numbers, and vacuoles significantly increased in the study group (p<0.05).

Conclusion

Acidotic intestinal injury secondary to blood pH changes following SAH may be considered as a generalized and dangerous complication with their multiorgan insuficiency effect.

Successful patient outcome following surgery of carotid body tumor and temporary hypoglossal nerve dysfunction

Carotid body tumors, also known as paragangliomas or chemodectomas, are rare tumors. They are mostly benign slow-growing tumors arising from neural crest cells, but can give rise to complications because of their location and close relation to carotid vessels and cranial nerves. A 40-year male patient diagnosed with a carotid body tumor is discussed along with a review of cranial nerve complications associated with the management of carotid body tumors. This case highlights the complete recovery after a temporary hypoglossal nerve deficit following surgery. Another important aspect is that syncopal attacks might occur in carotid body tumors and early surgery is required to prevent complications.

Broader adaptive range of sympathetic burst size in response to blood pressure change in older women with greater arterial stiffness

KEY POINTS

In this study, we focused on muscle sympathetic nerve activity (MSNA) burst size and occurrence separately as subcomponents of the sympathetic baroreflex in older adults, and we found that the distribution (variation) of burst size against burst occurrence was greater in women than men. Older women had greater carotid artery stiffness compared with older men, while blood pressure (BP) distribution (variation) was comparable between sexes. Sympathetic baroreflex sensitivity assessed with burst incidence was less sensitive as the carotid artery became stiffer in older men and women, while that assessed with burst area was more sensitive as the carotid artery became stiffer in older women but not in older men. These results help us understand the mechanisms underlying the compensation for the impaired response of MSNA burst occurrence in older women with greater carotid artery stiffness to regulate BP similar to that in older men.

ABSTRACT

There are sex differences in arterial stiffness and neural control of blood pressure (BP) among older adults. We examined whether the sympathetic response to BP is greater in older women than men in burst size but not burst occurrence. Burst occurrence and size were assessed with burst interval and area of muscle sympathetic nerve activity, respectively, and the distributions of these indices were evaluated by range during supine rest in 61 healthy older subjects (30 men (69 ± 6 years) and 31 women (68 ± 6 years); means ± SD). Also, we analysed sympathetic baroreflex sensitivity (BRS) with burst occurrence and area simultaneously. Carotid β-stiffness was measured with B-mode ultrasonic image and carotid BP. The range of burst interval was smaller in older women than men (P = 0.002), while there was no difference in the range of burst area. Carotid β-stiffness was greater in older women than men (6.7 ± 2.7 vs. 5.1 ± 2.7, P = 0.027). Sympathetic BRS assessed with burst incidence was lower in older women than men (-2.3 ± 1.4 vs. -3.3 ± 1.4 bursts·100 beats^-1  mmHg^-1 , P = 0.007), while this sex difference was observed when assessed with burst area after adjusting for carotid β-stiffness (-116.1 ± 135.0 vs. -185.9 ± 148.2 a.u. burst^-1  mmHg^-1 , P = 0.040), but not before. Sympathetic BRS assessed with burst area was negatively (more sensitive) correlated with carotid β-stiffness in older women (r = -0.53, P = 0.002) but not men. These data suggest that the response of burst size within each burst is augmented for the baroreflex BP control despite the impaired response of burst occurrence in older women with greater carotid stiffness.

Carotid Sinus Nerve: A Comprehensive Review of Its Anatomy, Variations, Pathology, and Clinical Applications

The carotid sinus nerve branches off the glossopharyngeal nerve just after its appearance from the jugular foramen, descends along the internal carotid artery, and enters the carotid sinus. There have been many studies of the pathway and the course of the carotid sinus nerve and its communications with surrounding nerves. The intercommunication is exceedingly complicated. Acknowledgment of its anatomic diversity can be important in specific operations dealing with this area. Herein we review the anatomy, variations, pathology, and clinical applications of the carotid sinus nerve.

Surgical Management of Bilateral Carotid Body Tumors

BACKGROUND

Carotid body tumors (CBTs) are rare neoplasms located in the carotid bifurcation. The majority of these tumors are unilateral; bilateral CBTs represent approximately 5% of all affected patients, and the recommended treatment is to surgically remove them in staged-planned surgeries. We describe the experience, outcomes, and the surgical management of bilateral CBTs in our institution.

METHODS

A retrospective review of CBTs patients was completed; patient demographics, comorbidities, lesion location, anatomic characteristics, surgical techniques, complications, reinterventions, and other factors that may influence outcomes were evaluated.

RESULTS

A total of 109 patients with CBTs were treated surgically; of these, 8 had bilateral CBTs (7%); the mean age was 56 years, and 7 (87%) were females. Thirteen surgical resections were performed, and in 2 of the cases, the pathology report was malignant (15%). Five were classified as Shamblin I (31%), 5 as Shamblin II (31%), and remaining 6 as Shamblin III (38%). The mean time between the first and second procedure was of 10.7 months. Complications included one case of neck hematoma requiring evacuation and postoperative neurologic complications occurred in three patients (one patient with facial and two with vocal cord palsies). None of the studied individuals had a family history of CBT, and all of them lived in altitude areas higher than 2000 meters above mean sea level (mamsl). The mean tumor size was 3.55 cm and 2.75 cm for right and left CBTs, respectively.

