-
Journal of Magnetic Resonance Imaging :... Apr 2024Thyroid eye disease (TED), particularly its sight-threatening complication, dysthyroid optic neuropathy (DON), profoundly impacts patients' visual health. The...
BACKGROUND
Thyroid eye disease (TED), particularly its sight-threatening complication, dysthyroid optic neuropathy (DON), profoundly impacts patients' visual health. The pathological changes in the white matter (WM) fibers within the intracranial visual pathway in TED have been infrequently studied. Understanding these changes holds crucial importance for exploring the pathogenesis and prognosis of TED.
PURPOSE
To utilize fixel-based analysis (FBA) to clarify the type of microstructural damage occurring in the visual pathway in TED.
STUDY TYPE
Prospective.
SUBJECTS
28 TED with DON patients (11 males and 17 females), 28 TED without DON (non-DON) patients (12 males and 16 females), and 28 healthy controls (HCs) (12 males and 16 females).
FIELD STRENGTH/SEQUENCE
3 T; multishell diffusion MRI using echo planar imaging.
ASSESSMENT
Fiber density (FD) and fiber-bundle cross-section (FC) were calculated to characterize WM microstructural alteration in TED visual pathway. The correlations between FBA metrics and visual field index and mean deviation were examined.
STATISTICAL TESTS
One-way analysis of variance, Kruskal-Wallis, t-tests, Mann-Whitney U, Chi-square, and Pearson correlation, were conducted with false discovery rate and family wise error corrections. Significance was set at P < 0.05.
RESULTS
Both DON and non-DON groups showed significant FD loss in the right optic tract compared with HCs, with DON patients experiencing more severe FD loss. Only DON patients had FD loss in the right optic radiation (OR) compared with the non-DON patients and HCs, with no FC difference across groups. FD in DON patients' ORs significantly correlated with visual field index (r = 0.857) and mean deviation (r = 0.751).
DATA CONCLUSION
Both DON and non-DON affect the WM microstructure of the visual pathway to varying extents. Visual field metrics can reflect the severity of FD damage to the OR in the visual pathway of DON patients.
EVIDENCE LEVEL
2.
TECHNICAL EFFICACY
Stage 3.
PubMed: 38682584
DOI: 10.1002/jmri.29387 -
International Journal of Molecular... Apr 2024Mild traumatic brain injury (mTBI) affects millions of people in the U.S. Approximately 20-30% of those individuals develop adverse symptoms lasting at least 3 months....
Mild traumatic brain injury (mTBI) affects millions of people in the U.S. Approximately 20-30% of those individuals develop adverse symptoms lasting at least 3 months. In a rat mTBI study, the closed-head impact model of engineered rotational acceleration (CHIMERA) produced significant axonal injury in the optic tract (OT), indicating white-matter damage. Because retinal ganglion cells project to the lateral geniculate nucleus (LGN) in the thalamus through the OT, we hypothesized that synaptic density may be reduced in the LGN of rats following CHIMERA injury. A modified SEQUIN (synaptic evaluation and quantification by imaging nanostructure) method, combined with immunofluorescent double-labeling of pre-synaptic (synapsin) and post-synaptic (PSD-95) markers, was used to quantify synaptic density in the LGN. Microglial activation at the CHIMERA injury site was determined using Iba-1 immunohistochemistry. Additionally, the effects of ketamine, a potential neuroprotective drug, were evaluated in CHIMERA-induced mTBI. A single-session repetitive (ssr-) CHIMERA (3 impacts, 1.5 joule/impact) produced mild effects on microglial activation at the injury site, which was significantly enhanced by post-injury intravenous ketamine (10 mg/kg) infusion. However, ssr-CHIMERA did not alter synaptic density in the LGN, although ketamine produced a trend of reduction in synaptic density at post-injury day 4. Further research is necessary to characterize the effects of ssr-CHIMERA and subanesthetic doses of intravenous ketamine on different brain regions and multiple time points post-injury. The current study demonstrates the utility of the ssr-CHIMERA as a rodent model of mTBI, which researchers can use to identify biological mechanisms of mTBI and to develop improved treatment strategies for individuals suffering from head trauma.
