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Carotid body tumours.

Carotid body tumours are rare, but important. Their reputation for slow growth and virtual non-malignancy has had, in the light of experience, to be revised. Sudden spurts of growth are well known, and the tumour may become irremovable in a relatively short time. Aggressive local invasion and widespread metastasis are now well recognized. Histological features are no guide to malignancy. These tumors can nearly all be removed with an acceptable mortality and morbidity, without damage to the internal carotid artery. Ideally the diagnosis should be made by clinical acumen and confirmatory X-ray examination. Biopsy makes subsequent removal of the tumour much more difficult, and should be avoided if at all possible. Eleven personal cases of carotid body tumours are reported, and the technique of surgical excision is discussed in detail.

Adult

Surgical management of carotid body tumor.

Carotid body tumor or chemodectoma is a slow-growing lesion; it should be diagnosed early to facilitate the technical surgical resection. When these lesions are large, the routine use of a carotid internal bypass shunt is advocated for their safe removal. With the newer vascular approaches, specifically the carotid internal bypass shunt, resection can be performed with acceptable risks. A patient with large bilateral carotid body tumors had successful resection of both these lesions.

Carotid Body Tumor

Chronically denervated rat carotid bodies.

The ninth nerve was severed and the rat carotid body studied in the light and electron microscopes and after formaldehyde-induced fluorescence for its catecholamine content from 3 weeks to 13 months after operation. Minimal changes in the carotid body were observed. Hyperthrophy of the capsule cell was noticed up to about 2 months, after which time these cells appeared normal. Lysosomes in the capsule cells occurred more frequently and were larger than in normal carotid bodies. Discernible pathological alterations did not occur in the glomus cells, despite the absence of afferent terminals upon them. Atrophy of the carotid body was not noticed. The catecholamine content of the denervated carotid body was comparable to its innervated control and no nerve terminals were found on the glomus cells. Autonomic ganglion cells intrinsic to the carotid body varied in number from 1 to 8 and in location. The glomus cells do not receive any significant autonomic innervation, and the ganglion cells in the carotid body, perhaps sympathetic, probably innervate blood vessels. It is concluded that deafferentation has minimal morphological effects on the carotid body. The reactions of other receptor cells to deafferentation are compared with those of the glomus cells.

Animals

Ultrastructural abnormalities of the carotid body in sudden infant death syndrome.

The carotid bodies of four infants who died of sudden infant death syndrome (SIDS) were compared, using electron microscopic techniques, with the carotid bodies of various control subjects. In the SIDS patients, there was a marked reduction or absence of the dense cytoplasmic granules of the carotid chemorecptor cells, as well as a reduction in cell number and size. These ultrastructural abnormalities may be pathophysiologically related to SIDS. A defect in this respiratory control organ could block normal stimulation of respiration during the periods of hypoxia that occur during episodes of sleep apnea in infancy. Further studies by electron microscopy are required to confirm degranulation of the carotid body as a pathognomonic sign of SIDS. Screening of high-risk infants should be directed at studying the carotid body and its mediated responses to hypoxia.

Carotid Body

The topographical anatomy and blood supply of the carotid body region of the domestic fowl.

The topographical anatomy of the carotid body region was investigated on both sides in 30 adult domestic fowls (Gallus gallus domesticus). On each side of the body the two parathyroid glands always adhered to each other, the caudal gland being the smaller. The right cranial parathyroid usually touched the thyroid gland, but on the left side the two glands were nearly always separate. The ultimobranchial gland was usually attached to the parathyroid glands on the left side, but was always well separated on the right side. The carotid body, the identity of which was checked by light and electron microscopy, was ovoid in shape, whitish in colour, and about 0.8 x 0.6 x 0.5 mm in size. It was almost always in direct contact with the medial surface of one or both parathyroid glands have commonly been portrayed astopographically separate from each other. The oesophagotracheobronchial artery, the artery to the carotid body, and the caudal thyroid artery arose close together, though in variable positions, from the lateral aspect of the common carotid artery. The artery to the carotid body was always the middle of the three. The venous drainage of the carotid body was associated with the veins of the parathyroid and ultimobranchial glands. The carotid body was innervated by a filament from the distal vagal ganglion. The topographical observations on the carotid body region have been compared with those of other authors. The cranial and caudal parathyroid glands have commonly been portrayed as topographically separate from each other. The carotid body has seldom been depicted in direct contact with the parathyroid glands. The size of the carotid body has invariably been shown far too large. These discrepancies are discussed and are attributed largely to the reliance by other authors on serial reconstruction rather than microdissection.