CONCLUSIONS

A better understanding of the clinical characteristics of patients with bilateral CBTs may lead to a more standardized and optimal management with fewer complications and a better quality of life afterward.

The Carotid Sinus Nerve-Structure, Function, and Clinical Implications

Interest has been renewed in the anatomy and physiology of the carotid sinus nerve (CSN) and its targets (carotid sinus and carotid body, CB), due to recent proposals of surgical procedures for a series of common pathologies, such as carotid sinus syndrome, hypertension, heart failure, and insulin resistance. The CSN originates from the glossopharyngeal nerve soon after its appearance from the jugular foramen. It shows frequent communications with the sympathetic trunk (usually at the level of the superior cervical ganglion) and the vagal nerve (main trunk, pharyngeal branches, or superior laryngeal nerve). It courses on the anterior aspect of the internal carotid artery to reach the carotid sinus, CB, and/or intercarotid plexus. In the carotid sinus, type I (dynamic) carotid baroreceptors have larger myelinated A-fibers; type II (tonic) baroreceptors show smaller A- and unmyelinated C-fibers. In the CB, afferent fibers are mainly stimulated by acetylcholine and ATP, released by type I cells. The neurons are located in the petrosal ganglion, and centripetal fibers project on to the solitary tract nucleus: chemosensory inputs to the commissural subnucleus, and baroreceptor inputs to the commissural, medial, dorsomedial, and dorsolateral subnuclei. The baroreceptor component of the CSN elicits sympatho-inhibition and the chemoreceptor component stimulates sympatho-activation. Thus, in refractory hypertension and heart failure (characterized by increased sympathetic activity), baroreceptor electrical stimulation, and CB removal have been proposed. Instead, denervation of the carotid sinus has been proposed for the "carotid sinus syndrome." Anat Rec, 302:575-587, 2019. © 2018 Wiley Periodicals, Inc.

A Contemporary Assessment of Carotid Body Tumor Surgery

Carotid body tumor resection remains a surgical challenge traditionally associated with a 15-30% incidence of cranial nerve injury. The authors reviewed their experience with carotid body tumor surgery to determine whether contemporary awareness of carotid body tumors is leading to earlier detection and operation, resulting in a lower incidence of postoperative cranial nerve injury. Twenty-seven carotid body tumors were resected in 25 patients between 1990 and 2000. No patient died and no patient had postoperative baroreflex failure syndrome. There was 1 stroke (4%) in a patient who required ligation of the internal carotid artery. There were 9 cranial nerve injuries (33%), most commonly to the vagus or hypoglossal nerves, which was not significantly different from the rate of cranial nerve injury (44%) in the 9 patients operated upon between 1984 and 1989 (p = 0.37, Fisher's exact test). Multivariate analysis demonstrated that tumor size was the only significant factor predicting cranial nerve injury (p = 0.045, logistic regression). Since carotid body tumors with large size or higher Shamblin grades had predictably high operative blood loss and rates of postoperative cranial nerve injury, a high index of suspicion and aggressive surgical management may lead to earlier detection and operation on smaller tumors, ultimately reducing the risk of nerve injury. Nevertheless, carotid body tumor surgery appears to be relatively free of mortality and major morbidity in contemporary practice.

Posterior reversible encephalopathy syndrome and reversible cerebral vasoconstriction syndrome after bilateral carotid paraganglioma resection: A case report

Background

Paraganglioma is a rare neuroendocrine tumour arising anywhere along the paravertebral sympathetic and parasympathetic chains. In the neck, paraganglioma may affect the carotid body (carotid body tumour).

Case report

We describe a 43-year-old woman who presented with a reversible vasoconstriction syndrome associated with a posterior reversible encephalopathy syndrome following a surgery for a left carotid paraganglioma (with a past medical history of surgery for a right carotid paraganglioma a few months before).

Conclusion

A consequence of a baroreflex modification is discussed in order to explain the rare occurrence of such symptoms.

Head and Neck Paragangliomas

Objective

Head and neck paragangliomas are a group of slow-growing hypervascular tumors associated with the paraganglion system. The approach to evaluate and treat these lesions has evolved over the last 2 decades. While radical surgery had been the traditional approach, improvements in diagnostic imaging as well as radiation therapy techniques have led to an emphasis on observation and nonsurgical therapy in many patients. This article reviews the contemporary approach to the workup and management of head and neck paragangliomas.

Data Source

Articles were identified from PubMed.

Review Methods

PubMed searches with the following keywords were performed: carotid body paraganglioma management, vagal paraganglioma management, jugulotympanic paraganglioma management, imaging of head and neck paragangliomas, head and neck paraganglioma embolization, paraganglioma radiation, head and neck paraganglioma management, observation of head and neck paragangliomas, bilateral carotid body paragangliomas, and genetics of paragangliomas. Review and original research articles available in the English language and published during or after 2009 were selected on the basis of their clinical relevance and scientific strength. Certain articles published prior to 2009 were also included if they provided background information that was relevant.