Topics: Animals; Ketamine; Microglia; Rats, Sprague-Dawley; Rats; Male; Synapses; Head Injuries, Closed; Axons; Disease Models, Animal; Geniculate Bodies; Brain Concussion; Disks Large Homolog 4 Protein; Synapsins; Neuroprotective Agents
PubMed: 38673871
DOI: 10.3390/ijms25084287 -
Bioengineering (Basel, Switzerland) Mar 2024Voicing: requires frequent starts and stops at various sound pressure levels (SPL) and frequencies. Prior investigations using rigid laryngoscopy with oral endoscopy...
UNLABELLED
Voicing: requires frequent starts and stops at various sound pressure levels (SPL) and frequencies. Prior investigations using rigid laryngoscopy with oral endoscopy have shown variations in the duration of the vibration delay between normal and abnormal subjects. However, these studies were not physiological because the larynx was viewed using rigid endoscopes. We adapted a method to perform to perform simultaneous high-speed naso-endoscopic video while simultaneously acquiring the sound pressure, fundamental frequency, airflow rate, and subglottic pressure. This study aimed to investigate voice onset patterns in normophonic males and females during the onset of variable SPL and correlate them with acoustic and aerodynamic data.
MATERIALS AND METHODS
Three healthy males and three healthy females were studied by simultaneous high-speed video laryngoscopy and recording with the production of the gesture [pa:pa:] at soft, medium, and loud voices. The fiber optic endoscope was threaded through a pneumotachograph mask for the simultaneous recording and analysis of acoustic and aerodynamic data.
RESULTS
The average increase in the sound pressure level (SPL) for the group was 15 dB, from 70 to 85 dB. The fundamental frequency increased by an average of 10 Hz. The flow was increased in two subjects, reduced in two subjects, and remained the same in two subjects as the SPL increased. There was a steady increase in the subglottic pressure from soft to loud phonation. Compared to soft to medium phonation, a significant increase in glottal resistance was observed with medium-to-loud phonation. Videokymogram analysis showed the onset of vibration for all voiced tokens without the need for full glottis closure. In loud phonation, there is a more rapid onset of a larger amplitude and prolonged closure of the glottal cycle; however, more cycles are required to achieve the intended SPL. There was a prolonged closed phase during loud phonation. Fast Fourier transform (FFT) analysis of the kymography waveform signal showed a more significant second- and third-harmonic energy above the fundamental frequency with loud phonation. There was an increase in the adjustments in the pharynx with the base of the tongue tilting, shortening of the vocal folds, and pharyngeal constriction.
CONCLUSION
Voice onset occurs in all modalities, without the need for full glottal closure. There was a more significant increase in glottal resistance with loud phonation than that with soft or middle phonation. Vibration analysis of the voice onset showed that more time was required during loud phonation before the oscillation stabilized to a steady state. With increasing SPL, there were significant variations in vocal tract adjustments. The most apparent change was the increase in tongue tension with posterior displacement of the epiglottis. There was an increase in pre-phonation time during loud phonation. Patterns of muscle tension dysphonia with laryngeal squeezing, shortening of the vocal folds, and epiglottis tilting with increasing loudness are features of loud phonation. These observations show that flexible high-speed video laryngoscopy can reveal observations that cannot be observed with rigid video laryngoscopy. An objective analysis of the digital kymography signal can be conducted in selected cases.
PubMed: 38671756
DOI: 10.3390/bioengineering11040334 -
Journal of Neuroscience Research Apr 2024Circadian rhythms synchronize to light through the retinohypothalamic tract (RHT), which is a bundle of axons coming from melanopsin retinal ganglion cells, whose...
