A rostral neurovascular system in the mosasaur Taniwhasaurus antarcticus.

Mosasaurs were a cosmopolitan group of marine squamate reptiles that lived during the Late Cretaceous period. Tylosaurinae mosasaurs were characterized for having an edentulous rostrum anterior to the premaxillary teeth. External morphology of the snout of the tylosaurine Taniwhasaurus antarcticus from the Upper Cretaceous beds at James Ross Island (Antarctic Peninsula) shows a complex anatomy with diverse large foramina and bone sculpture. A computed tomography scan of the Taniwhasaurus rostrum revealed a complex internal neurovascular system of branched channels in the anteriormost part of the snout. Systems like this are present in extant aquatic vertebrates such as cetaceans and crocodiles to aid them with prey detection, and are inferred to have functioned in a similar manner for several extinct reptile clades such as plesiosaurs and ichthyosaurs. Thus, it is probable that Taniwhasaurus also was able to detect prey with an enhanced neural system located in its rostrum. This condition may be more widespread than previously thought among mosasaurs and other marine reptiles.

Facial Paralysis in Patients With Hemifacial Microsomia: Frequency, Distribution, and Association With Other OMENS Abnormalities.

Although facial paralysis is a fundamental feature of hemifacial microsomia, the frequency and distribution of nerve abnormalities in patients with hemifacial microsomia remain unclear. In this study, the authors classified 1125 cases with microtia (including 339 patients with hemifacial microsomia and 786 with isolated microtia) according to Orbital Distortion Mandibular Hypoplasia Ear Anomaly Nerve Involvement Soft Tissue Dependency (OMENS) scheme. Then, the authors performed an independent analysis to describe the distribution feature of nerve abnormalities and reveal the possible relationships between facial paralysis and the other 4 fundamental features in the OMENS system. Results revealed that facial paralysis is present 23.9% of patients with hemifacial microsomia. The frontal-temporal branch is the most vulnerable branch in the total 1125 cases with microtia. The occurrence of facial paralysis is positively correlated with mandibular hypoplasia and soft tissue deficiency both in the total 1125 cases and the hemifacial microsomia patients. Orbital asymmetry is related to facial paralysis only in the total microtia cases, and ear deformity is related to facial paralysis only in hemifacial microsomia patients. No significant association was found between the severity of facial paralysis and any of the other 4 OMENS anomalies. These data suggest that the occurrence of facial paralysis may be associated with other OMENS abnormalities. The presence of serious mandibular hypoplasia or soft tissue deficiency should alert the clinician to a high possibility but not a high severity of facial paralysis.

Does Laser Surgery Interfere with Optical Nerve Identification in Maxillofacial Hard and Soft Tissue?--An Experimental Ex Vivo Study.

The protection of sensitive structures (e.g., nerves) from iatrogenic damage is of major importance when performing laser surgical procedures. Especially in the head and neck area both function and esthetics can be affected to a great extent. Despite its many benefits, the surgical utilization of a laser is therefore still limited to superficial tissue ablation. A remote feedback system which guides the laser in a tissue-specific way would provide a remedy. In this context, it has been shown that nerval structures can be specifically recognized by their optical diffuse reflectance spectra both before and after laser ablation. However, for a translation of these findings to the actual laser ablation process, a nerve protection within the laser pulse is of utmost significance. Thus, it was the aim of the study to evaluate, if the process of Er:YAG laser surgery--which comes with spray water cooling, angulation of the probe (60°) and optical process emissions--interferes with optical tissue differentiation. For the first time, no stable conditions but the ongoing process of laser tissue ablation was examined. Therefore, six different tissue types (nerve, skin, muscle, fat, cortical and cancellous bone) were acquired from 15 pig heads. Measurements were performed during Er:YAG laser ablation. Diffuse reflectance spectra (4500, wavelength range: 350-650 nm) where acquired. Principal component analysis (PCA) and quadratic discriminant analysis (QDA) were calculated for classification purposes. The clinical highly relevant differentiation between nerve and bone was performed correctly with an AUC of 95.3% (cortial bone) respectively 92.4% (cancellous bone). The identification of nerve tissue against the biological very similar fat tissue yielded good results with an AUC value of 83.4% (sensitivity: 72.3%, specificity: of 82.3%). This clearly demonstrates that nerve identification by diffuse reflectance spectroscopy works reliably in the ongoing process of laser ablation in spite of the laser beam, spray water cooling and the tissue alterations entailed by tissue laser ablation. This is an essential step towards a clinical utilization.

Complex rostral neurovascular system in a giant pliosaur.

Pliosaurs were a long-lived, ubiquitous group of Mesozoic marine predators attaining large body sizes (up to 12 m). Despite much being known about their ecology and behaviour, the mechanisms they adopted for prey detection have been poorly investigated and represent a mystery to date. Complex neurovascular systems in many vertebrate rostra have evolved for prey detection. However, information on the occurrence of such systems in fossil taxa is extremely limited because of poor preservation potential. The neurovascular complex from the snout of an exceptionally well-preserved pliosaur from the Kimmeridgian (Late Jurassic, c. 170 Myr ago) of Weymouth Bay (Dorset, UK) is described here for the first time. Using computed tomography (CT) scans, the extensive bifurcating neurovascular channels could be traced through the rostrum to both the teeth and the foramina on the dorsal and lateral surface of the snout. The structures on the surface of the skull and the high concentrations of peripheral rami suggest that this could be a sensory system, perhaps similar to crocodile pressure receptors or shark electroreceptors.

Attempted validation of a method to locate entry and exit foramens of the branches of the trigeminal nerve; benefits for an original cephalometric analysis technique.

