The tympanoperiotic complex of the blue whale, Balaenoptera musculus.

The tympanoperiotic complex of a blue whale Balaenoptera musculus is described and compared to the homologous structures in the other extant and fossil baleen whale species. The periotic and the tympanic bulla represent informative anatomical regions in both functional and phylogenetic studies and for this reason a micro-CT scan of the bones was performed in order to better characterize their external aspect and to reconstruct the inner structures. In particular, the cochlea, the semicircular canals and associated portions of the periotic are reconstructed so that these structures may be used in phylogenetic analyses. We observed that the blue whale periotic is characterized by the presence of a strong dorsal protrusion which is posteriorly bordered by a previously undescribed morphological character that we name the posterotransverse fossa. The peculiar shape of the anterior process and the en echelon organization of the posterior foramina of the pars cochlearis are also described and compared. From a phylogenetic perspective, the blue whale is confirmed to be closely related to the fin whale, Balaenoptera physalus, but it is suggested, based on ear bone characters only, that it diverged before the other balaenopterid species in the phylogeny of Balaenopteridae. This placement supports a series of morphological observations suggesting that the extant blue whale was an early-diverging member of Balaenoptera. Our results help to decipher the evolutionary origin of the blue whale, the largest living animal, by allowing new and more detailed morphological analyses of the balaenopterid fossil record.

The tympanic region of the skull in extant pinnipeds: A pilot study of auditory morphological disparity using linear morphometric principal component analysis.

Pinnipeds are unique semiaquatic taxa possessing adaptations to hear efficiently both in water and on land. Research over the past century is extremely limited on the auditory apparatus morphology of pinnipeds, which include the Families Phocidae (true seals), Otariidae (sea lions/fur seals), and Odobenidae (walruses). Our extensive literature review revealed inaccurate terminology of this region, with details corresponding only to terrestrial taxa, and a severe lack of information due to very few current studies. This demonstrates the need for evaluation and comparison of the auditory morphologies of modern terrestrial and semiaquatic carnivorans in relation to hearing. This initial study compares tympanic bullar morphologies of Phocidae to other pinnipeds and representatives of terrestrial carnivoran families. Morphological correlations of the basicranial auditory region were also compared within phocid subfamilies. Eleven skull measurements and about eleven calculated ratios were included in multiple principal component analyses to determine what areas of the auditory apparatus had the most significant morphological variation. This is the first study using this methodology, especially in reference to the hearing adaptations of pinnipeds, specifically in phocids. Results demonstrate distinct trends in phocid bullar morphology relative to other pinnipeds. Analyses reveal that: (1) phocids generally have different bullar morphology than otariids and odobenids; (2) Neomonachus schauinslandi (Hawaiian monk seal) and Neomonachus tropicalis (Caribbean monk seal) have unique morphology compared to phocids and other pinnipeds. Future work with increased number of specimens will further substantiate these findings and both ontogenetic and sexual variations will be examined.

The Middle Ear Microbiota in Healthy Dogs Is Similar to That of the External Ear Canal.

Otitis media can be a consequence of chronic otitis externa and could represent a perpetuating factor. While the microbiota of the EEC in healthy dogs and in the presence of otitis externa has been described, only sparse information is available concerning the normal microbiota of the middle ear. The objective was to compare the tympanic bulla (TB) with the external ear canal (EEC) microbiota in healthy dogs. Six healthy experimental Beagle dogs were selected based on the absence of otitis externa, negative cytology and bacterial culture from the TB. Samples from the EEC and TB were collected directly after death using a total ear canal ablation and lateral bulla osteotomy. The hypervariable segment V1-V3 of the 16S rDNA was amplified and sequenced with a MiSeq Illumina. The sequences were analyzed by the Mothur software using the SILVA database. No significant differences between the EEC and TB microbiota for the Chao1 richness index (p = 0.6544), the Simpson evenness index (p = 0.4328) and the reciprocal Simpson alpha diversity (p = 0.4313) were noted (Kruskal-Wallis test). A significant difference (p = 0.009) for the Chao1 richness index between the right and left EEC was observed. The microbiota profile was similar in the EEC and the TB of the Beagles.

MRI of a middle ear cholesteatoma in a cat.

