A population-averaged approach to diagnostic test meta-analysis.

The meta-analysis of diagnostic accuracy studies is often of interest in screening programs for many diseases. The typical summary statistics for studies chosen for a diagnostic accuracy meta-analysis are often two dimensional: sensitivities and specificities. The common statistical analysis approach for the meta-analysis of diagnostic studies is based on the bivariate generalized linear-mixed model (BGLMM), which has study-specific interpretations. In this article, we present a population-averaged (PA) model using generalized estimating equations (GEE) for making inference on mean specificity and sensitivity of a diagnostic test in the population represented by the meta-analytic studies. We also derive the marginalized counterparts of the regression parameters from the BGLMM. We illustrate the proposed PA approach through two dataset examples and compare performance of estimators of the marginal regression parameters from the PA model with those of the marginalized regression parameters from the BGLMM through Monte Carlo simulation studies. Overall, both marginalized BGLMM and GEE with sandwich standard errors maintained nominal 95% confidence interval coverage levels for mean specificity and mean sensitivity in meta-analysis of 25 of more studies even under misspecification of the covariance structure of the bivariate positive test counts for diseased and nondiseased subjects.

Atypical multiple system atrophy is a new subtype of frontotemporal lobar degeneration: frontotemporal lobar degeneration associated with α-synuclein.

Multiple system atrophy (MSA) is a sporadic neurodegenerative disease clinically characterized by cerebellar signs, parkinsonism, and autonomic dysfunction. Pathologically, MSA is an α-synucleinopathy affecting striatonigral and olivopontocerebellar systems, while neocortical and limbic involvement is usually minimal. In this study, we describe four patients with atypical MSA with clinical features consistent with frontotemporal dementia (FTD), including two with corticobasal syndrome, one with progressive non-fluent aphasia, and one with behavioral variant FTD. None had autonomic dysfunction. All had frontotemporal atrophy and severe limbic α-synuclein neuronal pathology. The neuronal inclusions were heterogeneous, but included Pick body-like inclusions. The latter were strongly associated with neuronal loss in the hippocampus and amygdala. Unlike typical Pick bodies, the neuronal inclusions were positive on Gallyas silver stain and negative on tau immunohistochemistry. In comparison to 34 typical MSA cases, atypical MSA had significantly more neuronal inclusions in anteromedial temporal lobe and limbic structures. While uncommon, our findings suggest that MSA may present clinically and pathologically as a frontotemporal lobar degeneration (FTLD). We suggest that this may represent a novel subtype of FTLD associated with α-synuclein (FTLD-synuclein).

Splice site, frameshift, and chimeric GFAP mutations in Alexander disease.

Alexander disease (AxD) is a usually fatal astrogliopathy primarily caused by mutations in the gene encoding glial fibrillary acidic protein (GFAP), an intermediate filament protein expressed in astrocytes. We describe three patients with unique characteristics, and whose mutations have implications for AxD diagnosis and studies of intermediate filaments. Patient 1 is the first reported case with a noncoding mutation. The patient has a splice site change producing an in-frame deletion of exon 4 in about 10% of the transcripts. Patient 2 has an insertion and deletion at the extreme end of the coding region, resulting in a short frameshift. In addition, the mutation was found in buccal DNA but not in blood DNA, making this patient the first reported chimera. Patient 3 has a single-base deletion near the C-terminal end of the protein, producing a short frameshift. These findings recommend inclusion of intronic splice site regions in genetic testing for AxD, indicate that alteration of only a small fraction of GFAP can produce disease, and provide caution against tagging intermediate filaments at their C-terminal end for cell biological investigations.

Mycoplasmal panencephalitis: a neuropathologic documentation.

