Homo- and heteroepitaxial growth of Sn-doped β-Ga2O3 layers by MOVPE

For the first time, n-type homoepitaxial semiconducting β-Ga₂O₃ layers were attained by MOVPE.

Effects of AlGaAs cladding layers on the luminescence of GaAs/GaAs1-xBix/GaAs heterostructures

The structural and optical properties of GaAs1-xBix quantum wells (QWs) symmetrically clad by GaAs barriers with and without additional confining AlGaAs layers are studied. It is shown that a GaAs/GaAs1-xBix/GaAs QW with x ~ 4% and well width of ~ 4 nm grown by molecular beam epitaxy demonstrates efficient photoluminescence (PL) that becomes significantly more thermally stable when a cladding AlGaAs layer is added to the QW structure. The PL behavior for temperatures between 10 and 300 K and for excitation intensities varying by seven orders of magnitude can be well described in terms of the dynamics of excitons including carrier capture in the QW layer, thermal emission and diffusion into the cladding barriers. Understanding the role of these processes in the luminescence of dilute GaAs1-xBix QW structures facilitates the creation of highly efficient devices with reduced thermal sensitivity and low threshold current.

X-ray diffraction from nonperiodic layered structures with correlations: analytical calculation and experiment on mixed Aurivillius films

X-ray diffraction from films consisting of layers with different thicknesses, structures and chemical contents is analysed. The disorder is described by probabilities for different sequences of layers. Closed analytical expressions for the diffracted X-ray intensity are obtained when the layers form a stationary Markov chain. The proposed model is applied to the diffraction data from epitaxial sodium bismuth titanate thin films with Aurivillius structure possessing such one-dimensional disorder. In this case, the disorder is caused by a random stacking of three and four perovskite units separated by bismuth oxide interlayers. The results of analytical calculations are in good agreement with the experimental data and indicate that the incorporation of sodium in the Bi(4)Ti(3)O(12) phase causes the formation of a fourth perovskite unit.

Optical evidence of a quantum well channel in low temperature molecular beam epitaxy grown Ga(AsBi)/GaAs nanostructure

A Ga(AsBi) quantum well (QW) with Bi content reaching 6% and well width of 11 nm embedded in GaAs is grown by molecular beam epitaxy at low temperature and studied by means of high-resolution x-ray diffraction, photoluminescence (PL), and time-resolved PL. It is shown that for this growth regime, the QW is coherently strained to the substrate with a low dislocation density. The low temperature PL demonstrates a comparatively narrow excitonic linewidth of ∼ 40 meV. For high excitation density distinct QW excited states evolve in the emission spectra. The origins of peculiar PL dependences on temperature and excitation density are interpreted in terms of intra-well optical transitions.

A novel multi-detection technique for three-dimensional reciprocal-space mapping in grazing-incidence X-ray diffraction

A new scattering technique in grazing-incidence X-ray diffraction geometry is described which enables three-dimensional mapping of reciprocal space by a single rocking scan of the sample. This is achieved by using a two-dimensional detector. The new set-up is discussed in terms of angular resolution and dynamic range of scattered intensity. As an example the diffuse scattering from a strained multilayer of self-assembled (In,Ga)As quantum dots grown on GaAs substrate is presented.

Late-onset metachromatic leukodystrophy: genotype strongly influences phenotype

BACKGROUND

P426L and I179S are the two most frequent mutations in juvenile and adult metachromatic leukodystrophy (late-onset MLD), which, in contrast to infantile MLD, show marked phenotypic heterogeneity.

OBJECTIVE

To search for genotype-phenotype correlations in late-onset MLD.

METHODS

The authors reviewed the clinical course of 22 patients homozygous for mutation P426L vs 20 patients heterozygous for mutation I179S, in which the second arylsulfatase A (ASA) mutation had also been determined.