A 9-year-old Maine coon cat presented with right-sided Horner and facial nerve paralysis. Magnetic resonance imaging (MRI) showed a heterogeneously contrast-enhancing mass occupying the right dorsolateral compartment of the tympanic cavity and extending into the ventromedial compartment, which was expanded and fluid filled. A ventral bulla osteotomy was performed to debulk the soft tissue mass. Histopathology revealed a cholesteatoma. The cat showed slow improvement of clinical signs and was euthanized eleven months postoperatively for unrelated causes. The MRI characteristics of middle ear cholesteatoma in the present case varied from those described in humans and dogs.

Ecological correlates of the morphology of the auditory bulla in rodents: Application to the fossil record.

For rodents, hearing is essential to survival. It enables predator evasion, prey detection, and conspecific recognition; it is also likely to be constrained by the physical environment. The resulting hypothetical link between tympanic bulla morphology and ecology has never been investigated across a broad array of rodent species before. Such link may enable the determination of the ecological affinities of many fossil species only known from partial skulls. In this study, we used geometric morphometrics to quantify the shape of the auditory bulla of 197 specimens representing 91 species from 17 families of extant rodents across four different locomotory modes. We used landmarks and semi-landmarks on the ventral and lateral views of the skull to capture morphological characteristics of the bulla and external auditory meatus (EAM). Our results demonstrate an association between bullar morphology and locomotion in rodents. Bullar shape enables the correct classification of 76% of the species in our training set. Fossorial taxa, in particular, show a characteristic morphology including an asymmetric bulla with a dorsally located and laterally expanded EAM that has a small opening diameter. A phylogenetically informed flexible discriminant analysis shows a weak phylogenetic effect on tympanic morphology. There is no evidence for differences in bullar hypertrophy across locomotory categories. The application of this approach to select fossil rodents from the Oligo-Miocene shows broad agreements with prior studies and yields new locomotory inferences for 14 fossil species, including the first proposed locomotion for members of the family Florentiamyidae. Such results call for the timing of burrowing diversification in rodents to be reevaluated.

Improved postauricular surgical approach to the round window of rats.

OBJECTIVES: Research using rat as an in-vivo model has played an important role in otological research. The rat ear anatomy has been described; however, detailed surgical procedures to access the temporal bone are limited. The authors present a technique to approach the inner ear of rat that was standardized by cadaveric dissections and later replicated in living animals. METHODS: Adult Wistar albino rats were dissected via the post-auricular approach. The emphasis was on early identification of the facial nerve that formed a reliable landmark for the tympanic bulla, which in turn houses the round window and stapedial artery. The point of identification of facial nerve was postero-inferior to the external auditory meatus. The procedure was then repeated in living animals. RESULTS: Seventeen cadaveric rats were dissected. Initially, the investigators attempted to identify the facial nerve at its crossing over the external auditory meatus. However, that method was found to be unsatisfactory. The facial nerve was then attempted to be identified in its course postero-inferior to the external auditory meatus. The technique improved drastically, and the facial nerve was identified promptly and reliably. The procedure was then repeated in seven living rats under general anaesthesia. The major issues encountered were bleeding from the stapedial artery, hematoma of the pinna in one rat. CONCLUSION: This study suggests that the post-auricular approach is a feasible and less time consuming route for round window drug delivery experiments in Wistar albino rats. Recognition of anatomical landmarks, particularly the facial nerve is the key to surgery.

Otitis media en el perro: diagnóstico, tratamiento quirúrgico y posibles complicaciones. Revisión / Otitis media in dogs: diagnosis and surgical treatment, and possible complications. Review

RESUMEN El propósito de este artículo es discutir los aspectos relativos al tratamiento y diagnóstico de la otitis media en el perro, haciendo énfasis en las complicaciones más frecuentes observadas luego de una ablación total del canal auditivo con osteotomía de la bulla timpánica, procedimiento que en la actualidad se considera el tratamiento de elección. Además, se expone el ámbito clínico en el cual se indica esta intervención considerando otras condiciones diferentes de la otitis media. Se contrasta de manera crítica la experiencia de los autores con la literatura publicada referente a este tema en algunos aspectos que conciernen a la técnica quirúrgica y el diagnóstico.

