Francisco J. Valderrama-Canales

The central projections of the laryngeal nerves in the rat.

The larynx serves respiratory, protective, and phonatory functions. The motor and sensory innervation to the larynx controlling these functions is provided by the superior laryngeal nerve (SLN) and the recurrent laryngeal nerve (RLN). Classical studies state that the SLN innervates the cricothyroid muscle and provides sensory innervation to the supraglottic cavity, whereas the RLN supplies motor innervation to the remaining intrinsic laryngeal muscles and sensory innervation to the infraglottic cavity, but recent data suggest a more complex anatomical and functional organisation. The current neuroanatomical tracing study was undertaken to provide a comprehensive description of the central brainstem connections of the axons within the SLN and the RLN, including those neurons that innervate the larynx. The study has been carried out in 41 adult male Sprague–Dawley rats. The central projections of the laryngeal nerves were labelled following application of biotinylated dextran amines onto the SLN, the RLN or both. The most remarkable result of the study is that in the rat the RLN does not contain any afferent axons from the larynx, in contrast to the pattern observed in many other species including man. The RLN supplied only special visceromotor innervation to the intrinsic muscles of the larynx from motoneurons in the nucleus ambiguus (Amb). All the afferent axons innervating the larynx are contained within the SLN, and reach the nucleus of the solitary tract. The SLN also contained secretomotor efferents originating from motoneurons in the dorsal motor nucleus of the vagus, and special visceral efferent fibres from the Amb. In conclusion, the present study shows that in the rat the innervation of the larynx differs in significant ways from that described in other species.

Reorganization of laryngeal motoneurons after crush injury in the recurrent laryngeal nerve of the rat

Motoneurons innervating laryngeal muscles are located in the nucleus ambiguus (Amb), but there is no general agreement on the somatotopic representation and even less is known on how an injury in the recurrent laryngeal nerve (RLN) affects this pattern. This study analyzes the normal somatotopy of those motoneurons and describes its changes over time after a crush injury to the RLN. In the control group (control group 1, n = 9 rats), the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were injected with cholera toxin‐B. In the experimental groups the left RLN of each animal was crushed with a fine tip forceps and, after several survival periods (1, 2, 4, 8, 12 weeks; minimum six rats per time), the PCA and TA muscles were injected as described above. After each surgery, the motility of the vocal folds was evaluated. Additional control experiments were performed; the second control experiment (control group 2, n = 6 rats) was performed labeling the TA and PCA immediately prior to the section of the superior laryngeal nerve (SLN), in order to eliminate the possibility of accidental labeling of the cricothyroid (CT) muscle by spread from the injection site. The third control group (control group 3, n = 5 rats) was included to determine if there is some sprouting from the SLN into the territories of the RLN after a crush of this last nerve. One week after the crush injury of the RLN, the PCA and TA muscles were injected immediately before the section of the SLN. The results show that a single population of neurons represents each muscle with the PCA in the most rostral position followed caudalwards by the TA. One week post‐RLN injury, both the somatotopy and the number of labeled motoneurons changed, where the labeled neurons were distributed randomly; in addition, an area of topographical overlap of the two populations was observed and vocal fold mobility was lost. In the rest of the survival periods, the overlapping area is larger, but the movement of the vocal folds tends to recover. After 12 weeks of survival, the disorganization within the Amb is the largest, but the number of motoneurons is similar to control, and all animals recovered the movement of the left vocal fold. Our additional controls indicate that no tracer spread to the CT muscle occurred, and that many of the labeled motoneurons from the PCA after 1 week post‐RLN injury correspond to motoneurons whose axons travel in the SLN. Therefore, it seems that after RLN injury there is a collateral sprouting and collateral innervation. Although the somatotopic organization of the Amb is lost after a crush injury of the RLN and does not recover in the times studied here, the movement of the vocal folds as well as the number of neurons that supply the TA and the PCA muscles recovered within 8 weeks, indicating that the central nervous system of the rat has a great capacity of plasticity.

Somatotopy of the Neurons Innervating the Cricothyroid, Posterior Cricoarytenoid, and Thyroarytenoid Muscles of the Rat's Larynx

Neurons innervating the intrinsic muscles of the larynx are located within the nucleus ambiguus but the precise distribution of the neurons for each muscle is still a matter for debate. The purpose of this study was to finely determine the position and the number of the neurons innervating the intrinsic laryngeal muscles cricothyroid, posterior cricoarytenoid, and thyroarytenoid in the rat. The study was carried out in a total of 28 Sprague Dawley rats. The B subunit of the cholera toxin was employed as a retrograde tracer to determine the locations, within the nucleus ambiguus, of the neurons of these intrinsic laryngeal muscles following intramuscular injection. The labelled neurons were found ipsilaterally in the nucleus ambiguus grouped in discrete populations with reproducible rostrocaudal and dorsoventral locations among the sample of animals. Neurons innervating the cricothyroid muscle were located the most rostral of the three populations, neurons innervating the posterior cricoarytenoid were found more caudal, though there was a region of rostrocaudal overlap between these two populations. The most caudal were the neurons innervating the thyroarytenoid muscle, presenting a variable degree of overlap with the posterior cricoarytenoid muscle. The mean number (±SD) of labelled neurons was found to be 41 ± 9 for the cricothyroid, 39 ± 10 for the posterior cricoarytenoid and 33 ± 12 for the thyroarytenoid. Anat Rec, 296:470–479, 2013.

