[1-11C]-Butanol Positron Emission Tomography reveals an impaired brain to nasal turbinates pathway in aging amyloid positive subjects

BACKGROUND

Reduced clearance of cerebrospinal fluid (CSF) has been suggested as a pathological feature of Alzheimer's disease (AD). With extensive documentation in non-human mammals and contradictory human neuroimaging data it remains unknown whether the nasal mucosa is a CSF drainage site in humans. Here, we used dynamic PET with [1-11C]-Butanol, a highly permeable radiotracer with no appreciable brain binding, to test the hypothesis that tracer drainage from the nasal pathway reflects CSF drainage from brain. As a test of the hypothesis, we examined whether brain and nasal fluid drainage times were correlated and affected by brain amyloid.

METHODS

24 cognitively normal subjects (≥ 65 years) were dynamically PET imaged for 60 min. using [1-11C]-Butanol. Imaging with either [11C]-PiB or [18F]-FBB identified 8 amyloid PET positive (Aβ+) and 16 Aβ- subjects. MRI-determined regions of interest (ROI) included: the carotid artery, the lateral orbitofrontal (LOF) brain, the cribriform plate, and an All-turbinate region comprised of the superior, middle, and inferior turbinates. The bilateral temporalis muscle and jugular veins served as control regions. Regional time-activity were used to model tracer influx, egress, and AUC.

RESULTS

LOF and All-turbinate 60 min AUC were positively associated, thus suggesting a connection between the brain and the nose. Further, the Aβ+ subgroup demonstrated impaired tracer kinetics, marked by reduced tracer influx and slower egress.

CONCLUSION

The data show that tracer kinetics for brain and nasal turbinates are related to each other and both reflect the amyloid status of the brain. As such, these data add to evidence that the nasal pathway is a potential CSF drainage site in humans. These data warrant further investigation of brain and nasal contributions to protein clearance in neurodegenerative disease.

Unmasking the Masquerade: Lessons from a Case of Spontaneous Mid-Clival CSF Leak Mimicking an Ethmoidal Leak

Spontaneous cerebrospinal fluid (CSF) leaks are an uncommon clinical entity, often challenging to diagnose accurately. We present a unique case of a patient with symptoms suggestive of an ethmoidal CSF leak, initially supported by radiological findings, but ultimately revealed to be a mid-clival CSF leak (from the posterior wall of the sphenoid sinus). This case underscores the complexities of diagnosing CSF leaks and highlights the importance of surgical exploration in cases where radiological evidence appears contradictory. The patient's Computed Tomography scan indicated a CSF leak in the cribriform plate, prompting a surgical approach to address this region. However, intraoperative findings surprisingly revealed no evidence of leak in the cribriform plate but instead a posterior wall of the sphenoid defect as the culprit. This report emphasizes the critical role of interdisciplinary collaboration, meticulous preoperative and intraoperative assessment, and adaptability in managing challenging cases of CSF leaks, ultimately leading to successful surgical repair and improved patient outcomes. It serves as a valuable reminder for clinicians to consider the possibility of a masquerading CSF leak when clinical and radiological findings do not align, thereby facilitating more precise diagnosis and targeted treatment.

"Sealing the Gap" : CSF Leakage Demystified-A Comprehensive Analysis of our Experience in CSF Rhinorrhea Management

CSF (Cerebro Spinal Fluid) rhinorrhoea occurs when the fluid leaks from subarachnoid space into the nasal cavity. The study aims to find out the prevalence and demographic distribution of CSF leak and to describe the site of the CSF leak along with the management. We did a prospective study on 180 patients admitted with head injury in neurosurgery department, along with the patients who came to ENT department with unilateral nasal discharge during the time period from March 2017 to March 2021. A total of 36 cases of CSF leak were obtained during the time period. The etiology in 18 cases was head injury & the other 18 cases were either due to infectious or nontraumatic causes. In our study, 26(72.22%) patients were aged less than 50 years. Incidence was more among males compared to females. The most common etiology was head injury - 18(50%) patients followed by the spontaneous leak- 16 (44.44%) patients with the most common site as the cribriform plate. Endoscopic repair using a hadad flap was done in most of the patients. Trauma due to head injury is the most common etiology in CSF rhinorrhea with more number of patients aged less than 50 years. Most of the leaks can be repaired successfully with the use of endoscope with excellent illumination & localizing the exact site of the leak.

