Spinal cord glioneuronal tumor with "rosetted" neuropil islands and meningeal dissemination: a case report

Distinctive glioneuronal tumors arising within the cerebrum and displaying neuropil-like islands and tumor cells immunoreactive for neuronal and glial antigens have recently been described. We report a similar tumor in the cervico-thoracic region of the spinal cord in a 44-year-old woman that recurred 1 year later with dissemination to the lumbar dura and cauda equina. The tumor was composed of "rosetted" neuropil islands displaying immunoreactivity for synaptophysin, whereas the intervening tumor cells were more fibrillar and immunoreactive for GFAP. The tumor cell nuclei immediately surrounding these neuropil islands were immunoreactive to the newly characterized neuronal marker, anti-Hu. While several cases of neurocytomas have been described in the spinal cord, to the best of our knowledge, this is the first example of a glioneuronal tumor with "rosetted" neuropil islands to be reported in the spinal cord.

Glioneuronal tumor with neuropil-like islands

Mixed glioneuronal neoplasms are relatively uncommon tumors in the central nervous system. Recently, an unusual glioneuronal tumor arising in adults marked histologically by neuropil-like islands was described. We present a similar case arising in a 23-year-old woman who presented with headaches and seizures and on imaging studies was noted to have a frontal-temporal lobe mass. The patient underwent partial resection of the tumor, which histologically resembled anaplastic astrocytoma, and received a course of radiation therapy and chemotherapy. Increasing seizure frequency and expanding size on neuroimaging prompted a re-excision of the tumor. The second resection was marked by islands of tissue resembling gray matter with slightly atypical neuronal and glial cells situated in the white matter. These islands stained positively with synaptophysin and did not stain with glial fibrillary acid protein. Mild vascular proliferation and moderate nuclear pleomorphism also characterized the tumor. Areas of necrosis were not noted. A MIB-1 labeling index of 18.1% was noted. P53 immunoreactivity was observed in approximately 40% of tumor cell nuclei. This lesion is felt to represent a clinically aggressive glioneuronal neoplasm with an unusual and distinctive histologic phenotype. HUM PATHOL 31:1435-1438.

The expression of the calcium binding protein calretinin in the rat striatum: effects of dopamine depletion and L-DOPA treatment

The activity of the striatum is regulated by glutamate and dopamine neurotransmission. Consequent to striatal dopamine depletion the corticostriatal excitatory input is increased, which in turn can raise intracellular calcium levels. We investigated changes in the neuronal expression of the calcium binding protein calretinin related to dopamine depletion and l-DOPA administration. Immunohistochemical methods were used to assess calretinin in the striatum of rats with unilateral lesions of the nigrostriatal system. In these animals we observed a loss of the patchy distribution of calretinin fibers. Moreover, after dopaminergic depletion we detected two new, not previously described, calretinin cell types, the presence of which could be related to morphological changes induced by loss of a dopaminergic input. We also found an increase in the number of calretinin-labeled cells in the striatum ipsilateral to the lesion compared to the contralateral striatum or to the striatum of normal rats. This increase was mostly evident at 3 weeks postlesion and tended to decrease toward normal levels at 6, 10, and 18 weeks postlesion. In unlesioned animals, l-DOPA administration did not induce changes in the expression of calretinin. In unilaterally lesioned animals, l-DOPA reversed the increase in the number of calretinin-positive cells induced by the lesion. However, chronic l-DOPA administration was less effective than acute l-DOPA in reversing the effect of the lesion. The present data suggests that striatal calretinin neurons are sensitive to dopamine depletion. Increased expression of calretinin in striatal cells may be consequent to enhanced striatal excitatory input.

