Mesoscale Brain Mapping: Bridging Scales and Modalities in Neuroimaging - A Symposium Review.

Advances in the spatiotemporal resolution and field-of-view of neuroimaging tools are driving mesoscale studies for translational neuroscience. On October 10, 2023, the Center for Mesoscale Mapping (CMM) at the Massachusetts General Hospital (MGH) Athinoula A. Martinos Center for Biomedical Imaging and the Massachusetts Institute of Technology (MIT) Health Sciences Technology based Neuroimaging Training Program (NTP) hosted a symposium exploring the state-of-the-art in this rapidly growing area of research. "Mesoscale Brain Mapping: Bridging Scales and Modalities in Neuroimaging" brought together researchers who use a broad range of imaging techniques to study brain structure and function at the convergence of the microscopic and macroscopic scales. The day-long event centered on areas in which the CMM has established expertise, including the development of emerging technologies and their application to clinical translational needs and basic neuroscience questions. The in-person symposium welcomed more than 150 attendees, including 57 faculty members, 61 postdoctoral fellows, 35 students, and four industry professionals, who represented institutions at the local, regional, and international levels. The symposium also served the training goals of both the CMM and the NTP. The event content, organization, and format were planned collaboratively by the faculty and trainees. Many CMM faculty presented or participated in a panel discussion, thus contributing to the dissemination of both the technologies they have developed under the auspices of the CMM and the findings they have obtained using those technologies. NTP trainees who benefited from the symposium included those who helped to organize the symposium and/or presented posters and gave "flash" oral presentations. In addition to gaining experience from presenting their work, they had opportunities throughout the day to engage in one-on-one discussions with visiting scientists and other faculty, potentially opening the door to future collaborations. The symposium presentations provided a deep exploration of the many technological advances enabling progress in structural and functional mesoscale brain imaging. Finally, students worked closely with the presenting faculty to develop this report summarizing the content of the symposium and putting it in the broader context of the current state of the field to share with the scientific community. We note that the references cited here include conference abstracts corresponding to the symposium poster presentations.

Recommendations for quantitative cerebral perfusion MRI using multi-timepoint arterial spin labeling: Acquisition, quantification, and clinical applications.

Accurate assessment of cerebral perfusion is vital for understanding the hemodynamic processes involved in various neurological disorders and guiding clinical decision-making. This guidelines article provides a comprehensive overview of quantitative perfusion imaging of the brain using multi-timepoint arterial spin labeling (ASL), along with recommendations for its acquisition and quantification. A major benefit of acquiring ASL data with multiple label durations and/or post-labeling delays (PLDs) is being able to account for the effect of variable arterial transit time (ATT) on quantitative perfusion values and additionally visualize the spatial pattern of ATT itself, providing valuable clinical insights. Although multi-timepoint data can be acquired in the same scan time as single-PLD data with comparable perfusion measurement precision, its acquisition and postprocessing presents challenges beyond single-PLD ASL, impeding widespread adoption. Building upon the 2015 ASL consensus article, this work highlights the protocol distinctions specific to multi-timepoint ASL and provides robust recommendations for acquiring high-quality data. Additionally, we propose an extended quantification model based on the 2015 consensus model and discuss relevant postprocessing options to enhance the analysis of multi-timepoint ASL data. Furthermore, we review the potential clinical applications where multi-timepoint ASL is expected to offer significant benefits. This article is part of a series published by the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group, aiming to guide and inspire the advancement and utilization of ASL beyond the scope of the 2015 consensus article.

MRI Assessment of Cerebral White Matter Microvascular Hemodynamics Across the Adult Lifespan.