RESULTS

P426L homozygotes principally presented with progressive gait disturbance caused by spastic paraparesis or cerebellar ataxia; mental disturbance was absent or insignificant at the onset of disease but became more apparent as the disease evolved. In contrast, compound heterozygotes for I179S presented with schizophrenia-like behavioral abnormalities, social dysfunction, and mental decline, but motor deficits were scarce. Reduced peripheral nerve conduction velocities and less residual ASA activity were present in P426L homozygotes vs I179S heterozygotes.

CONCLUSION

The characteristic clinical differences between homozygous P426L and compound heterozygous I179S patients establish a distinct genotype-phenotype correlation in late-onset metachromatic leukodystrophy.

Controlling planar and vertical ordering in three-dimensional (In,Ga)As quantum dot lattices by GaAs surface orientation

Anisotropic surface diffusion and strain are used to explain the formation of three-dimensional (In,Ga)As quantum dot lattices. The diffusion characteristics of the surface, coupled with the elastic anisotropy of the matrix, provides an excellent opportunity to influence the dot positions. In particular, quantum dots that are laterally organized into long chains or chessboard two-dimensional arrays vertically organized with strict vertical ordering or vertical ordering that is inclined to the sample surface normal are accurately predicted and observed.

Ungew�hnlicher Verlauf einer ?-Mannosidose mit Symptomen einer paranoid-halluzinatorischen Psychose

We report the case of a 27-year-old female with recurrent paranoid-hallucinatory episodes who was initially diagnosed as suffering from schizophrenic psychosis. After 10 years of treatment under this diagnosis, alpha-mannosidosis was identified to be the underlying cause of her psychiatric symptoms. alpha-Mannosidosis is a rare autosomal recessive lysosomal storage disorder associated with decreased activity of the enzyme mannosidase. In the present case, diagnosis was made late in the illness after failure of a response to antipsychotic treatment and with the patient additionally showing progressive cognitive decline. Only after extensive investigation was the diagnosis made by showing decreased alpha-mannosidase enzyme activity in serum and blood leukocytes. This case demonstrates that an unusual clinical course or striking symptom patterns, especially in association with somatic comorbidity, in psychotic patients should lead to diagnostic consideration of inherited metabolic disease.

Expression of major histocompatibility complex class I molecules on the different cell types in multiple sclerosis lesions

Multiple sclerosis is considered to be an immune-mediated disease of the central nervous system, characterized by chronic inflammation, primary demyelination and axonal damage. The mechanisms of demyelination and axonal injury are heterogeneous and complex. One possible mechanism is direct damage of oligodendrocytes and neurons by Class I MHC restricted cytotoxic T-cells. In this study we analyzed the expression of functional MHC class I molecule complex, consisting of alpha-chain and beta2-microglobulin, in a large sample of human autopsy material, containing 10 cases of acute MS, 10 cases of chronic active MS, 10 cases of chronic inactive MS and 21 controls. To examine the expression of MHC class I and II molecules on the different cell-types in brain, we used quantitative immunohistochemical techniques, double staining and confocal laser microscopy scans on paraffin embedded sections. We found constitutive expression of MHC class I molecule on microglia and endothelial cells. A hierarchical up-regulation of MHC class I was present on astrocytes, oligodendrocytes, neurons and axons, depending upon the severity of the disease and the activity of the lesions. MHC class II molecules were expressed on microglia and macrophages, but not on astrocytes. These data indicate that in MS lesions all cells of the central nervous system are potential targets for Class I MHC restricted cytotoxic T-cells.

Guillain-Barré syndrome with marked pleocytosis or a significant proportion of polymorphonuclear granulocytes in the cerebrospinal fluid: neuropathological investigation of five cases and review of differential diagnoses