Immunocytochemical study of the dorsal and median raphe nuclei in patients with Alzheimer's disease prospectively assessed for behavioural changes

The dorsal and median raphe nuclei were examined with immunocytochemistry to display the 5-HT neurones in 16 cases of post-mortem-proven Alzheimer's disease (AD) and 12 age and sex-matched controls. The AD cases had been prospectively assessed during life for expression of behavioural changes as well as for cognitive decline. A significant (P < 0.001) 41% reduction in density of dorsal raphe neurones was found along with a significant (P < 0.02) 29% reduction in density of median raphe neurones in AD. There were significantly more neurofibrillary tangles in both dorsal and median raphe nuclei in AD than in controls (P < 0.001). There was no correlation between reduction in neurone density in these nuclei and behavioural change, cognitive decline, neurofibrillary tangle counts in these nuclei or plaque and tangle pathology in frontal and temporal cortex. It was concluded from these findings that the raphe nuclei are significantly affected by the pathology of AD and that plasticity in the 5-HT system is the probable reason for the lack of correlation of reduced 5-HT neurone density and clinical disease parameters.

Age-related synaptic changes in sensorimotor cortex of the Brown Norway X fischer 344 rat

Investigations of age-related changes in synapse density have yielded contradictory conclusions. The goal of the present study was to determine whether there is a significant decline in the number of cortical synapses in old age. Therefore, brains from 10-, 15-, and 32-month-old Brown Norway X Fischer 344 rats were prepared for electron microscopy and synapses were counted in a stereotaxically-identified region of sensorimotor cortex. Within this cortical area, synapses were counted in layers 2 and 4 and the data have been presented both as number of synapses per volume of neuropil and as the ratio of synapses per neuron. Results indicated that there was a decline in synapse density between 15 and 32 months in layer 2, but not in layer 4. This decline was significant not only for total synapses, but also for subcategories of synapses when classified by presynaptic features or postsynaptic element. Specifically, there was a significant decline in presumptive inhibitory synaptic terminals, i.e., those containing nonround synaptic vesicles, as well as a significant decline in synapses that contact dendritic spines.

Myelination defects and neuronal hyperexcitability in the neocortex of connexin 32-deficient mice

Morphological and electrophysiological studies were performed on neocortices of adult Connexin 32 (Cx32)-deficient mice and wild-type mice to investigate the consequences of a lack of the gap junction subunit Cx32 on neocortical structure and function. Morphometrical analysis revealed a reduced volume fraction of myelin within the neuropil and a decreased thickness of the axonal myelin sheaths in the neocortex of Cx32-deficient mice. Intracellular recordings from neurons in neocortical slice preparations provided evidence for an increased membrane input resistance in neurons of Cx32-null mutant mice as compared to neurons of wild-type mice. Consequently, neurons of Cx32-deficient mice displayed an enhanced intrinsic excitability. In addition, approximately 50% of the neurons investigated in slices of Cx32-deficient mice responded to afferent stimulation with delayed and large glutamatergic excitatory postsynaptic potentials resembling paroxysmal depolarizations. GABAergic inhibition sufficient to efficiently control synaptic excitability was virtually absent in these cells. The changes in intrinsic membrane properties observed in neurons of Cx32-null mutant mice were independent of the alterations in synaptic function, since increased membrane resistances were observed also in neurons with normal synaptic response pattern. Thus, in the neocortex, lack of Cx32 correlates with myelination defects, alterations in intrinsic membrane properties and dysfunction of inhibitory synaptic transmission.

Intraparenchymal meningioma originating from underlying meningioangiomatosis. Case report and review of the literature

The authors present the case of a 20-year-old woman with right-sided temporal intraparenchymal meningioma originating from underlying meningioangiomatosis. The patient manifested temporal-type seizures as the initial symptom. She had no stigmata of neurofibromatosis Type 2. Neuroradiological studies revealed an intraaxial, contrast-enhancing lesion in the right temporal lobe. After gross-total removal of the tumor, histological examination revealed a transitional meningioma with surrounding neural parenchyma and features of meningioangiomatosis. Although there were no signs of anaplasia, necrosis, or increased mitosis, tumor islands were observed in the adjacent neuropil. The rare association of meningioangiomatosis and meningioma is discussed, along with radiological and surgical findings.

