The Intramuscular Course of the Greater Occipital Nerve: Novel Findings with Potential Implications for Operative Interventions and Occipital Neuralgia

Background: A better understanding of the etiologies of occipital neuralgia would help the clinician treat patients with this debilitating condition. Since few studies have examined the muscular course of the greater occipital nerve (GON), this study was performed. Methods: Thirty adult cadaveric sides underwent dissection of the posterior occiput with special attention to the intramuscular course of the GON. Nerves were typed based on their muscular course. Results: The GON traveled through the trapezius (type I; n = 5, 16.7%) or its aponeurosis (type II; n = 15, 83.3%) to become subcutaneous. Variations in the subtrapezius muscular course were found in 10 (33%) sides. In two (6.7%) sides, the GON traveled through the lower edge of the inferior capitis oblique muscle (subtype a). On five (16.7%) sides, the GON coursed through a tendinous band of the semispinalis capitis, not through its muscular fibers (subtype b). On three (10%) sides the GON bypassed the semispinalis capitis muscle to travel between its most medial fibers and the nuchal ligament (subtype c). For subtypes, eight were type II courses (through the aponeurosis of the trapezius), and two were type I courses (through the trapezius muscle). The authors identified two type IIa courses, four type IIb courses, and two type IIc courses. Type I courses included one type Ib and one type Ic courses. Conclusions: Variations in the muscular course of the GON were common. Future studies correlating these findings with the anatomy in patients with occipital neuralgia may elucidate nerve courses vulnerable to nerve compression. This enhanced classification scheme describes the morphology in this region and allows more specific communications about GON variations

A new segment of the trochlear nerve: cadaveric study with application to skull base surgery

Objectives The trochlear nerve is important to preserve during approaches to the skull base. Traditionally, this nerve has been divided into cisternal, cavernous, and orbital segments. However, the authors anecdotally observed an additional segment during routine cadaveric dissections. Therefore, they performed this study to better elucidate this anatomy. Design Twenty latex-injected cadaveric sides (10 adult cadavers) were dissected with the aid of an operating microscope. Standard microdissection techniques were used to examine the course of the distal cisternal and precavernous segments of the trochlear nerve. Setting Cadaver laboratory. Main Outcome Measures Measurements were made using a microcaliper. Digital images were made of the dissections. Results The authors identified a previously undescribed segment of the trochlear nerve in all specimens. This part of the nerve coursed between the entrance of the trochlear nerve into the posterior corner of the oculomotor trigone to the posterior wall of the cavernous sinus. This segment of trochlear nerve was, on average, 4 mm in length. Conclusions The authors have identified a new segment of the trochlear nerve not previously described. They propose that this be referred to as the trigonal segment. Knowledge of the microanatomy of the trochlear nerve is useful to skull base surgeons

The Effect of Coherent Structures on Stochastic Acceleration in MHD Turbulence

We investigate the influence of coherent structures on particle acceleration in the strongly turbulent solar corona. By randomizing the Fourier phases of a pseudo-spectral simulation of isotropic MHD turbulence (Re $\sim 300$), and tracing collisionless test protons in both the exact-MHD and phase-randomized fields, it is found that the phase correlations enhance the acceleration efficiency during the first adiabatic stage of the acceleration process. The underlying physical mechanism is identified as the dynamical MHD alignment of the magnetic field with the electric current, which favours parallel (resistive) electric fields responsible for initial injection. Conversely, the alignment of the magnetic field with the bulk velocity weakens the acceleration by convective electric fields - \bfu \times \bfb at a non-adiabatic stage of the acceleration process. We point out that non-physical parallel electric fields in random-phase turbulence proxies lead to artificial acceleration, and that the dynamical MHD alignment can be taken into account on the level of the joint two-point function of the magnetic and electric fields, and is therefore amenable to Fokker-Planck descriptions of stochastic acceleration.Comment: accepted for publication in Ap

Diffusion tensor and volumetric magnetic resonance imaging using an MR-compatible hand-induced robotic device suggests training-induced neuroplasticity in patients with chronic stroke

