Exquisite air sac histological traces in a hyperpneumatized nanoid sauropod dinosaur from South America

This study reports the occurrence of pneumosteum (osteohistological structure related to an avian-like air sac system) in a nanoid (5.7-m-long) saltasaurid titanosaur from Upper Cretaceous Brazil. We corroborate the hypothesis of the presence of an air sac system in titanosaurians based upon vertebral features identified through external observation and computed tomography. This is the fifth non-avian dinosaur taxon in which histological traces of air sacs have been found. We provided a detailed description of pneumatic structures from external osteology and CT scan data as a parameter for comparison with other taxa. The camellate pattern found in the vertebral centrum (ce) of this taxon and other titanosaurs shows distinct architectures. This might indicate whether cervical or lung diverticula pneumatized different elements. A cotylar internal plate of bone tissue sustains radial camellae (rad) in a condition similar to Alamosaurus and Saltasaurus. Moreover, circumferential chambers (cc) near the cotyle might be an example of convergence between diplodocoids and titanosaurs. Finally, we also register for the first time pneumatic foramina (fo) and fossae connecting camellate structures inside the neural canal in Titanosauria and the second published case in non-avian dinosaurs. The extreme pneumaticity observed in this nanoid titanosaur contrasts with previous assumptions that this feature correlates with the evolution of gigantic sizes in sauropodomorphs. This study reinforces that even small-bodied sauropod clades could present a hyperpneumatized postcranial skeleton, a character inherited from their large-bodied ancestors.

Computed Tomographic Evaluation of the Accuracy of Minimally Invasive Sacroiliac Screw Fixation in Cats

Objectives The aim of this study was to report the use of computed tomography (CT) for postoperative evaluation of the accuracy of sacroiliac reduction and minimally invasive screw fixation in a series of five cats. Materials and Methods Medical records between January 2016 and March 2017 of cats presenting to the author's institution were reviewed. Included were cats that had undergone minimally invasive sacroiliac screw fixation with a complete medical record and pre- and postoperative radiographs. Screw size was obtained from the medical records. CT images were acquired prospectively and evaluated to assess joint reduction, relative screw size and screw positioning. Results Six sacroiliac luxations and 6 screws were available. Fixation was achieved with either a 2.4 (n = 1) or 2.7 mm (n = 5), 316L stainless steel, cortical bone screw. Mean screw size as a proportion of sacral diameter was 47.7%. Sacroiliac reduction >90% in the craniocaudal plane and sacral screw purchase >60% of the sacral width were achieved in 3/5 cases. Mean dorsoventral screw angulation was 1.6 degrees (range: −9.7 to 11.7 degrees) and craniocaudal angulation was −4.5 degrees (range: −16.6 to 6.6 degrees). Complications included screw loosening in the one case of bilateral repair and penetration of the neural canal in one case which was not detected with postoperative radiographic evaluation. Clinical Significance CT evaluation provides a useful method for the assessment of sacroiliac reduction and the accuracy of screw placement.

Effects of myopia and glaucoma in the prelaminar neural canal and anterior lamina cribrosa using 1060-nm swept-source OCT

Purpose: Investigate the effects of myopia and glaucoma in the prelaminar neural canal and anterior lamina cribrosa using 1060-nm swept-source optical coherence tomography Design: Retrospective, cross-sectional study Methods: - Setting: Clinical practice - Patient or study population: 19 controls (38 eyes); 38 glaucomatous subjects (63 eyes). Inclusion criteria for glaucomatous subjects: i) optic disc neural rim loss; ii) peripapillary nerve fibre layer (NFL) loss on spectral domain optical coherence tomography (SD-OCT); iii) glaucomatous visual field defect with an abnormal pattern standard deviation (P<.05); iv) stable SD-OCT, visual field, and optic disc clinical examination for 6 or more months. Inclusion criteria for control subjects: no evidence of retinal or optic nerve pathology. Exclusion criteria: i) retinal diseases or optic neuropathy other than primary open-angle glaucoma; ii) intraocular pressure ≤ 10 mmHg or ≥ 20 mmHg; iii) ocular media opacities; iv) any surgery-related complication deemed inappropriate for the study. - Intervention or observation procedures: Swept-source optical coherence tomography - Main Outcome Measure(s): Bruchs membrane opening (BMO) and anterior laminar insertion (ALI) dimension, prelaminar neural canal dimension, anterior lamina cribrosa surface (ALCS) depth Results: Glaucomatous eyes had more bowed and nasally rotated BMO and ALI, more horizontally skewed prelaminar neural canal, and deeper ALCS than the control eyes. Increased axial length was associated with a wider, longer, and more horizontally skewed neural canal, and decrease in the ALCS depth and curvature. Conclusion: Our findings suggest that glaucomatous posterior bowing or cupping of lamina cribrosa can be significantly confounded by the myopic expansion of the neural canal. This may be related to higher glaucoma risk associated with myopia from decreased compliance and increased susceptibility to IOP-related damage of LC being pulled taut.

The Enigmatic Reissner’s Fiber and the Origin of Chordates

Reissner’s fiber (RF) is a secreted filament that floats in the neural canal of chordates. Since its discovery in 1860, there has been no agreement on its primary function, and its strong conservation across chordate species has remained a mystery for comparative neuroanatomists. Several findings, including the chemical composition and the phylogenetic history of RF, clinical observations associating RF with the development of the neural canal, and more recent studies suggesting that RF is needed to develop a straight vertebral column, may shed light on the functions of this structure across chordates. In this article, we will briefly review the evidence mentioned above to suggest a role of RF in the origin of fundamental innovations of the chordate body plan, especially the elongation of the neural tube and maintenance of the body axis. We will also mention the relevance of RF for medical conditions like hydrocephalus, scoliosis of the vertebral spine and possibly regeneration of the spinal cord.