Mitochondrial ultrastructure and density in a primate model of persistent tardive dyskinesia

The use of neuroleptic drugs to treat schizophrenia is almost invariably associated with extrapyramidal movement disorders. One of these disorders, tardive dyskinesia (TD), can persist long after neuroleptic withdrawal suggesting that permanent neurological damage is produced. However, there appears to be no convincing pathology of TD and its pathogenesis remains unknown. Findings that neuroleptics interfere with normal mitochondrial function and produce mitochondrial ultrastructural changes in the basal ganglia of patients and animals suggest that mitochondrial dysfunction plays a role in TD. We have established a model for persistent TD in baboons that appears to involve compromised mitochondrial function. In this study, we evaluated two animals treated for 41 weeks with a derivative of haloperidol and two treated with vehicle only. Treatment was then withdrawn and the animals observed for a further 17-18 weeks. Treated animals developed abnormal orofacial signs that were consistent with TD. These symptoms persisted during the drug-free period. The animals were euthanased, the brains perfused-fixed then post-fixed in 4% paraformaldehyde and the caudate and putamen prepared for electron microscopy. Regardless of whether mitochondria were located in neural soma, excitatory terminals, glia or in non-somal neuropil there was no consistent difference either in size or number between treated and control animals. Thus, even if mitochondria in striatal neurons undergo ultrastructural alterations during neuroleptic therapy, these changes do not persist after drug withdrawal.

Histochemically-reactive zinc in amyloid plaques, angiopathy, and degenerating neurons of Alzheimer's diseased brains

Excess brain zinc has been implicated in Alzheimer's neuropathology. Here we evaluated that hypothesis by searching the brains of Alzheimer's patients for abnormal zinc deposits. Using histochemical methods, we found vivid Zn2+ staining in the amyloid deposits of dense-core (senile) plaques, in the amyloid angiopathy surrounding diseased blood vessels, and in the somata and dendrites of neurons showing the characteristic neurofibrillary tangles (NFT) of Alzheimer's. In contrast, brains from age-matched, non-demented subjects showed only occasional staining for Zn2+ in scattered neurons and possible plaques. A role of abnormal zinc metabolism in Alzheimer's neuropathology is suggested.

Pathology of the hippocampus in experimental feline infantile hydrocephalus

Hydrocephalus is responsible for many pediatric neurological deficits presumed to be caused by neocortical pathophysiology. Relatively little is known about the role of non-neocortical CNS structures in this condition. In the present work experimental infantile hydrocephalus produced by intracisternal kaolin injection was studied in a neonate kitten model. The hippocampal formation was processed for electron microscopy, and the neuropil of the CA3 region was examined in untreated, severely hydrocephalic and age-matched normal animals. Both macroscopically and microscopically the thickness of the hippocampus was not decreased. Hippocampal pyramidal neurons were found in varying stages of cytoplasmic densification, and dendritic and axonal processes exhibited hydropic cellular deterioration. The number of synaptic contacts was decreased. However, there was no indication of edematous extracellular space and the ependymal covering of the hippocampus was intact. The macroscopic structural integrity of the hippocampus, as well as the dendritic, axonal and synaptic alterations, suggest that the dark pyramidal neurons are the result of deafferentation, which may have profound effects on learning and memory.

Effect of age and neuroleptics on tyrosine hydroxylase-IR in sector CA2 of schizophrenic brain

The density of TH-IR varicosities was analyzed in the hippocampus of 15 normal controls and 11 schizophrenics. The average density of varicosities in apposition with pyramidal cells and in the neuropil was 30-35% lower in CA2, but not other sectors of schizophrenics. Age was correlated with varicosity density in all sectors, particularly in CA2 where young patients showed a 50% reduction on non-pyramidal cells. Neuroleptic dose showed a negative correlation with the density of varicosities, and notably the dose of young schizophrenics was four times higher than that of older subjects. Thus, antipsychotic dose appears to be associated with a suppression of a normal age-related increase of dopamine projections to CA2 during the early phases of schizophrenia.