Circadian rhythms synchronize to light through the retinohypothalamic tract (RHT), which is a bundle of axons coming from melanopsin retinal ganglion cells, whose synaptic terminals release glutamate to the ventral suprachiasmatic nucleus (SCN). Activation of AMPA-kainate and NMDA postsynaptic receptors elicits the increase in intracellular calcium required for triggering the signaling cascade that ends in phase shifts. During aging, there is a decline in the synchronization of circadian rhythms to light. With electrophysiological (whole-cell patch-clamp) and immunohistochemical assays, in this work, we studied pre- and postsynaptic properties between the RHT and ventral SCN neurons in young adult (P90-120) and old (P540-650) C57BL/6J mice. Incremental stimulation intensities (applied on the optic chiasm) induced much lesser AMPA-kainate postsynaptic responses in old animals, implying a lower recruitment of RHT fibers. Conversely, a higher proportion of old SCN neurons exhibited synaptic facilitation, and variance-mean analysis indicated an increase in the probability of release in RHT terminals. Moreover, both spontaneous and miniature postsynaptic events displayed larger amplitudes in neurons from aged mice, whereas analysis of the NMDA and AMPA-kainate components (evoked by RHT electrical stimulation) disclosed no difference between the two ages studied. Immunohistochemistry revealed a bigger size in the puncta of vGluT2, GluN2B, and GluN2A of elderly animals, and the number of immunopositive particles was increased, but that of PSD-95 was reduced. All these synaptic adaptations could be part of compensatory mechanisms in the glutamatergic signaling to ameliorate the loss of RHT terminals in old animals.
Topics: Animals; Mice, Inbred C57BL; Mice; Suprachiasmatic Nucleus; Synaptic Transmission; Aging; Glutamic Acid; Male; Excitatory Postsynaptic Potentials; Visual Pathways; Vesicular Glutamate Transport Protein 2; Patch-Clamp Techniques; Receptors, N-Methyl-D-Aspartate; Disks Large Homolog 4 Protein
PubMed: 38651314
DOI: 10.1002/jnr.25331 -
Annual Review of Neuroscience Apr 2024Seeing in three dimensions is a major property of the visual system in mammals. The circuit underlying this property begins in the retina, from which retinal ganglion... (Review)
Review
Seeing in three dimensions is a major property of the visual system in mammals. The circuit underlying this property begins in the retina, from which retinal ganglion cells (RGCs) extend to the same or opposite side of the brain. RGC axons decussate to form the optic chiasm, then grow to targets in the thalamus and midbrain, where they synapse with neurons that project to the visual cortex. Here we review the cellular and molecular mechanisms of RGC axonal growth cone guidance across or away from the midline via receptors to cues in the midline environment. We present new views on the specification of ipsi- and contralateral RGC subpopulations and factors implementing their organization in the optic tract and termination in subregions of their targets. Lastly, we describe the functional and behavioral aspects of binocular vision, focusing on the mouse, and discuss recent discoveries on the evolution of the binocular circuit.
PubMed: 38635868
DOI: 10.1146/annurev-neuro-111020-093230 -
Neuroradiology Apr 2024Diffusion tensor imaging (DTI) is a valuable non-invasive imaging modality for mapping white matter tracts and assessing microstructural integrity, and can be used as a...
INTRODUCTION
Diffusion tensor imaging (DTI) is a valuable non-invasive imaging modality for mapping white matter tracts and assessing microstructural integrity, and can be used as a "biomarker" in diagnosis, differentiation, and therapeutic monitoring. Although it has gained clinical importance as a marker of neuropathology, limitations in its interpretation underscore the need for caution.
METHODS
This review provides an overview of the principles and clinical applicability of DTI. We focus on major white matter fiber bundles, detailing their normal anatomy and pathological DTI patterns, with emphasis on tracts routinely requested in our neurosurgical department in the preoperative context (uncinate fasciculus, arcuate fasciculus, pyramidal pathway, optic radiation, and dentatorubrothalamic tract).