BACKGROUND: Changes in cerebral hemodynamics with aging are important for understanding age-related variation in neuronal health. While many prior studies have focused on gray matter, less is known regarding white matter due in part to measurement challenges related to the lower vascular density in white matter. PURPOSE: To investigate the impact of age and sex on white matter hemodynamics in a Human Connectome Project in Aging (HCP-A) cohort using tract-based spatial statistics (TBSS). STUDY TYPE: Retrospective cross-sectional. POPULATION: Six hundred seventy-eight typically aging individuals (381 female), aged 36-100 years. FIELD STRENGTH/SEQUENCE: Multi-delay pseudo-continuous arterial spin labeling (ASL) and diffusion-weighted pulsed-gradient spin-echo echo planar imaging sequences at 3.0 T. ASSESSMENT: A skeleton of mean fractional anisotropy (FA) was produced using TBSS. This skeleton was used to project ASL-derived cerebral blood flow (CBF) and arterial transit time (ATT) measures onto white matter tracts. STATISTICAL TESTS: General linear models were applied to white matter FA, CBF, and ATT maps, while covarying for age and sex. Threshold-free cluster enhancement multiple comparisons correction was performed for the effects of age and sex, thresholded at PFWE < 0.05. CBF, ATT, and FA were compared between sex for each tract using analysis of covariance, with multiple comparisons correction for the number of tracts at PFDR < 0.05. RESULTS: Significantly lower white matter CBF and significantly prolonged white matter ATTs were associated with older age. These effects were widespread across tracts for ATT. Significant (PFDR < 0.05) sex differences in ATT were observed across all tracts, and significant sex differences in CBF were observed in all tracts except the bilateral uncinate fasciculus. Females demonstrated significantly higher CBF compared to males across the lifespan. Few tracts demonstrated significant sex differences in FA. DATA CONCLUSION: This study identified significant sex- and age-associated differences in white matter hemodynamics across tracts. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 3.

Associations between age, sex, APOE genotype, and regional vascular physiology in typically aging adults.

Altered blood flow in the human brain is characteristic of typical aging. However, numerous factors contribute to inter-individual variation in patterns of blood flow throughout the lifespan. To better understand the mechanisms behind such variation, we studied how sex and APOE genotype, a primary genetic risk factor for Alzheimer's disease (AD), influence associations between age and brain perfusion measures. We conducted a cross-sectional study of 562 participants from the Human Connectome Project - Aging (36 to >90 years of age). We found widespread associations between age and vascular parameters, where increasing age was associated with regional decreases in cerebral blood flow (CBF) and increases in arterial transit time (ATT). When grouped by sex and APOE genotype, interactions between group and age demonstrated that females had relatively greater CBF and lower ATT compared to males. Females carrying the APOEε4 allele showed the strongest association between CBF decline and ATT incline with age. This demonstrates that sex and genetic risk for AD modulate age-associated patterns of cerebral perfusion measures.

Cardiovascular and metabolic health is associated with functional brain connectivity in middle-aged and older adults: Results from the Human Connectome Project-Aging study.

Several cardiovascular and metabolic indicators, such as cholesterol and blood pressure have been associated with altered neural and cognitive health as well as increased risk of dementia and Alzheimer's disease in later life. In this cross-sectional study, we examined how an aggregate index of cardiovascular and metabolic risk factor measures was associated with correlation-based estimates of resting-state functional connectivity (FC) across a broad adult age-span (36-90+ years) from 930 volunteers in the Human Connectome Project Aging (HCP-A). Increased (i.e., worse) aggregate cardiometabolic scores were associated with reduced FC globally, with especially strong effects in insular, medial frontal, medial parietal, and superior temporal regions. Additionally, at the network-level, FC between core brain networks, such as default-mode and cingulo-opercular, as well as dorsal attention networks, showed strong effects of cardiometabolic risk. These findings highlight the lifespan impact of cardiovascular and metabolic health on whole-brain functional integrity and how these conditions may disrupt higher-order network integrity.

Mean Arterial Pressure and Cerebral Hemodynamics Across The Lifespan: A Cross-Sectional Study From Human Connectome Project-Aging.