Assessing Olfactory Fossa Depth and Its Relationship with the Variations in Adjacent Anatomical Structures by Using Cone Beam Computed Tomography (CBCT)

This study aimed to investigate the olfactory fossa anatomy (Keros types) and its relationship with changes in adjacent anatomical structures using cone-beam computed tomography (CBCT). In this descriptive-analytical study, the paranasal CBCT of 120 healthy adults over 18 years of age were evaluated. The olfactory fossa depth on both sides and the degree of asymmetry on both sides were reported. Correlation of olfactory fossa depth with the size of adjacent anatomical structures such as middle concha length, maximum orbital height and distance from ethmoid roof to nasal floor and ethmoid roof height to the palate in the anterior and posterior, length, and lateral angle of the lamella and cribriform plate distance. The lower concha junction was examined. The most common olfactory fossae on both sides of the Keros classification were Type II, Type I, and Type III, respectively. The mean dimensions of adjacent anatomical structures on the right and left did not differ significantly. The length and lateral angle of the lamella and the height of the ethmoid roof to the floor of the nose, and the height of the ethmoid roof to the palate in the back, on the right, and left in Type III were greater. The lateral angle of the left lamella was greater in Type III. The relationship between olfactory fossa depth and changes in anatomical structures were not significantly correlated with increasing olfactory fossa depth.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03538-2.

A comparative analysis of the CP and CG using 2D and 3D visualisation approaches

Investigations on the structural variations in the cribriform plate (CP), olfactory foramina and the Crista Galli showcase the benefits of using 3D imaging on smaller structures. These techniques reveal accurate details about bone morphology and density. Comparing different techniques, this project aims to examine the correlation between the CP, olfactory foramina, and Crista Galli. Computed tomography was used to translate and apply the findings acquired from the samples in radiographic studies on CPs for potential clinical significance. The findings show that the surface area measurements were significantly larger when using 3D imaging techniques in comparison with the 2D counterpart. Using 2D imaging, the maximum surface area of the CPs was 239.54 mm², however, paired 3D samples showed the maximum surface area was 355.51 mm². The findings show that Crista Galli's dimensions varied greatly, with length ranging from 15 to 26 mm, height ranging from 5 to 18 mm, and width ranging from 2 to 7 mm. The 3D imaging allowed for surface area measurements on the Crista Galli, and the surface area ranged from 130 to 390 mm². When 3D imaging was used, significant correlations were found between the surface area of the CP and the length of the Crista Galli (p = 0.001). The findings show that measurements on the Crista Galli using 2D and 3D reconstructed radiographic imaging reflect similar ranges of dimensions to 3D imaging measurements. The findings also suggest that the Crista Galli may increase in length with the CP to support the latter and olfactory bulb during trauma which may be used by clinicians alongside 2D CT scans for optimal diagnosis.

Movement of cerebrospinal fluid tracer into brain parenchyma and outflow to nasal mucosa is reduced at 24 h but not 2 weeks post-stroke in mice

BACKGROUND

Recent data indicates that cerebrospinal fluid (CSF) dynamics are disturbed after stroke. Our lab has previously shown that intracranial pressure rises dramatically 24 h after experimental stroke and that this reduces blood flow to ischaemic tissue. CSF outflow resistance is increased at this time point. We hypothesised that reduced transit of CSF through brain parenchyma and reduced outflow of CSF via the cribriform plate at 24 h after stroke may contribute to the previously identified post-stroke intracranial pressure elevation.

METHODS

Using a photothrombotic permanent occlusion model of stroke in C57BL/6 adult male mice, we examined the movement of an intracisternally infused 0.5% Texas Red dextran throughout the brain and measured tracer efflux into the nasal mucosa via the cribriform plate at 24 h or two weeks after stroke. Brain tissue and nasal mucosa were collected ex vivo and imaged using fluorescent microscopy to determine the change in CSF tracer intensity in these tissues.

RESULTS

At 24 h after stroke, we found that CSF tracer load was significantly reduced in brain tissue from stroke animals in both the ipsilateral and contralateral hemispheres when compared to sham. CSF tracer load was also reduced in the lateral region of the ipsilateral hemisphere when compared to the contralateral hemisphere in stroke brains. In addition, we identified an 81% reduction in CSF tracer load in the nasal mucosa in stroke animals compared to sham. These alterations to the movement of CSF-borne tracer were not present at two weeks after stroke.

CONCLUSIONS

Our data indicates that influx of CSF into the brain tissue and efflux via the cribriform plate are reduced 24 h after stroke. This may contribute to reported increases in intracranial pressure at 24 h after stroke and thus worsen stroke outcomes.

Open pathways for cerebrospinal fluid outflow at the cribriform plate along the olfactory nerves

BACKGROUND

Routes along the olfactory nerves crossing the cribriform plate that extend to lymphatic vessels within the nasal cavity have been identified as a critical cerebrospinal fluid (CSF) outflow pathway. However, it is still unclear how the efflux pathways along the nerves connect to lymphatic vessels or if any functional barriers are present at this site. The aim of this study was to anatomically define the connections between the subarachnoid space and the lymphatic system at the cribriform plate in mice.