In cases with otherwise clinically typical Guillain-Barré syndrome (GBS), pronounced cerebrospinal fluid (CSF) pleocytosis or the mere presence of CSF-polymorphonuclear granulocytes should alert the physician to consider alternative diagnoses. Therefore, we retrospectively studied the neuropathology of central and peripheral nervous system in two cases with a CSF cell count of more than 50/microl and in three cases with a significant proportion of polymorphonuclear granulocytes in the CSF sediment. All cases fulfilled the required criteria for the diagnosis of GBS, the duration from onset to death ranged from 4 to 100 days. Neuropathological investigations included routine staining procedures and immunohistochemistry for antigens of glial and haematopoetic cells as well as for products of relevant neurotropic viruses. Demyelinating polyradiculitis was present in four cases, in one patient with a survival time of 4 days the type of damage to myelinated fibres was unclassifiable. In the central nervous system a consistent finding was diffuse activation of microglia, only one case showed mild meningeal and lower brainstem inflammation. Viral products were generally absent. In summary, the neuropathological findings confirm that marked CSF pleocytosis or the presence of polymorphonuclear granulocytes does not rule out the diagnosis of GBS.

Lethal fulminate S. aureus sepsis in M. Behçet overnight cold exposure

Whether patients with Behçet's disease (BD) and immunosuppressive therapy are generally prone to acquire severe infectious diseases is unknown. A 48-year-old man under corticosteroids and azathioprine for BD since 1995 was admitted because of a transitory ischemic attack. Between the third and fourth hospital day he was accidentally locked up, insufficiently dressed, in the hospital's chapel over night. On the following day, he developed fever and deteriorating consciousness until he became comatose. CT scans of the brain were normal and there was only a slight pleocytosis. Despite adequate therapy, the patient's condition further deteriorated such that he died. Responsible for his decline was a fulminate sepsis, diagnosed upon fever, increased C-reactive protein, thrombocyte decline, multi-organ failure, rhabdomyolysis, growth of S. aureus on blood culture, and autopsy. Patients with BD and immunosuppressive therapy, may be more vulnerable to infections and may develop lethal overwhelming sepsis already after overnight cold exposure.

Altered expression of voltage-dependent calcium channel alpha(1) subunits in temporal lobe epilepsy with Ammon's horn sclerosis

Voltage-dependent calcium channels, the initial components in the calcium signalling cascade, are increasingly being recognised as relevant factors in the pathology of epilepsy. To further characterise their role in temporal lobe epilepsy associated with Ammon's horn sclerosis, we investigated the immunohistochemical distribution of five different voltage-dependent calcium channel alpha(1) subunits (alpha(1A), alpha(1B), alpha(1C), alpha(1D), alpha(1E)) in 14 hippocampal specimens of patients with Ammon's horn sclerosis in comparison with eight autopsy control cases. In epilepsy specimens an increased immunoreactivity was observed for alpha(1A), alpha(1B), alpha(1D) and alpha(1E) in the neuropil of the dentate gyrus molecular layer. Dentate gyrus granule cells and residual CA3 pyramidal neurones showed enhanced immunoreactivity for alpha(1A), while labelling of these neurones was decreased for alpha(1C). Astrocytes in Ammon's horn sclerosis specimens were strongly immunoreactive for the alpha(1C) subunit contrasting with an absent astrocytic alpha(1C) labelling in controls. Our results suggest that the expression of calcium channels in neurones and glial cells is dynamically regulated in temporal lobe epilepsy, supporting the relevance of calcium signalling pathways for this disease.

Distribution of a calcium channel subunit in dystrophic axons in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) are immune-mediated diseases of the CNS. They are characterized by widespread inflammation, demyelination and a variable degree of axonal loss. Recent magnetic resonance spectroscopy studies have indicated that axonal damage and loss are a reliable correlate of permanent clinical disability. Accordingly, neuropathological studies have confirmed the presence and timing of axonal injury in multiple sclerosis lesions. The mechanisms of axonal degeneration, however, are unclear. Since calcium influx may mediate axonal damage, we have studied the distribution of the pore-forming subunit of neuronal (N)-type voltage-gated calcium channels in the lesions of multiple sclerosis and EAE. We found that alpha(1B), the pore-forming subunit of N-type calcium channels, was accumulated within axons and axonal spheroids of actively demyelinating lesions. The axonal staining pattern of alpha(1B) was comparable with that of beta-amyloid precursor protein, which is an early and sensitive marker for disturbance of axonal transport. Importantly, within these injured axons, alpha(1B) was not only accumulated, but also integrated in the axoplasmic membrane, as shown by immune electron microscopy on the EAE material. This ectopic distribution of calcium channels in the axonal membrane may result in increased calcium influx, contributing to axonal degeneration, possibly via the activation of neutral proteases. Our data suggest that calcium influx through voltage-dependent calcium channels is one possible candidate mechanism for axonal degeneration in inflammatory demyelinating disorders.

