Anterior Skull Base Analysis from Coronal and Reconstructed Computed Tomography: Radio-Anatomical Study

Endoscopic sinus and skull base Surgery has gained significant improvement widely all over the world. A computerized tomography (CT) scan provides a detailed anatomy of the skull base especially the bone framework. This study aims to analyze the fixed anatomical bony landmarks of the anterior skull base through coronal and reconstructed CT in the context of the Nepalese population and guide the surgeon to perform endoscopic sinus and skull base surgery safely. This Prospective study includes 70 Computerized Tomography scans of Paranasal sinuses. The different measurement from nasal floor to skull base was taken in coronal and reformatted sagittal CT scan. Mean, standard deviation, minimum and maximum values were analyzed using descriptive statistics. Student T-test was applied to compare between right and left side. This study includes 75 patients between 18 to 77 years. The measurement from nasal floor to the cribriform plate and ethmoidal roof in right and left side were, mean± SD (47± 4.1, 45.3±4.3, 47.9±5.1, and 49±8.5 mm) respectively. Mean Take off angle at the cribriform plate was 43.9 ±10.9°on right side and 43 ± 9.4° on the left side. The distance from the nasal spine to the skull base (mean ± SD) at nasofrontal recess, bulla ethmoidalis, and the junction of sphenoethmoid levels at right sides were 51.5 ± 4.7, 52.9 ± 4.1, and 61.2 ±4.7 little higher at left side. This study provides a detailed analysis of the anterior skull base in coronal and sagittal CT scans which helps to reduces complications.

Iatrogenic cerebrospinal fluid leak after repeated nasal swab tests for COVID-19: illustrative case

BACKGROUND Nasal swab tests are one of the most essential tools for screening coronavirus disease 2019 (COVID-19). The authors report a rare case of iatrogenic cerebrospinal fluid (CSF) leak from the anterior skull base after repeated nasal swab tests for COVID-19, which was treated with endoscopic endonasal repair. OBSERVATIONS A 41-year-old man presented with clear continuous rhinorrhea through his left nostril for 5 days after repeated nasal swabbing for COVID-19. There were no obvious risk factors for spontaneous CSF leak. Computed tomography cisternography showed contrast accumulation in the left olfactory fossa and along the left nasal cavity. Such findings aligned with a preliminary diagnosis of CSF leakage through the left cribriform plate. Magnetic resonance imaging confirmed the presence of a CSF fistula between his left cribriform plate and superior nasal concha. The patient underwent endoscopic endonasal repair. CSF rhinorrhea ceased after the surgery, and no recurrence was noted during the 12-week postoperative follow-up period. LESSONS Although rare, iatrogenic CSF leakage can be a serious complication following COVID-19 nasal swab tests, especially when infection may cause significant neurological sequelae. Healthcare providers should become familiar with nasal cavity anatomy and be well trained in performing nasal swab tests.

Impairment of CSF Egress through the Cribriform Plate plays an Apical Role in Alzheimer's disease Etiology

Cerebrospinal fluid (CSF) clears the brain's interstitial spaces, and disruptions in CSF flow or egress impact homeostasis, contributing to various neurological conditions. Here, we recast the human cribriform plate from innocuous bony structure to complex regulator of CSF egress with an apical role in Alzheimer's disease etiology. It includes the pathological evaluation of 70 post-mortem samples using high-resolution contrast-enhanced micro-CT and cutting-edge machine learning, a novel ferret model of neurodegeneration, and a clinical study with 560 volunteers, to provide conclusive evidence of a relationship between cribriform plate aging/pathology and cognitive impairment. Interstitial spaces within the medial temporal lobe and basal forebrain are cleared by CSF flow that drains through olfactory structures to the olfactory bulb, directly above the cribriform plate. We characterized CSF flow channels from subarachnoid spaces under the olfactory bulb to the nasal mucosa through subarachnoid evaginations that subdivide into tiny tubules that connect to an elaborate conduit system within the cribriform plate. These conduits form an internal watershed that runs from the crista galli's vault to a bony manifold within the olfactory fossa's back wall, connecting with large apertures in between. We found that the cross-sectional area of apertures limits CSF flux through the cribriform plate, which declines with increasing age. Subjects with a confirmed post-mortem diagnosis of Alzheimer's disease had the smallest CSF flux capacity, which reduces CSF-mediated clearance in upstream areas and leads to the accumulation of toxic macromolecules that seen AD pathology. We surgically occluded apertures in adult ferrets and found that this manipulation induced progressive deficits in spatiotemporal memory and significant atrophy of the temporal lobe, olfactory bulbs, and lateral olfactory stria. Finally, we explored human cribriform plate aging/pathology and cognition in a clinical study with 560 participants (20-95y). We evaluated cribriform plate morphology with CT and Deep Learning, assessed memory with a novel touch screen platform, tested olfactory discrimination, and asked questions about family history and relevant life events, like broken noses. Deep learning algorithms effectively parsed subjects and established the feasibility of predicting Alzheimer's disease years before a clinical presentation of cognitive impairment. This study provides a new perspective of the cribriform plate as a critical regulator of CSF egress and brain homeostasis.