SUMARY The purpose of this article is to discuss the aspects related to the treatment and diagnosis of otitis media in dogs, emphasizing the most frequent complications observed after a total ablation of the auditory canal with osteotomy of the tympanic bulla, a procedure that is currently considered the treatment of choice. Additionally, the clinical setting in which this intervention is indicated is exposed, considering other conditions other than otitis media. The experience of the authors with the published literature regarding this topic is critically contrasted in some aspects that concern the surgical technique and the diagnosis.

The tympanic region of Otaria byronia (Otariidae, Carnivora) - morphology, ontogeny, age classes and dimorphism.

Here we describe and explore for the first time the ontogeny and sexual dimorphism of the auditory region of Otaria byronia. We studied the tympanic region of skulls of 237 specimens of different ages and sexes. Geometric morphometric methods were used to analyze the tympanic bulla. In addition, 3D reconstructions of the tympanic bulla were performed using computed tomography analysis scans and a serial wearing technique. We provide a description of the external and internal morphology of the tympanic bulla in both sexes and across different stages (bioclasses). The average shape of the bulla in O. byronia has a subtriangular contour, with variations between sexes and ages. Each stage (bioclasses I, II, and III) is characterized by the respective mean shape of the tympanic bulla and designated as a morphoclass (1, 2, and 3). In all cases, the ectotympanic shows greater surface area than the endotympanic, as in other otariids, in contrast to Phocidae. During ontogeny, the relative size of the ectotympanic increases, growing in all directions and covering the endotympanic. This pattern is seen to the greatest extent in adult males, in which the ectotympanic forms an extremely well-developed apophysis jugulare. No differences in internal morphology of the tympanic cavity were recorded between ages and sexes. The bulla does not increase in thickness in successive age classes; in fact, the walls are extremely thin in the adult stages, despite the extensive development of its processes. This pattern is opposite that observed in Phocidae. In morphoclass 3, adult males older than 7 years undergo hypermorphic change that results in a peramorphic condition when compared to adult females. These changes probably follow the same pattern shown by the rest of the skull and contribute to the marked sexual dimorphism of the species.

Computed tomographic morphometry of tympanic bulla shape and position in brachycephalic and mesaticephalic dog breeds.

Anatomic variations in skull morphology have been previously described for brachycephalic dogs; however there is little published information on interbreed variations in tympanic bulla morphology. This retrospective observational study aimed to (1) provide detailed descriptions of the computed tomographic (CT) morphology of tympanic bullae in a sample of dogs representing four brachycephalic breeds (Pugs, French Bulldogs, English Bulldog, and Cavalier King Charles Spaniels) versus two mesaticephalic breeds (Labrador retrievers and Jack Russell Terriers); and (2) test associations between tympanic bulla morphology and presence of middle ear effusion. Archived head CT scans for the above dog breeds were retrieved and a single observer measured tympanic bulla shape (width:height ratio), wall thickness, position relative to the temporomandibular joint, and relative volume (volume:body weight ratio). A total of 127 dogs were sampled. Cavalier King Charles Spaniels had significantly flatter tympanic bullae (greater width:height ratios) versus Pugs, English Bulldogs, Labrador retrievers, and Jack Russell terriers. French Bulldogs and Pugs had significantly more overlap between tympanic bullae and temporomandibular joints versus other breeds. All brachycephalic breeds had significantly lower tympanic bulla volume:weight ratios versus Labrador retrievers. Soft tissue attenuating material (middle ear effusion) was present in the middle ear of 48/100 (48%) of brachycephalic breeds, but no significant association was found between tympanic bulla CT measurements and presence of this material. Findings indicated that there are significant interbreed variations in tympanic bulla morphology, however no significant relationship between tympanic bulla morphology and presence of middle ear effusion could be identified.

Extensively remodeled, fractured cetacean tympanic bullae show that whales can survive traumatic injury to the ears.