RESULTS
We guide neuroradiologists and neurosurgeons in defining volumes of interest for mapping individual tracts and demonstrating their 3D reconstructions. The intricate trajectories of white matter tracts pose a challenge for accurate fiber orientation recording, with each bundle exhibiting specific characteristics. Tracts adjacent to brain lesions are categorized as displaced, edematous, infiltrated, or disrupted, illustrated with clinical cases of brain neoplasms. To improve structured reporting, we propose a checklist of topics for inclusion in imaging evaluations and MRI reports.
CONCLUSION
DTI is emerging as a powerful tool for assessing microstructural changes in brain disorders, despite some challenges in standardization and interpretation. This review serves an educational purpose by providing guidance for fiber monitoring and interpretation of pathological patterns observed in clinical cases, highlighting the importance and potential pitfalls of DTI in neuroradiology and surgical planning.
PubMed: 38635028
DOI: 10.1007/s00234-024-03362-7 -
Frontiers in Neuroscience 2024Optical Projection Tomography (OPT) and light sheet fluorescence microscopy (LSFM) are high resolution optical imaging techniques, ideally suited for ex vivo 3D whole...
INTRODUCTION
Optical Projection Tomography (OPT) and light sheet fluorescence microscopy (LSFM) are high resolution optical imaging techniques, ideally suited for ex vivo 3D whole mouse brain imaging. Although they exhibit high specificity for their targets, the anatomical detail provided by tissue autofluorescence remains limited.
METHODS
T1-weighted images were acquired from 19 BABB or DBE cleared brains to create an MR template using serial longitudinal registration. Afterwards, fluorescent OPT and LSFM images were coregistered/normalized to the MR template to create fusion images.
RESULTS
Volumetric calculations revealed a significant difference between BABB and DBE cleared brains, leading to develop two optimized templates, with associated tissue priors and brain atlas, for BABB (OCUM) and DBE (iOCUM). By creating fusion images, we identified virus infected brain regions, mapped dopamine transporter and translocator protein expression, and traced innervation from the eye along the optic tract to the thalamus and superior colliculus using cholera toxin B. Fusion images allowed for precise anatomical identification of fluorescent signal in the detailed anatomical context provided by MR.
DISCUSSION
The possibility to anatomically map fluorescent signals on magnetic resonance (MR) images, widely used in clinical and preclinical neuroscience, would greatly benefit applications of optical imaging of mouse brain. These specific MR templates for cleared brains enable a broad range of neuroscientific applications integrating 3D optical brain imaging.
PubMed: 38601090
DOI: 10.3389/fnins.2024.1328815 -
The European Journal of Neuroscience May 2024The posterior parietal cortex (PPC) integrates multisensory and motor-related information for generating and updating body representations and movement plans. We used...
Pathways from the superior colliculus and the nucleus of the optic tract to the posterior parietal cortex in macaque monkeys: Functional frameworks for representation updating and online movement guidance.
The posterior parietal cortex (PPC) integrates multisensory and motor-related information for generating and updating body representations and movement plans. We used retrograde transneuronal transfer of rabies virus combined with a conventional tracer in macaque monkeys to identify direct and disynaptic pathways to the arm-related rostral medial intraparietal area (MIP), the ventral lateral intraparietal area (LIPv), belonging to the parietal eye field, and the pursuit-related lateral subdivision of the medial superior temporal area (MSTl). We found that these areas receive major disynaptic pathways via the thalamus from the nucleus of the optic tract (NOT) and the superior colliculus (SC), mainly ipsilaterally. NOT pathways, targeting MSTl most prominently, serve to process the sensory consequences of slow eye movements for which the NOT is the key sensorimotor interface. They potentially contribute to the directional asymmetry of the pursuit and optokinetic systems. MSTl and LIPv receive feedforward inputs from SC visual layers, which are potential correlates for fast detection of motion, perceptual saccadic suppression and visual spatial attention. MSTl is the target of efference copy pathways from saccade- and head-related compartments of SC motor layers and head-related reticulospinal neurons. They are potential sources of extraretinal signals related to eye and head movement in MSTl visual-tracking neurons. LIPv and rostral MIP receive efference copy pathways from all SC motor layers, providing online estimates of eye, head and arm movements. Our findings have important implications for understanding the role of the PPC in representation updating, internal models for online movement guidance, eye-hand coordination and optic ataxia.