Application of the National Institute on Aging (NIA)-Reagan Institute criteria for the neuropathological diagnosis of Alzheimer disease

The Khachaturian criteria and the Consortium to Establish a Registry for Alzheimer Disease (CERAD) criteria for the neuropathological assessment of Alzheimer disease (AD) emphasize senile or neuritic plaques, age, and clinical history. A new scheme stressing topographic staging of neurofibrillary changes in addition to neuritic plaques has been proposed by the National Institute on Aging (NIA)-Reagan Institute Consensus Conference. This scheme assigns cases to high, intermediate, or low likelihood categories that the dementia is due to AD. We applied this method to 84 brains from subjects with clinical and neuropathological diagnoses of AD (n = 33), non-AD dementing illnesses (n = 34), including dementia with Lewy bodies (DLB) and progressive supranuclear palsy (PSP), and no neurological disease (n = 17). We also used Khachaturian and CERAD criteria. Neurofibrillary tangle and neuropil thread densities were assessed on 6-micrometer-thick modified Bielschowsky-stained paraffin sections from entorhinal-perirhinal cortex, CA1 of hippocampus, and neocortex including inferior temporal, visual association, and primary visual cortices. Each case was assigned a Braak and Braak stage. Using the NIA-Reagan criteria, we found excellent agreement between clinical history of AD dementia and brains assigned to the high likelihood category that dementia was due to AD. Among brains diagnosed neuropathologically with other degenerative diseases, NIA-Reagan criteria were more conservative than previous criteria, and these cases were likely to be categorized as intermediate or low likelihood that dementia was due to AD. All brains from nondemented subjects were assigned to the low (81%) or intermediate (19%) categories. In summary, we found good correlation between the NIA-Reagan criteria and clinical dementia, and there was generally good agreement between these criteria and existing neuropathological methods, Khachaturian and CERAD, in diagnosing AD. In studying several other neurodegenerative diseases, such as DLB, which shows neuropathological and clinical overlap with AD, the staging of neurofibrillary changes offered potential diagnostic refinement.

Gallyas- and tau-positive glial structures in motor neuron disease with dementia

We have studied Gallyas- and tau-positive glial structures in three autopsied cases of motor neuron disease with dementia (MND-D). Gallyas-positive, tau-immunoreactive thread-like structures in the neuropil and crescent/coiled inclusions in the glial cells were mainly observed in the hippocampus, parahippocampal gyrus, and amygdaloid nucleus. Double staining using Gallyas staining and carbonic anhydrase 2 (CA2) immunohistochemistry revealed that some crescent/coiled inclusions occurred in the CA2-immunopositive cytoplasm of the oligodendroglia. Electron microscopic study with the Gallyas-Braak method revealed that the inclusion was a reticular, partly compact mass, containing 15 nm fibrils around round or oval nuclei. Since the regions where these structures appeared exhibited neuronal loss with gliosis, these data suggest that a cytoskeletal abnormality involving tau protein in glia might be associated with the degenerative process of MND-D.

[Morphologic bases of clinical neurotransplantology]

Results of long term investigation performed at the Department of Morphology (Institute of the Experimental Medicine, RAMS) and data on problems of neurotransplantology and nervous tissue histogenesis in human prenatal development available in literature were summarized. Materials concerning the development of transplants of human embryonic nervous tissue (ENT) in the definitive brain of animal recipients (rats and monkeys) without immunosuppression and on the background of the effect of cyclosporine A and hydrocortisone are presented. Influence of the embryo and recipient age, as well as the volume, location (homo- and heterotopy) and method of transplantation (tissue grafts or cellular suspensions) on viability and realization of ENT histoblastic potentialities were analyzed. These data along with the findings on peculiarities of transplant structure at remote stages following the operation and authors own clinical observations were the base of practical recommendations for working out the strategy and tactics of repair and correction of functions of CNS impaired during different diseases by means of ENT transplantation.