Stroke is the third leading cause of mortality and a frequent cause of long-term adult impairment. Improved strategies to enhance motor function in individuals with chronic disability from stroke are thus required. Post-stroke therapy may improve rehabilitation and reduce long-term disability; however, objective methods for evaluating the specific impact of rehabilitation are rare. Brain imaging studies on patients with chronic stroke have shown evidence for reorganization of areas showing functional plasticity after a stroke. In this study, we hypothesized that brain mapping using a novel magnetic resonance (MR)-compatible hand device in conjunction with state-of-the-art magnetic resonance imaging (MRI) can serve as a novel biomarker for brain plasticity induced by rehabilitative motor training in patients with chronic stroke. This hypothesis is based on the premises that robotic devices, by stimulating brain plasticity, can assist in restoring movement compromised by stroke-induced pathological changes in the brain and that these changes can then be monitored by advanced MRI. We serially examined 15 healthy controls and 4 patients with chronic stroke. We employed a combination of diffusion tensor imaging (DTI) and volumetric MRI using a 3-tesla (3T) MRI system using a 12-channel Siemens Tim coil and a novel MR-compatible hand-induced robotic device. DTI data revealed that the number of fibers and the average tract length significantly increased after 8 weeks of hand training by 110% and 64%, respectively (p<0.001). New corticospinal tract (CST) fibers projecting progressively closer to the motor cortex appeared during training. Volumetric data analysis showed a statistically significant increase in the cortical thickness of the ventral postcentral gyrus areas of patients after training relative to pre-training cortical thickness (p<0.001). We suggest that rehabilitation is possible for a longer period of time after stroke than previously thought, showing that structural plasticity is possible even after 6 months due to retained neuroplasticity. Our study is an example of personalized medicine using advanced neuroimaging methods in conjunction with robotics in the molecular medicine era

The ℓs\ell^s-boundedness of a family of integral operators on UMD Banach function spaces

We prove the $\ell^s$-boundedness of a family of integral operators with an operator-valued kernel on UMD Banach function spaces. This generalizes and simplifies earlier work by Gallarati, Veraar and the author, where the $\ell^s$-boundedness of this family of integral operators was shown on Lebesgue spaces. The proof is based on a characterization of $\ell^s$-boundedness as weighted boundedness by Rubio de Francia.Comment: 13 pages. Generalization of arXiv:1410.665

Choroid Plexus of the Fourth Ventricle: Review and Anatomic Study Highlighting Anatomical Variations

Relatively few studies have been performed that analyze the morphology of the choroid plexus of the fourth ventricle. Due to the importance of this tissue as a landmark on imaging and during surgical intervention of the fourth ventricle, the authors performed a cadaveric study to better characterize this important structure. The choroid plexus of the fourth ventricle of 60 formalin fixed adult human brains was examined and measured. The horizontal distance from the midline to the lateral most point of the protruding tip of the horizontal limbs was measured. In the majority of the 60 brain specimens, right and left horizontal limbs of the choroid plexus were seen extending from the midline and protruding out of their respective lateral apertures of the fourth ventricle and into the subarachnoid space. However, on 3.3% of sides, there was absence of an extension into the foramen of Luschka and in one specimen, this lack of extension into the foramen of Luschka was bilateral. On two sides, there was discontinuity between the midline choroid plexus and the tuft of choroid just outside the foramen of Luschka. For specimens in which the choroid plexus did protrude through the foramen of Luschka (96.7%), these tufts were located anterior to the flocculus and inferolateral to the facial/vestibulocochlear nerve complex and posterosuperior to the glossopharyngeal/vagal/accessory complex. A thorough understanding of the normal and variant anatomy of the fourth ventricular choroid plexus is necessary for those who operate in, or interpret imaging of, this region

Functional MRI using robotic MRI compatible devices for monitoring rehabilitation from chronic stroke in the molecular medicine era (Review)

The number of individuals suffering from stroke is increasing daily, and its consequences are a major contributor to invalidity in today’s society. Stroke rehabilitation is relatively new, having been hampered from the longstanding view that lost functions were not recoverable. Nowadays, robotic devices, which aid by stimulating brain plasticity, can assist in restoring movement compromised by stroke-induced pathological changes in the brain which can be monitored by MRI. Multiparametric magnetic resonance imaging (MRI) of stroke patients participating in a training program with a novel Magnetic Resonance Compatible Hand-Induced Robotic Device (MR_CHIROD) could yield a promising biomarker that, ultimately, will enhance our ability to advance hand motor recovery following chronic stroke. Using state-of-the art MRI in conjunction with MR_CHIROD-assisted therapy can provide novel biomarkers for stroke patient rehabilitation extracted by a meta-analysis of data. Successful completion of such studies may provide a ground breaking method for the future evaluation of stroke rehabilitation therapies. Their results will attest to the effectiveness of using MR-compatible hand devices with MRI to provide accurate monitoring during rehabilitative therapy. Furthermore, such results may identify biomarkers of brain plasticity that can be monitored during stroke patient rehabilitation. The potential benefit for chronic stroke patients is that rehabilitation may become possible for a longer period of time after stroke than previously thought, unveiling motor skill improvements possible even after six months due to retained brain plasticity