Somatotopic Changes in the Nucleus Ambiguus After Section and Regeneration of the Recurrent Laryngeal Nerve of the Rat

Changes in motoneurons innervating laryngeal muscles after section and regeneration of the recurrent laryngeal nerve (RLN) are far from being understood. Here, we report the somatotopic changes within the nucleus ambiguus (Amb) after the nerve injury and relates it to the resulting laryngeal fold impairment. The left RLN of each animal was transected and the stumps were glued together using surgical fibrin glue. After several survival periods (1, 2, 4, 8, 12, 16 weeks; at least six rats at each time point) the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) muscles were injected with fluorescent‐conjugated cholera toxin and the motility of the vocal folds evaluated. After section and subsequent repair of the RLN, no movement of the vocal folds could be detected at any of the survival times studied and the somatotopy and the number of labeled motoneurons changed. From 4 wpi award, the somatotopy was significantly disorganized, with the PCA motoneurons being located rostrally relative to their normal location. A rostrocaudal overlap between the two pools of motoneurons supplying the PCA and TA muscles was observed from 2 wpi onwards. Hardly any labeled neurons were found in the contralateral Amb in any of the experimental groups. An injury of the RLN leads to a reinnervation of the denervated motor endplates of PCA and TA. However, misdirected axons sprout and regrowth from the proximal stump to the larynx. As a result, misplaced innervation of muscles results in a lack of functional recovery of the laryngeal folds movement following a RLN injury. Anat Rec, 297:955–963, 2014.

Human laryngeal ganglia contain both sympathetic and parasympathetic cell types.

The presence of ganglia associated with the laryngeal nerves is well documented. In man, these ganglia have been less well studied than in other species and, in particular, the cell types within these ganglia are less well characterized. Using a panel of antibodies to a variety of markers found in the paraganglion cells of other species, we were able to show the existence of at least two populations of cells within human laryngeal paraganglia. One population contained chromogranin and tyrosine hydroxylase representing a neurosecretory population possibly secreting dopamine. A second population of choline acetyltransferase positive cells would appear to have a putative parasympathetic function. Further work is needed to characterize these cell populations more fully before it will be possible to assign functions to these cell types but our results are consistent with the postulated functions of these ganglia as chemoreceptors, neurosecretory cells, and regulators of laryngeal mucus secretion. Clin. Anat. 23:673–682, 2010.

Anatomical variations of the renal arteries: Cadaveric and radiologic study, review of the literature, and proposal of a new classification of clinical interest

PURPOSE To analyse the variations of the renal arteries in two samples, cadaveric and computerized tomographic (CT) images, as well as to propose a simple classification of such variations based on the obtained results and an extensive review of the literature on the topic. MATERIAL AND METHODS Sixty human dissected kidneys and their vessels, and 583 abdominal CT were studied. RESULTS A total of 86 arteries were described in the cadaveric sample, whereas 1223 were analysed in the radiological one. Five types (a-e) and patterns (I-V) have been stablished in the classification. Type a, aortic hilar artery, incidences were 79% in cadavers and 95% in CT; Type b, hilar upper polar artery, incidences were 10% in cadavers and 2% in CT; Type c, aortic upper polar artery, incidences were 5% in cadavers and 2% in CT; Type d, aortic lower polar artery, incidences were 3% in cadavers and 1% in CT; Type e, hilar lower polar artery, incidences were 2% in cadaver and less than 0.1% in CT. The pattern represents the number of arteries reaching one kidney. Patterns I-IV were found in cadavers (I: 78%; II: 19%; III and IV: 2%); in CT sample only patterns I (88%) and II (12%). Pattern V was added because it has been described in the reviewed literature. CONCLUSIONS Type a and pattern I are the most prevalent, both in the cadaveric and the CT samples. Also in the consulted literature. There are no differences in the types and pattern incidences by side or sex. A simple, comprehensive and useful classification is proposed.

Anatomic Study of Human Laryngeal Ganglia: Number and Distribution

We have studied 12 laryngeal nerves: six internal branches of the superior laryngeal nerve (ILN) and six recurrent laryngeal nerves (RLN) from three human adult larynges (two males and one female). After dissection of each individual laryngeal nerve using a surgical microscope, the nerves were preserved in 10% formalin, embedded in paraffin wax, serially sectioned transversely at a thickness of 10 μm and stained with hematoxylin and eosin. We found 2–4 ganglia associated with the ILN. At least two ganglia were always present (six out of six cases), the largest one being associated with the branch of the nerve innervating the vestibule and the smallest one associated with the branch innervating the aryepiglottic fold. Other ganglia were found associated with the branches for the glosso‐epiglottic fold and vallecula (four out of six cases) and interarytenoid muscle (three out of six cases). The RLN showed from two to six ganglia, all of them located in its anterior terminal division. Two of the ganglia were located in the part of the nerve between the origin of the branches for the interarytenoid and lateral cricoarytenoid muscles (three out of six cases). The remaining ganglia were located close to or at the origin of the muscular branches innervating the intrinsic laryngeal muscles. The cytology of the ganglia reported suggests that they were all autonomic in nature, probably parasympathetic. Clin. Anat. 21:641–646, 2008.