An ultrastructural analysis of tissue surrounding a microdialysis probe

Microdialysis is a widely used in vivo sampling technique commonly used to monitor extracellular levels of a variety of molecules including neurotransmitters and metabolites. To facilitate interpretation of microdialysis results, this study critically examines changes in synaptic morphology induced by microdialysis. Tissue surrounding microdialysis probes was examined using light and electron microscopy at three distances from the probe tract. Microdialysis probes were implanted into rat striatum, and after 40 h of post-operative recovery were perfused with a modified Ringer's solution. Light microscope analysis revealed tissue disruption up to 1.4 mm from the probe site. Axonal damage indicative of non-excitotoxic insult was also seen as far away from the probe as was examined. The presence of dark-degenerating neurons was also noted and estimates of neuronal densities revealed loss up to 400 microm from the probe tract. This study, the first qualitative ultrastructural investigation of neuropil surrounding the probe site, indicated swollen processes up to 1.4 mm from the probe tract. Swollen mitochondria and bloated endoplasmic reticulum suggest intracellular chemical disruption. Tissue damage resulting in synaptic and neuronal disruption may affect neurotransmitter efflux or extracellular concentrations of metabolites.

Neurodegeneration in hereditary nucleotide repair disorders

Both xeroderma pigmentosum group A (XPA) and Cockayne syndrome (CS) are rare autosomal disorders, have a genetic defect in the step of nucleotide repair, and involve various neurological abnormalities caused by progressive neurodegeneration. We performed comprehensive neuropathological analysis of five cases of XPA and four cases of CS. The XPA cases showed widespread neuronal loss throughout the central nervous system, in sharp contrast to the comparative preservation of neurons in the CS cases, who rather exhibited patchy demyelination in the cerebral and cerebellar white matter, and multifocal calcium deposition in the basal ganglia and cerebral white matter, respectively. Exceptionally in the cerebellar cortex, neuronal loss was more severe in CS than in XPA. Grumose or foamy spheroid bodies occurred in the globus pallidus and substantia nigra, and axonal torpedoes were increased in the cerebellar cortex in both disorders. Neither silver impregnation nor immunohistochemistry for ubiquitin or tau succeeded in visualizing neurofibrillary tangles, senile plaques or augmented ubiquitination in either disorder, and these findings did not support the involvement of facilitated aging in the neurodegeneration in XPA or CS.

Nuclear and neuropil aggregates in Huntington's disease: relationship to neuropathology

The data we report in this study concern the types, location, numbers, forms, and composition of microscopic huntingtin aggregates in brain tissues from humans with different grades of Huntington's disease (HD). We have developed a fusion protein antibody against the first 256 amino acids that preferentially recognizes aggregated huntingtin and labels many more aggregates in neuronal nuclei, perikarya, and processes in human brain than have been described previously. Using this antibody and human brain tissue ranging from presymptomatic to grade 4, we have compared the numbers and locations of nuclear and neuropil aggregates with the known patterns of neuronal death in HD. We show that neuropil aggregates are much more common than nuclear aggregates and can be present in large numbers before the onset of clinical symptoms. There are also many more aggregates in cortex than in striatum, where they are actually uncommon. Although the striatum is the most affected region in HD, only 1-4% of striatal neurons in all grades of HD have nuclear aggregates. Neuropil aggregates, which we have identified by electron microscopy to occur in dendrites and dendritic spines, could play a role in the known dendritic pathology that occurs in HD. Aggregates increase in size in advanced grades, suggesting that they may persist in neurons that are more likely to survive. Ubiquitination is apparent in only a subset of aggregates, suggesting that ubiquitin-mediated proteolysis of aggregates may be late or variable.

Progression of Alzheimer-related neuritic plaque pathology in the entorhinal region, perirhinal cortex and hippocampal formation

