The prosubiculum in the human hippocampus: A rostrocaudal, feature-driven, and systematic approach.

The hippocampal subfield prosubiculum (ProS), is a conserved neuroanatomic region in mouse, monkey, and human. This area lies between CA1 and subiculum (Sub) and particularly lacks consensus on its boundaries; reports have varied on the description of its features and location. In this report, we review, refine, and evaluate four cytoarchitectural features that differentiate ProS from its neighboring subfields: (1) small neurons, (2) lightly stained neurons, (3) superficial clustered neurons, and (4) a cell sparse zone. ProS was delineated in all cases (n = 10). ProS was examined for its cytoarchitectonic features and location rostrocaudally, from the anterior head through the body in the hippocampus. The most common feature was small pyramidal neurons, which were intermingled with larger pyramidal neurons in ProS. We quantitatively measured ProS pyramidal neurons, which showed (average, width at pyramidal base = 14.31 µm, n = 400 per subfield). CA1 neurons averaged 15.57 µm and Sub neurons averaged 15.63 µm, both were significantly different than ProS (Kruskal-Wallis test, p < .0001). The other three features observed were lightly stained neurons, clustered neurons, and a cell sparse zone. Taken together, these findings suggest that ProS is an independent subfield, likely with distinct functional contributions to the broader interconnected hippocampal network. Our results suggest that ProS is a cytoarchitecturally varied subfield, both for features and among individuals. This diverse architecture in features and individuals for ProS could explain the long-standing complexity regarding the identification of this subfield.

Assessing individual variability of the entorhinal subfields in health and disease.

Investigating interindividual variability is a major field of interest in neuroscience. The entorhinal cortex (EC) is essential for memory and affected early in the progression of Alzheimer's disease (AD). We combined histology ground-truth data with ultrahigh-resolution 7T ex vivo MRI to analyze EC interindividual variability in 3D. Further, we characterized (1) entorhinal shape as a whole, (2) entorhinal subfield range and midpoints, and (3) subfield architectural location and tau burden derived from 3D probability maps. Our results indicated that EC shape varied but was not related to demographic or disease factors at this preclinical stage. The medial intermediate subfield showed the highest degree of location variability in the probability maps. However, individual subfields did not display the same level of variability across dimensions and outcome measure, each providing a different perspective. For example, the olfactory subfield showed low variability in midpoint location in the superior-inferior dimension but high variability in anterior-posterior, and the subfield entorhinal intermediate showed a large variability in volumetric measures but a low variability in location derived from the 3D probability maps. These findings suggest that interindividual variability within the entorhinal subfields requires a 3D approach incorporating multiple outcome measures. This study provides 3D probability maps of the individual entorhinal subfields and respective tau pathology in the preclinical stage (Braak I and II) of AD. These probability maps illustrate the subfield average and may serve as a checkpoint for future modeling.

Stereology neuron counts correlate with deep learning estimates in the human hippocampal subregions.

Hippocampal subregions differ in specialization and vulnerability to cell death. Neuron death and hippocampal atrophy have been a marker for the progression of Alzheimer's disease. Relatively few studies have examined neuronal loss in the human brain using stereology. We characterize an automated high-throughput deep learning pipeline to segment hippocampal pyramidal neurons, generate pyramidal neuron estimates within the human hippocampal subfields, and relate our results to stereology neuron counts. Based on seven cases and 168 partitions, we vet deep learning parameters to segment hippocampal pyramidal neurons from the background using the open-source CellPose algorithm, and show the automated removal of false-positive segmentations. There was no difference in Dice scores between neurons segmented by the deep learning pipeline and manual segmentations (Independent Samples t-Test: t(28) = 0.33, p = 0.742). Deep-learning neuron estimates strongly correlate with manual stereological counts per subregion (Spearman's correlation (n = 9): r(7) = 0.97, p < 0.001), and for each partition individually (Spearman's correlation (n = 168): r(166) = 0.90, p <0 .001). The high-throughput deep-learning pipeline provides validation to existing standards. This deep learning approach may benefit future studies in tracking baseline and resilient healthy aging to the earliest disease progression.

Atretic cephalocele and encephalocele: A single-institution clinicopathological study.