Mycoplasmas, particularly Mycoplasma pneumoniae, have been implicated as causative agents in a large variety of central nervous system diseases, especially acute childhood encephalitis. Postulated pathomechanisms for mycoplasma-mediated neurological disease have included: direct infection, autoimmunity, and vascular occlusion. Neuropathologic data are meager and are reviewed. We report a 3-year-old boy, who developed signs and symptoms of encephalitis 7 days after the onset of fever with cough and death 5 days later. At autopsy, he displayed diffuse vasogenic edema and perivascular to infiltrative inflammatory cells, the latter most prominent in gray matter of brainstem and amygdala. The predominant cell was the CD68-positive macrophage, followed by the T-lymphocyte. Cells immunolabeled with a polyclonal antibody to M. pneumoniae included perivascular to parenchymal macrophages/microglia, occasional oligodendrocytes, and neurons, particularly in brainstem. Affected neurons varied from morphologically normal to profoundly degenerate and necrotic. Ultrastructural study of the inferior olive confirmed the presence of 260-600 nm cell-wall-free microorganisms, consistent with mycoplasma, in perivascular cells and neurons. Foci of acute disseminated encephalomyelitis also were rarely identified. This case report confirms the postulated role of direct infection of brain by mycoplasma in acute childhood encephalitis, but also reveals a virus-like infection of central neurons. The pathogenesis of acute childhood encephalitis due to mycoplasma seems to be multifactorial.

Hyaline protoplasmic astrocytopathy of neocortex.

Eosinophilic inclusions in the cytoplasm of protoplasmic astrocytes of the neocortex, usually in the clinical setting of epilepsy and/or psychomotor retardation, were first recognized and illustrated by Alois Alzheimer in 1910. Traditional special stains have failed to elucidate the specific nature of these inclusions. Ultrastructurally, the material was composed predominantly of highly electron-dense, non-membrane-bound, granular material distinct from Rosenthal fibers. Immunohistochemical examination has been informative but also sometimes inconsistent; it has recently been suggested that they may represent a filaminopathy (filamin A). We examined 5 cases with neocortical eosinophilic inclusions (3 autopsies, 2 surgical resections) using a standardized immunohistochemical protocol at a single institution. The specimens were immunostained with 32 antibodies to 30 potentially relevant proteins using several antigen retrieval protocols. We confirmed the presence of filamin A in these inclusions, but several additional proteins, particularly cytoglobin and glutamate transporter 1, were also identified. By electron microscopy in 2 cases, the granular fine structure of the inclusions was confirmed; mitochondria adjacent to, and perhaps within, the inclusions that contained many pleomorphic vesicular and membranous elements were also noted in 1 case. The pathophysiologic relevance of these proteins and the clinical significance of the hyaline inclusions are discussed.

A novel cerebral microangiopathy with endothelial cell atypia and multifocal white matter lesions: a direct mycoplasmal infection?

We present 3 sporadic cases of a subacute to chronic, progressive motor (i.e. weakness, ataxia, spasticity, dysarthria, and dysphagia) and cognitive disorder in adults of both sexes, without proven immunocompromise or malignancy. Neuroimaging studies revealed tiny calcifications with atrophy of the cerebrum, pons, and midbrain in 1 patient, cerebral atrophy in another, and cerebral atrophy and periventricular white matter hyperintensities in the third. Clinical diagnoses included cortico-pontine-cerebellar degeneration, mixed neurodegenerative disorder, progressive supranuclear palsy, diffuse Lewy body disease, and Lyme disease. One atrophic brain revealed widely disseminated, millimeter-sized gray lesions in cerebral white matter and obscured anatomic markings of the basis pontis. The most conspicuous microscopic feature in all was capillaries with focally piled up endothelial nuclei, some of which appeared to be multinucleated, or enlarged, hyperchromatic crescentic single nuclei. Although seen mostly without associated damage, they were also noted with white matter lesions displaying vacuolation, demyelination, spheroids, necrosis, vascular fibrosis, and mineralization; these were most severe in the basis pontis. Immunostains and probes to herpes simplex virus-I, -II, and -8; adenovirus, cytomegalovirus, varicella-zoster, Epstein-Barr virus, measles, JC virus, and herpes hominis virus-6 were negative. Electron microscopy revealed no virions in endothelial cells with multilobed or multiple nuclei and duplicated basal laminae. However, mycoplasma-like bodies, mostly 400 to 600 nm in size, were found in endothelial cell cytoplasm and capillary lumina. Platelets adhered to affected endothelial cells. Polymerase chain reaction and immunohistochemistry of fixed samples for Mycoplasma fermentans were negative; other species of Mycoplasma remain viable pathogenic candidates.