Extracellular deposits of the beta-amyloid protein and intraneuronal neurofibrillary changes are hallmarks of Alzheimer's disease. Neurofibrillary changes in the cell body of neurons are the neurofibrillary tangles, while beta-amyloid deposits containing dystrophic neurites with neurofibrillary changes are called neuritic plaques. beta-Amyloid deposits and neurofibrillary tangles display a sequential accumulation in the cerebral cortex. In the present study, the topographical distribution of beta-amyloid deposits and neuritic plaques in the entorhinal region, perirhinal cortex and hippocampal formation was investigated in relationship to the amyloid and neurofibrillary staging proposed by Braak. The number of subregions displaying beta-amyloid deposits and neuritic plaques continuously increases in correlation with the amyloid stage (for beta-amyloid deposits r = 0.90, p < 0.0001, for neuritic plaques r = 0.74, p < 0.0001) and neurofibrillary stage (for beta-amyloid deposits r = 0.53, p < 0.0001, for neuritic plaques r = 0.68, p < 0. 0001). Parallel to the advancement in the neurofibrillary stage, early and late predilection sites of beta-amyloid deposits and neuritic plaques can be distinguished. The early predilection sites correspond to projection areas of regions which exhibit incipient neurofibrillary tangles. Furthermore, neuritic plaques only occur in the presence of neurofibrillary tangles in the areas investigated. The findings indicate that neuritic plaques gradually develop in the projection areas of tangle-bearing neurons.

The reduced neuropil hypothesis: a circuit based model of schizophrenia

In recent years, quantitative studies of the neuropathology of schizophrenia have reignited interest in the cerebral cortex and focused attention on the cellular and subcellular constituents that may be altered in this disease. Findings have ranged from compromised circuitry in prefrontal areas to outright neuronal loss in temporal and cingulate cortices. Herein, we propose that a reduction in interneuronal neuropil in the prefrontal cortex is a prominent feature of cortical pathology in schizophrenia and review the growing evidence for this view from reports of altered neuronal density and immunohistochemical markers in various cortical regions. The emerging picture of neuropathology in schizophrenia is one of subtle changes in cellular architecture and brain circuity that nonetheless have a devastating impact on cortical function.

Striation is the characteristic neuritic abnormality in Alzheimer disease

In this study, we found that neuropil threads of Alzheimer disease, rather than being continuous filaments along cell processes, show multiple interruptions. They are segmental in nature and therefore appear as striations rather than continuous filaments along the length of the neurite. Neuritic striation is not an artifact of section thickness since the majority of abnormal filament accumulations are extremely short. The dominance of short striations demonstrates that argyrophilic grains, rather than being distinct structures, simply represent a short variant of striation and that longer striations are arbitrarily considered neuropil threads. Ultrastructural examination showed that the intervals between striations lack a cytoskeleton. We suggest that neuritic striations may interrupt the microtubule system functionally blocking fast neuritic transport as well as playing a role in loss of neuronal connectivity.

Progressive tetraparesis and laryngeal paralysis in a young rottweiler with neuronal vacuolation and axonal degeneration: an Australian case

A 5-month-old female Rottweiler dog was diagnosed to have a neurodegenerative disease that has been recently reported in Rottweilers from North America and Europe. The dog was presented with progressive signs of ataxia, tetraparesis and inspiratory stridor. The clinical investigation included analysis of CSF, radiography, myelography and electrophysiological testing. No evidence of vertebral malformation or inflammatory CNS disease was identified. Bilateral laryngeal paralysis was identified in the lightly anaesthetised dog. Electromyography showed abnormal spontaneous activity from the intrinsic musculature of the larynx. At necropsy there were no gross abnormalities of the nervous system but there was atrophy of the dorsal cricoarytenoid muscles of the larynx. There were widespread histological abnormalities throughout the nervous system including neuronal vacuolation, spongiform changes in the neuropil and axonal degeneration which was most prominent in the spinal cord. These clinical and pathological findings are consistent with the diagnosis of a new neurodegenerative disease reported from North America and Europe. This diagnosis is of particular significance in Australia where transmissible spongiform encephalopathies have not been identified.