Animals

Carotid body hypertrophy in patients with cystic fibrosis and cyanotic congenital heart disease.

The carotid bodies from 71 patients ranging in age from 28 weeks' gestation to 30 years were obtained at autopsy. Patients were divided into two groups based on the presence or absence of chronic hypoxemia. There was a high correlation between the weight of individual carotid bodies in each case. Among the 12 patients with chronic hypoxemia, eight patients had carotid bodies heavier than predicted by statistical analysis. Of these eight patients, six had cystic fibrosis and two had cyanotic heart disease. Morphometric and cell population analyses of the carotid bodies from these eight patients and from those of the control population indicated that enlargement of the carotid bodies during normal or abnormal growth results from proportionate increases in lobule parenchyma and stroma. There was also an increase in the width and length of the lobules without an increase in the diameter of the cell cords or a change in the size or proportion of the chief cells. Growth and development of the carotid bodies were studied in a control group of 59 patients without chronic hypoxemia. There were no sex related differences in carotid body weights. The combined weight of the carotid bodies correlated most strongly with body weight, although there was some correlation with age and body length. A regression equation reflecting the data relating to body weight (BW) is: Combined weight of carotid bodies (in mg.) = 0.29 BW (in kg.) +3.0. Leukemic infiltrates were present in two patients with acute lymphocytic leukemia, and diffuse lymphocytic infiltration with nodule formation was present in one patient with mental retardation. Metaplastic cartilage was present in a carotid body of one patient.

Adolescent

Canine ventilation after acid-base infusions, exercise, and carotid body denervation.

We studied the effect of exercise and carotid body denervation on the ventilatory response which occurs following acute acid-base infusions. Studies were done in 6 dogs prepared with chronic tracheostomies and carotid loops. Ventilation (VE) and arterial pH were measured at rest and during exercise before and after infusions of lactic acid (70 meq), HCl (26 meq), NaHCO3 (45 and 90 meq), or normal saline alone (250 ml). The VE response to [H+] is expressed as 1.min-1/[H+] in nmol.kgH2O-1. Before carotid body denervation (CBD), the response was 0.1 l.min-1[H+] at rest, 1.2 1.min-1/[H+] during exercise. After CBD there was no ventilatory response to [H+] at rest or during exercise. We conclude that 1) Exercise potentiates the [H+] stimulus to breathing. 2) For small changes in arterial [H+], this exercise potentiation is a function of the carotid body. 3) Therefore, that exercise potentiates the carotid body response directly and/or the central projection of this input in the central nervous system. 4) Finally, since carotid body denervation eliminates only 7% (0.8 1.min-1) of ventilation at pH 7.35 in these dogs, that the effective threshold for this ventilatory response approximates a pH slightly greater than 7.35.

Acid-Base Imbalance

Freeze-fracture study of the carotid body.

Replicas of freeze-fractured rat carotid body chief (Type I) cells reveal the normal complement of cytoplasmic organelles. En face fractures of the chief cell plasmalemma exhibit occasional sites of fusion of the amine-containing vesicles which characterize the carotid body. The endothelial cells lining the capillary network of the carotid body display numerous pinocytotic vesicles often oriented in linear arrays, and occasional fenestrae. The endothelial cells are joined together by tight junctions which appear as grooves (B face) forming a continuous network over the membrane.

Animals

Effects of temperature on some membrane characteristics of carotid body cells.

Excised cat carotid bodies and nerves were placed in a Lucite chamber through which saline flowed at different temperatures. Action potentials were recorded with a suction electrode. Glomus cells were impaled with microelectrodes and identified by ejecting Procion navy blue from the micropipette. Membrane potentials (MP) averaged 20 mV and input resistances (R0), 40 Momega. Cooling induced depolarization and decreased R0. This effect had a reversal potential of about -6 mV. [K+]0 did not affect MP, R0, or cooling effects. Lack of sodium increased MP, R0, and depressed cooling effects. Low chloride had opposite effects. Ca2+ and Mg2+ influenced MP and R0 but had little effects on temperature actions. Ouabain decreased MP and R0. Results indicate that glomus cells are exquisitely sensitive to temperature changes; their MP and R0 increase with high temperatures and decrease when temperature is lowered. These effects are mostly dependent on the external concentration of Cl- and Na+. Glomus cells may be the site of the intense metabolism of this tissue and thus contribute to the generation of chemosensory impulses.