Topics: Animals; Superior Colliculi; Parietal Lobe; Optic Tract; Male; Movement; Macaca mulatta; Eye Movements
PubMed: 38544445
DOI: 10.1111/ejn.16314 -
International Journal of Molecular... Feb 2024We recently identified PKN1 as a developmentally active gatekeeper of the transcription factor neuronal differentiation-2 (NeuroD2) in several brain areas. Since NeuroD2...
We recently identified PKN1 as a developmentally active gatekeeper of the transcription factor neuronal differentiation-2 (NeuroD2) in several brain areas. Since NeuroD2 plays an important role in amacrine cell (AC) and retinal ganglion cell (RGC) type formation, we aimed to study the expression of NeuroD2 in the postnatal retina of WT and animals, with a particular focus on these two cell types. We show that PKN1 is broadly expressed in the retina and that the gross retinal structure is not different between both genotypes. Postnatal retinal NeuroD2 levels were elevated upon knockout, with retinae showing more NeuroD2 cells in the lower portion of the inner nuclear layer. Accordingly, immunohistochemical analysis revealed an increased amount of AC in postnatal and adult retinae. There were no differences in horizontal cell, bipolar cell, glial cell and RGC numbers, nor defective axon guidance to the optic chiasm or tract upon knockout. Interestingly, we did, however, see a specific reduction in SMI-32 α-RGC in retinae. These results suggest that PKN1 is important for retinal cell type formation and validate PKN1 for future studies focusing on AC and α-RGC specification and development.
Topics: Animals; Retina; Retinal Ganglion Cells; Amacrine Cells; Optic Chiasm; Transcription Factors
PubMed: 38474095
DOI: 10.3390/ijms25052848 -
The Journal of Emergency Medicine Apr 2024Multiple sclerosis (MS) is a rare but serious condition associated with significant morbidity. (Review)
Review
BACKGROUND
Multiple sclerosis (MS) is a rare but serious condition associated with significant morbidity.
OBJECTIVE
This review provides a focused assessment of MS for emergency clinicians, including the presentation, evaluation, and emergency department (ED) management based on current evidence.
DISCUSSION
MS is an autoimmune disorder targeting the central nervous system (CNS), characterized by clinical relapses and radiological lesions disseminated in time and location. Patients with MS most commonly present with long tract signs (e.g., myelopathy, asymmetric spastic paraplegia, urinary dysfunction, Lhermitte's sign), optic neuritis, or brainstem syndromes (bilateral internuclear ophthalmoplegia). Cortical syndromes or multifocal presentations are less common. Radiologically isolated syndrome and clinically isolated syndrome (CIS) may or may not progress to chronic forms of MS, including relapsing remitting MS, primary progressive MS, and secondary progressive MS. The foundation of outpatient management involves disease-modifying therapy, which is typically initiated with the first signs of disease onset. Management of CIS and acute flares of MS in the ED includes corticosteroid therapy, ideally after diagnostic testing with imaging and lumbar puncture for cerebrospinal fluid analysis. Emergency clinicians should evaluate whether patients with MS are presenting with new-onset debilitating neurological symptoms to avoid unnecessary testing and admissions, but failure to appropriately diagnose CIS or MS flare is associated with increased morbidity.
CONCLUSIONS
An understanding of MS can assist emergency clinicians in better diagnosing and managing this neurologically devastating disease.
Topics: Humans; Multiple Sclerosis; Multiple Sclerosis, Chronic Progressive; Multiple Sclerosis, Relapsing-Remitting; Radiography; Optic Neuritis; Magnetic Resonance Imaging
PubMed: 38472027
DOI: 10.1016/j.jemermed.2023.12.003