Methylmercury intoxication and histochemical demonstration of NADPH-diaphorase activity in the striate cortex of adult cats

The effects of methylmercury (MeHg) on histochemical demonstration of the NADPH-diaphorase (NADPH-d) activity in the striate cortex were studied in 4 adult cats. Two animals were used as control. The contaminated animals received 50 ml milk containing 0.42 microgram MeHg and 100 g fish containing 0.03 microgram MeHg daily for 2 months. The level of MeHg in area 17 of intoxicated animals was 3.2 micrograms/g wet weight brain tissue. Two cats were perfused 24 h after the last dose (group 1) and the other animals were perfused 6 months later (group 2). After microtomy, sections were processed for NADPHd histochemistry procedures using the malic enzyme method. Dendritic branch counts were performed from camera lucida drawings for control and intoxicated animals (N = 80). Average, standard deviation and Student t-test were calculated for each data group. The concentrations of mercury (Hg) in milk, fish and brain tissue were measured by acid digestion of samples, followed by reduction of total Hg in the digested sample to metallic Hg using stannous chloride followed by atomic fluorescence analysis. Only group 2 revealed a reduction of the neuropil enzyme activity and morphometric analysis showed a reduction in dendritic field area and in the number of distal dendrite branches of the NADPHd neurons in the white matter (P < 0.05). These results suggest that NADPHd neurons in the white matter are more vulnerable to the long-term effects of MeHg than NADPHd neurons in the gray matter.

Ballooning of myelin sheaths in normally aged macaques

In aged animal brains, a variety of "holes" are formed in the neuropil. One type of hole, here designated as the myelin balloon, is an abnormality of the myelin sheath and is found in a number of diverse sites in the brain. Profiles of myelin balloons display rather smoothly rounded peripheral contours and typically range up to 10 microm in diameter, although exceptionally large examples may be twice this size. The balloons are bounded by lamellae of myelin, and to accommodate the contents of the balloon, the myelin sheath becomes split at the intraperiod line. Since the intraperiod line is formed by the apposition of the outer faces of the myelin-forming plasma membrane, the contents of the myelin balloons are, in effect, in continuity with the extracellular space, and it is suggested that the contents of the balloons are fluid, with the fluid exerting an outward pressure on the walls of the balloons to produce their spherical shapes. Myelin balloons are not only produced during aging but also occur in a number of genetic strains of mice and in a number of human disease states. They thus represent a non-specific, though distinctive and common, alteration of the myelin sheath and are a reflection of the fact that under a variety of conditions, including normal aging, oligodendrocytes are unable to maintain the integrity of their sheaths.

Frontotemporal dementia: neuropil spheroids and presynaptic terminal degeneration

We compared the neuropathological changes of 6 patients with clinically diagnosed lobar dementia. In the 4 patients with histopathology consistent with frontotemporal dementia (FTD), moderate neuronal loss contrasted with marked cortical and subcortical gliosis. We found silver-positive, carbohydrate-rich, spheroidal enlargements of presynaptic terminals within the neuropil of specific central nervous system regions. The spheroids were immunopositive for the cytoskeletal proteins tau, the high molecular weight neurofilament subunit (NF-H), and beta-tubulin. No abnormal tau phosphorylation and only rare ubiquitin immunoreactivity were detected in these structures. Carbohydrate modifications, including advanced glycation end products within the spheroid matrix, were confirmed by lectin binding, and by anti-pentosidine immunoreactivity, an indicator of oxidative stress. Ultrastructurally, the spheroids consisted of unmyelinated, membrane-enclosed structures filled with randomly arrayed pairs of filaments, approximately 8 to 10 nm in diameter, that were sparsely labeled with antibodies to unmodified tau (T14) and NF-H. Despite clinical overlap, the central nervous systems of our FTD patients are distinguishable from those of other patients with other lobar dementias, including Pick's disease and corticobasal degeneration, by the absence of abnormally phosphorylated neuronal or glial tau inclusions. The neuropil spheroids are dystrophic changes of certain selectively vulnerable presynaptic terminals, suggesting a retrograde degenerative process in FTD.

Atypical neuronal inclusion bodies in meningioangiomatosis

A case of meningioangiomatosis not associated with neurofibromatosis 2 in a 24-year-old man is reported. Abundant neurofibrillary tangles and threads, shown by immunohistochemistry and ultrastructural analysis to be similar to those seen in Alzheimer's disease, were found in the residual neuropil. Another lesion consisting of argyrophilic globular inclusion bodies with radial fibrils was found at the periphery. Single and double immunostaining with a panel of antibodies showed similarities between these inclusions and Pick bodies.