Estudio del número de neuronas del núcleo ambiguo y sus parámetros morfométricos tras lesión y regeneración del nervio laríngeo recurrente de la rata

Introduccion y objetivo Para conseguir la reinervacion funcional y/o el trasplante ortotopico tras lesiones de los nervios laringeos es esencial conocer la reorganizacion morfofuncional de las neuronas que inervan la laringe. Debido a la escasez de este tipo de estudios en la literature consultada, en nuestro trabajo estudiamos la organizacion de las motoneuronas laringeas del nucleo ambiguo (NA) tras seccion y posterior regeneracion del nervio laringeo recurrente (NLR) de la rata adulta. Material y metodos El trazador utilizado fue la dextranamina biotinada (BDA) de peso molecular 3 kDa, lo que representa una innovacion en la literatura cientifica consultada, nunca antes utilizada en este modelo. Los sujetos se distribuyeron en un grupo control de 14 animales y cuatro grupos experimentales de entre 10 y 16 animales cada uno. En los grupos experimentales se estudio la regeneracion en cuatro intervalos de tiempo tras la axotomia: entre 21 y 28 dias, entre 42 y 60 dias, entre 90 y 120 dias y entre 150 y 180 dias. En el grupo control se trazo el NLR intacto y en los grupos experimentales el NLR axotomizado despues de cada intervalo de regeneracion. Resultados El numero de neuronas marcadas en el grupo control fue de 143 ± 38; en los grupos experimentales el numero de neuronas trazadas fue siempre menor que en el grupo control (21-28 dias: 14 ± 23 neuronas; 42-60 dias: 46 ± 49; 90-120 dias: 55 ± 57; 150-180 dias: 61 ± 60). No se encontraron diferencias estadisticamente significativas entre el grupo control y los grupos experimentales en los parametros morfometricos analizados para los somas neuronales. Conclusiones Los resultados muestran que la axotomia del NLR de la rata comporta una disminucion en el numero de neuronas trazadas del NA, pero no afecta al tamano ni su forma en los periodos estudiados.

Proyecciones centrales del nervio laríngeo superior de la rata

Laryngeal nerves contain the fibres that control the laryngeal function. On the rat, the studies on the functional components and the real origin of the fibres conveyed by the superior laryngeal nerve (SLN) are few. No one of such works were developed using biotinylated dextrane amines (BDA), a powerful tool for tracing neural pathways. The aim of our study was to identify by using BDA, in the rat, the nuclei of real origin of the fibres of the SLN, knowing in this way the functional components of this nerve. The study has been developed in 11 adult male Sprague-Dawley rats, applying the BDA into the damaged SLN. The results obtained in all the animals shown that the rat SLN carries efferent fibres originated within the ipsilateral nucleus ambiguous (NA) and dorsal nucleus of the vagus (DNV), and that afferent fibres reach the tractus solitari and the nucleus tractus solitari. So, in the rat, the SLN seems to convey efferent fibres from the NA and DNV and, probably, all the laryngeal afferent fibres.

Cadaveric and radiologic study of the anatomical variations of the prostatic arteries: A review of the literature and a new classification proposal with application to prostatectomy.

Development of prostatic arterial embolization (PAE) to treat benign prostatic hyperplasia (BPH) has raised interest in the variations of the prostatic arteries (PA). The aim of this study is to identify these vascular variations, to compare them with previous data, and to propose a simple classification. Ten adult male pelvis sides from embalmed cadavers were dissected, ages 69 to 92 years, and 10 PA were examined. In a retrospective analysis of 34 DSA pelvic angiographies on 28 patients aged 50 to 90 years, 48 PA were identified. A total of 58 PA were therefore analyzed. Six types are defined. Type I: PA originates from the anterior division (AD) of the internal iliac artery (IIA), 20.7%; Type II: PA emerges from the obturator artery (OA), 5.2%; type III: PA arises from the gluteal‐pudendal trunk (GPT), 27.5%; Type IV: PA originates from the internal pudendal artery (IPA), 29.3%; Type V: PA comes from the middle rectal artery (MRA), 15.5%. Other origins, not observed in our sample but described in the literature, were amalgamated under Type VI. The AD/GPT/IPA stem is the main source of the PA. Analysis of the definitions of IIA branches and the associated terminology is necessary for interpreting the results reported by several authors on different samples, but in general the results fit the meta‐analysis well. A new, simple, and complete classification for vascular variations of the PA is proposed. Clin. Anat. 30:71–80, 2017.