BACKGROUND: Cerebral perfusion is directly affected by systemic blood pressure, which has been shown to be negatively correlated with cerebral blood flow (CBF). The impact of aging on these effects is not fully understood. PURPOSE: To determine whether the relationship between mean arterial pressure (MAP) and cerebral hemodynamics persists throughout the lifespan. STUDY TYPE: Retrospective, cross-sectional study. POPULATION: Six hundred and sixty-nine participants from the Human Connectome Project-Aging ranging between 36 and 100+ years and without a major neurological disorder. FIELD STRENGTH/SEQUENCE: Imaging data was acquired at 3.0 Tesla using a 32-channel head coil. CBF and arterial transit time (ATT) were measured by multi-delay pseudo-continuous arterial spin labeling. ASSESSMENT: The relationships between cerebral hemodynamic parameters and MAP were evaluated globally in gray and white matter and regionally using surface-based analysis in the whole group, separately within different age groups (young: <60 years; younger-old: 60-79 years; oldest-old: ≥80 years). STATISTICAL TESTS: Chi-squared, Kruskal-Wallis, ANOVA, Spearman rank correlation and linear regression models. The general linear model setup in FreeSurfer was used for surface-based analyses. P < 0.05 was considered significant. RESULTS: Globally, there was a significant negative correlation between MAP and CBF in both gray (ρ = -0.275) and white matter (ρ = -0.117). This association was most prominent in the younger-old [gray matter CBF (ß = -0.271); white matter CBF (ß = -0.241)]. In surface-based analyses, CBF exhibited a widespread significant negative association with MAP throughout the brain, whereas a limited number of regions showed significant prolongation in ATT with higher MAP. The associations between regional CBF and MAP in the younger-old showed a different topographic pattern in comparison to young subjects. DATA CONCLUSION: These observations further emphasize the importance of cardiovascular health in mid-to-late adulthood for healthy brain aging. The differences in the topographic pattern with aging indicate a spatially heterogeneous relationship between high blood pressure and CBF. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 3.

Current state and guidance on arterial spin labeling perfusion MRI in clinical neuroimaging.

This article focuses on clinical applications of arterial spin labeling (ASL) and is part of a wider effort from the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group to update and expand on the recommendations provided in the 2015 ASL consensus paper. Although the 2015 consensus paper provided general guidelines for clinical applications of ASL MRI, there was a lack of guidance on disease-specific parameters. Since that time, the clinical availability and clinical demand for ASL MRI has increased. This position paper provides guidance on using ASL in specific clinical scenarios, including acute ischemic stroke and steno-occlusive disease, arteriovenous malformations and fistulas, brain tumors, neurodegenerative disease, seizures/epilepsy, and pediatric neuroradiology applications, focusing on disease-specific considerations for sequence optimization and interpretation. We present several neuroradiological applications in which ASL provides unique information essential for making the diagnosis. This guidance is intended for anyone interested in using ASL in a routine clinical setting (i.e., on a single-subject basis rather than in cohort studies) building on the previous ASL consensus review.

Subperiosteal inferior maxillectomy in mucormycosis patients: case series.

OBJECTIVE: Mucormycosis is a rapidly progressive and fulminant fungal infection mainly affecting the nose and paranasal sinuses and often requiring aggressive surgical debridement, which commonly includes inferior maxillectomy. Conventional inferior maxillectomy involves removal of the bony hard palate and its mucoperiosteum. This can lead to formation of an oroantral fistula and thereby increase the morbidity in these patients leading to prolonged rehabilitation. Subperiosteal inferior maxillectomy involves sparing of the uninvolved mucoperiosteum of the hard palate. This flap is used for closure of the oroantral fistula, which preserves the functional capabilities of the patient, such as speech, mastication and deglutination. METHOD: This case series describes the experience of using the technique of mucosa-preserving subperiosteal inferior maxillectomy in five patients with mucormycosis. RESULTS: With the technique used in this study, complete oronasal separation was achieved in all six patients. The overall surgery time was also decreased when compared with free tissue transfer. Patients also did not have to bear the weight of prosthesis. CONCLUSION: Mucoperiosteal palatal flap-preserving subperiosteal inferior maxillectomy is an excellent approach for all patients with mucormycosis and healthy palatal mucosa.