METHODS

PEGylated fluorescent microbeads were infused into the CSF space in Prox1-GFP reporter mice and decalcification histology was utilized to investigate the anatomical connections between the subarachnoid space and the lymphatic vessels in the nasal submucosa. A fluorescently-labelled antibody marking vascular endothelium was injected into the cisterna magna to demonstrate the functionality of the lymphatic vessels in the olfactory region. Finally, we performed immunostaining to study the distribution of the arachnoid barrier at the cribriform plate region.

FINDINGS

We identified that there are open and direct connections from the subarachnoid space to lymphatic vessels enwrapping the olfactory nerves as they cross the cribriform plate towards the nasal submucosa. Furthermore, lymphatic vessels adjacent to the olfactory bulbs form a continuous network that is functionally connected to lymphatics in the nasal submucosa. Immunostainings revealed a discontinuous distribution of the arachnoid barrier at the olfactory region of the mouse.

INTERPRETATION

Our data supports a direct bulk flow mechanism through the cribriform plate allowing CSF drainage into nasal submucosal lymphatics in mice.

FUNDING

This study was supported by the Swiss National Science Foundation (310030_189226), Dementia Research Switzerland-Synapsis Foundation, the Heidi Seiler Stiftung and the Fondation Dr. Corinne Schuler.

Study of frontal and ethmoid sinus of sinonasal complex along with olfactory fossa: anatomical considerations for endoscopic sinus surgery

The Functional endoscopic sinus surgery through transnasal approach is a common modality of treatment for disorders of the nasal cavity, paranasal air sinuses as well as cranial cavity. The olfactory fossa (OF) is located along the superior aspect of cribriform plate which varies in shape and depth. This variable measurement of the depth of OF is mostly responsible for greater risk of intracranial infiltration during endoscopic procedures in and around the nasal cavity. The morphology of frontal and ethmoid sinus (ES) vary from simple to complex. This cadaveric study is planned to improve the ability of the otolaryngologist, radiologist to understand the possible morphological variations and plan steps of less invasive "precision surgery" to have a safe and complication free procedures. A total of 37 human head regions were included in the study. For classification of OF, Modified Kero's classification was used. The size, shape and cells of frontal and ES were noted. We found, type II (60.8%) OF was more common followed by type I (29.7%) than type III (9.5%). The shape of frontal sinus was comma shaped (55.4%) followed by oval (18.9%) than irregular (16.2%). Most common two cells type of ES was seen in 50.0% of both anterior and posterior ES. Out of 74 ES, 8.1% of Onodi cells and 14.9% of agger nasi cells were seen.

Radiological relationship of the ethmoid slit with the frontal sinus and the anterior ethmoidal artery and applications to the frontal sinus drillout

PURPOSE

To compare two types of CT acquisition parameters: CT scan of the facial bone and CT scan of the sinuses, for studying the ethmoidal slit and its relationship with the frontal sinus and anterior ethmoidal artery.

MATERIALS AND METHODS

Retrospective study of 145 scans of the sinuses and 79 of the facial bones performed between 2012 and 2016. On each scan, the visibility of the ethmoidal slits, their length, their distance from the ethmoidal artery, and their relationship with the anterior and posterior wall of the frontal sinus were studied.

RESULTS

The ethmoidal slit was better visualized on CT scans of the facial bone (58.2%) than on those of the sinuses (43.1%) (p = 0.02). The distance between the anterior ethmoidal artery and the anterior part of the cribriform plate was 9.3 mm for CT scans of the facial bone and 8.4 mm for CT scans of the sinuses. The theoretical risk of damaging the glabellar soft tissue and that of damaging the meninges during a frontal sinusotomy was evaluated, respectively, at 9.6% and 26.1% for CT scans of the facial bone, and at 6.2% and 21.5% for sinus scans.

CONCLUSIONS

CT scans of the facial bone are better than CT scans of the sinuses for identifying ethmoidal slits and their distance from the canal of the anterior ethmoidal artery. The identification of these elements is relevant for the surgeon during frontal sinus surgery and makes it possible to assess the risk of damaging the glabellar soft tissue or meninges. Performing a CT scan of the facial bone seems preferable to that of a CT scan of the sinuses in certain pathological situations, such as cerebrospinal rhinorrhea or revision surgeries of the frontal sinus.