A comparative morphologic analysis of adult onset leukodystrophy with neuroaxonal spheroids and pigmented glia--a role for oxidative damage.

We performed a blinded study on 5 cases of hereditary diffuse leukoencephalopathy with spheroids and 10 cases of the pigmentary type of orthochromatic leukodystrophy, 6 of the latter having a family history of neurologic illness. Patients presented in the third to sixth decade with behavioral, cognitive, and motor symptoms. All cases displayed widespread myelin loss, predominantly frontotemporal with relative sparing of subcortical U-fibers, and variable numbers of both neuroaxonal spheroids and pigmented glia. Immunohistochemically, spheroids contained amyloid precursor/neurofilament proteins, several neurotransmitters or neuropeptides, and ubiquitin. Cytoplasmic inclusions in glia and numerous pigmented macrophages were autofluorescent and stained consistently with diastase-periodic acid-Schiff, prolonged Ziehl-Nielsen, and Sudan black, but the same cells labeled inconsistently for iron or ferritin. Ultrastructurally, the most characteristic autofluorescent glial lipopigments consisted of bosselated masses of granular, electron-dense material. These morphologic features are those of ceroid, an end-product of oxidative damage. Glial immunoreactivity for markers of oxidative stress (hemeoxygenase-1 and superoxide dismutase 2) and damage (4-hydroxynonenal, malondialdehyde, and nitrotyrosine) was noted, particularly in cases with increased iron and ferritin. These data support the hypothesis that the similar clinicopathologic features of hereditary diffuse leukoencephalopathy with spheroids and the pigmentary type of orthochromatic leukodystrophy reflect a common disease due, at least in part, to an oxidative insult.

p53-mediated apoptosis, neuroglobin overexpression, and globin deposits in a patient with hereditary ferritinopathy.

The apoptotic death of putaminal neurons and glia in a patient with hereditary ferritinopathy is studied immunohistochemically with antibodies to p53, activated caspase-3, PUMA, BAX, cytochrome c, and inducible nitric oxide synthase. In addition to the overexpression of ferritin and the iron accumulations assumed to result from the genetically incompetent ferritin molecule, additional contributions to the iron, heme, and hyaline deposits in this disease are sought with antibodies to 2 recently discovered globins in humans, neuroglobin and cytoglobin. The "pathognomonic" swollen to vacuolated nuclei are immunoreactive for both p53 and activated caspase-3, indicating the intervention of the p53-mediated apoptotic pathway. The immunohistochemical demonstration of neuroglobin in the swollen nuclei and both globins in the hyaline deposits highlights the potential pathogenic importance of 2 other iron-containing proteins in this disease that is largely restricted to brain. Hereditary ferritinopathy is the first human disease in which abnormalities in these heme-containing proteins are demonstrated.

Glia-specific activation of all pathways of the unfolded protein response in vanishing white matter disease.

Leukoencephalopathy with vanishing white matter (VWM) is a childhood white matter disorder with an autosomal-recessive mode of inheritance. The clinical course is chronic progressive with episodes of rapid neurologic deterioration after febrile infections. The disease is caused by mutations in the genes encoding the subunits of eukaryotic initiation factor 2B (eIF2B), a protein complex that is essential for protein synthesis. In VWM, mutations in the eIF2B genes are thought to impair the ability of cells to regulate protein synthesis under normal and stress conditions. It has been suggested that the pathophysiology of VWM involves inappropriate activation of the unfolded protein response (UPR). The UPR is a protective mechanism activated by an overload of unfolded or malfolded proteins in the endoplasmic reticulum. Activation of one pathway of the UPR, in which eIF2B is involved, has already been described in brain tissue of patients with VWM. In the present study, we demonstrate activation of all 3 UPR pathways in VWM brain tissue using real-time quantitative polymerase chain reaction and immunohistochemistry. We show that activation occurs exclusively in the white matter, predominantly in oligodendrocytes and astrocytes. The selective involvement of these cells suggests that inappropriate UPR activation may play a key role in the pathophysiology of VWM.

