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Concept: Cranial nerves

190

We describe Sarmientosaurus musacchioi gen. et sp. nov., a titanosaurian sauropod dinosaur from the Upper Cretaceous (Cenomanian-Turonian) Lower Member of the Bajo Barreal Formation of southern Chubut Province in central Patagonia, Argentina. The holotypic and only known specimen consists of an articulated, virtually complete skull and part of the cranial and middle cervical series. Sarmientosaurus exhibits the following distinctive features that we interpret as autapomorphies: (1) maximum diameter of orbit nearly 40% rostrocaudal length of cranium; (2) complex maxilla-lacrimal articulation, in which the lacrimal clasps the ascending ramus of the maxilla; (3) medial edge of caudal sector of maxillary ascending ramus bordering bony nasal aperture with low but distinct ridge; (4) ‘tongue-like’ ventral process of quadratojugal that overlaps quadrate caudally; (5) separate foramina for all three branches of the trigeminal nerve; (6) absence of median venous canal connecting infundibular region to ventral part of brainstem; (7) subvertical premaxillary, procumbent maxillary, and recumbent dentary teeth; (8) cervical vertebrae with ‘strut-like’ centroprezygapophyseal laminae; (9) extremely elongate and slender ossified tendon positioned ventrolateral to cervical vertebrae and ribs. The cranial endocast of Sarmientosaurus preserves some of the most complete information obtained to date regarding the brain and sensory systems of sauropods. Phylogenetic analysis recovers the new taxon as a basal member of Lithostrotia, as the most plesiomorphic titanosaurian to be preserved with a complete skull. Sarmientosaurus provides a wealth of new cranial evidence that reaffirms the close relationship of titanosaurs to Brachiosauridae. Moreover, the presence of the relatively derived lithostrotian Tapuiasaurus in Aptian deposits indicates that the new Patagonian genus represents a ‘ghost lineage’ with a comparatively plesiomorphic craniodental form, the evolutionary history of which is missing for at least 13 million years of the Cretaceous. The skull anatomy of Sarmientosaurus suggests that multiple titanosaurian species with dissimilar cranial structures coexisted in the early Late Cretaceous of southern South America. Furthermore, the new taxon possesses a number of distinctive morphologies-such as the ossified cervical tendon, extremely pneumatized cervical vertebrae, and a habitually downward-facing snout-that have rarely, if ever, been documented in other titanosaurs, thus broadening our understanding of the anatomical diversity of this remarkable sauropod clade. The latter two features were convergently acquired by at least one penecontemporaneous diplodocoid, and may represent mutual specializations for consuming low-growing vegetation.

Concepts: Skull, Cranial nerves, Cretaceous, Patagonia, Sauropoda, Dinosaur, Titanosaur, Maxillary nerve

184

Euchambersia mirabilis is an iconic species of Permo-Triassic therapsid because of its unusually large external maxillary fossa linked through a sulcus to a ridged canine. This anatomy led to the commonly accepted conclusion that the large fossa accommodated a venom gland. However, this hypothesis remains untested so far. Here, we conducted a μCT scan assisted reappraisal of the envenoming capacity of Euchambersia, with a special focus on the anatomy of the maxillary fossa and canines. This study shows that the fossa, presumably for the venom-producing gland, is directly linked to the maxillary canal, which carries the trigeminal nerve (responsible for the sensitivity of the face). The peculiar anatomy of the maxillary canal suggests important reorganisation in the somatosensory system and that a ganglion could possibly have been present in the maxillary fossa instead of a venom gland. Nevertheless, the venom gland hypothesis is still preferred since we describe, for the first time, the complete crown morphology of the incisiform teeth of Euchambersia, which strongly suggests that the complete dentition was ridged. Therefore Euchambersia manifests evidence of all characteristics of venomous animals: a venom gland (in the maxillary fossa), a mechanism to deliver the venom (the maxillary canal and/or the sulcus located ventrally to the fossa); and an apparatus with which to inflict a wound for venom delivery (the ridged dentition).

Concepts: Cranial nerves, Mandibular nerve, Venom, Trigeminal nerve, Maxillary nerve, Therapsida, Therocephalia

171

Neural stimulation can reduce the frequency of seizures in persons with epilepsy, but rates of seizure-free outcome are low. Vagus nerve stimulation prevents seizures by continuously activating noradrenergic projections from the brainstem to the cortex. Cortical norepinephrine then increases GABAergic transmission and increases seizure threshold. Another approach, responsive nervous stimulation, prevents seizures by reactively shocking the seizure onset zone in precise synchrony with seizure onset. The electrical shocks abort seizures before they can spread and manifest clinically. The goal of this study was to determine whether a hybrid platform in which brainstem activation triggered in response to impending seizure activity could prevent seizures. We chose the zebrafish as a model organism for this study because of its ability to recapitulate human disease, in conjunction with its innate capacity for tightly controlled high-throughput experimentation. We first set out to determine whether electrical stimulation of the zebrafish hindbrain could have an anticonvulsant effect. We found that pulse train electrical stimulation of the hindbrain significantly increased the latency to onset of pentylenetetrazole-induced seizures, and that this apparent anticonvulsant effect was blocked by noradrenergic antagonists, as is also the case with rodents and humans. We also found that the anticonvulsant effect of hindbrain stimulation could be potentiated by reactive triggering of single pulse electrical stimulations in response to impending seizure activity. Finally, we found that the rate of stimulation triggering was directly proportional to pentylenetetrazole concentration and that the stimulation rate was reduced by the anticonvulsant valproic acid and by larger stimulation currents. Taken as a whole, these results show that that the anticonvulsant effect of brainstem activation can be efficiently utilized by reactive triggering, which suggests that alternative stimulation paradigms for vagus nerve stimulation might be useful. Moreover, our results show that the zebrafish epilepsy model can be used to advance our understanding of neural stimulation in the treatment of epilepsy.