Oxygen extraction efficiency and white matter lesion burden in older adults exhibiting radiological evidence of capillary shunting.

White matter lesions (WML) have been linked to cognitive decline in aging as well as in Alzheimer's disease. While hypoperfusion is frequently considered a cause of WMLs due to the resulting reduction in oxygen availability to brain tissue, such reductions could also be caused by impaired oxygen exchange. Here, we tested the hypothesis that venous hyperintense signal (VHS) in arterial spin labeling (ASL) magnetic resonance imaging (MRI) may represent a marker of impaired oxygen extraction in aging older adults. In participants aged 60-80 years (n = 30), we measured cerebral blood flow and VHS with arterial spin labeling, maximum oxygen extraction fraction (OEFmax) with dynamic susceptibility contrast, and WML volume with T1-weighted MRI. We found a significant interaction between OEFmax and VHS presence on WML volume (p = 0.02), where lower OEFmax was associated with higher WML volume in participants with VHS, and higher OEFmax was associated with higher WML volume in participants without VHS. These results indicate that VHS in perfusion-weighted ASL data may represent a distinct cerebrovascular aging pattern involving oxygen extraction inefficiency as well as hypoperfusion.

Coronavirus disease 2019 associated mucormycosis meandering its way into the orbit: a pictorial review.

BACKGROUND: There has been a recent deluge of coronavirus disease 2019 associated mucormycosis in our country. It affects the paranasal sinuses; however, it has a rapid extrasinus progression (the orbit being most common), which can be fatal if not detected early. It may meander into the orbit through various foramina without frank bone destruction. METHODS: This paper reviews the various gateways of the spread of coronavirus disease 2019 associated mucormycosis to the orbit, even before advent of bone destruction or ocular symptoms. Plausible pathways of invasion and subtle imaging findings are depicted, to enable an early diagnosis. RESULTS: Relevant anatomy and imaging examples have been illustrated to familiarise the surgeons with various routes of coronavirus disease 2019 associated mucormycosis spread to the orbit. Emphasis is laid on searching for subtle imaging findings for the detection of early orbital invasion. CONCLUSION: Early detection and extension of coronavirus disease 2019 associated mucormycosis is facilitated by knowledge of its gateways of spread, which aids the surgeon in prognostication and planning of the surgical approach.

A Prospective, Longitudinal Magnetic Resonance Imaging Evaluation of Cerebrovascular Reactivity and Infarct Development in Patients With Intracranial Stenosis.

BACKGROUND: Patients with symptomatic atherosclerotic and non-atherosclerotic (i.e., moyamoya) intracranial steno-occlusive disease experience high 2-year infarct rates. PURPOSE: To investigate whether cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) measures may provide biomarkers of 1-to-2-year infarct risk. STUDY TYPE: Prospective, longitudinal study. SUBJECTS: Adult participants (age = 18-85 years) with symptomatic intracranial atherosclerotic disease (N = 26) or non-atherosclerotic (i.e., moyamoya; N = 43) and stenosis ≥50% of a major intracranial artery were initially scanned within 45 days of stroke. Follow-up imaging (target  = 1.5 years) was acquired for new infarct assessment. FIELD STRENGTH/SEQUENCE: 3.0 Tesla with normocapnic arterial spin labeling (ASL) and blood oxygenation level-dependent (BOLD) imaging acquired during an interleaved hypercapnic (3 minutes) and normocapnic (3 minutes) respiratory stimulus. ASSESSMENT: CBF, maximum CVR, and time-to-maximum CVR (i.e., CVRDELAY ) were calculated. Laterality indices (difference between infarcted and contralesional hemispheres divided by sum of absolute values) of metrics at enrollment were contrasted between participants with vs. without new infarcts on follow-up. STATISTICAL TESTS: Laterality indices were compared using non-parametric Wilcoxon tests (significance: two-sided P < 0.05) and effect sizes as Cohen's d. Continuous variables are presented as mean ± SD. RESULTS: New infarcts were observed on follow-up in 15.0% of participants. The laterality index of the CVRDELAY was elevated (P = 0.01) in participants with atherosclerosis with new infarcts (index = 0.13) compared to participants without new infarcts (index = 0.05). DATA CONCLUSION: Elevated CVRDELAY may indicate brain parenchyma at increased risk for new infarcts in patients with symptomatic intracranial atherosclerotic disease treated with standard-of-care medical management. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 3.