Management of neglected complex hangman’s fracture by reforming the C2 pedicle: new innovative technique of motion preservation at the C1–2 joint in 2 cases

Hangman’s fracture, also known as traumatic spondylolisthesis of the axis, causes widening of the neural canal and thus a low rate of neurological deficits. This low rate is one of the reasons it is neglected and patients present with late neurological deficits. In an effort to preserve motion at the C1–2 joint, the authors devised a new technique of bilateral C2 pedicle reconstruction. They describe the first two cases in the literature of an old hangman’s fracture with resorbed C2 pedicles due to chronic fracture, in which bilateral C2 pedicles were reconstructed. One of the two cases (case 2) is the first reported case of severe C2–3 spondyloptosis with C2 displaced up to the level of C4. Case 1 had a follow up of 21 months, while case 2 had a follow up of 12 months. Both patients experienced neurological improvement with evidence of fusion and artificial pedicle formation at last follow-up. Bilateral C2 pedicle reconstruction is a feasible technique that can be used with a good outcome in select patients.

A Small-Bodied Troodontid (Dinosauria, Theropoda) from the Upper Cretaceous Wulansuhai Formation of Inner Mongolia, China

A new small-bodied troodontid (LH PV39) recovered from the Upper Cretaceous Wulansuhai Formation, Suhongtu, Inner Mongolia, China, is described. The new specimen preserves six postaxial cervical vertebrae, five completely fused sacral and four posterior caudal vertebrae in addition to two manual unguals. The completely fused neurocentral junctions indicate that a skeletally mature individual of the same species of LH PV39 would be smaller than Philovenator and comparable in body size to a skeletal mature individual of Almas. The extremely dorsoventrally compressed sacral centra and neural canal, and the middle three sacral centra that are shorter and wider than the first and the last one distinguishing LH PV39 from other known troodontids. A series of phylogenetic analyses were conducted using modified published matrices. By coding LH PV39 in different strategies, the troodontid affinity of LH PV39 is confirmed and it was recovered as the sister taxon of either Mei and Sinovenator (LH PV39 scored as a separate OTU) or Linhevenator (incorporating LH PV39 into Philovenator) in the best resolved coelurosaurian interrelationships. The referral of LH PV39 to Philovenator does not seriously alter the phylogenetic position of Philovenator nor the interrelationships of troodontids. This new finding confirms that the small and large sized troodontids are coexisted in the Gobi Desert of the Mongolia Plateau until the end of Cretaceous.

New Classification for Bifurcated Mandibular Neural Canal

Background: To analyze the occurrence rate of bifurcated neural canal (BMC) by cone beam CT(CBCT) and summarise a new classification for further clinical work and academic communication. Method: Randomly collected the CBCT images of 350 patients. Firstly, we analysed and summarized the BMCs into four types. Second, we did statistics about occurrence. Then we have measured three kinds of distance of Type I and Type II. At last, we compared the advantages and disadvantages about different classifications. Results: Among these 350 patients, we found 110 people with BMC which indicated the occurrence rate of BMC was 31.43%. The most common type was Type I, especially Type I B , and the least was Type III. Vertical distance between the apex of the second molar, the third molar and mandibular canal are 4.36±2.51 mm and 2.45±2.23 mm. Distance from the apex of two molars to the bifurcated spot are 15.87±6.82mm and 9.32±5.37mm. And the distance between the apex and retromolar foramen in Type I are 22.19±5.97mm and 15.82±4.68mm. Conclusion: Comparing with former typing theory, we summarized a new classification which is simpler and more convenient, which should attach scholars’ attention to BMC during clinical work.

What do we mean by the directions “cranial” and “caudal” on a vertebra?

In illustrating vertebrae, it is important to consistently depict their orientation, so we can objectively assess and compare the slope of the neural arch, neural canal, or articular surfaces. However, differing vertebral shapes across taxa and across regions of the spinal column make it difficult to maintain consistency, or even define what we mean by the directions “cranial” and “caudal”. Consequently, characters such as “Neural arch slopes cranially 30° relative to the vertical” are disputable rather than objective measurements. Cranial and caudal are defined as directed along the horizontal axis, but several different notions of “horizontal” are possible: 1. Long axis of centrum is horizontal. This is appealing for elongate vertebrae such as sauropod cervicals, but is not always well defined, and is difficult to determine for craniocaudally short vertebrae such as most caudals. 2. Articular surfaces of centrum are vertical. Difficult to determine when dealing with facets that are concave or (worse) convex; and ambiguous for “keystoned” vertebrae in which the facets are not parallel. 3. Neural canal is horizontal. Anatomically informative, but difficult to determine in vertebrae that have not been fully prepared or CT-scanned, and impossible to see in lateral view. Ambiguous for vertebrae where the dorsal and ventral margins of the canal are not straight or not parallel. 4. Similarity in articulation (“horizontal” is defined as a line joining the same point on two similarly oriented copies of the same vertebra when optimally articulated). This is less intuitive than definitions 1–3, but takes the entire vertebra into account. We advocate explicitly stating a definition and using it consistently. In most cases, definition 3 (“Neural canal is horizontal”) best reflects anatomical and developmental realities, and it is therefore preferred. Low-tech techniques can be used to determine neural canal orientation with adequate precision for most purposes.