Hereditary ferritinopathy: a novel mutation, its cellular pathology, and pathogenetic insights.

We report a family of French Canadian and Dutch ancestry with hereditary ferritinopathy (neuroferritinopathy) and a novel mutation (C insertion at nt646-647 in exon 4) in the ferritin light chain gene, resulting in a longer than normal protein. Our failure to immunostain most of the abnormal ferritin deposits in the proband with a conformation-dependent monoclonal antibody to ferritin light chain supported a previously postulated conformational change of ferritin light chain in this disease. The posterior putamen and cerebellum were the primary pathologic loci in our proband, but asymptomatic hepatocytic intranuclear accumulations of iron and ferritin also were present. Both neurons and glia displayed highly distinctive, if not pathognomonic, swollen to vacuolated nuclei containing ferritin and iron. Hyaline deposits, again staining for both ferritin and iron, were additional morphologic features that may be unique to the ferritinopathies. The iron, at least in putamen where there was a nearly 40-fold increase, appeared to be both in the ferrous (Fe2+) and ferric (Fe3+) form; it was the most likely cause of the observed neuronal and glial apoptosis. We found morphologic evidence of both lipid peroxidation and abnormal nitration of proteins in putaminal neurons and glia, confirming the expected oxidative stress due to this excessive iron. Biochemical and immunohistochemical abnormalities in mitochondria also were demonstrated, probably due to an imbalance in iron homeostasis that had a deleterious effect on the respiratory chain.

Adreno-leukodystrophy: oxidative stress of mice and men.

X-linked adreno-leukodystrophy is a progressive, systemic peroxisomal disorder that affects primarily nervous system myelin and axons as well as the adrenal cortex. Several divergent clinical phenotypes can occur in the same family; thus, there is no correlation between the clinical phenotype and the mutation in the ABCD1 gene in this disease. The most urgent and unresolved clinical issue is the fulminant inflammatory (immune) demyelination of the central nervous system in which a variety of cellular participants, cytokines, and chemokines are noted. A knockout mouse model exhibits mitochondrial deficits and axonal degeneration, but not inflammatory demyelination. To determine whether oxidative stress and damage might play a pathogenic role, we assessed standard biochemical and immunohistochemical markers of such activity both in our knockout mouse model and patients. We find that oxidative stress, as judged by increased immunoreactivity for the mitochondrial manganese-superoxide dismutase, is present in the knockout mouse liver, adrenal cortex, and renal cortex, tissues that normally express high levels of ABCD1 but no evidence of oxidative damage. The brain does not exhibit either oxidative stress or damage. On the other hand, both the human adrenal cortex and brain show evidence of oxidative stress (e.g. hemoxygenase-1 and manganese-superoxide dismutase) and oxidative damage, particularly from lipid peroxidation (4-hydroxynonenal and malondialdehyde). The presence of nitrotyrosylated proteins is strong circumstantial evidence for the participation of the highly toxic peroxynitrite molecule, whereas the demonstration of interferon gamma and interleukin-12 is indicative of a TH1 response in the inflammatory demyelinative lesions of the cerebral phenotype. These differences between the adreno-leukodystrophy mouse and human patients are intriguing and may provide a clue to the phenotypic divergence in this disease.

The unfolded protein response in vanishing white matter disease.