9-Arylimino noscapinoids as potent tubulin binding anticancer agent: chemical synthesis and cellular evaluation against breast tumour cells.

A library of 9-arylimino derivatives of noscapine was developed by coupling of Schiff base containing imine groups. Virtual screening using molecular docking with tubulin revealed three molecules, 12-14 that bind with high affinity. An improved predicted free energy of binding (FEB) of -5.390, -6.506 and -6.679 kcal/mol for the molecules 12-14 was found compared to noscapine (-5.135 kcal/mol). Furthermore, molecular dynamics simulation in combination with Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) revealed robust binding free energy of -166.03, -169.75 and -170.63 kcal/mol for the molecules 12, 13 and 14, respectively. These derivatives were strategically synthesized and experimentally validated for their anticancer activity. Tubulin binding assay revealed substantial binding of molecules 12-14 with purified tubulin. Further, their anticancer activity was demonstrated using two cancer cell lines (MCF-7 and MDAMB-231) and a panel of primary breast tumour cells. All these derivatives inhibited cellular proliferation in all the cancer cells that ranged between 30.1 and 5.8 µM, which is 1.7 to 7.52 fold lower than that of noscapine. Further, these novel derivatives arrest cell cycle in the G2/M-phase followed by induction of apoptosis. Thus, 9-arylimino noscapinoids 12-14 have a great potential to be a novel therapeutic agent for breast cancers.

Elevated cerebral blood flow in patients with pure autonomic failure.

PURPOSE: Pure autonomic failure (PAF) results from an impaired peripheral autonomic nervous system, and clinical symptoms present with orthostatic hypotension. While the impact on cardiovascular indices of orthostatic intolerance are well-characterized, more limited information is available regarding cerebral hemodynamic dysfunction in PAF. The objective of this study was to test the hypothesis that cerebral blood flow (CBF) is reduced in PAF, and to quantify the relationship between CBF and clinical indicators of disease severity, including peripheral supine arterial blood pressure. METHODS: Participants with PAF (n = 17) and age- and sex-matched normotensive healthy controls (n = 17) were examined using established clinical rating scales, cardiovascular autonomic function tests, and 3T MRI measurements of CBF. CBF-weighted images were also used to determine the prevalence of venous hyperintensities from the major dural sinuses as evidence of abnormal capillary flow. Nonparametric tests and general linear models were used to evaluate differences and correlations between study variables. RESULTS: Gray matter CBF was higher in PAF (51.1 ± 13.4 mL/100 g/min) compared to controls (42.9 ± 6.5 mL/100 g/min, p = 0.007). Venous hyperintensities were more prevalent in PAF relative to controls, and the presence and degree of venous hyperintensities was associated with higher mean CBF (p = 0.027). In PAF participants, CBF and supine systolic blood pressure were inversely related (Spearman's rho = -0.545, p = 0.024). CONCLUSIONS: Findings suggest that PAF patients may exhibit elevated CBF and provide evidence that this condition exerts a hemodynamic impact in the central nervous system.

Characterizing cerebral hemodynamics across the adult lifespan with arterial spin labeling MRI data from the Human Connectome Project-Aging.