BACKGROUND: Encephaloceles are neural tube defects characterized by herniation of meninges, neural tissue and cerebrospinal fluid, while atretic cephaloceles denote a rudimentary connection to the intracranial space with absence of herniated neural tissue and represent an infrequent dermatopathologic diagnosis. Limited reports of these entities confound the challenge in their histopathologic distinction. Accurate classification is important given associated anomalies and neurologic manifestations that impact prognosis. METHODS: We describe the clinicopathological and immunohistochemical [glial fibrillary acidic protein (GFAP), S100, epithelial membrane antigen (EMA), and somatostatin receptor subtype 2A (SSTR2A)] features in a retrospective series encountered at a single institution between 1994 and 2020. RESULTS: We identified 13 cases classified as atretic cephalocele (n = 11) and encephalocele (n = 2). Hamartomatous changes and multinucleated cells were unique to atretic cephaloceles while myxoid areas were unique to encephaloceles. At least focal staining for SSTRA was seen in all atretic cephaloceles with the majority (87.5%) staining for EMA; negative staining for GFAP and S100 confirmed absence of neural tissue. Encephaloceles were GFAP and S100 positive, and negative for SSTR2 and EMA. Atretic cephaloceles had a favorable prognosis compared to encephaloceles, with severe morbidity present in both encephalocele cases. CONCLUSION: Our study raises awareness of atretic cephalocele and encephalocele among dermatopathologists and reveals a mutually exclusive immunophenotype that facilitates their distinction for prognostication and management.

Vasculopathy and Increased Vascular Congestion in Fatal COVID-19 and Acute Respiratory Distress Syndrome.

Rationale: The leading cause of death in coronavirus disease 2019 (COVID-19) is severe pneumonia, with many patients developing acute respiratory distress syndrome (ARDS) and diffuse alveolar damage (DAD). Whether DAD in fatal COVID-19 is distinct from other causes of DAD remains unknown. Objective: To compare lung parenchymal and vascular alterations between patients with fatal COVID-19 pneumonia and other DAD-causing etiologies using a multidimensional approach. Methods: This autopsy cohort consisted of consecutive patients with COVID-19 pneumonia (n = 20) and with respiratory failure and histologic DAD (n = 21; non-COVID-19 viral and nonviral etiologies). Premortem chest computed tomography (CT) scans were evaluated for vascular changes. Postmortem lung tissues were compared using histopathological and computational analyses. Machine-learning-derived morphometric analysis of the microvasculature was performed, with a random forest classifier quantifying vascular congestion (CVasc) in different microscopic compartments. Respiratory mechanics and gas-exchange parameters were evaluated longitudinally in patients with ARDS. Measurements and Main Results: In premortem CT, patients with COVID-19 showed more dilated vasculature when all lung segments were evaluated (P = 0.001) compared with controls with DAD. Histopathology revealed vasculopathic changes, including hemangiomatosis-like changes (P = 0.043), thromboemboli (P = 0.0038), pulmonary infarcts (P = 0.047), and perivascular inflammation (P < 0.001). Generalized estimating equations revealed significant regional differences in the lung microarchitecture among all DAD-causing entities. COVID-19 showed a larger overall CVasc range (P = 0.002). Alveolar-septal congestion was associated with a significantly shorter time to death from symptom onset (P = 0.03), length of hospital stay (P = 0.02), and increased ventilatory ratio [an estimate for pulmonary dead space fraction (Vd); p = 0.043] in all cases of ARDS. Conclusions: Severe COVID-19 pneumonia is characterized by significant vasculopathy and aberrant alveolar-septal congestion. Our findings also highlight the role that vascular alterations may play in Vd and clinical outcomes in ARDS in general.

Quantitative and histologically validated measures of the entorhinal subfields in ex vivo MRI.

Neuroimaging studies have routinely used hippocampal volume as a measure of Alzheimer's disease severity, but hippocampal changes occur too late in the disease process for potential therapies to be effective. The entorhinal cortex is one of the first cortical areas affected by Alzheimer's disease; its neurons are especially vulnerable to neurofibrillary tangles. Entorhinal atrophy also relates to the conversion from non-clinical to clinical Alzheimer's disease. In neuroimaging, the human entorhinal cortex has so far mostly been considered in its entirety or divided into a medial and a lateral region. Cytoarchitectonic differences provide the opportunity for subfield parcellation. We investigated the entorhinal cortex on a subfield-specific level-at a critical time point of Alzheimer's disease progression. While MRI allows multidimensional quantitative measurements, only histology provides enough accuracy to determine subfield boundaries-the pre-requisite for quantitative measurements within the entorhinal cortex. This study used histological data to validate ultra-high-resolution 7 Tesla ex vivo MRI and create entorhinal subfield parcellations in a total of 10 pre-clinical Alzheimer's disease and normal control cases. Using ex vivo MRI, eight entorhinal subfields (olfactory, rostral, medial intermediate, intermediate, lateral rostral, lateral caudal, caudal, and caudal limiting) were characterized for cortical thickness, volume, and pial surface area. Our data indicated no influence of sex, or Braak and Braak staging on volume, cortical thickness, or pial surface area. The volume and pial surface area for mean whole entorhinal cortex were 1131 ± 55.72 mm3 and 429 ± 22.6 mm2 (mean ± SEM), respectively. The subfield volume percentages relative to the entire entorhinal cortex were olfactory: 18.73 ± 1.82%, rostral: 14.06 ± 0.63%, lateral rostral: 14.81 ± 1.22%, medial intermediate: 6.72 ± 0.72%, intermediate: 23.36 ± 1.85%, lateral caudal: 5.42 ± 0.33%, caudal: 10.99 ± 1.02%, and caudal limiting: 5.91 ± 0.40% (all mean ± SEM). Olfactory and intermediate subfield revealed the most extensive intra-individual variability (cross-subject variance) in volume and pial surface area. This study provides validated measures. It maps individuality and demonstrates human variability in the entorhinal cortex, providing a baseline for approaches in individualized medicine. Taken together, this study serves as a ground-truth validation study for future in vivo comparisons and treatments.

