Experimental study of the frontal sinus development on Goettingen miniature pigs

When the lung invades: a review of avian postcranial skeletal pneumaticity

Birds are unique among extant tetrapods in exhibiting air-filled cavities that arise from the respiratory system and invade postcranial bones, a phenomenon called postcranial skeletal pneumaticity (PSP). These intraosseous cavities originate from diverticula of the ventilatory air sacs or directly from the gas-exchanging lung. Despite a long history of study, many of the basic characteristics of this system remain poorly understood. In this hybrid review, we synthesize insights from the anatomical, developmental, biomechanical and paleontological literature to review the functional and evolutionary significance of PSP. Leveraging new data, we confirm that the skeletons of pneumatic birds are not less heavy for their mass than those of apneumatic birds. Pneumatic skeletons may nonetheless be lightweight with respect to body volume, but this is a hypothesis that remains to be empirically tested. We also use micro-computed tomography scanning and deep learning-based segmentation to produce a pilot model of the pneumatized spaces in the neck of a Mallard (Anas platyrhynchos). This approach facilitates accurate modelling of bone architecture for quantitative comparative analysis within and between pneumatic taxa. Future work on PSP should focus on the cellular mechanisms and developmental processes that govern the onset and extent of pneumatization, which are essentially unknown.This article is part of the theme issue 'The biology of the avian respiratory system'.

Variation in air sac morphology and postcranial skeletal pneumatization patterns in the African grey parrot

The anatomy of the avian lower respiratory system includes a complex interaction between air-filled pulmonary tissues, pulmonary air sacs, and much of the postcranial skeleton. Hypotheses related to the function and phylogenetic provenance of these respiratory structures have been posed based on extensive interspecific descriptions for an array of taxa. By contrast, intraspecific descriptions of anatomical variation for these features are much more limited, particularly for skeletal pneumatization, and are essential to establish a baseline for evaluating interspecific variation. To address this issue, we collected micro-computed tomography (μCT) scans of live and deceased African grey parrots (Psittacus erithacus) to assess variation in the arrangement of the lungs, the air sacs, and their respective invasion of the postcranial skeleton via pneumatic foramina. Analysis reveals that the two pairs of caudalmost air sacs vary in size and arrangement, often exhibiting an asymmetric morphology. Further, locations of the pneumatic foramina are more variable for midline, non-costal skeletal elements when compared to other pneumatized bones. These findings indicate a need to better understand contributing factors to variation in avian postcranial respiratory anatomy that can inform future intraspecific and interspecific comparisons.

Research Relevant Background Lesions and Conditions: Ferrets, Dogs, Swine, Sheep, and Goats

Animal models provide a valuable tool and resource for biomedical researchers as they investigate biological processes, disease pathogenesis, novel therapies, and toxicologic studies. Interpretation of animal model data requires knowledge not only of the processes/diseases being studied but also awareness of spontaneous conditions and background lesions in the model that can influence or even confound the study results. Species, breed/stock, sex, age, anatomy, physiology, diseases (noninfectious and infectious), and neoplastic processes are model features that can impact the results as well as study interpretation. Here, we review these features in several common laboratory animal species, including ferret, dog (beagle), pig, sheep, and goats.

Characterization of Motor and Somatosensory Evoked Potentials in the Yucatan Micropig Using Transcranial and Epidural Stimulation

Yucatan micropigs have brain and spinal cord dimensions similar to humans and are useful for certain spinal cord injury (SCI) translational studies. Micropigs are readily trained in behavioral tasks, allowing consistent testing of locomotor loss and recovery. However, there has been little description of their motor and sensory pathway neurophysiology. We established methods to assess motor and sensory cortical evoked potentials in the anesthetized, uninjured state. We also evaluated epidurally evoked motor and sensory stimuli from the T6 and T9 levels, spanning the intended contusion injury epicenter. Response detection frequency, mean latency and amplitude values, and variability of evoked potentials were determined. Somatosensory evoked potentials were reliable and best detected during stimulation of peripheral nerve and epidural stimulation by referencing the lateral cortex to midline Fz. The most reliable hindlimb motor evoked potential (MEP) occurred in tibialis anterior. We found MEPs in forelimb muscles in response to thoracic epidural stimulation likely generated from propriospinal pathways. Cranially stimulated MEPs were easier to evoke in the upper limbs than in the hindlimbs. Autopsy studies revealed substantial variations in cortical morphology between animals. This electrophysiological study establishes that neurophysiological measures can be reliably obtained in micropigs in a time frame compatible with other experimental procedures, such as SCI and transplantation. It underscores the need to better understand the motor control pathways, including the corticospinal tract, to determine which therapeutics are suitable for testing in the pig model.

Frontoethmoidal mucocele following pediatric craniofacial surgery

BACKGROUND

Mucoceles occur as a result of accumulation and retention of mucous secretions in a paranasal sinus and are uncommon in the pediatric age group. Persistent or intermittent closure of its ostium through a variety of causes, including previous surgery, is implicated in etiology. The authors report 2 cases of frontoethmoidal mucocele that followed box osteotomies for the treatment of orbital dystopia, with medical literature review and discussion of possible causal factors and events.