Experiences and Outcomes in Olfactory Neuroblastoma Over A Decade at a Tertiary Cancer Center

Background  Olfactory neuroblastoma is a rare epithelial malignancy arising from the odorant receptors in the nasal mucosa or along the cribriform plate of the ethmoid bone. Clinical presentation includes nasal stuffiness, local pain, epistaxis, anosmia, visual impairment, proptosis, headache, and seizures. Radiologic imaging with CT or MRI, an ophthalmic evaluation, and histopathologic confirmation with immunohistochemistry are parts of the initial diagnostic workup. Although surgery, chemotherapy, and radiation have an equally important role in the management, earlier stages may preferably be treated with surgery or radiotherapy and the later stages with a multimodality approach. Materials and Methods  We conducted a retrospective review of 13 patients diagnosed with olfactory neuroblastoma, registered at Mehdi Nawaz Jung Regional Cancer Center over a decade (2010-2019). We analyzed the age and sex distribution, performance status at presentation, clinical symptomatology, and the Kadish stage. In addition, the therapeutic aspects of patients were studied. Results  The most common presentation noted was nasal stuffiness, followed by epistaxis and proptosis. The majority of patients had good performance status at presentation. Ten patients presented with a Kadish stage C, while the remaining patients presented with Kadish stage B. Cervical nodal metastasis was seen in three patients, four patients received multimodality treatment with neoadjuvant chemoradiotherapy followed by surgery, two patients received neoadjuvant chemotherapy followed by radiation, two patients received only surgery, and one patient received surgery followed by adjuvant radiation. Conformal radiation techniques were used to deliver doses as high as 50 to 66 Gy in 2 Gy per fraction. Two patients presented with distant metastasis during follow-up, one with bone metastasis, and the other with retroperitoneal nodal metastasis; they received palliative chemotherapy and conformal radiation to the primary site. Conclusion  This study concludes that neoadjuvant chemotherapy followed by radiation gives the best outcomes. It has been observed that in multi-modality treatment, radiotherapy played a significant role in improving overall survival and better outcomes. Multidisciplinary discussions provide a better sequencing of management.

Visualization of ex vivo rabbit olfactory mucosa and foramina with three-dimensional optical coherence tomography

There is increasing interest in developing a minimally invasive imaging modality to safely evaluate dynamic microscopic changes of the olfactory mucosa and cribriform foramina. Herein, we utilized three-dimensional (3D) optical coherence tomography (OCT) to characterize the ex vivo stratified substructure of olfactory mucosa in rabbits and create 3D reconstructed images of olfactory foramina. Olfactory mucosa and cribriform plates from four New Zealand White rabbits were dissected and imaged using two swept-source OCT systems: (1) 1.3-µm (μm) center wavelength, 100-nm bandwidth, 200-kHz sweep rate, and (2) 1.7-μm center wavelength, 120-nm bandwidth, 90-kHz sweep rate. Volumetric OCT images were compiled to create a 3D reconstruction of the cribriform plate. The ability of OCT to distinguish the olfactory mucosa substructure and foramina was compared to histology. To estimate imaging penetration depth of each system, the first-order exponential decays of depth-resolved intensity were calculated and compared using a paired t-test. Three-dimensional OCT depicted the stratified layered structures within the olfactory mucosa correlating with histology. The epithelium and lamina propria were measured to be 32 μm and 107 μm in 1.3-μm OCT compared to 30 μm and 105 μm in histology. Olfactory foramina were visualized via 3D reconstruction. The 1.7-μm system provided greater depth penetration compared to the 1.3-μm system, allowing for improved foramina visualization. We have shown that OCT can be used to image non-pathologic olfactory mucosa and foramina. Implications for this work include diagnostic and therapeutic potentials for neurorhinological and neurodegenerative diseases.

A computed tomography study on the olfactory fossa in dried skulls

PURPOSE

The computed tomography (CT) study investigates the olfactory fossa (OF) morphometry and morphology.

METHODS

Fifty Greek adult dried skulls were macroscopically investigated for the detection of the OF morphological patterns and after a multiplanar CT reconstruction, the OF morphometry was accurately calculated using a digital ruler.

RESULTS

Types I and II surface contour patterns were the most frequently identified (36 and 32%), followed by types III, IV, and V (16, 12, and 4%). Crista galli mean length, height, and width were 19.46 ± 2.34 mm, 12.69 ± 2.7 mm, and 5.18 ± 1.11 mm. The OF mean maximum length was 22.29 ± 2.16 mm on the right and 22.10 ± 2.44 mm on the left side, and symmetry was detected. The OF median values of the maximum depth for its anterior, middle, and posterior third were 4.91 mm, 4.72 mm, and 2.78 mm on the right and 4.55 mm, 4.75 mm, and 2.55 mm on the left side. Symmetry was observed in any third of the OF. The OF median values of the surface maximum width for the anterior, middle, and posterior thirds were 9.29 mm, 11.48 mm, and 13.07 mm. A significant gradual increase of the OF surface maximum width was detected in the anteroposterior direction in the total sample (p < 0.001), with the highest value (23.12 mm) in the posterior third. A significant (p < 0.001) very strong (r_s = -0.798) and a moderate (r_s = -0.524) negative linear correlation in the OF anterior and middle third were, respectively, identified between its maximum depth and width. No gender impact was identified.