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) has become a popular approach for studying cerebral hemodynamics in a range of disorders and has recently been included as part of the Human Connectome Project-Aging (HCP-A). Due to the high spatial resolution and multiple post-labeling delays, ASL data from HCP-A holds promise for localization of hemodynamic signals not only in gray matter but also in white matter. However, gleaning information about white matter hemodynamics with ASL is challenging due in part to longer blood arrival times in white matter compared to gray matter. In this work, we present an analytical approach for deriving measures of cerebral blood flow (CBF) and arterial transit times (ATT) from the ASL data from HCP-A and report on gray and white matter hemodynamics in a large cohort (n = 234) of typically aging adults (age 36-90 years). Pseudo-continuous ASL data were acquired with labeling duration = 1500 ms and five post-labeling delays = 200 ms, 700 ms, 1200, 1700 ms, and 2200 ms. ATT values were first calculated on a voxel-wise basis through normalized cross-correlation analysis of the acquired signal time course in that voxel and an expected time course based on an acquisition-specific Bloch simulation. CBF values were calculated using a two-compartment model and with age-appropriate blood water longitudinal relaxation times. Using this approach, we found that white matter CBF reduces (ρ = 0.39) and white matter ATT elongates (ρ = 0.42) with increasing age (p < 0.001). In addition, CBF is lower and ATTs are longer in white matter compared to gray matter across the adult lifespan (Wilcoxon signed-rank tests; p < 0.001). We also found sex differences with females exhibiting shorter white matter ATTs than males, independently of age (Wilcoxon rank-sum test; p < 0.001). Finally, we have shown that CBF and ATT values are spatially heterogeneous, with significant differences in cortical versus subcortical gray matter and juxtacortical versus periventricular white matter. These results serve as a characterization of normative physiology across the human lifespan against which hemodynamic impairment due to cerebrovascular or neurodegenerative diseases could be compared in future studies.

Deep learning-based T1-enhanced selection of linear attenuation coefficients (DL-TESLA) for PET/MR attenuation correction in dementia neuroimaging.

PURPOSE: The accuracy of existing PET/MR attenuation correction (AC) has been limited by a lack of correlation between MR signal and tissue electron density. Based on our finding that longitudinal relaxation rate, or R1 , is associated with CT Hounsfield unit in bone and soft tissues in the brain, we propose a deep learning T1 -enhanced selection of linear attenuation coefficients (DL-TESLA) method to incorporate quantitative R1 for PET/MR AC and evaluate its accuracy and longitudinal test-retest repeatability in brain PET/MR imaging. METHODS: DL-TESLA uses a 3D residual UNet (ResUNet) for pseudo-CT (pCT) estimation. With a total of 174 participants, we compared PET AC accuracy of DL-TESLA to 3 other methods adopting similar 3D ResUNet structures but using UTE R2∗ , or Dixon, or T1 -MPRAGE as input. With images from 23 additional participants repeatedly scanned, the test-retest differences and within-subject coefficient of variation of standardized uptake value ratios (SUVR) were compared between PET images reconstructed using either DL-TESLA or CT for AC. RESULTS: DL-TESLA had (1) significantly lower mean absolute error in pCT, (2) the highest Dice coefficients in both bone and air, (3) significantly lower PET relative absolute error in whole brain and various brain regions, (4) the highest percentage of voxels with a PET relative error within both ±3% and ±5%, (5) similar to CT test-retest differences in SUVRs from the cerebrum and mean cortical (MC) region, and (6) similar to CT within-subject coefficient of variation in cerebrum and MC. CONCLUSION: DL-TESLA demonstrates excellent PET/MR AC accuracy and test-retest repeatability.

Reduced oxygen extraction efficiency in sickle cell anemia patients with evidence of cerebral capillary shunting.

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) utilizes arterial blood water as an endogenous contrast agent to provide a quantitative measure of cerebral blood flow (CBF). Recently, hyperintense signal within dural venous sinuses in ASL images of sickle cell anemia (SCA) patients has been shown to be consistent with elevated flow velocities and may indicate capillary shunting and reduced oxygen extraction. Here, we performed oxygen extraction fraction (OEF) and CBF measurements in adults (cumulative n = 114) with (n = 69) and without (n = 45) SCA to test the hypothesis that hyperintense venous ASL signal is associated with reduced OEF. Higher categorical scores of shunting on ASL MRI were associated with lower OEF in participants with silent cerebral infarcts or white matter hyperintensities (p = 0.003), but not in those without lesions (p = 0.551). These findings indicate that venous hyperintense signal in ASL images in SCA patients may represent a marker of capillary-level disturbances in oxygen exchange efficiency and small vessel pathology.