Underwater human activities and anthropogenic noise in our oceans may be a major source of habitat degradation for marine life. This issue was highlighted by the opening of the United States Eastern Seaboard for seismic oil and gas exploration in 2014, which generated massive media coverage and widespread concern that seismic surveys could kill or deafen whales. We discovered 11 new specimens of fractured and healed cetacean ear bones, out of a survey of 2127 specimens housed in museum collections. This rare condition has been previously reported only in two specimens of blue whales (Balaenoptera musculus) from the early 1900s, summarized by Fraser & Purves (1953). All of our new specimens are represented by species for which this condition had never been reported previously, including both baleen and toothed whales. The baleen whale specimens (Balaenoptera physalus, Balaenoptera borealis, Balaenoptera acutorostrata) were collected during Canadian commercial whaling operations in the Atlantic Ocean in the 1970s; the specimens include ear bones with well-healed fractures, demonstrating that baleen whales are capable of overcoming traumatic injury to the ears. The toothed whale specimens (Delphinus sp., Berardius bairdii) were found dead on beaches in 1972 and 2001, respectively, with less remodeled fractures. Thus, ear injuries may be more lethal to the echolocating toothed whales, which rely on hearing for navigation and foraging. We explore several hypotheses regarding how these injuries could have occurred, and conclude that the most parsimonious explanations appear to be both direct and indirect effects of lytic processes from disease or calcium depletion, or damage from external pressure waves. Although further research is required to confirm whether the fractures resulted from natural or human-induced events, this study underscores the importance of museum collections and the work of stranding networks in understanding the potential effects of modern human activities on marine mammal health.

Precocious Ossification of the Tympanoperiotic Bone in Fetal and Newborn Dolphins: An Evolutionary Adaptation to the Aquatic Environment?

The present study, performed with a dual-energy X-ray (DXA) bone densitometer on a series of fetal and newborn striped and short-beaked common dolphins, shows that the bone density of the area of the tympanic bulla within the tympanoperiotic complex starts with 0.483 g cm(-2) in 5- to 6-month-old specimens of striped (or common) dolphin fetuses and reaches 1.841 g cm(-2) in newborn striped dolphins, with values consistently higher than in other parts of the skull or elsewhere in the skeleton. The same results apply to the common bottlenose dolphins, in which the area of the tympanic bulla has a density of 0.312 g cm(-2) in 5-month-old specimens and becomes four times as much in newborns. Regardless of the areal bone density results correlated to the DXA-technique, comparisons with DXA-bone density data in the literature referred to other mammals emphasize the presence of very high mineral deposition in the area of the tympanoperiotic bone in fetal and newborn dolphins and the most dense part of it belongs to the tympanic bulla. The early osseous maturation of the tympanic bulla area may be compared to what described in fin whales and may represent an unique ontogenetic and phylogenetic feature of cetaceans, possibly related to the development of essential acoustic sense and establishment of immediate post-natal mother-calf relationship.

Mucoperiosteal exostoses in the tympanic bulla of African lions (Panthera leo).

Mucoperiosteal exostoses (MpEs) of the tympanic bulla (TB), also referred as middle-ear otoliths, have been occasionally described in dogs and cats in association with clinical signs of otitis media or as an incidental finding, but they have not been recorded in other species. In this report, we describe the radiographic, gross, and histopathologic features of MpEs in 8 African lions (Panthera leo). All animals (5 males and 3 females) were adults that had been kept in captivity and had their skeletons conserved as part of an anatomic academic collection. A radiographic study revealed mineralized structures in the TB consistent with MpEs in 7 of the 16 examined TB; a computed tomography study identified MpEs in 12 of the 16 TB. Six TB from 4 lions were sectioned, and several MpEs were demineralized for histopathologic analysis. Grossly, MpEs appeared variable in number and shape. Some were globular structures that were loosely attached to the mucosal surface of the TB; others were isolated to coalescent bone spicules extending from the mucoperiosteum. Position was also variable, but MpEs frequently developed in the hypotympanum, especially on the ventromedial aspect of the TB wall. Microscopically, MpEs were composed of osteonal bone growing from the periosteum and not by dystrophic calcification of necrotic tissue debris, as is hypothesized in dogs.

Cholesterol granuloma associated with otitis media in a cat.

