-
Neuroimaging Clinics of North America Aug 2022The ventricular system, subarachnoid spaces, and meninges are structures that lend structure, support, and protection to the brain and spinal cord. This article provides... (Review)
Review
The ventricular system, subarachnoid spaces, and meninges are structures that lend structure, support, and protection to the brain and spinal cord. This article provides a detailed look at the anatomy of the intracranial portions of these structures with a particular focus on neuroimaging methods.
Topics: Brain; Humans; Meninges; Spinal Cord; Subarachnoid Space
PubMed: 35843664
DOI: 10.1016/j.nic.2022.04.005 -
Journal of Anatomy Aug 2020Traumatic brain injury (TBI) is a common injury modality affecting a diverse patient population. Axonal injury occurs when the brain experiences excessive deformation as...
Traumatic brain injury (TBI) is a common injury modality affecting a diverse patient population. Axonal injury occurs when the brain experiences excessive deformation as a result of head impact. Previous studies have shown that the arachnoid trabeculae (AT) in the subarachnoid space significantly influence the magnitude and distribution of brain deformation during impact. However, the quantity and spatial distribution of cranial AT in humans is unknown. Quantification of these microstructural features will improve understanding of force transfer during TBI, and may be a valuable dataset for microneurosurgical procedures. In this study, we quantify the spatial distribution of cranial AT in seven post-mortem human subjects. Optical coherence tomography (OCT) was used to conduct in situ imaging of AT microstructure across the surface of the human brain. OCT images were segmented to quantify the relative amounts of trabecular structures through a volume fraction (VF) measurement. The average VF for each brain ranged from 22.0% to 29.2%. Across all brains, there was a positive spatial correlation, with VF significantly greater by 12% near the superior aspect of the brain (p < .005), and significantly greater by 5%-10% in the frontal lobes (p < .005). These findings suggest that the distribution of AT between the brain and skull is heterogeneous, region-dependent, and likely contributes to brain deformation patterns. This study is the first to image and quantify human AT across the cerebrum and identify region-dependencies. Incorporation of this spatial heterogeneity may improve the accuracy of computational models of human TBI and enhance understanding of brain dynamics.
Topics: Adult; Aged; Aged, 80 and over; Arachnoid; Brain; Female; Humans; Male; Middle Aged; Pia Mater; Skull; Tomography, Optical Coherence
PubMed: 32202332
DOI: 10.1111/joa.13186 -
The Indian Journal of Tuberculosis Jul 2022There is no satisfactory treatment for post tubercular arachnoiditis (TB arachnoiditis). We did this study to investigate the efficacy and safety of cyclophosphamide as...
INTRODUCTION
There is no satisfactory treatment for post tubercular arachnoiditis (TB arachnoiditis). We did this study to investigate the efficacy and safety of cyclophosphamide as adjuvant therapy for post TB arachnoiditis refractory to corticosteroids and anti-tubercular therapy (ATT).
METHODS
This was a retrospective case series of patients of refractory post TB arachnoiditis leading to paraparesis and vision loss who received cyclophosphamide as an adjuvant therapy along with standard ATT and corticosteroids. These patients were treated with intravenous cyclophosphamide (dose 500 mg/m) once a month for 4 consecutive months after informed written consent and were assessed clinically and radiologically before and after cyclophosphamide therapy.
RESULTS
We had 4 patients with refractory post TB arachnoiditis of whom three became independently ambulatory. There was significant clinical as well as radiological improvement in all the patients.
CONCLUSIONS
Cyclophosphamide therapy could be an effective therapy for patients with refractory post TB arachnoiditis. Well-designed randomized controlled studies are essential to study the safety and efficacy of cyclophosphamide in this condition.
Topics: Humans; Adrenal Cortex Hormones; Arachnoiditis; Cyclophosphamide; Retrospective Studies; Vision Disorders; Tuberculosis
PubMed: 35760482
DOI: 10.1016/j.ijtb.2021.05.002 -
Neurology Jul 2021
Topics: Aneurysm, Ruptured; Humans; Intracranial Aneurysm; Magnesium; Subarachnoid Hemorrhage; Subarachnoid Space
PubMed: 34158386
DOI: 10.1212/WNL.0000000000012247 -
Fluids and Barriers of the CNS Jun 2023Despite recent attention, pathways and mechanisms of fluid transposition in the brain are still a matter of intense discussion and driving forces underlying waste...