Concepts: Nervous system, Neurology, Cranial nerves, Epilepsy, Vagus nerve stimulation, Anticonvulsant, Seizure, Status epilepticus

168

Aims : To derive a reliable estimate of the frequency of pupillary involvement and to study the patterns and course of anisocoria in conjunction with ophthalmoplegia in diabetes-associated oculomotor nerve palsy. Materials and Methods: In this prospective analytical study, standardized enrolment criteria were employed to identify 35 consecutive patients with diabetes-associated oculomotor nerve palsy who were subjected to a comprehensive ocular examination. Standardized methods were used to evaluate pupil size, shape, and reflexes. The degree of anisocoria, if present and the degree of ophthalmoplegia was recorded at each visit. Results: Pupillary involvement was found to be present in 25.7% of the total number of subjects with diabetic oculomotor nerve palsy. The measure of anisocoria was < 2 mm, and pupil was variably reactive at least to some extent in all cases with pupillary involvement. Majority of patients in both the pupil-involved and pupil-spared group showed a regressive pattern of ophthalmoplegia. Ophthalmoplegia reversed much earlier and more significantly when compared to anisocoria. Conclusions: Pupillary involvement in diabetes-associated oculomotor nerve palsy occurs in about 1/4 th of all cases. Certain characteristics of the pupil help us to differentiate an ischemic insult from an aneurysmal injury to the 3 rd nerve. Ophthalmoplegia resolves much earlier than anisocoria in diabetic oculomotor nerve palsies.

Concepts: Eye, Cranial nerves, Oculomotor nerve, Pupil, Oculomotor nerve palsy, Edinger-Westphal nucleus, Anisocoria, Mydriasis

168

BACKGROUND: Trigeminal nerve is a major source of the sensory input of the face, and trigeminal neuropathology models have been reported in rodents with injury to branches of the maxillary or mandibular division of the trigeminal nerve. Non-human primates are neuroanatomically more closely related to human than rodents; however, nerve injury studies in non-human primates are limited. RESULTS: We describe here a nerve injury model of maxillary nerve compression (MNC) in the cynomolgus macaque monkey, Macaca fascicularis, and the initial characterization of the consequences of damage to this trigeminal nerve branch. The nerve injury from the compression appeared to be mild, as we did not observe overt changes in home-cage behavior in the monkeys. When mechanical stimulation was applied to the facial area, monkeys with MNC displayed increased mechanical sensitivity, as the avoidance response scores were lower than those from the control animals. Such a change in mechanical sensitivity appeared to be somewhat bilateral, as the contralateral side also showed increased mechanical sensitivity, although the change on the ipsilateral side was more robust. Multiple-unit recording of the maxillary nerve showed a general pattern of increasing responsiveness to escalating force in mechanical stimulation on the contralateral side. Ipsilateral side of the maxillary nerve showed a lack of responsiveness to escalating force in mechanical stimulation, possibly reflecting a maximum stimulation threshold effect from sensitized nerve due to MNC injury. CONCLUSIONS: These results suggest that MNC may produce increased sensitivity of the ipsilateral maxillary nerve, and that this model may serve as a non-human primate model to evaluate the effect of injury to trigeminal nerve branches.

Concepts: Macaque, Cranial nerves, Primate, Mandibular nerve, Monkey, Trigeminal nerve, Maxillary nerve, Simian

151

Glossopharyngeal and/or vagus nerve involvement is infrequent in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We herein report the case of a 69-year-old Japanese woman who presented with muscle weakness and numbness of the extremities with dysphagia. The serum anti-ganglioside GM1 immunoglobulin IgM antibody levels were elevated, and treatment with intravenous immunoglobulin (IVIg) resulted in a dramatic improvement; the weakness, numbness and dysphagia all resolved. However, relapse comprising dysphagia alone occurred on hospital day 26, and treatment with IVIg again proved extremely effective. IVIg therapy can be effective against cranial nerve involvement in cases of CIDP.