An 8-year-old, male neutered Siamese cat was presented with Horner syndrome and right head tilt. A soft tissue mass was observed in the right tympanic cavity, and bulla osteotomy was performed. Tissue samples retrieved from the tympanic cavity were sent for histology, and a middle ear fluid swab was sent for bacterial culture and sensitivity. Histologic diagnosis was of otitis media associated with cholesterol granuloma (CG). Bacterial culture yielded Pasteurella multocida and Leifsonia (Corynebacterium) aquaticum. Middle ear CG is frequently seen in human beings and is associated with a variety of middle ear diseases including otitis media. Cholesterol granuloma of the middle ear has been experimentally induced in cats. The clinical and pathological findings of a spontaneous case of CG in the tympanic cavity of a cat with otitis media are described herein.

Avaliação ultrassonográfica do meato acústico em cães / Ultrasonographic evaluation of the external ear in dogs

O propósito deste trabalho foi determinar a viabilidade da ultrassonografia para avaliar o canal auditivo externo de cães, aferindo a espessura e arquitetura da parede do conduto auditivo e bula timpânica. Foram avaliados 10 cães da raça Retriever do Labrador não portadores de otite externa. O exame foi realizado com o aparelho de ultrassonografia bidimensional e transdutor linear de 14 MHz, com todos os animais sob efeito de anestesia geral. O exame foi efetivado antes e depois do conduto ser preenchido com solução salina, promovendo uma janela acústica anecóica. A artéria maxilar foi identificada com o Doppler colorido o que facilitou a localização da bula timpânica em todos os cães. A definição da imagem da parede proximal ao transdutor foi pior quando comparada à parede distal em todos os animais, isto devido à proximidade da parede com a face de leitura do transdutor. Nos cães que apresentavam uma maior quantidade de cerúmen a superfície do epitélio estava com uma camada hiperecóica mais evidente. A membrana timpânica não foi identificada em nenhum animal. Conclui-se que ultrassonografia é viável e deve ser mais pesquisada na contribuição diagnóstica das doenças óticas em cães.

The purpose of this study was to determine the viability of ultrasonographic evaluation of the external ear in dogs. The thickness and architecture of the ear wall and tympanic bulla of 10 Labrador Retrievers without ear disease was evaluated. The examination was performed with an ultrasound system and a 14 MHz bidimentional linear-array transducer and general anesthesia, before and after the infusion of saline solution into the ear canal. The maxillary artery was identified with color Doppler and helped to establish the location of the tympanic bulla in all dogs. The proximal wall was less well-defined when compared with the distal wall of the ear canal. Dogs with increased ceruminal content within the ear canal showed a hypoechoic epithelium. The tympanic membrane was not identified. It was concluded that ultrasound evaluation is feasible and needs to be explored as clinical diagnostic tool for the diagnosis of ear diseases in dogs.

The Hypertrophy of the Tympanic Bulla in Three Species of Dasypodids (Mammalia, Xenarthra) from Argentina / La Hipertrofia de la Bula Timpánica en Tres Especies de Dasipódidos (Mammalia, Xenarthra) de Argentina

The morphology and relative size of the tympanic bulla of three species of dasypodids from Argentina, Chaetophractus villosus, C. vellerosus and Zaedyus pichiy, were studied. The bulla was observed to be morphologically similar and evidently hypertrophied in the three species. The degree of hypertrophy was higher in C. vellerosus and C. villosus than in Z pichiy. By means of ANCOVA it was clear that, although C. villosus has a bigger skull than C. vellerosus, the relative size of their tympanic cavity was similar in both species. On the other hand, the skull of C. vellerosus and Z pichiy are of similar size but the bulla was relatively shorter in the later.

Fueron estudiados la morfología y el tamaño relativo de la bula timpánica, en tres especies de dasipódidos de la Argentina, Chaetophractus villosus, C. vellerosus and Zaedyus pichiy. Se observaron una morfología similar y una hipertrofia evidente en la bula en las tres especies. El grado de hipertrofia fue mayor en C. vellerosus y C. villosus que en Z pichiy. Mediante ANCOVA se demostró que, aunque el cráneo de C. villosus es mayor que el de C. vellerosus, el tamaño relativo de la bula fue similar en ambas especies. Por otra parte, la bula de Z pichiy es relativamente más pequeña que la de C. vellerosus, a pesar que sus cráneos son de tamaño similar.