BACKGROUND
Despite recent attention, pathways and mechanisms of fluid transposition in the brain are still a matter of intense discussion and driving forces underlying waste clearance in the brain remain elusive. Consensus exists that net solute transport is a prerequisite for efficient clearance. The individual impact of neuronal activity and cerebrospinal fluid (CSF) formation, which both vary with brain state and anesthesia, remain unclear.
METHODS
To separate conditions with high and low neuronal activity and high and low CSF formation, different anesthetic regimens in naive rat were established, using Isoflurane (ISO), Medetomidine (MED), acetazolamide or combinations thereof. With dynamic contrast-enhanced MRI, after application of low molecular weight contrast agent (CA) Gadobutrol to cisterna magna, tracer distribution was monitored as surrogate for solute clearance. Simultaneous fiber-based Ca-recordings informed about the state of neuronal activity under different anesthetic regimen. T2-weighted MRI and diffusion-weighted MRI (DWI) provided size of subarachnoidal space and aqueductal flow as surrogates for CSF formation. Finally, a pathway and mechanism-independent two-compartment model was introduced to provide a measure of efficiency for solute clearance from the brain.
RESULTS
Anatomical imaging, DWI and Ca-recordings confirmed that conditions with distinct levels of neuronal activity and CSF formation were achieved. A sleep-resembling condition, with reduced neuronal activity and enhanced CSF formation was achieved using ISO+MED and an awake-like condition with high neuronal activity using MED alone. CA distribution in the brain correlated with the rate of CSF formation. The cortical brain state had major influence on tracer diffusion. Under conditions with low neuronal activity, higher diffusivity suggested enlargement of extracellular space, facilitating a deeper permeation of solutes into brain parenchyma. Under conditions with high neuronal activity, diffusion of solutes into parenchyma was hindered and clearance along paravascular pathways facilitated. Exclusively based on the measured time signal curves, the two-compartment model provided net exchange ratios, which were significantly larger for the sleep-resembling condition than for the awake-like condition.
CONCLUSIONS
Efficiency of solute clearance in brain changes with alterations in both state of neuronal activity and CSF formation. Our clearance pathway and mechanism agnostic kinetic model informs about net solute transport, solely based on the measured time signal curves. This rather simplifying approach largely accords with preclinical and clinical findings.
Topics: Animals; Rats; Brain; Cerebral Ventricles; Acetazolamide; Anesthesia; Cisterna Magna; Contrast Media
PubMed: 37316849
DOI: 10.1186/s12987-023-00443-2 -
Acta Biomaterialia Dec 2019To better understand the onset of damage occurring in the brain upon traumatic events, it is essential to analyze how external mechanical loads propagate through the...
To better understand the onset of damage occurring in the brain upon traumatic events, it is essential to analyze how external mechanical loads propagate through the skull and meninges and down to the brain cortex. However, despite their crucial role as structural dampers protecting the brain, the mechanical properties and dynamic behavior of the meningeal layers are still poorly understood. Here, we characterized the local mechanical heterogeneity of rat pia-arachnoid complex (PAC) at the microscale via atomic force microscopy (AFM) indentation experiments to understand how microstructural variations at the tissue level can differentially affect load propagation. By coupling AFM mechanical testing with fresh tissue immunofluorescent staining, we could directly observe the effect of specific anatomical features on the local mechanical properties of tissue. We observed a two-fold stiffening of vascularized tissue when compared to non-vascularized PAC (with instantaneous Young's modulus distribution means of 1.32 ± 0.03 kPa and 2.79 ± 0.08 kPa, respectively), and statistically significant differences between regions of low- and high-vimentin density, reflecting trabecular density (with means of 0.67 ± 0.05 kPa and 1.29 ± 0.06 kPa, respectively). No significant differences were observed between cortical and cerebellar PAC. Additionally, by performing force relaxation experiments at the AFM, we identified the characteristic time constant τ of PAC tissue to be in the range of 2.7 ± 1.2 s to 3.1 ± 0.9 s for the different PAC regions analyzed. Taken together, the results presented point at the complex biomechanical nature of the meningeal tissue, and underscore the need to account for its heterogeneity when modeling its behavior into finite element simulations or other computational methods enabling the prediction of load propagation during injury events. STATEMENT OF SIGNIFICANCE: The meningeal layers are pivotal in shielding the brain during injury events, yet the mechanical properties of this complex biological interface are still under investigation. Here, we present the first anatomically-informed micromechanical characterization of mammalian pia-arachnoid complex (PAC). We developed a protocol for the isolation and fresh immunostaining of rat PAC and subjected the tissue to AFM indentation and relaxation experiments, while visualizing the local anatomy via fluorescence microscopy. We found statistically significant variations in regional PAC stiffness according to the degree of vascularization and trabecular cell density, besides identifying the tissue's characteristic relaxation constant. In essence, this study captures the relationship between anatomy and mechanical heterogeneity in a key component of the brain-skull interface for the first time.