CONCLUSIONS

The study helps to familiarize with the calculation of the OF dimensions and simplifies the understanding of its complex anatomy, to reach successful surgical planning and minimize perioperative complications.

Current concepts on communication between the central nervous system and peripheral immunity via lymphatics: what roles do lymphatics play in brain and spinal cord disease pathogenesis?

The central nervous system (CNS) lacks conventional lymphatics within the CNS parenchyma, yet still maintains fluid homeostasis and immunosurveillance. How the CNS communicates with systemic immunity has thus been a topic of interest for scientists in the past century, which has led to several theories of CNS drainage routes. In addition to perineural routes, rediscoveries of lymphatics surrounding the CNS in the meninges revealed an extensive network of lymphatics, which we now know play a significant role in fluid homeostasis and immunosurveillance. These meningeal lymphatic networks exist along the superior sagittal sinus and transverse sinus dorsal to the brain, near the cribriform plate below the olfactory bulbs, at the base of the brain, and surrounding the spinal cord. Inhibition of one or all of these lymphatic networks can reduce CNS autoimmunity in a mouse model of multiple sclerosis (MS), while augmenting these lymphatic networks can improve immunosurveillance, immunotherapy, and clearance in glioblastoma, Alzheimer's disease, traumatic brain injury, and cerebrovascular injury. In this review, we will provide historical context of how CNS drainage contributes to immune surveillance, how more recently published studies fit meningeal lymphatics into the context of CNS homeostasis and neuroinflammation, identify the complex dualities of lymphatic function during neuroinflammation and how therapeutics targeting lymphatic function may be more complicated than currently appreciated, and conclude by identifying some unresolved questions and controversies that may guide future research.

Nuances of Olfactory Groove Meningioma Surgery: 2-Dimensional Operative Video

Olfactory groove meningiomas frequently present as large or giant-size tumors associated with marked frontal lobe edema and significant frontal lobe dysfunction. Simpson grade I removal was rare in early reports due to their invasion of the ethmoid sinuses and skull base bone,1 which resulted in high recurrence rates.2,3 Indeed, recurrence occurred in the most celebrated case of olfactory groove meningioma.4,5  To achieve Simpson grade I removal (tumor, dura, bone), protect the frontal lobes from additional injury, and provide the best chance for recovery, we demonstrate a few nuances for olfactory groove meningioma surgery: Utilizing a skull base approach with a low dural opening, the frontal veins are preserved, and the frontal lobe is protected from retraction, manipulation, and venous injury. By the time of diagnosis, although the patient's olfaction is often absent, there still remains a role to preserve at least 1 olfactory tract, which might yield some preservation in a limited number of patients. Emphasis has been rightly made on the preservation of the A2 segments, which can be dissected using microsurgical technique. Lastly, multilayer reconstruction of the skull base is required, using an inlay graft, resting on a vascularized pericranial flap, and occlusion of the sinuses with a fat graft. The endonasal endoscopic approach has fallen out of favor due to limitations for complete tumor resection and higher complication rates.6  We present a case of a relatively small olfactory groove meningioma in a 36-yr-old male with partial olfactory loss. The patient consented for surgery.  Images at 2:07, 2:29, and 2:54 from Al-Mefty O, Operative Atlas of Meningiomas, © LWW, 1997, with permission. Image at 8:31 public domain by age.

Elucidation of the role of the lamina cribrosa in glaucoma using optical coherence tomography

Glaucoma is a chronic and progressive optic neuropathy characterized by the death of retinal ganglion cells and corresponding visual field loss. Despite the growing number of studies on the subject, the pathogenesis of the disease remains unclear. Notwithstanding, several studies have shown that the lamina cribrosa (LC) is considered an anatomic site of glaucomatous optic nerve injury, thus having a key role in the pathophysiology of glaucoma development and progression. Different morphological alterations of the LC have been described in vivo in glaucomatous eyes after the evolution of optical coherence tomography (OCT) devices. The most relevant findings were the reduction of laminar thickness, the presence of localized defects, and the posterior LC displacement. These new laminar parameters documented through OCT are not only promising as possible additional tools for glaucoma diagnosis and monitoring, but also as predictors of disease progression. In spite of the advance of technology, however, proper evaluation of the LC is not yet viable in all eyes. We describe OCT-identified LC changes related to the development and progression of glaucoma and provide future directions based on a critical data analysis, focusing on its clinical relevance and applicability.