Leukoencephalopathy with vanishing white matter (VWM) is an autosomal-recessive disorder in which febrile infections may provoke major neurologic deterioration. Characteristic pathologic findings include cystic white matter degeneration, foamy oligodendrocytes, dysmorphic astrocytes and oligodendrocytes, oligodendrocytosis, and apoptotic losses of oligodendrocytes. VWM is caused by mutations in eukaryotic initiation factor (eIF) 2B (eIF2B). eIF2B plays an important role in the regulation of protein synthesis. Mutant eIF2B may impair the ability of cells to regulate protein synthesis in response to stress and perhaps even under normal conditions. An overload of misfolded proteins in the endoplasmic reticulum activates the unfolded protein response (UPR), a compensatory mechanism that inhibits synthesis of new proteins and induces both prosurvival and proapoptotic signals. We have studied the activation of the UPR in VWM through the immunohistochemical expression of its upstream components PERK and phosphorylated eIF2alpha (eIF2alphaP) and combined immunohistochemical and Western blot analysis of the downstream effector proteins activating transcription factor-4 (ATF4) and C/EBP homologous protein (CHOP) in 4 VWM brains and 3 age-matched controls. We demonstrate activation of the UPR in glia of patients with VWM. Our findings may point to a possible explanation for the dysmorphic glia, the increased numbers of oligodendrocytes, and the apoptotic loss of oligodendrocytes in VWM.

MLC1: a novel protein in distal astroglial processes.

Megaloencephalic leukoencephalopathy with subcortical cysts (MLC) is a progressive cerebral white matter disease in children caused by mutations in the MLC1 gene. This disease is histopathologically characterized by myelin splitting and intramyelinic vacuole formation. MLC1 encodes a novel protein, MLC1, which is mainly expressed in the brain and leukocytes. The function is unknown, although a transport function has been suggested. In this article, we provide experimental data addressing the membrane topology and cellular localization of MLC1. We show that MLC1 contains an even number of transmembrane domains, supporting the possible transport function of MLC1. We demonstrate that MLC1 is specifically expressed in distal astroglial processes in perivascular, subependymal, and subpial regions. This localization suggests a role for MLC1 in a transport process across the blood-brain and brain-cerebrospinal fluid barriers. Astrocyte functions have long been debated. It is becoming increasingly clear that these cells are of fundamental importance in maintaining the structural and functional integrity of neural tissue. Elucidation of the function of MLC1 will contribute to a better understanding of not only the pathophysiology of the disease, but also the role of astrocytes in normal neural tissue.

Histopathologic correlates of radial stripes on MR images in lysosomal storage disorders.

BACKGROUND AND PURPOSE: Radially oriented hypointense stripes in hyperintense cerebral white matter are recognized on T2-weighted images of certain lysosomal storage disorders. We compared in vivo and postmortem MR imaging with histopathologic findings in three patients with metachromatic leukodystrophy (MLD), globoid cell leukodystrophy (GLD), and infantile GM1 gangliosidosis (GM1) to understand this characteristic MR imaging pattern. METHODS: The in vivo MR imaging protocol comprised T1- and T2-weighted spin-echo and fluid-attenuated inversion recovery imaging. Postmortem MR imaging, including coronal 1-cm-thick brain sections, was performed after at least 5 weeks of formalin fixation and included T2-weighted spin-echo images and 3D fluid-attenuated inversion recovery images with high spatial resolution. Afterward, the sections were embedded in paraffin, whole-mount sections were made, and neuropathologic stains were applied. RESULTS: Similar imaging features were found in the three patients on in vivo and postmortem images, with more prominent stripes in GLD and MLD than in GM1. Neuropathologic examination revealed that the stripes were related to relative sparing of myelin in the perivenular regions in GM1 and MLD, but lipid-containing glial cells were also present in these areas in MLD. Perivenular clusters of globoid cells containing lipid material in absence of any myelin corresponded to the stripes in GLD. CONCLUSION: Results of our postmortem study showed that radial stripes of white matter on MR images represented relative myelin sparing in some lysosomal storage disorders, but they may also represent lipid storage.

Access to transportation and health care utilization in a rural region.