Conclusions/Implications for Practice

Workup and treatment of head and neck paragangliomas are changing. With more now known regarding the longitudinal behavior of these tumors, observation and nonsurgical therapy are indicated in many instances. For patients where surgery is the most appropriate option, improved diagnostic and perioperative techniques are allowing patients to tolerate resection, often with reduced morbidity.

Surgical management of carotid body tumors: a 15-year single institution experience employing an interdisciplinary approach

Cervical paragangliomas are rare neoplasms that arise from extraadrenal paraganglia in close association with the cranial nerves and extracranial arterial system of the head and neck, and therefore surgical extirpation can be challenging. A retrospective study was conducted of all patients undergoing surgical excision of a cervical paraganglioma between 2000 and 2015. The demographic characteristics, clinical features, surgical approach, and outcomes were reviewed. A total of 20 cervical paragangliomas were excised in 17 patients. There were 14 female and 3 male patients with a mean age of 56.6 ± 17.0 at the time of operation. Twelve patients had unilateral tumors and 5 patients had bilateral tumors. Familial involvement was confirmed by history or direct genetic analysis in 8 (47%) of the 17 patients. There were no malignant paragangliomas, and only 3 patients had tumors that were determined to be functional. Tumor size ranged from 1.3 to 6.0 cm. Two patients required combined arterial resection as part of complete excision of the tumor. There were no permanent operative cranial nerve injuries, no recurrences, minimal morbidity, and no mortality. In conclusion, optimal management of cervical paragangliomas should include a thorough preoperative evaluation, accurate definition of the surgical anatomy, and exclusion of synchronous paragangliomas. A combined therapeutic approach by a multidisciplinary team including surgeons and interventional radiologists provides safe and effective management of cervical paragangliomas with very low morbidity and excellent outcomes.

Multidisciplinary Management of Carotid Body Tumors in a Tertiary Urban Institution

Objective. Aim of this study is to present the experience of our institution in carotid body tumors (CBTs) treatment. Methods. All cases treated in a Vascular Surgery Department within 2.5 years (03/2013-09/2015) were retrospectively evaluated. Demographics, diagnostic, and treatment strategy were recorded. All patients with known CBT underwent ultrasound and magnetic resonance imaging preoperatively. All cases were classified according to the Shamblin type and evaluated by a radiologist, otolaryngologist, and anesthesiologist before and after surgery. Major outcomes included mortality, stroke, cranial nerve injury, and recurrence. Results. Overall, nine patients (mean age: 59.5 ± 16.3 years) with a total of ten CBTs were treated. There was no gender prevalence and most of the cases (55%) were asymptomatic. There were no functional or familial cases. There was only one bilateral case treated in a staged manner. No preoperative embolization of CBTs was performed. Mortality and stroke rates were null. No severe complication was observed in the early and late setting. No malignancy was recorded. Mean follow-up was 15.6 ± 7.8 months. Conclusions. Multidisciplinary management of patients with CBTs is imperative for optimal results, especially in type III tumors, bilateral or functional cases. After careful treatment planning and intraoperative manipulations, complications could be avoided even without preoperative embolization.

Management of multicentric paragangliomas: Review of 24 patients with 60 tumors

BACKGROUND

The purpose of this study was to reflect our experience in the management of multicentric head and neck paragangliomas, including genetic study and counseling, diagnostic tools, types of treatment, and the need for monitoring.

METHODS

A retrospective review of 24 patients with multicentric paraganglioma, including a total of 60 paragangliomas: 37 carotid body tumors, 13 jugulotympanic paragangliomas, and 10 vagal paragangliomas.

RESULTS

A total of 26 surgical procedures were performed, including the resection of 36 paragangliomas. Four tumors were pending surgery at the time of this review. Radiotherapy was administered in 7 patients with 9 tumors. A "wait-and-scan" policy with periodic MRI imaging tests was instituted for 9 patients with 12 paragangliomas.

CONCLUSION

The knowledge of the different modalities of management is especially relevant in patients with multicentric paragangliomas. In every case, benefits and potential risks of all treatment options may be taken into consideration for every individual patient.

Effect of bilateral carotid body resection on cardiac baroreflex control of blood pressure during hypoglycemia

Hypoglycemia results in a reduction in cardiac baroreflex sensitivity and a shift in the baroreflex working range to higher heart rates. This effect is mediated, in part, by the carotid chemoreceptors. Therefore, we hypothesized hypoglycemia-mediated changes in baroreflex control of heart rate would be blunted in carotid body-resected patients when compared with healthy controls. Five patients with bilateral carotid body resection for glomus tumors and 10 healthy controls completed a 180-minute hyperinsulinemic, hypoglycemic (≈3.3 mmol/L) clamp. Changes in heart rate, blood pressure, and spontaneous cardiac baroreflex sensitivity were assessed. Baseline baroreflex sensitivity was not different between groups (P>0.05). Hypoglycemia resulted in a reduction in baroreflex sensitivity in both the groups (main effect of time, P<0.01) and responses were lower in resected patients when compared with controls (main effect of group, P<0.05). Hypoglycemia resulted in large reductions in systolic (-17±7 mm Hg) and mean (-14±5 mm Hg) blood pressure in resected patients that were not observed in controls (interaction of group and time, P<0.05). Despite lower blood pressures, increases in heart rate with hypoglycemia were blunted in resected patients (interaction of group and time, P<0.01). Major novel findings from this study demonstrate that intact carotid chemoreceptors are essential for increasing heart rate and maintaining arterial blood pressure during hypoglycemia in humans. These data support a contribution of the carotid chemoreceptors to blood pressure control and highlight the potential widespread effects of carotid body resection in humans.