Seronegative necrotizing autoimmune myopathy with favorable response to intravenous immunoglobulin.

We describe a 68-year-old man who presented with progressive weakness in proximal muscles of all four limbs and was found to have autoantibody-negative necrotizing autoimmune myopathy (NAM). His myopathy was refractory to corticosteroids and methotrexate, but subsequently demonstrated successful response to intravenous immunoglobulin (IVIG). The patient also received rituximab, but the timing of his recovery favored IVIG as the more important factor in terms of efficacy. Treatment guidelines for seronegative necrotizing myopathies are lacking. This case suggests a potential efficacious treatment option for the seronegative subset of NAM.

Pathology of the Brain and the Eye in Severe Acute Respiratory Syndrome Coronavirus-2-Infected Patients: A Review.

BACKGROUND: Patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may present or eventually develop central nervous system and ophthalmic signs and symptoms. Varying reports have emerged regarding isolation of viral RNA from these tissue sites, as well as largely autopsy-based histopathologic descriptions of the brain and the eye in patients with COVID-19. EVIDENCE ACQUISITION: A primary literature search was performed in literature databases such as PubMed, Google Scholar, and Cochrane Library. Keywords were used alone and in combination including the following: SARS CoV-2, COVID-19, eye, brain, central nervous system, histopathology, autopsy, ocular pathology, aqueous, tears, vitreous, neuropathology, and encephalitis. RESULTS: The reported ophthalmic pathologic and neuropathologic findings in patients with SARS-CoV-2 are varied and inconclusive regarding the role of direct viral infection vs secondary pathology. The authors own experience with autopsy neuropathology in COVID-19 patients is also described. There is a particular paucity of data regarding the histopathology of the eye. However, it is likely that the ocular surface is a potential site for inoculation and the tears a source of spread of viral particles. CONCLUSIONS: Additional large postmortem studies are needed to clarify the role of SARS-CoV in the ophthalmic and neuropathologic manifestations of COVID-19.

Susceptibility-weighted imaging reveals cerebral microvascular injury in severe COVID-19.

We evaluated the incidence, distribution, and histopathologic correlates of microvascular brain lesions in patients with severe COVID-19. Sixteen consecutive patients admitted to the intensive care unit with severe COVID-19 undergoing brain MRI for evaluation of coma or neurologic deficits were retrospectively identified. Eleven patients had punctate susceptibility-weighted imaging (SWI) lesions in the subcortical and deep white matter, eight patients had >10 SWI lesions, and four patients had lesions involving the corpus callosum. The distribution of SWI lesions was similar to that seen in patients with hypoxic respiratory failure, sepsis, and disseminated intravascular coagulation. Brain autopsy in one patient revealed that SWI lesions corresponded to widespread microvascular injury, characterized by perivascular and parenchymal petechial hemorrhages and microscopic ischemic lesions. Collectively, these radiologic and histopathologic findings add to growing evidence that patients with severe COVID-19 are at risk for multifocal microvascular hemorrhagic and ischemic lesions in the subcortical and deep white matter.

Nelson Syndrome: Clival Invasion of Corticotroph Pituitary Adenoma Resulting in Alternating Sixth Nerve Palsies.