Streptococcus pneumoniae rapidly translocates from the nasopharynx through the cribriform plate to invade and inflame the dura

The entry routes and translocation mechanisms of bacterial pathogens into the central nervous system remain obscure. We report here that Streptococcus pneumoniae (Sp) or polystyrene microspheres, applied to the nose of a mouse, appeared in the meninges of the dorsal cortex within minutes. Recovery of viable bacteria from dissected tissue and fluorescence microscopy showed that up to at least 72h, Sp and microspheres were predominantly in the outer of the two meninges, the pachymeninx. No Sp were found in blood or cerebrospinal fluid. Evidence that this was not an artifact of the method of administration is that in mice infected by horizontal transmission, Sp were also predominantly in the meninges and absent from blood. Intravital imaging through the skull, and flow cytometry showed recruitment and activation of LysM+ cells in the dorsal pachymeninx at 5h and 10h following intranasal infection. Imaging of the cribriform plate suggested that both Sp and microspheres entered through its foramina via an inward flow of fluid connecting the nose to the pachymeninx. Our findings bring further insight into the invasion mechanisms of bacterial pathogens such as Sp into the central nervous system, but are also pertinent to the delivery of drugs to the brain, and the entry of air-borne particles into the cranium.

Computed Tomography Analysis of Nasal Anatomy in Dorsal Preservation Rhinoplasty

Background Subdorsal septal resection and radix osteotomy are distinctive surgical steps in preservation rhinoplasty. Objectives The aim of this study was to evaluate the nasal bone thickness, the level of the septal bony-cartilaginous junction (K area), and the distances of the frontal sinus and skull base from the transverse osteotomy line in the Turkish population by means of conventional computed tomography (CT). Methods A retrospective evaluation was made of 203 consecutive preoperative paranasal CT scans of patients (classified in terms of age and gender) who had undergone rhinoplasty surgery between January 2020 and June 2021. The nasal bone thickness at the medial canthus level, and the distances between the transverse osteotomy line and the K area, the frontal sinus, and the cribriform plate were measured. Results The mean measurements were similar in terms of age groups (P = 0.402, P = 0.542, P = 0.134 and P = 0.276 for ages 18-30, 30-40, 40-50, and >50 years, respectively). The mean nasal bone thickness and the distance between the transverse osteotomy line and the K area showed statistical significance (P = 0.001 and P = 0.001, respectively). In both genders, the mean distances between the transverse osteotomy line and the frontal sinus and the cribriform plate were similar (P = 0.921 and P = 0.280, respectively). The nasal bone was thinner and the K area position more cephalic in females. Conclusions CT plays an important role in preoperative planning. The need for resection of the ethmoid perpendicular bone may be greater in males when lowering the dorsal hump, and hence they may be more prone to skull base complications. It is therefore necessary to be more careful in the surgical stage of subdorsal septal excision in males.

Neuroinflammation-Driven Lymphangiogenesis in CNS Diseases

The central nervous system (CNS) undergoes immunosurveillance despite the lack of conventional antigen presenting cells and lymphatic vessels in the CNS parenchyma. Additionally, the CNS is bathed in a cerebrospinal fluid (CSF). CSF is continuously produced, and consequently must continuously clear to maintain fluid homeostasis despite the lack of conventional lymphatics. During neuroinflammation, there is often an accumulation of fluid, antigens, and immune cells to affected areas of the brain parenchyma. Failure to effectively drain these factors may result in edema, prolonged immune response, and adverse clinical outcome as observed in conditions including traumatic brain injury, ischemic and hypoxic brain injury, CNS infection, multiple sclerosis (MS), and brain cancer. Consequently, there has been renewed interest surrounding the expansion of lymphatic vessels adjacent to the CNS which are now thought to be central in regulating the drainage of fluid, cells, and waste out of the CNS. These lymphatic vessels, found at the cribriform plate, dorsal dural meninges, base of the brain, and around the spinal cord have each been implicated to have important roles in various CNS diseases. In this review, we discuss the contribution of meningeal lymphatics to these processes during both steady-state conditions and neuroinflammation, as well as discuss some of the many still unknown aspects regarding the role of meningeal lymphatics in neuroinflammation. Specifically, we focus on the observed phenomenon of lymphangiogenesis by a subset of meningeal lymphatics near the cribriform plate during neuroinflammation, and discuss their potential roles in immunosurveillance, fluid clearance, and access to the CSF and CNS compartments. We propose that manipulating CNS lymphatics may be a new therapeutic way to treat CNS infections, stroke, and autoimmunity.