The contribution of chemoreceptor-network injury to the development of respiratory arrest following subarachnoid hemorrhage

OBJECTIVE

Respiratory arrest following brainstem herniation has been attributed to injuries resulting from compression of the respiratory centers. While it is widely perceived that the chemoreceptor network, consisting of the glossopharyngeal nerve and carotid body (GPN-CB), is essential for the modulation of respiration, its contribution to the development of respiratory arrest has not been investigated. Therefore, the aim of this study was to investigate whether injury to the GPN-CB occurs in animals with respiratory arrest caused by experimentally-induced subarachnoid hemorrhage.

MATERIALS AND METHODS

Eighteen hybrid rabbits were used in this study. Four rabbits (n=4) were used to determine the normal structure of the GPN-CB. The remaining rabbits (n=14) received an autologous blood injection into the cisterna magna to produce a subarachnoid hemorrhage, after which they were observed for 20 days. The number of axons and the neuron density in the glossopharyngeal nerve and carotid body, respectively, were counted by stereological methods. The Mann-Whitney U test was used to analyze the results.

RESULTS

Six of 14 rabbits died within the first week, likely due to brain swelling and crushing injuries that were observed in the brain stem and related structures. In control rabbits, the average neuronal density of the carotid body was 4250 ±1250/mm(3), while the axonal density in the glossopharyngeal nerve was 18000±5100 mm(2). Conversely, in the dead rabbits, the degenerated neuron density of the carotid body was 2100±500/mm(3), while the degenerated axon density in the glossopharyngeal nerve was 8500±2550 mm(2). In addition, histopathological lesions were more severe in the dead rabbits in terms of their glossopharyngeal nerve and carotid body.

CONCLUSION

There is an important relationship between neurodegeneration in the GPN-CB and mortality rates following experimentally-induced hemorrhage. This relationship suggests that injury to the GPN-CB network disrupts the breathing reflex and results in respiratory arrest following a subarachnoid hemorrhage (SAH).

A two-decade experience of head and neck paragangliomas in a whole population-based single centre cohort

Paragangliomas are rare neuroendocrine tumours arising from neural crest-derived tissue. In the head and neck region typical locations are the carotid bifurcation, vagal nerve or jugulotympanic region. Paragangliomas are normally benign, and malignant transformation is rare. During the past decade the understanding of the genetic and molecular aetiology has had an important clinical impact on the management of PGs. This is a retrospective review of all histologically verified paragangliomas diagnosed and managed at an academic tertiary care referral centre between 1990 and 2010. Data on age, sex, symptoms, tumour location, management and follow-up were recorded. There were 64 patients with 74 tumours. Thirty-six per cent of the tumours were located in the carotid body region, 48 % in the jugulotympanic region and 15 % in the vagal nerve. One tumour was located in the dorsal neck. Most (95 %) of the patients were treated primarily with surgery and with curative intent. Definitive radiation therapy was primarily given to two patients. Recurrent or residual tumours were treated with surgery in three patients and with radiation therapy in nine patients. The typical long-term post-operative sequel was vocal cord paralysis. Local recurrence was found in 6 % of patients. Symptoms and findings related to paragangliomas are variable and management should be individualized. Surgery remains the primary choice of the current treatment options, but often is challenging and warrants a multidisciplinary approach. We present an algorithm on the management of head and neck paragangliomas based on current knowledge.

The management of head-and-neck paragangliomas

Paragangliomas (PGLs) are tumours originating from neural crest-derived cells situated in the region of the autonomic nervous system ganglia. Head-and-neck PGLs (HNPGLs) originate from the sympathetic and parasympathetic paraganglia, most frequently from the carotid bodies and jugular, tympanic and vagal paraganglia, and are usually non-catecholamine secreting. Familial PGLs are considered to be rare, but recently genetic syndromes including multiple PGLs and/or phaeochromocytomas have been more thoroughly characterised. Nowadays, genetic screening for the genes frequently implicated in both familial and sporadic cases is routinely being recommended. HNPGLs are mostly benign, generally slow-growing tumours. Continuous growth leads to the involvement of adjacent neurovascular structures with increased morbidity rates and treatment-related complications. Optimal management mostly depends on tumour location, local involvement of neurovascular structures, estimated malignancy risk, patient age and general health. Surgery is the only treatment option offering the chance of cure but with significant morbidity rates, so a more conservative approach is usually considered, especially in the more difficult cases. Radiotherapy (fractionated or stereotactic radiosurgery) leads to tumour growth arrest and symptomatic improvement in the short term in many cases, but the long-term consequences are unclear. Early detection is essential in order to increase the chance of cure with a lower morbidity rate. The constant improvement in diagnostic imaging, surgical and radiation techniques has led to a safer management of these tumours, but there are still many therapeutic challenges, and no treatment algorithm has been agreed upon until now. The management of HNPGLs requires a multidisciplinary effort addressing the genetic, surgical, radiotherapeutic, oncological, neurological and endocrinological implications. Further progress in the understanding of their pathogenesis will lead to more effective screening and earlier diagnosis, both critical to successful treatment.