Differences in transcription between free-living and CO_2-activated third-stage larvae of Haemonchus contortus

Background: The disease caused by Haemonchus contortus, a blood-feeding nematode of small ruminants, is of major economic importance worldwide. The infective third-stage larva (L3) of this gastric nematode is enclosed in a cuticle (sheath) and, once ingested with herbage by the host, undergoes an exsheathment process that marks the transition from the free-living (L3) to the parasitic (xL3) stage. This study explored changes in gene transcription associated with this transition and predicted, based on comparative analysis, functional roles for key transcripts in the metabolic pathways linked to larval development. Results: Totals of 101,305 (L3) and 105,553 (xL3) expressed sequence tags (ESTs) were determined using 454 sequencing technology, and then assembled and annotated; the most abundant transcripts encoded transthyretin-like, calcium-binding EF-hand, NAD(P)-binding and nucleotide-binding proteins as well as homologues of Ancylostoma-secreted proteins (ASPs). Using an in silico-subtractive analysis, 560 and 685 sequences were shown to be uniquely represented in the L3 and xL3 stages, respectively; the transcripts encoded ribosomal proteins, collagens and elongation factors (in L3), and mainly peptidases and other enzymes of amino acid catabolism (in xL3). Caenorhabditis elegans orthologues of transcripts that were uniquely transcribed in each L3 and xL3 were predicted to interact with a total of 535 other genes, all of which were involved in embryonic development. Conclusion: The present study indicated that some key transcriptional alterations taking place during the transition from the L3 to the xL3 stage of H. contortus involve genes predicted to be linked to the development of neuronal tissue (L3 and xL3), formation of the cuticle (L3) and digestion of host haemoglobin (xL3). Future efforts using next-generation sequencing and bioinformatic technologies should provide the efficiency and depth of coverage required for the determination of the complete transcriptomes of different developmental stages and/or tissues of H. contortus as well as the genome of this important parasitic nematode. Such advances should lead to a significantly improved understanding of the molecular biology of H. contortus and, from an applied perspective, to novel methods of intervention

Changes in duodenal tissue-associated microbiota following hookworm infection and consecutive gluten challenges in humans with coeliac disease

A reduced diversity of the gastrointestinal commensal microbiota is associated with the development of several inflammatory diseases. Recent reports in humans and animal models have demonstrated the beneficial therapeutic effects of infections by parasitic worms (helminths) in some inflammatory disorders, such as inflammatory bowel disease (IBD) and coeliac disease (CeD). Interestingly, these studies have described how helminths may alter the intestinal microbiota, potentially representing a mechanism by which they regulate inflammation. However, for practical reasons, these reports have primarily analysed the faecal microbiota. In the present investigation, we have assessed, for the first time, the changes in the microbiota at the site of infection by a parasitic helminth (hookworm) and gluten-dependent inflammation in humans with CeD using biopsy tissue from the duodenum. Hookworm infection and gluten exposure were associated with an increased abundance of species within the Bacteroides phylum, as well as increases in the richness and diversity of the tissue-resident microbiota within the intestine, results that are consistent with previous reports using other helminth species in humans and animal models. Hence, this may represent a mechanism by which parasitic helminths may restore intestinal immune homeostasis and exert a therapeutic benefit in CeD, and potentially other inflammatory disorders.This work was supported by grants 613718 to P.G., and 1037304 and 1020114 to A.L. from the National Health and Medical Research Council of Australia (NHMRC), and by the Royal Society and the Isaac Newton Trust/Wellcome Trust ISSF/University of Cambridge Joint Research Grants Scheme to C.C. T.J. is supported by scholarships from the Biotechnology and Biological Sciences Research Council (BBSRC) Doctoral Training Partnerships program