Cerebrospinal fluid outflow: a review of the historical and contemporary evidence for arachnoid villi, perineural routes, and dural lymphatics

Cerebrospinal fluid (CSF) is produced by the choroid plexuses within the ventricles of the brain and circulates through the subarachnoid space of the skull and spinal column to provide buoyancy to and maintain fluid homeostasis of the brain and spinal cord. The question of how CSF drains from the subarachnoid space has long puzzled scientists and clinicians. For many decades, it was believed that arachnoid villi or granulations, outcroppings of arachnoid tissue that project into the dural venous sinuses, served as the major outflow route. However, this concept has been increasingly challenged in recent years, as physiological and imaging evidence from several species has accumulated showing that tracers injected into the CSF can instead be found within lymphatic vessels draining from the cranium and spine. With the recent high-profile rediscovery of meningeal lymphatic vessels located in the dura mater, another debate has emerged regarding the exact anatomical pathway(s) for CSF to reach the lymphatic system, with one side favoring direct efflux to the dural lymphatic vessels within the skull and spinal column and another side advocating for pathways along exiting cranial and spinal nerves. In this review, a summary of the historical and contemporary evidence for the different outflow pathways will be presented, allowing the reader to gain further perspective on the recent advances in the field. An improved understanding of this fundamental physiological process may lead to novel therapeutic approaches for a wide range of neurological conditions, including hydrocephalus, neurodegeneration and multiple sclerosis.

How to identify the anterior cribriform plate in the medial approach to the frontal sinus

Draf III frontal sinusotomy is one of the most complex surgical procedures on the frontal sinus, designed to limit the risks of restenosis by ensuring unification of the two ostia and resection of the floor of the sinus. This procedure requires a good knowledge of anatomy and sufficient surgical expertise to avoid the risk of CSF leak and to limit the risk of restenosis. The surgeon can use various landmarks, consisting of foramina, bone grooves and arteries located on the anterior part of the cribriform plate to guide the procedure. The purpose of this technical note is to explain the use of these landmarks to ensure safe Draf III frontal sinusotomy via a medial approach.

Microsurgical Anatomy Review of Bifrontal Limited Transbasal Approach - Quantitative and Anatomy Study

INTRODUCTION

The bifrontal transbasal approach is an anterior midline skull base approach to anterior skull base, sellae region and, if needed, to posterior skull base in the midline, often used for tumoral lesions but also useful for vascular or infectious pathologies.

METHODS

Descriptive anatomic study, 5 formalin-fixed human cadaveric heads were used injected with colored silicone. The dissection was made step-by-step to describe every anatomic structure encountered. The working distance was obtained from the posterior wall of the frontal sinus with and without orbital rim to the pituitary stalk, the sellae, the pontomedullary sulcus, and the anterior margin of the foramen magnum.

RESULTS

Stepwise anatomic dissection was performed dividing the surgical technique into 6 stages: soft-tissue stage, bone stage, sinus stage, clival stage, intradural, and measurements. The objective of making the supraorbital osteotomy was to improve the vision over the neural structures without brain retraction and limited to the midline supraorbital rim to avoid aggressive manipulation and injury to the orbit. The working distances measured with the orbital rim were on average: to the pituitary stalk, 70.5 mm; to the sellae, 81.3 mm; to the pontomedullary sulcus, 97 mm; and the foramen magnum, 99.5 mm. Without the orbital rim measures were: to the pituitary stalk, 57 mm; to the sellae, 62.5 mm; to the pontomedullary sulcus, 96 mm; and the foramen magnum, 98.5 mm.

CONCLUSIONS

The addition of osteotomies including removing of the orbital rim improves the access to the central skull base with special benefits on the working distances to the sellae region.

New detailed description of the anterior part of the cribriform plate using anatomic specimens and computed tomography

PURPOSE

Ethmoidal slit (ES) and cribroethmoidal foramen (CF) have been poorly studied, without any radiological description. They may ease cribriform plate's diseases. The objective was to describe the frequency, size, and computed tomography (CT) appearance of these foramina.

METHODS

A two-part anatomoradiological study was performed: first on dry skulls using a surgical microscope and CT, second on patients CT scans. For each, foramina were searched for, described, and measured when possible.