Carotid body paragangliomas: a systematic study on management with surgery and radiotherapy

The definitive universally accepted treatment for carotid body tumors (CBT) is surgery. The impact of surgery on cranial nerves and the carotid artery has often been underestimated. Alternatively, a few CBTs have been followed without treatment or irradiation. The goal of this study is to summarize the existing evidence concerning the efficacy and safety of surgery and external beam radiotherapy (EBRT) for CBT. Relevant articles were identified using strict criteria for systematic searches. Sixty-seven articles met the criteria which included 2,175 surgically treated patients. On the other hand, 17 articles including 127 patients treated with EBRT were found. Long-term control of the disease was obtained in 93.8% of patients who received surgical treatment and in 94.5% of the radiotherapy group. Surgery resulted in 483 (483/2,175 = 22.2%) new cranial nerve permanent deficits, whereas in the EBRT group, no new deficits were recorded (p = 0.004). The common/internal carotid artery was resected in 271 (12.5%) patients because of injury or tumor encasement, with immediate reconstruction in 212 (9.7%) patients. Three percent (60) of patients developed a permanent stroke and 1.3% (26) died due to postoperative complications. The major complications rates and the mortality after completion of the treatment also were significantly higher in surgical series compared to EBRT series. This systematic analysis highlights evidence that EBRT offers a similar chance of tumor control with lower risk of morbidity as compared to surgery in patients with CBT. This questions the traditional notion that surgery should be the mainstay of treatment.

Treatment of cervical paragangliomas

OBJECTIVE

Review of the treatment of cervical paraganglioma.

MATERIAL AND METHODS

Review of the literature based on a Medline database.

RESULTS

The treatment of choice consists of a multidisciplinary approach based on a detailed clinical, laboratory and radiological work-up. Vascular reconstruction may be necessary when the tumour invades the artery wall. The main complication of surgery is damage to cranial nerves involved in speech and/or swallowing. Treatment of bilateral tumours must be conducted in two stages. The first side to be operated depends on the sites and size of the tumours, as the primary objective is to avoid bilateral vagus nerve palsy. Radiotherapy has been used to treat paragangliomas for several years and achieves tumour stabilization in the majority of cases. Potential indications reported in the literature are: inoperable tumours, recurrence after surgery, some bilateral tumours and malignant tumours.

CONCLUSION

Surgery is the standard treatment for cervical paraganglioma. Radiotherapy can be proposed when surgery is contraindicated.

Carotid baroreceptor stimulation for the treatment of resistant hypertension

Interventional activation of the carotid baroreflex has been an appealing idea for the management of resistant hypertension for several decades, yet its clinical application remained elusive and a goal for the future. It is only recently that the profound understanding of the complex anatomy and pathophysiology of the circuit, combined with the accumulation of relevant experimental and clinical data both in animals and in humans, has allowed the development of a more effective and well-promising approach. Indeed, current data support a sustained over a transient reduction of blood pressure through the resetting of baroreceptors, and technical deficits have been minimized with a subsequent recession of adverse events. In addition, clinical outcomes from the application of a new implantable device (Rheos) that induces carotid baroreceptor stimulation point towards a safe and effective blood pressure reduction, but longer experience is needed before its integration in the everyday clinical practice. While accumulating evidence indicates that carotid baroreceptor stimulation exerts its benefits beyond blood pressure reduction, further research is necessary to assess the spectrum of beneficial effects and evaluate potential hazards, before the extraction of secure conclusions.

Carotid baroreceptor stimulation as a therapeutic target in hypertension and other cardiovascular conditions

BACKGROUND

The role of the carotid baroreflex in blood pressure regulation has been known for a long time but its effects were thought to be short lived. Recent data indicate that stimulation of carotid baroreceptors may lower blood pressure not only for short periods of time, but also in the long run.

OBJECTIVE/METHODS

Recent advances in technology permitted the development of a new device (Rheos) that addresses problems with older devices. Several questions remain to be addressed before Rheos can be used widely, and several potential clinical applications remain to be clarified. This review examines these issues and comprehensively describes this therapeutic approach.

RESULTS/CONCLUSIONS

The carotid baroreceptor reflex is probably not completely in control of blood pressure. Baroreflexes are one of many control systems acting in concert.

Baroreceptor failure after bilateral resection of carotid artery parangliomas

Multiple head and neck parangliomas are unusual pathologies. We report a case of a 24-year-old patient operated on at our centre for bilateral carotid artery parangliomas who developed baroreceptor failure after their resection. Albeit an infrequent complication, it is important to be aware of it in order to ensure is speedy diagnosis and treatment so as to avoid major post-surgical complications.