Concepts: Immune system, Antibody, Cranial nerves, Myelin, Intravenous immunoglobulin, Chronic inflammatory demyelinating polyneuropathy, Accessory nerve, Nucleus ambiguus

147

Background Rates of hearing preservation following surgery via middle fossa craniotomy in patients harboring tumors with unfavorable characteristics are significantly lower than for those patients with “favorable” tumors. Objectives We will present two cases both with unfavorable conditions, which underwent endoscopic-assisted middle fossa craniotomy (MFC) resection of intracanalicular vestibular schwannomas with preserved postoperative hearing. Methods Chart reviews were conducted on both patients. Their presentation, intraoperative details, and techniques, pre- and postoperative audiograms, and facial nerve outcomes are presented. Results Patient A had 5.6 × 6.8 × 13.2 mm intracanalicular tumor with unserviceable hearing (pure tone audiometry [PTA], 41; speech determination score [SDS], 47%; class D) but was blind so hearing preservation was attempted. Postoperative hearing was preserved (PTA, 47; SDS, 60%; class B). Patient B had a 5 mm round intracanalicular tumor immediately adjacent to the vestibule and cochlea without any fundal fluid present. Preoperative audiogram showed serviceable hearing (PTA, 48; SDS, 88%; class B). Postoperatively, aidable hearing was preserved (PTA, 51; SDS, 76%; class C). Conclusion Hearing preservation surgery via MFC can be enhanced with endoscopic-assisted dissection, especially in the lateral internal auditory canal. The superior optical view allows for preservation of cochlear nerve function and removal of residual tumor not otherwise seen on microscopy.

Concepts: Auditory system, Cochlea, Cranial nerves, Audiogram, Pure tone audiometry, Vestibular schwannoma, Schwannoma, Internal auditory meatus

41

Hyaenodonta is a diverse clade of carnivorous mammals that were part of terrestrial faunas in the Paleogene of Eurasia and North America, but the oldest record for the group is Afro-Arabian, making the record there vital for understanding the evolution of this wide-spread group. Previous studies show an ancient split between two major clades of hyaenodonts that converged in hypercarnivory: Hyainailourinae and Hyaenodontinae. These clades are each supported by cranial characters. Phylogenetic analyses of hyaenodonts also support the monophyly of Teratodontinae, an Afro-Arabian clade of mesocarnivorous to hypercarnivorous hyaenodonts. Unfortunately, the cranial anatomy of teratodontines is poorly known, and aligning the clade with other lineages has been difficult. Here, a new species of the phylogenetically controversial teratodontine Masrasector is described from Locality 41 (latest Priabonian, late Eocene) from the Fayum Depression, Egypt. The hypodigm includes the most complete remains of a Paleogene teratodontine, including largely complete crania, multiple dentaries, and isolated humeri. Standard and “tip-dating” Bayesian analyses of a character-taxon matrix that samples cranial, postcranial, and dental characters support a monophyletic Masrasector within Teratodontinae, which is consistently placed as a close sister group of Hyainailouridae. The cranial morphology of Masrasector provides new support for an expanded Hyainailouroidea (Teratodontinae + Hyainailouridae), particularly characters of the nuchal crest, palate, and basicranium. A discriminant function analysis was performed using measurements of the distal humerus from a diverse sample of extant carnivorans to infer the locomotor habits of Masrasector. Masrasector was assigned to the “terrestrial” locomotor category, a result consistent with the well-defined medial trochlear ridges, and moderately developed supinator crests of the specimens. Masrasector appears to have been a fast-moving terrestrial form with a diverse diet. These specimens considerably improve our understanding of Teratodontinae, an ancient member of the Afro-Arabian mammalian fauna, and our understanding of hyaenodont diversity before the dispersal of Carnivora to the continent near the end of the Paleogene.

Concepts: Phylogenetic nomenclature, Mammal, Cranial nerves, Phylogenetics, Cladistics, Polyphyly, Clade, Eocene

35

Recent animal studies demonstrate that vagus nerve stimulation (VNS) paired with movement induces movement-specific plasticity in motor cortex and improves forelimb function after stroke. We conducted a randomized controlled clinical pilot study of VNS paired with rehabilitation on upper-limb function after ischemic stroke.

Concepts: Stroke, Traumatic brain injury, Vagus nerve, Cranial nerves, Vagus nerve stimulation, Vagus

30

Background: Topography and fascicular arrangement of the inferior alveolar nerve (IAN) can provide critical information for the estimation of damage to IAN based on patient symptoms, or conversely to evaluate the symptoms resulting from injury to the IAN. Purpose: The fascicular composition and organization of the IAN were determined to confirm the microarchitecture of the IAN bundles into each of the mandibular teeth, including the composition of the mental nerve. Materials and Methods: The IAN within the mandibular canal (MC) was examined in 30 hemifaces of embalmed Korean cadavers. Results: The most common patterns of nerve fascicle innervation to the mandibular teeth could be grossly classified into three: (1) the superior buccal portion of the IAN innervating the molars, (2) the superior portion innervating the premolars, and (3) the superior lingual or the superior lingual and inferior lingual portions in the posterior MC and the lingual portions in the anterior MC, innervating the incisors and canine. The buccal two-thirds portion of the IAN was composed of the mental nerve. Conclusion: The IAN had distinctive fascicular organizations, which make it possible to forecast the degree, location, and extent of nerve damage according to presenting symptoms.

Concepts: Cranial nerves, Teeth, Mandibular nerve, Incisor, Canine tooth, Inferior alveolar nerve, Mandibular canal, Mental nerve