RESULTS

Thirteen dry macerated skulls were studied. The orbitomeatal plane was relevant for studying ES. With microscope, ES and CF were identified in, respectively, 92% and 100% of cases. Using CT, all ES and CF were visible, with a mean length and width of, respectively, 3.9 ± 1.7 mm and 0.9 ± 0.3 mm for ES and 1.6 ± 1 mm and 0.9 ± 0.3 mm for CF. CT scans from 153 patients were reviewed. ES and CF were identified in, respectively, 80% and 91% of cases, with a mean length and width of, respectively, 3.9 ± 0.8 mm and 0.8 ± 0.2 mm for ES.

CONCLUSION

Large-sized ES was found frequently, and were clearly visible in patients CT scans. CF was markedly smaller, but seen in most patient scans. ES and CF could be areas of least resistance in the anterior part of the cribriform plate. CT might be helpful in understanding their pathological implications.

Brain Herniation into Nasal Cavity Secondary to Large Convexity Meningioma

Acquired (nontraumatic) brain herniation through the ethmoid is rarely associated with an intracranial mass away from the anterior skull base. A 55-year-old diabetic woman presented with progressive frontal headache, anosmia, and blurred vision without rhinorrhea. Brain magnetic resonance imaging showed an intracranial tumor of the left frontal convexity associated with a herniation of the frontal brain (encephalocele) into the left nasal cavity. A computed tomography scan confirmed the anterior skull base defect. The intracranial tumor was totally excised after a left frontal craniotomy with a good outcome. Pathologic examination revealed a meningothelial meningioma. However, the patient and her family refused any surgery for the ethmoidal encephalocele. In our case report, this rare phenomenon (secondary nontraumatic encephalocele) probably occurred due to long-term increase of the intracranial pressure generated by the meningioma.

An undescribed venous pathway intervening between the olfactory fossa and nasal vestibule

PURPOSE

A curvilinear pathway intervening between the olfactory fossa and nasal vestibule has not been well documented. Therefore, the aim of this study was to examine its structure using magnetic resonance imaging (MRI).

METHODS

In total, 84 patients underwent thin-sliced, contrast MRI. Among these patients, 31 underwent additional thin-sliced, sagittal T2-weighted imaging.

RESULTS

A curvilinear pathway intervening between the olfactory fossa and nasal vestibule was delineated on sagittal and coronal imaging in 98% and 82% of patients, respectively. All of these pathways demonstrated communication with the lower limit of the superior sagittal sinus (SSS) or fine venous channels connecting to the SSS in the vicinity of the crista galli. The pathway was identified in the parasagittal regions on both sides with varying lengths, diameters, and curvatures. In 94% of the patients who underwent sagittal T2-weighted imaging, the pathways appeared as linear high-intensity signals. Most pathways were delineated as a single channel coursing extracranially adjacent to the olfactory fossa. In 38% of the patients, post-contrast sagittal images showed variable filling defects between the olfactory bulb and floor of the olfactory fossa, furthermore traversing the venous pathway. Additionally, in 73% of the patients, post-contrast images identified diploic venous channels, variably in the nasal bone and communicating with the venous pathway.

CONCLUSIONS

A curvilinear pathway intervening between the olfactory fossa and nasal vestibule is a consistent venous structure and may function as an extracranial route of cerebrospinal fluid drainage.

Outcome of Endoscopic Cerebrospinal Fluid Rhinorrhoea Repair: An Institutional Study

Cerebrospinal fluid Rhinorrhoea is caused by an abnormal open communication between the subarachnoid space and the nasal cavity. The most common anatomic sites of such abnormal communication are found in the anterior skull base, namely, ethmoid roof, olfactory groove, roof of the sphenoid sinus and the posterior wall of the frontal sinus. It can be classified into traumatic or spontaneous. Spontaneous leaks are associated with highest recurrence rates following surgical repair. The repair of CSF Rhinorrhoea has rapidly evolved over the past 30 years. Prior to the advent of the endoscopic approach, craniotomy was used for repairs which carried a variable success rate and morbidity. The purpose of our study was to ascertain the outcome after Transnasal Endoscopic Repair of spontaneous CSF leaks. This was a prospective study conducted at the Department of ENT at Safdarjung Hospital, New Delhi between January 2015 and June 2016. The study comprised of eleven patients who presented with the complaint of watery nasal discharge and were diagnosed to have spontaneous CSF Rhinorrhoea. Proper clinical examination, nasal endoscopy and biochemical and cytological analysis of nasal secretions of the patient was done. High Resolution Computed Tomography and MRI scans of the nose and paranasal sinuses were done to identify precise location of CSF leak and the size of fistula. CT cisternography was done wherever required. Fistula was repaired via Transnasal endoscopic approach in a multi layered underlay fashion. Out of all eleven patients with spontaneous CSF leaks, most common site of leak was from left cribriform area. Four patients (36.36%) were found to have meningoencephalocele. No associated intracranial lesion was found and all patients did not have any benign intracranial hypertension. Our success rate of endoscopic repair on first attempt was 100% with recurrence in 1 patient after 4 months of repair. Endoscopic repair of CSF rhinorrhoea is safe and effective, with a very low complication rate. It has almost completely replaced the older open techniques. Accurate localization of leak site followed by multilayered closure of dural defect appear to be essential for successful endoscopic repair.