Surgical management of carotid body tumors

BACKGROUND

Carotid body tumors (CBT) should be considered when evaluating every lateral neck mass.

METHODS

A retrospective study was conducted of 52 patients with 57 CBT. The surgical approach and complications were reviewed. All patients were operated on without preoperative embolization.

RESULTS

Multifocal paraganglioma (PG) were detected in six cases. A succinate dehydrogenase subunit D (SDHD) mutation was discovered in four patients. Vascular peroperative complication occurred in one case. Vascular reconstruction was decided peroperatively in five cases (8.8%). Vascular reconstruction was 0% for Shamblin 1 or 2 tumors, but 28.5% for Shamblin 3. A postoperative nerve paresis was reported in 24 patients (42.1%) and vagal nerve paralysis persisted in four cases (7.01%). The rate of serious complications, e.g., permanent nerve palsy, preoperative and postoperative complications, was 14.03%; it was 2.3% for Shamblin 1 or 2 tumors and 35.7% for Shamblin 3. One patient had malignant PG with node metastasis and was not referred for radiotherapy. No recurrence or metastasis was reported after 6-year follow-up.

CONCLUSION

Early surgical treatment is recommended in almost all patients after preoperative evaluation and detection of multifocal tumors. Surgical excision of small tumors was safe and without complication, but resection of Shamblin 3 tumors can be challenging. Routine preoperative embolization of carotid body paragangliomas is not required.

Postlaryngectomy hypertensive crisis: a manifestation of perioperative acute baroreflex failure?

Hemodynamic instability as a result of altered baroreflex mechanism is common in surgeries involving manipulation around the carotid sheath. We report a case in which hypertensive crisis was associated with laryngectomy during general anesthesia. Perioperative use of vasoactive agents such as alpha(2) agonists may help in maintaining hemodynamic stability in such procedures.

A multidisciplinary approach to carotid paragangliomas

The surgical management of carotid paragangliomas can be problematic. A multidisciplinary approach was used to include vascular surgery, otolaryngology, and neuroradiology to treat these patients over 9 years. From January 1992 to July 2001, a multidisciplinary team evaluated patients with carotid paragangliomas. Analyzed patient data included age, gender, diagnostic evaluation, tumor size, preoperative tumor embolization, operative exposure, need for extracranial arterial sacrifice/reconstruction, postoperative morbidity including cranial nerve dysfunction, and long-term follow-up. Twenty-five carotid paragangliomas in 20 patients underwent multidisciplinary evaluation and management. Average age was 51 years (range, 28-83 years), and 52% were male. Diagnostic evaluation included computed tomography in 76%, magnetic resonance imaging/magnetic resonance angiography in 52%, catheter angiography in 60%, and duplex ultrasonography in 16%. An extended neck exposure was required in 11 cases (44%), mandibulotomy was used once (4%), and mandibular subluxation was never required. The external carotid artery (ECA) was sacrificed in 8 cases (32%). The carotid bifurcation was resected in 1 patient (4%) requiring interposition reconstruction of the internal carotid artery. Preoperative tumor embolization was performed for 13 tumors (52%). Operative blood loss for patients undergoing preoperative embolization (Group I) was comparable to the nonembolized group (group II): group I lost 365 +/-180 mL versus 360 +/- 101 mL for group II (P = .48). This occurred despite larger tumors (group I - 4.2 cm versus group II - 2.1 cm, P = .03) and a higher mean Shamblin class (group I - 2.5 versus group II - 1.45, P = .001) for group I. There were no perioperative mortalities. Transient cranial nerve dysfunction occurred in 13 CBTs (52%), 2 (8%) of which remained present after 4 months. Patients with carotid paragangliomas benefit from a multidisciplinary team approach. Neuroradiology has been used for selective preoperative embolization, which has decreased estimated blood loss during excision of larger complex tumors. A combined surgical team of otolaryngology and vascular surgery provides for exposure of the distal internal carotid artery as high as the skull base, limited permanent cranial nerve dysfunction, and selective early division and excision of the external carotid artery for complete tumor resection.

Baroreflex Failure: A Rare Complication of Carotid Paraganglioma Surgery

Multiple head and neck paragangliomas are a rare occurrence. We report a patient with removal of bilateral carotid paragangliomas who subsequently developed baroreflex failure 1 month after surgery. The pathology and physiology of this presentation is extremely interesting because it exhibits the complex homeostatic mechanisms involved in the maintenance of steady-state blood pressure. Although rare, it is important to be aware of baroreflex failure and its variable course. Most postsurgical cases occur within days of surgery but, as this report demonstrates, hypertensive urgency can occur weeks to months after surgery; and if not recognized early, it can lead to disastrous postoperative complications such as stroke and myocardial infarction.