Topics: Animals; Arachnoid; Biomechanical Phenomena; Elasticity; Fluorescence; Image Processing, Computer-Assisted; Mice; Microscopy, Atomic Force; Pia Mater; Rats, Sprague-Dawley; Staining and Labeling; Tomography, Optical Coherence; Vimentin; Viscosity
PubMed: 31585202
DOI: 10.1016/j.actbio.2019.09.044 -
World Neurosurgery Jan 2024Idiopatic normal pressure hydrocephalus (iNPH) is a progressive neurologic syndrome featured by the triad of gait disturbance, mental deterioration and urinary... (Review)
Review
BACKGROUND
Idiopatic normal pressure hydrocephalus (iNPH) is a progressive neurologic syndrome featured by the triad of gait disturbance, mental deterioration and urinary incontinence, associated with ventriculomegaly and normal cerebrospinal fluid (CSF) pressure. The clinical presentation may be atypical or incomplete, or mimicked by other diseases, so conventional neuroradiologic imaging plays an important role in defining this pathology. iNPH pathophysiologic mechanisms have not yet been fully elucidated, although several studies have demonstrated the involvement of the glymphatic system, a highly organized fluid transport system, the malfunction of which is involved in the pathogenesis of several disorders including normotensive hydrocephalus.
METHODS
Recent studies have shown how crucial in the diagnosis of this pathology is the definition of morphologic biomarkers, such as ventricular enlargement disproportionate to cerebral atrophy and associated ballooning of frontal horns; periventricular hyperintensities; and corpus callosum thinning and elevation, with callosal angle <90 degrees.
RESULTS
Another interesting feature that is becoming a well-recognized factor to look for and useful for the diagnosis of iNPH is disproportionately enlarged subarachnoid space hydrocephalus, which includes enlarged ventricles, tight high-convexity and medial surface subarachnoid spaces, and expanded Sylvian fissures. A correct choice of MRI sequences is important for a proper characterization identification of others diseases that may underlie this pathology. Magnetic resonance imaging allows us to evaluate CSF flow, enabling us to define qualitative and quantitative parameters necessary for the purpose of accurate iNPH diagnosis.
CONCLUSIONS
iNPH can represent a real diagnostic challenge; a proper correlation among clinical features, traditional MRI, and CSF dynamics analysis can lead to a correct diagnosis.
Topics: Humans; Hydrocephalus, Normal Pressure; Magnetic Resonance Imaging; Subarachnoid Space; Glymphatic System; Movement Disorders
PubMed: 37898265
DOI: 10.1016/j.wneu.2023.10.110 -
Clinical Neurology and Neurosurgery May 2020Lumbar arachnoiditis is a rare and debilitating neurologic disorder with multiple etiologies and a spectrum of imaging and clinical characteristics. Prior reports have... (Observational Study)
Observational Study
OBJECTIVES
Lumbar arachnoiditis is a rare and debilitating neurologic disorder with multiple etiologies and a spectrum of imaging and clinical characteristics. Prior reports have anecdotally claimed that no association exists between findings of arachnoiditis observed on magnetic resonance imaging (MRI) and those assessed clinically. The purpose of this study was to determine if MRI features of lumbar arachnoiditis associate with the clinical findings of the disorder.