Lymphatic drainage of cerebrospinal fluid in mammals - are arachnoid granulations the main route of cerebrospinal fluid outflow?

The outflow of the cerebrospinal fluid (CSF) in animals was over the years the subject of detailed analysis. For a long time it was stated that arachnoid granulations of the venous sinuses play a key role in CSF circulation. However, recent studies on this subject have shown that a considerable part of the CSF is drained to the lymphatic vessels. Moreover, disorders in the CSF passage may result in severe central nervous system diseases such as e.g. hydrocephalus. In this paper, we summarize the current knowledge concerning the lymphatic drainage of the CSF in mammals. We present in detail comparative anatomy of different species taking into account cranial and spinal compartment. In addition, we clarified role of the lymphatic vessels in the CSF outflow and the relationship between impairment in this transport and central nervous system diseases. In the author’s opinion knowledge on CSF circulation is still poorly examined and therefore required comment.

Rostral cranial fossa as a site for cerebrospinal fluid drainage - volumetric studies in dog breeds of different size and morphotype

Background

Hydrocephalus is a multifactorial condition, whose aetiology is not fully understood. Congenital hydrocephalus frequently occurs in small and brachycephalic dog breeds. Although it is widely accepted that the cribriform plate located in the rostral cranial fossa (RCF) is a site of cerebrospinal fluid (CSF) drainage, the RCF has not been studied extensively. Literature reports indicate that a decreased caudal cranial fossa (CCF) volume in the course of the Chiari-like malformation may obstruct CSF circulation. We hypothesised that morphological diversity among different breeds in the volume of the RCF may affect CSF circulation. The aim of the study was to carry out a volumetric analysis of the RCF and the cranial cavity and to determine the ratio between them in dog breeds of different size and morphotype. We performed computed tomography (CT) morphometric analysis of the RCF compartment by obtaining volume measurements from the transverse and reformatted sagittal and dorsal planes.

Results

The rostral cranial fossa percentage – volume of the rostral cranial fossa/volume of cranial cavity × 100 (volRCF/volCC × 100) was lower in small and brachycephalic dog breeds than in the other dogs.

Conclusions

A reduced RCF volume was detected in small and brachycephalic dog breeds, some of which are predisposed to congenital hydrocephalus. This may lead to overcrowding of brain parenchyma in the RCF and may impede CSF circulation. Our observations may be useful for future studies focusing on the causes and new therapies to treat conditions such as hydrocephalus and syringomyelia.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1483-3) contains supplementary material, which is available to authorized users.

Endoscopic Repair of CSF Rhinorrhea: An Institutional Experience

INTRODUCTION

Endoscopic repair is considered the treatment of choice in cerebrospinal fluid (CSF) rhinorrhea. The aim of our study was to analyze the etiopathogenesis of CSF rhinorrhea, the outcome of treatment and the causes of failure in a developing-country setting.

MATERIALS AND METHODS

A retrospective review of patients treated with endoscopic repair for CSF rhinorrhea at a tertiary care hospital in southern India from January 2002 to December 2009 identified 36 patients, the majority of them being women. The defects were closed in three layers using fat, fascia lata and nasal mucosa along with a fibrin sealant in the majority of the patients. Per-operatively, a subarachnoid drain was placed in all patients. Patients were followed up for 1 year.

RESULTS

Spontaneous onset of CSF rhinorrhea was noted in 61% of patients. The most common site of leak was found to be the left cribriform plate area. Hence the most common cause of CSF rhinorrhea in our study was spontaneous and the second most common was post-traumatic. Our success rate on the first attempt at endoscopic repair was 100%, with a recurrence rate of 6%. A large defect, failure of localization of the defect, or other co-morbid conditions such as chronic cough may be the most likely causes of recurrence of leak.

CONCLUSION

Accurate localization of the site of lesion using a high-resolution computed tomography (CT) scan with magnetic resonance imaging (MRI) and confirmation of the site of leak by intraoperative Valsalva maneuver along with multilayered closure of the dural defect and post-operative lumbar drain appear to be essential for the successful endoscopic repair of CSF rhinorrhea.