CONTEXT: Access to transportation to transverse the large distances between residences and health services in rural settings is a necessity. However, little research has examined directly access to transportation in analyses of rural health care utilization. PURPOSE: This analysis addresses the association of transportation and health care utilization in a rural region. METHODS: Using survey data from a sample of 1,059 households located in 12 western North Carolina counties, this analysis tests the relationship of different transportation measures to health care utilization while adjusting for the effects of personal characteristics, health characteristics, and distance. FINDINGS: Those who had a driver's license had 2.29 times more health care visits for chronic care and 1.92 times more visits for regular checkup care than those who did not. Respondents who had family or friends who could provide transportation had 1.58 times more visits for chronic care than those who did not. While not significant in the multivariate analysis, the small number who used public transportation had 4 more chronic care visits per year than those who did not. Age and lower health status were also associated with increased health care visits. The transportation variables that were significantly associated with health care visits suggest that the underlying conceptual frameworks, the Health Behavior Model and Hagerstrand's time geography, are useful for understanding transportation behavior. CONCLUSIONS: Further research must address the transportation behavior related to health care and the factors that influence this behavior. This information will inform policy alternatives to address geographic barriers to health care in rural communities.

The life and death of oligodendrocytes in vanishing white matter disease.

Vanishing white matter disease (VWM) is a progressive cavitating disease of central white matter due to a deficiency of the translation initiation factor eIF2B. Oligodendrocytes appear to be numerically increased in some white matter areas, while decreased in others. We compared oligodendrocytes of cerebral, cerebellar, and pontine white matter from 5 VWM patients with those of age-matched controls by light microscopy and immunohistochemistry using antibodies to activated caspase-3, bak, bax, bcl-2, survivin, and Ki-67, as well as by the TUNEL technique. Oligodendrocytes were identified morphologically and quantified using an ocular grid. We observed statistically significant increases in their densities at all sites; Ki-67-labeled oligodendrocytes were identified in 2 of 5 patients. Apoptotic oligodendrocytes were documented in 3 of 5 patients, while bcl-2 and survivin labeling was observed in 2 of 5 and 2 of 2 patients, respectively. There was a trend toward an increase in apoptotic labeling of oligodendrocytes that was strongest in the cerebrum, the major locus of VWM, in the youngest and most severely affected patients. These data conclusively demonstrate increased oligodendrocytic densities in VWM; the increase is not an artifact of white matter contraction. Our data also document that oligodendrocytes undergo apoptosis, perhaps in conjunction with major neurologic crises, and that a subset of oligodendrocytes are able to persist and proliferate. Conflicting proliferative, cell-death, and survival signals impact the oligodendrocytes of VWM.

September 2001: 51-year-old man with seizures since childhood.

The September 2001 COM. A 51 year old man with refractory seizures presented with a recent seizure while at work but no other neurologic deficit. Imaging studies demonstrated a solid and cystic lesion of the right temporal lobe. Microscopic and immunohistochemical studies demonstrated an atypical ganglioglioma due to the presence of neurofibrillary tangles within the neoplastic ganglion cell component. This is the fifth case reported in the literature. Neoplastic ganglion cells and neurofibrillary tangles are discussed both separately and as integral components of this rare tumor.

Myelin lesions associated with lysosomal and peroxisomal disorders.

Abnormalities of myelin are common in lysosomal and peroxisomal disorders. Most display a primary loss of myelin in which the myelin sheath and/or oligodendrocytes are selectively targeted by diverse pathogenetic processes. The most severe and, hence, clinically relevant are heritable diseases predominantly of infants and children, the leukodystrophies: metachromatic, globoid cell (Krabbe disease) and adreno-leukodystrophy. Our still limited understanding of these diseases has derived from multiple sources: originally, neurological-neuropathologic-neurochemical correlative studies of the natural disease in humans or other mammals, which has been enhanced by more sophisticated and contemporary techniques of cell and molecular biology. Transgenic mouse models seem to be the most promising methodology, allowing the examination of the cellular role of lysosomes and peroxisomes for formation and maintenance of both myelin and axons, and providing initial platforms to evaluate therapies. Treatment options are woefully inadequate and in their nascent stages, but still inspire some hope for the future.