[Development of academic clinical neurology in Europe; a successful concept and its consequences]

Clinical medicine in the 18th century is devoted to Hippocratic tradition. Pathology is not a requisite in this concept. The viewpoint of the pathologists is obscured by traditional philosophy and hampered by insufficient methods. In the 19th century, concepts of correlation between clinical signs and local organ pathology occur. The catastrophic increase of traumatic injury of the nervous system during world war I results in better concepts of clinical localization. At the beginning of the 21st century, the traditional view of the neurological science has changed the image of the patient profoundly, by the emergence of new diseases, disappearance of others and an altered view of the traditional neurologist.

Central nervous system pathology in patients with the Guillain-Barré syndrome

Thirteen autopsy cases of patients with clinical criteria of the Guillain-Barré syndrome were investigated for pathological changes and cellular composition of inflammatory infiltrates in the CNS and PNS. The survival times from the onset of neurological symptoms until death ranged from 1 day to 12 months. In the CNS, degeneration of spinal posterior tracts was seen in three cases. Mononuclear infiltrates consisted of evenly proportioned lymphocytes and macrophages in cases with survival of 1 and 2 days, whereas macrophages predominated in cases with survival of 5 days and longer. Infiltrates presented as nodular clusters around blood vessels and neurons, or were scattered diffusely. They were found within the spinal cord in eight out of 13 cases, within the medulla oblongata in eight out of 12 cases, within the pons in five out of nine cases, and in one out of four midbrains. Activation of microglia, either focal or diffuse, was found in various degrees in 11 out of 13 cases, involving the spinal cord (six out of 13 cases), the medulla oblongata (10 out of 12 cases), the pons (five out of nine cases) or as subependymal rims along the walls of the ventricular system and the central canal of the spinal cord (seven out of 13 cases). In the PNS, myelin loss (12 out of 13 cases), axonal degeneration (six out of 13 cases) and mononuclear cell infiltrates (13 out of 13 cases) were seen in segmental and cranial nerves, spinal ganglia and spinal roots in varying distribution and severity. Mononuclear cell infiltrates were composed of macrophages and T lymphocytes, with even distribution in cases with short survival (1 and 2 days), and predominance of macrophages in cases with protracted clinical course. T lymphocytes were equally composed of OPD4+ and CD8+ cells without obvious differences between cases of short and long duration, or between PNS and CNS infiltrates in 11 out of 12 cases, whilst two cases had a dominant OPD4+ subset. We conclude that CNS pathology is frequent in patients with Guillain-Barré syndrome. It involves axons with secondary myelin impairment, microglial activation and inflammatory infiltration. In this series, primary demyelination is not found in the CNS. Changes such as degeneration of spinal posterior tracts are secondary to pathology in the PNS. Inflammatory cell reactions in the CNS are similar to those in the PNS and to CNS pathology in experimental allergic neuritis. This inflammation might reflect CNS immune activation in the absence of the relevant antigen, in addition to cellular reactions accompanying secondary CNS changes. The presence of distinct pathology in the CNS is in contrast with other recent studies on the pathology of Guillain-Barré syndrome which, unlike this study, may have been influenced by recently introduced treatments.

[Sporadic juvenile amyotrophic lateral sclerosis with neuronal basophil inclusion bodies--a nosologic entity?]