ABSTRACT: A 44-year-old woman presented with 2 painful and self-limited episodes of binocular horizontal diplopia within 1 year that at the beginning were thought to be secondary to microvascular insult. Her medical history was significant for Cushing syndrome status post transsphenoidal resection with bilateral adrenalectomy 4 years prior, hypertension, and diabetes mellitus. Neuro-ophthalmic evaluation was significant for left abduction deficit and incomitant esotropia consistent with left abducens nerve palsy. Of note, the patient had experienced a similar episode but on the contralateral side a few months prior. Although initially MRI of the brain demonstrated stable residual postoperative finding in the sella, upon review, an heterogenous T-1 hypointense marrow in the clivus was noted. Hypermetabolism of the clivus was also noted on computed tomography positron emission tomography of the skull base. A clival biopsy demonstrated a corticotroph adenoma with elevated proliferation index and scattered mitoses. A corticotroph pituitary adenoma after adrenalectomy, also known as Nelson syndrome, was diagnosed. Radiation therapy was offered to the patient, and resolution of symptoms was gradually observed.

Cerebral Microvascular Injury in Severe COVID-19.

IMPORTANCE: Microvascular lesions are common in patients with severe COVID-19. Radiologic-pathologic correlation in one case suggests a combination of microvascular hemorrhagic and ischemic lesions that may reflect an underlying hypoxic mechanism of injury, which requires validation in larger studies. OBJECTIVE: To determine the incidence, distribution, and clinical and histopathologic correlates of microvascular lesions in patients with severe COVID-19. DESIGN: Observational, retrospective cohort study: March to May 2020. SETTING: Single academic medical center. PARTICIPANTS: Consecutive patients (16) admitted to the intensive care unit with severe COVID-19, undergoing brain MRI for evaluation of coma or focal neurologic deficits. EXPOSURES: Not applicable. MAIN OUTCOME AND MEASURES: Hypointense microvascular lesions identified by a prototype ultrafast high-resolution susceptibility-weighted imaging (SWI) MRI sequence, counted by two neuroradiologists and categorized by neuroanatomic location. Clinical and laboratory data (most recent measurements before brain MRI). Brain autopsy and cerebrospinal fluid PCR for SARS-CoV 2 in one patient who died from severe COVID-19. RESULTS: Eleven of 16 patients (69%) had punctate and linear SWI lesions in the subcortical and deep white matter, and eight patients (50%) had >10 SWI lesions. In 4/16 patients (25%), lesions involved the corpus callosum. Brain autopsy in one patient revealed that SWI lesions corresponded to widespread microvascular injury, characterized by perivascular and parenchymal petechial hemorrhages and microscopic ischemic lesions. CONCLUSIONS AND RELEVANCE: SWI lesions are common in patients with neurological manifestations of severe COVID-19 (coma and focal neurologic deficits). The distribution of lesions is similar to that seen in patients with hypoxic respiratory failure, sepsis, and disseminated intravascular coagulation. Collectively, these radiologic and histopathologic findings suggest that patients with severe COVID-19 are at risk for multifocal microvascular hemorrhagic and ischemic lesions in the subcortical and deep white matter.

Immune checkpoint inhibitor associated myocarditis occurs in both high-grade and low-grade forms.

Immune checkpoint inhibitor therapy for malignancy has been associated with adverse events including myocarditis. It has been unclear if there are distinct pathologic grades of this myocarditis that are associated with distinct clinical outcomes. Cardiac tissue from ten patients with immune checkpoint inhibitor myocarditis (nine biopsies and one autopsy) were evaluated using immunohistochemistry for CD3, CD8, CD68, tryptase, PD-L1, and C4D. The immune checkpoint inhibitor myocarditis cases were classified as either high grade (>50 CD3+ cells/hpf) or low grade (≤50 CD3+ cells/hpf). The densities of macrophages, T cells, eosinophils, necrotic myocytes, and PD-L1+ macrophages and myocytes were compared between the two groups and with 13 cases of grade 2R acute cellular allograft rejection. Three patients were classified as high-grade myocarditis and seven as low grade. There were higher densities of CD3+ cells and CD8+ cells in high-grade immune checkpoint inhibitor myocarditis and rejection compared with low-grade myocarditis. The number of CD68+ macrophages was higher in high-grade myocarditis compared with low-grade myocarditis and rejection. For both grades of myocarditis, there was a higher CD68/CD3 ratio and a higher density of PD-L1+ macrophages and myocytes compared with rejection. Clinically, there were trends toward higher serum troponin levels and shorter interval from first immune checkpoint inhibitor treatment in the high-grade myocarditis group compared with the low-grade group. All the patients with high-grade myocarditis died, while all the patients with low-grade myocarditis were still living. These data suggest that immune checkpoint inhibitor myocarditis occurs in two forms, a high-grade form with increased inflammatory cell infiltration and a more fulminant clinical course, and a low-grade form with a lower degree of inflammatory cell infiltration and a more indolent clinical course. Compared with acute cellular rejection, immune checkpoint inhibitor myocarditis is characterized by a more lymphohistiocytic inflammatory infiltrate with an increased CD68/CD3 ratio and increased PD-L1+ macrophages and myocytes.