Cardiovascular Responses to Stress after Carotid Baroreceptor Denervation in Humans

Iatrogenic bilateral denervation of carotid sinus baroreceptors may occur as a complication of carotid body tumor resection and radiation therapy of the neck. The acute phase of the resulting syndrome of baroreflex failure is characterized by a limited blood pressure buffering capacity against excessive rise or fall in response to emotional and physical stimuli like sexual arousal and cold. Paroxysms of severe hypertension and tachycardia, accompanied by excessive increments in sympathetic tone and catecholamine plasma levels, were ascribed to loss of tonic inhibitory influence of baroreceptors on sympathetic tone. Bilateral anesthetic blockade of baroreceptor afferent nerves was shown to result in a strong increase in muscle sympathetic nerve activity and disruption of its normal patterning. This chapter reviews our findings on the long-term effects of iatrogenic baroreflex trauma on the hemodynamic responses to pharmacological, physical, and emotional stress in the autonomic function laboratory as well as under daily life conditions. Chronic attenuation of baroreflex sensitivity after carotid body tumor resection and neck irradiation results in an increased blood pressure variability. However, unopposed sympathetic activation in response to physical and emotional stress appears to be limited to the acute phase of baroreflex failure.

Denervation of carotid baro- and chemoreceptors in humans

Experimental denervation in animals has shown that carotid baro- and chemoreceptors play an eminent role in maintaining blood pressure and blood gas homeostasis. Denervation of carotid sinus baro- and chemoreceptors in humans may occur as a complication of invasive interventions on the neck or after experimental surgical treatment in asthma. In this topical review, the short- and long-term effects of carotid baro- and chemoreceptor denervation on the control of circulation and ventilation in humans are discussed. Carotid baroreceptor denervation in humans causes a persistent decrease in vagal and sympathetic baroreflex sensitivity and an increase in blood pressure variability; however, carotid denervation does not lead to chronic hypertension. Therefore, although carotid baroreceptors contribute to short-term blood pressure control, other receptors are able to maintain normal chronic blood pressure levels in the absence of carotid baroreceptors. Conversely, carotid chemoreceptor denervation leads to permanent abolition of normocapnic ventilatory responses to hypoxia and reduced ventilatory responses to hypercapnia.

Baroreflex control of muscle sympathetic nerve activity after carotid body tumor resection

Bilateral carotid body tumor resection causes a permanent attenuation of vagal baroreflex sensitivity. We retrospectively examined the effects of bilateral carotid body tumor resection on the baroreflex control of sympathetic nerve traffic. Muscle sympathetic nerve activity was recorded in 5 patients after bilateral carotid body tumor resection (1 man and 4 women, 51+/-11 years) and 6 healthy control subjects (2 men and 4 women, 50+/-7 years). Baroreflex sensitivity was calculated from changes in R-R interval and muscle sympathetic nerve activity in response to bolus injections of phenylephrine and nitroprusside. In addition, sympathetic responses to the Valsalva maneuver and cold pressor test were measured. The integrated neurogram of patients and control subjects contained a similar pattern of pulse synchronous burst of nerve activity. Baroreflex control of both heart rate and sympathetic nerve activity were attenuated in patients as compared with control subjects [heart rate baroreflex sensitivity: 3.68+/-0.93 versus 11.61+/-4.72 ms/mm Hg (phenylephrine, P=0.011) and 2.53+/-1.36 versus 5.82+/-1.94 ms/mm Hg (nitroprusside, P=0.05); sympathetic baroreflex sensitivity: 3.70+/-2.90 versus 7.53+/-4.12 activity/100 beats/mm Hg (phenylephrine, P=0.10) and 3.93+/-4.43 versus 15.27+/-10.03 activity/100 beats/mm Hg (nitroprusside, P=0.028)]. The Valsalva maneuver elicited normal reflex changes in muscle sympathetic nerve activity, whereas heart rate responses were blunted in the patients with bilateral carotid body tumor resection. Maximal sympathetic responses to the cold pressor test did not differ between the two groups. Denervation of carotid sinus baroreceptors as the result of bilateral carotid body tumor resection produces chronic impairment of baroreflex control of both heart rate and sympathetic nerve activity. During the Valsalva maneuver, loss of carotid baroreflex control of heart rate is less well compensated for by the extra carotid baroreceptors than the control of muscle sympathetic nerve activity.

Baroreflex and chemoreflex function after bilateral carotid body tumor resection

OBJECTIVE

To investigate whether bilateral carotid body tumor resection invariably and chronically affects arterial baroreflex or peripheral chemoreflex function.

METHODS

We studied eight consecutive patients (two men and six women; ages 48.1 +/- 11.8 years), a median time of 3.4 years (range 1.3-20.6 years) after bilateral carotid body tumor resection, and 12 healthy control individuals (eight men and four women; ages 53.7 +/- 10.1 years). Baroreflex sensitivity (phenylephrine), blood pressure and its variability (24 h Spacelabs and 5 h Portapres recordings), responses to standard cardiovascular reflex tests and the ventilatory responses to normocapnic and hypercapnic hypoxia were assessed.