INTRODUCTION: Trigeminal analysis focuses on the skeletal entrance and exit orifices of the sensitive fibers of the trigeminal nerve. The aim of this study was to validate the techniques used to locate these landmarks as described by the creator of trigeminal analysis of the face. MATERIALS AND METHOD: This descriptive study was performed on a dry human skull. Two tin balls forming markers R1 and R2 were fixed at random on the skull in a median sagittal position. Two headfilms of the skull were made. The first showed tin balls fixed at the entrance and exit foramens of the sensitive fibers of the trigeminal nerve. The second showed the foramens without the tin balls. The position of the reference point corresponding to the entrance and exit points of the trigeminal fibers was entered on a tracing made from the headfilm (without the balls on the foramens) by 16 operators using an ad hoc guide supplied by Crocquet. A comparison was made between the points as positioned by these operators and the true points as revealed by the X-rays of the balls on the first image (Gold Standard) by calculating the difference between their coordinates on an axis connecting R1 et R2 (X-axis) and the line perpendicular to it passing through R2 (Y-axis). Trigeminal cephalometric analysis was then performed on each of the tracings. The angles and linear values were compared. The validity of the positioning of the points and of the values provided by the analysis was demonstrated by the existence of a difference of less than 2units (mm or degrees). RESULTS: No difference in the means between the trigeminal points found by the operators and the Gold Standard points represented by the X-rays of the balls placed on the foramens exceeded 2mm in absolute value on the Y-axis. On the X-axis, the differences greater than 2mm in absolute value related to: the supra-orbital notch (ESO) and the foramen ovale (FO) (2.12 and 8.19mm, respectively). The angles (ESO-TGR-TO) and (TGR-ESO-TSO) were the only ones to display differences exceeding 2° in absolute value between the two images. CONCLUSION: The detection method advanced by Crocquet for the positioning of the eight points of reference used for analyzing the entrance and exit foramens of the trigeminal nerve is valid apart from the TO and ESO points. Consequently, the validity of the angle measurements involving these points is affected. Further research is required to confirm these findings. If necessary, new recommendations should be devised in order to improve the localization of the TO and ESO cephalometric points.

Krox-20 gene expression: influencing hindbrain-craniofacial developmental interactions.

Krox-20 is a C(2)H(2)-type zinc-finger transcription factor that plays an essential role in hindbrain development. The Krox-20 null mutation results in hindbrain anomalies that result in neonatal death due to respiratory and feeding deficits. Here we review our studies of how the Krox- 20 null mutation impacts the development of motor and sensory systems critical for the production of consummatory behaviors (suckling/chewing). First, we demonstrated that Krox-20 null mutants suffer a selective loss of primary jaw-opening muscles during prenatal development. In vivo and in vitro studies are reviewed that highlight intrinsic defects in mutant jaw-opener muscles that contribute to muscle degeneration. Next we focus on the impact of the mutation on proprioceptive neurons activated during consummatory behaviors. Mesencephalic trigeminal (Me5) neurons are primary sensory neurons that relay jaw proprioception to the central nervous system. These cells are unique because their cell bodies are located in the central as opposed to the peripheral nervous system. Data are reviewed that demonstrate the impact of the mutation on Me5 neurons, a cell group traditionally thought to emerge from the mesencephalon. We show that Krox-20 null mutants have twice as many Me5 neurons relative to wildtypes at E15, but by birth have half the number of Me5 cells as wildtypes. TUNEL assays performed in each set of studies reveal that Krox-20 expression acts to protect both muscle and mesencephalic trigeminal neurons against apoptosis, suggesting that Krox-20, in addition to its role in hindbrain patterning, has a broader, long-lasting role in development.

Trigeminal foraminal patterns in "skeletal" Class II and Class III adults--a radiocephalometric study.

Radiocephalometric analysis, based mainly on the foramina of the trigeminal nerve branches, was applied to three samples of adults, two representing fairly extreme profile types, the third representing "normal" dentofacial build. The aim of the study was to find out whether the analytical method could be used to differentiate between facial types. It appeared that some elements of the method had diagnostic powers, and could substitute for traditional methods. Many dimensions inspected, however, were fairly similar in all facial types, thus suggesting a general basic role of the trigeminal nerve in relation to craniofacial structure. Generally speaking, the foraminal pattern was relatively stable in "normal" faces, but more variable in deviant faces.

Neuro-osteology.

Neuro-osteology stresses the biological connection during development between nerve and hard tissues. It is a perspective that has developed since associations were first described between pre-natal peripheral nerve tissue and initial osseous bone formation in the craniofacial skeleton (Kjaer, 1990a). In this review, the normal connection between the central nervous system and the axial skeleton and between the peripheral nervous system and jaw formation are first discussed. The early central nervous system (the neural tube) and the axial skeleton from the lumbosacral region to the sella turcica forms a unit, since both types of tissue are developmentally dependent upon the notochord. In different neurological disorders, the axial skeleton, including the pituitary gland, is malformed in different ways along the original course of the notochord. Anterior to the pituitary gland/sella turcica region, the craniofacial skeleton develops from prechordal cartilage, invading mesoderm and neural crest cells. Also, abnormal development in the craniofacial region, such as tooth agenesis, is analyzed neuro-osteologically. Results from pre-natal investigations provide information on the post-natal diagnosis of children with congenital developmental disorders in the central nervous system. Examples of these are myelomeningocele and holoprosencephaly. Three steps are important in clinical neuro-osteology: (1) clinical definition of the region of an osseous or dental malformation, (2) embryological determination of the origin of that region and recollection of which neurological structure has developed from the same region, and (3) clinical diagnosis of this neurological structure. If neurological malformation is the first symptom, step 2 results in the determination of the osseous region involved, which in step 3 is analyzed clinically. The relevance of future neuro-osteological diagnostics is emphasized.