Computed tomographic analysis of the prevalence of International Frontal Sinus Anatomy Classification cells and their association with frontal sinusitis.

OBJECTIVES: To determine the radiological prevalence of frontal cells according to the International Frontal Sinus Anatomy Classification in patients undergoing computed tomography of the paranasal sinuses for clinical symptoms of chronic rhinosinusitis, and to examine the association between cell classification and frontal sinusitis development. METHODS: A total of 180 (left and right) sides of 90 patients were analysed. The prevalence of each International Frontal Sinus Anatomy Classification cell was assessed. Logistic regression analysis was used to compare the distribution of various cells in patients with and without frontal sinusitis. RESULTS: The agger nasi cell was the most commonly occurring cell, seen in 95.5 per cent of patients. The prevalence rates for supra agger cells, supra agger frontal cells, supra bullar frontal cells, supra bullar cells, supra-orbital ethmoid cells and frontal septal cells were 33.3 per cent, 22.2 per cent, 21.1 per cent, 36.1 per cent, 39.4 per cent and 21.1 per cent, respectively. There was no significant difference in the occurrence of any of the cell types in patients with frontal sinusitis compared to those without (p > 0.05). CONCLUSION: The presence of any of the International Frontal Sinus Anatomy Classification cells was not significantly associated with frontal sinusitis.

High-resolution computed tomography evaluation of congenital aural atresia - how useful is this?

OBJECTIVE: To depict various temporal bone abnormalities on high-resolution computed tomography in congenital aural atresia patients, and correlate these findings with auditory function test results and microtia subgroup. METHODS: Forty patients (56 ears) with congenital malformation of the auricle and/or external auditory canal were evaluated. Auricles were graded according to Marx's classification, divided into subgroups of minor (grades I and II) and major (III and IV) microtia. Other associated anomalies of the external auditory canal, tympanic cavity, ossicular status, oval and round windows, facial nerve, and inner ear were evaluated. RESULTS: Minor and major microtia were observed in 53.6 and 46.4 per cent of ears respectively. Mean hearing levels were 62.47 and 62.37 dB respectively (p = 0.98). The malleus was the most commonly dysplastic ossicle (73.3 vs 80.8 per cent of ears respectively, p = 0.53). Facial nerve (mastoid segment) abnormalities were associated (p = 0.04) with microtia subgroup (80 vs 100 per cent in minor vs major subgroups). CONCLUSION: Microtia grade was not significantly associated with mean hearing levels or other ear malformations, except for external auditory canal and facial nerve (mastoid segment) anomalies. High-resolution computed tomography is essential in congenital aural atresia, before management strategy is decided.

Endoscopic visualisation of the round window during cochlear implantation.

BACKGROUND: Endoscopes provide a magnified view of the middle ear and visualisation of hidden areas. Otoendoscopes facilitate excellent visualisation of the round window niche during cochlear implantation. OBJECTIVE: To compare microscopic and endoscopic visualisation of the round window membrane during cochlear implantation in 20 patients. METHODS: Twenty patients who underwent cochlear implantation were included in the study. After maximum exposure of the round window, the accessibility of the round window membrane was graded according to the St Thomas Hospital classification, first by microscope and then by endoscope. RESULTS: With the use of the endoscope, visualisation of the round window membrane improved in all the patients as compared to the microscope. The electrode array was inserted via a round window or extended round window approach in all but two cases; the latter cases required bony cochleostomy because of unfavourable anatomy. CONCLUSION: The main benefit of endoscope-assisted cochlear implantation is improved visibility of the round window region.