PATIENTS AND METHODS
Twenty eight patients with lumbar arachnoiditis reported on MRI between 2012 and 2018 were retrospectively identified. A variety of MRI and clinical features of lumbar arachnoiditis were cataloged for these patients based on common findings discovered through literature review. Imaging findings included cauda equina nerve root contour and thickening, adhesion location, level of involvement, enhancement, and Delamarter group. Clinical findings included demographics, etiology, symptom dynamics, and signs/symptoms. Fisher's exact tests were used to determine associations between the imaging and clinical features of lumbar arachnoiditis.
RESULTS
In general, MRI findings did not associate with the clinical features of lumbar arachnoiditis with a few exceptions. Most notably, confounding lumbar pathology was associated with symptom dynamics (p = 0.004) and nerve root contour was associated with motor and sensory symptoms (p = 0.01). The suspected arachnoiditis etiology of the majority of patients was either post-operative or post-infectious in nature.
CONCLUSION
MRI findings in lumbar arachnoiditis offer limited insight into the clinical presentation of the disorder.
Topics: Aged; Arachnoiditis; Cauda Equina; Female; Humans; Infections; Lumbar Vertebrae; Magnetic Resonance Imaging; Male; Middle Aged; Muscle Weakness; Postoperative Complications; Radiculopathy; Retrospective Studies; Severity of Illness Index; Spinal Nerve Roots; Tissue Adhesions; Wounds and Injuries
PubMed: 32062307
DOI: 10.1016/j.clineuro.2020.105717 -
Neurosurgery Jul 2022The flow of cerebrospinal fluid (CSF) has been described as a unidirectional system with the choroid plexus serving as the primary secretor of CSF and the arachnoid... (Review)
Review
BACKGROUND
The flow of cerebrospinal fluid (CSF) has been described as a unidirectional system with the choroid plexus serving as the primary secretor of CSF and the arachnoid granulations as primary reabsorption site. This theory of neurosurgical forefathers has been universally adopted and taught as dogma. Many neuroscientists have found difficulty reconciling this theory with common pathologies, and recent studies have found that this "classic" hypothesis may not represent the full picture.
OBJECTIVE
To review modern CSF dynamic theories and to call for medical education reform.
METHODS
We reviewed the literature from January 1990 to December 2020. We searched the PubMed database using key terms "cerebrospinal fluid circulation," "cerebrospinal fluid dynamics," "cerebrospinal fluid physiology," "glymphatic system," and "glymphatic pathway." We selected articles with a primary aim to discuss either CSF dynamics and/or the glymphatic system.
RESULTS
The Bulat-Klarica-Orešković hypothesis purports that CSF is secreted and reabsorbed throughout the craniospinal axis. CSF demonstrates similar physiology to that of water elsewhere in the body. CSF "circulates" throughout the subarachnoid space in a pulsatile to-and-fro fashion. Osmolarity plays a critical role in CSF dynamics. Aquaporin-4 and the glymphatic system contribute to CSF volume and flow by establishing osmolarity gradients and facilitating CSF movement. Multiple studies demonstrate that the choroid plexus does not play any significant role in CSF circulation.
CONCLUSION
We have highlighted major studies to illustrate modern principles of CSF dynamics. Despite these, the medical education system has been slow to reform curricula and update learning resources.
Topics: Aquaporin 4; Cerebrospinal Fluid; Choroid Plexus; Education, Medical; Glymphatic System; Humans; Subarachnoid Space
PubMed: 35522666
DOI: 10.1227/neu.0000000000002000 -
World Neurosurgery Nov 2022Traumatic subarachnoid-pleural fistula is an uncommon occurrence. We present a case of a patient sustaining a subarachnoid-pleural fistula after a gunshot wound to the...
Traumatic subarachnoid-pleural fistula is an uncommon occurrence. We present a case of a patient sustaining a subarachnoid-pleural fistula after a gunshot wound to the neck, which ultimately resulted in substantial pneumocephalus. The patient underwent successful operative repair of the fistula with notable improvement and resolution of pneumocephalus.
Topics: Humans; Pneumocephalus; Wounds, Gunshot; Pleural Diseases; Pleura; Subarachnoid Space; Fistula
PubMed: 35917920
DOI: 10.1016/j.wneu.2022.07.080