METHODS

Case histories and radiological imaging are presented on 2 patients presenting with frontoethmoidal mucoceles following craniofacial surgery. Both had transcranial craniofacial techniques where all orbital walls and globe are moved en bloc as a "box."

RESULTS

Patient 1, a 12-year-old male patient with Crouzon syndrome, developed mucoceles within 18 months of monobloc distraction surgery and box osteotomies. This was successfully marsupialized with a combined external and endoscopic surgical approach. The second patient, a 15-year-old boy with previously corrected right-sided facial cleft, developed mucocele 9 years following box osteotomies; this was successfully managed by endoscopic drainage. Of 3 other patients having similar box osteotomies in our unit, no other mucoceles were noted as complications.

CONCLUSIONS

Mucoceles are a rare complication of craniofacial surgery, and literature review confirms a paucity of reports. Only 1 case has previously been alluded to of mucocele complicating box osteotomy for orbital dystopia. Our 2 cases illustrate and highlight a successful management approach in a multidisciplinary craniofacial unit.

Delayed development of frontal mucocele after fronto-orbital advancement in a child with craniosynostosis

BACKGROUND

Sinus mucoceles rarely develop as a consequence of inadequate sinus ventilation that arises due to inflammation, allergy, polyps, tumors, surgery, and trauma. The development of frontal sinus is delayed until older than 6 years. Therefore, the development of the mucocele in the frontal sinus after fronto-orbital advancement surgery in young children with craniosynostosis may provide essential information for the development of the frontal sinus.

CASE DESCRIPTION

We report a rare case of a 22-year-old man presenting with a frontal mucocele manifested by dull headache, proptosis, and diplopia, and which developed 16 years after fronto-orbital advancement surgery for craniosynostosis. Magnetic resonance imaging demonstrated that a multiple cystic mass extended from the frontal sinus to the retro-orbital space along the optic nerve. During surgery, we found that the cyst consisted of mostly thin, yellow mucosa, which developed from an anomalously overdeveloped frontal sinus containing yellow pus-like intracystic fluid. There was no gross local invasion by the cyst. We easily dissected and removed the mucosal cyst from the large frontal sinus completely with frontal sinus obliteration. We cranialized the anomalously large frontal sinus by removal of the posterior wall of the frontal sinus and then widening the ethmoidal drainage with endoscopic ethmoidectomy.

CONCLUSION

We report the first case of a frontal sinus mucocele that developed after fronto-orbital advancement surgery in the literature and suggest that the mucocele development after fronto-orbital advancement supports the hypothesis of frontal bone-inducing role in frontal sinus development.

Postcranial pneumaticity: An evaluation of soft-tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs

Postcranial pneumaticity has been reported in numerous extinct sauropsid groups including pterosaurs, birds, saurischian dinosaurs, and, most recently, both crurotarsan and basal archosauriform taxa. By comparison with extant birds, pneumatic features in fossils have formed the basis for anatomical inferences concerning pulmonary structure and function, in addition to higher-level inferences related to growth, metabolic rate, and thermoregulation. In this study, gross dissection, vascular and pulmonary injection, and serial sectioning were employed to assess the manner in which different soft tissues impart their signature on the axial skeleton in a sample of birds, crocodylians, and lizards. Results from this study indicate that only cortical foramina or communicating fossae connected with large internal chambers are reliable and consistent indicators of pneumatic invasion of bone. As both vasculature and pneumatic diverticula may produce foramina of similar sizes and shapes, cortical features alone do not necessarily indicate pneumaticity. Noncommunicating (blind) vertebral fossae prove least useful, as these structures are associated with many different soft-tissue systems. This Pneumaticity Profile (PP) was used to evaluate the major clades of extinct archosauriform taxa with purported postcranial pneumaticity. Unambiguous indicators of pneumaticity are present only in certain ornithodiran archosaurs (e.g., sauropod and theropod dinosaurs, pterosaurs). In contrast, the basal archosauriform Erythrosuchus africanus and other nonornithodiran archosaurs (e.g., parasuchians) fail to satisfy morphological criteria of the PP, namely, that internal cavities are absent within bone, even though blind fossae and/or cortical foramina are present on vertebral neural arches. An examination of regional pneumaticity in extant avians reveals remarkably consistent patterns of diverticular invasion of bone, and thus provides increased resolution for inferring specific components of the pulmonary air sac system in their nonavian theropod ancestors. By comparison with well-preserved exemplars from within Neotheropoda (e.g., Abelisauridae, Allosauroidea), the following pattern emerges: pneumaticity of cervical vertebrae and ribs suggests pneumatization by lateral vertebral diverticula of a cervical air sac system, with sacral pneumaticity indicating the presence of caudally expanding air sacs and/or diverticula. The identification of postcranial pneumaticity in extinct taxa minimally forms the basis for inferring a heterogeneous pulmonary system with distinct exchange and nonexchange (i.e., air sacs) regions. Combined with inferences supporting a rigid, dorsally fixed lung, osteological indicators of cervical and abdominal air sacs highlight the fundamental layout of a flow-through pulmonary apparatus in nonavian theropods.