RESULTS

Baroreflex sensitivity was lower in patients (6.4 +/- 7.2 ms/mmHg) than in controls (14.7 +/- 6.6 ms/mmHg; P +/- 0.011). Mean office blood pressure and heart rate were normal in patients (123.3 +/- 11.9/79.0 +/- 7.3 mmHg and 67.5 +/- 9.4 beats/min, respectively) and controls (117.8 +/- 10.6/74.0 +/- 6.8 mmHg and 61.1 +/- 9.2 beats/min, respectively). Blood pressure variability was increased during ambulatory measurements. Three patients exhibited orthostatic hypotension. The Valsalva ratio, an index of baroreflex-mediated cardiovagal innervation, was lower in patients (1.4 +/- 0.2) than in controls (1.8 +/- 0.5; P +/- 0.008). The normocapnic ventilatory response to hypoxia was absent in all patients, whereas a small residual response to hypoxia was observed under hypercapnic conditions in two patients.

CONCLUSIONS

Bilateral carotid body tumor resection results in heterogeneous expression of arterial baroreflex dysfunction, whereas the normocapnic hypoxic drive is invariably abolished as a result of peripheral chemoreflex failure.

Arterial baroreflex and peripheral chemoreflex function after radiotherapy for laryngeal or pharyngeal cancer

PURPOSE

Denervation of the carotid sinus causes baroreflex and chemoreflex failure, resulting in labile hypertension and loss of hypoxic responsiveness. We investigated whether radiation therapy for laryngeal or pharyngeal cancer affects baroreflex and chemoreflex function.

METHODS AND MATERIALS

Twelve patients were studied after radiation therapy for locally advanced laryngeal or pharyngeal cancer (11 male, 1 female, age: 56.0 +/- 7.9 years), 3.3 years (median; range 1.0-4.7) after radiotherapy and 15 healthy controls (11 male, 4 female, 53.4 +/- 9.2 years). We measured baroreflex sensitivity (phenylephrine), blood pressure level and variability (24-h Spacelabs and 5-h Portapres recordings), responses to cardiovascular reflex tests, and the ventilatory responses to normocapnic and hypercapnic hypoxia.

RESULTS

Baroreflex sensitivity was lower in patients (9.7 +/- 7.8 ms/mm Hg) than in controls (17.5 +/- 10.3 ms/mm Hg, p = 0.011). Mean office blood pressure was significantly higher in patients (141.5 +/- 27.8/89.2 +/- 10.6 mm Hg, 63.3 +/- 12.3 bpm) than in controls (117.3 +/- 10.1/75.1 +/- 6.8 mm Hg, 61.8 +/- 10.8 bpm). Blood pressure variability was not different between groups, nor were the responses to reflex tests. The normo/hypercapnic ventilatory response to hypoxia was similar in patients (0.21 +/- 0.10/1.37 +/- 0.60 L/min/%) and controls (0.22 +/- 0.16/1.19 +/- 0.78 L/min/%).

CONCLUSIONS

Radiation therapy for laryngeal or pharyngeal carcinoma does not affect chemoreflex function, but results in an attenuated baroreflex sensitivity. Clinically relevant blood pressure lability is absent however.

Four faces of baroreflex failure: hypertensive crisis, volatile hypertension, orthostatic tachycardia, and malignant vagotonia

BACKGROUND

The baroreflex normally serves to buffer blood pressure against excessive rise or fall. Baroreflex failure occurs when afferent baroreceptive nerves or their central connections become impaired. In baroreflex failure, there is loss of buffering ability, and wide excursions of pressure and heart rate occur. Such excursions may derive from endogenous factors such as stress or drowsiness, which result in quite high and quite low pressures, respectively. They may also derive from exogenous factors such as drugs or environmental influences.

METHODS AND RESULTS

Impairment of the baroreflex may produce an unusually broad spectrum of clinical presentations; with acute baroreflex failure, a hypertensive crisis is the most common presentation. Over succeeding days to weeks, or in the absence of an acute event, volatile hypertension with periods of hypotension occurs and may continue for many years, usually with some attenuation of pressor surges and greater prominence of depressor valleys during long-term follow-up. With incomplete loss of baroreflex afferents, a mild syndrome of orthostatic tachycardia or orthostatic intolerance may appear. Finally, if the baroreflex failure occurs without concomitant destruction of the parasympathetic efferent vagal fibers, a resting state may lead to malignant vagotonia with severe bradycardia and hypotension and episodes of sinus arrest.

CONCLUSIONS

Although baroreflex failure is not the most common cause of the above conditions, correct differentiation from other cardiovascular disorders is important, because therapy of baroreflex failure requires specific strategies, which may lead to successful control.

[Baroreflex failure syndrome: an uncommon case of an extreme blood pressure variability]

INTRODUCTION

The arterial baroreflex operates in physiological conditions. It induces sympathetic and vagal activity modulation resulting in arterial tone and heart rate changes. These appropriate responses limit blood pressure fluctuations and blood pressure is therefore regulated since the baroreflex constantly buffers the changes.

EXEGESIS

Bilateral carotid body tumor excision resulted in excessive fluctuations of blood pressure. Indices of spontaneous baroreflex activity were markedly altered in the patient described herein.

CONCLUSION

The excessive fluctuations of blood pressure due to the sinoaortic denervation demonstrate how powerful is this negative feedback control mechanism in control conditions.