Animals

Hyperplasia of vagal and carotid body paraganglia in patients with chronic hypoxemia.

Vagal and carotid body paraganglia were obtained from 43 randomly selected autopsies performed at the National Naval Medical Center. In each case, tissue from both sides was step sectioned and comparatively studied. The mean combined weight of carotid bodies in 37 control patients was 25.9 mg. There was good correlation between size and number of separate paraganglia comprising the vagal body (seven left, six right). Lobules were closely related to the ganglion nodosum and were actually within it in three instances. Tissue resembling parathyroid was encountered within 4 of the 86 resected vagus nerves. Lymphocytic infiltration occurred in carotid and vagal body paraganglia of 28% and 16% of patients, respectively. There was Schwann cell proliferatation in carotid body lobules of 2 patients; in another patient, talc emboli were present. The mean combined weight of carotid bodies in 6 patients with chronic hypoxemia was 47.6 mg, significantly greater than in the control group; in each case, lobules were enlarged. Chief cell hyperplasia occurred in vagal body paraganglia of 2 patients; in two other patients, lobules were large with equal proliferation of constituent cells. These morphologic findings indicate that in patients with chronic hypoxemia some vagal body paraganglia can be ascribed a chemoreceptor role similar to but probably less important than that of the carotid body.

Adolescent

Cyanotic heart disease: "low altitude" risk for carotid body tumor?

A young woman with hypoplastic right heart syndrome developed a carotid body tumor at age 28. High altitude habitation is known to predispose to hyperplastic and neoplastic carotid bodies; emphysema and congenital cyanotic heart disease have recently been shown to induce hyperplasia of this oxytrophic tissue. Therefore, a link between congenital cyanosis and carotid body tumor is suggested by this patient. Carotid bodies are nonchromaffin paraganglionic analogues of the adrenal medulla. Congenital cyanosis has an association with pheochromocytoma. In the cyanotic milieu carotid body tumor may be a histological analogue of pheochromocytoma.

Adult

Axonal transport of labeled material into sensory nerve ending of cat carotid body.

The origin of nerve endings on glomus cells in the carotid body has been the subject of much controversy in recent years. Specifically, the problem is whether these nerve endings, which contain clear-core ("synaptic") vesicles and mitochondria arise from sensory neurons in the petrosal ganglion or from efferent neurons located in the brain stem or elsewhere. To study this problem, [3H]proline was applied to cat petrosal ganglia, the animals were allowed to survive for 3 h-7 days, and the peripheral distribution of the label was analyzed by sample oxidation/scintillation counting and by EM autoradiography. The time courses of distribution of label along the nerves and the accumulation of label in the carotid body indicated the presence of fast, intermediate and slow components of axonal flow. EM autoradiographs of carotid bodies showed the label localized almost exclusively to nerve fibers and to nerve terminals on glomus cells. As much as 60--90% of the nerve terminals were labeled in a given ultrathin-section autoradiograph. Passive movement of label from the injection site, or fibers of passage (efferent) through the ganglion, did not contribute to the labeled material since administration of [3H]proline onto the desheathed nerve away from the ganglion was ineffective in labeling the carotid body. The results suggest that most, if not all, nerve terminals on glomus cells in cat carotid body arise from neurons in the petrosal ganglion.

Animals

Computed tomography of a carotid body tumor.

A patient with a carotid body tumor was evaluated by computed tomography. The tumor demonstrated an enhanced rim and a central lower density. This corresponds to the "eggshell" appearance described angiographically in carotid body tumors.

Adult

Respiratory response to HCl acidosis in dogs after carotid body denervation.

To test the participation of the carotid bodies in the respiratory response to metabolic acidosis, six dogs were infused with HCl for 2 h followed by HCl feeding to prolong the acidosis to 48 h. This protocol was repeated after carotid body denervation (CBD). Mean control PCO2 rose by 7.3 Torr after CBD. PCO2 fell comparably during acidosis before and after CBD at all time periods from 30 to 48 h and returned to control levels by 72 h. The pH ranged from 7.10 to 7.30 during acidosis pre- and post-CBD. The decreases in pH and bicarbonate concentration did not differ significantly at any time interval between the pre- and post-CBD studies. This study indicates that in dogs moderately severe HCl acidosis stimulates ventilation acutely and chronically through a central mechanism in the absence of the carotid bodies.

Acidosis