Among the very few cases of juvenile sporadic amyotrophic lateral sclerosis (ALS), 6 cases with neuronal basophilic inclusion bodies (BI) and clinical features uncommon to "classical" adult sporadic ALS have been reported. We present here two further cases and review the relevant literature. There are clinical and neuropathological similarities of systemic degeneration between juvenile cases with or without BI and juvenile and adult sporadic ALS when the latter is allowed to run a protracted course in patients on respirators. Because of overlapping topology and neuronal cytoskeletal pathology, the nosologic distinction within the ALS spectrum is questionable.

Suprasellar meningioma with expression of glial fibrillary acidic protein: a peculiar variant

A 24-year-old female presented with a 3-year history of a suprasellar and intraventricular solid midline process measuring about 3 x 4 cm. At surgery, this tumour was sharply delineated and of stone-like firmness and was removed completely. Histology suggested meningioma, featuring nests and cords of epithelium-like cells with prominent cytoplasm amidst abundant fibrous stroma with prominent lymphoplasmocellular infiltration. Immunocytochemically, the tumour cells expressed vimentin, S-100 protein, epithelial membrane antigen, cytokeratins, and most surprisingly, glial fibrillary acidic protein (GFAP). Ultrastructural investigation revealed abundant intermediate filaments and occasionally dense secretory granules in tumour cells with short, finger-like cytoplasmic processes joined by very rare small, but well-developed desmosomes. This tumour most likely represents a peculiar variant of meningioma with prominent production of GFAP, as previously described [Budka H (1986) Acta Neuropathol (Berl) 72: 43-54].

Posterior ischemic optic neuropathy following bilateral radical neck dissection

A patient is presented with posterior ischemic optic neuropathy (PION) after bilateral radical neck dissection, probably caused by hemodynamic hypotension, combined with other factors. A postmortem histologic study of the optic nerve was performed to analyze the pathogenic mechanism of blindness. To prevent this complication, one should favor a two-stage procedure, avoiding drug-induced hypotension, overtransfusion, and anemia. During the postoperative period, visual acuity should be monitored regularly, and proper positioning of the patient's head is necessary.

[Reversible changes in brain volume in anorexia nervosa]

Cranial computed tomography (CT) was performed in three different samples of young women with anorexia nervosa before and after treatment. The biggest changes in cerebrospinal fluid volume were observed in the supratentorial and extracerebral-subarachnoid area, with smaller changes in the ventricles. These changes, as assessed by different methods of volumetric and planimetric measurement, were statistically significant and were correlated with the changes in body weight. Two patient groups could be distinguished on the basis of the presence or absence of cerebellar pseudoatrophy in the initial CT, and these groups also showed differences in preclinical and clinical course.

[School refusal--a catamnestic study on the diagnostic concept ov "school phobia" and "school anxiety"]

Twenty-six patients diagnosed with school refusal were examined 2.4 years after inpatient treatment. The long-term course of patients with "school phobia" (school refusal unrelated to school) and that of patients with "school anxiety" (school refusal related to school) were compared. In addition, an attempt was made to identify variables predictive of a good outcome. The mean age of the 12 patients with "school phobia" and the 14 patients with "school anxiety" was 12.7 years at the start of inpatient treatment. The assessment of psychiatric disturbances was based on structured interviews for parents and adolescents (MEI and MADEL, 1989) and the dimensional assessment scales of functioning for children and adolescents (MSBF). The variables assessed for predictive value were taken from the patients' records during inpatient treatment and from the hospital documentation system. There was no difference in outcome between the two syndrome groups. There was a tendency to less autonomy in the patients with "school phobia". Girls had a better outcome than boys, as did patients with less absence from school prior to inpatient treatment. Overall there was no difference in the outcome of "school phobia" and "school anxiety". Therefore a new classification should be considered.

Devic's neuromyelitis optica and Schilder's myelinoclastic diffuse sclerosis

An adult patient developed both Devic's neuromyelitis optica and Schilder's myelinoclastic diffuse sclerosis, suggesting that these entities represent rare topographical and aggressive variants within the spectrum of multiple sclerosis.

Morphological spectrum, distribution and clinical correlation of white matter lesions in AIDS brains

This paper analyses the histopathological characteristics and the topographical distribution of 'pure' HIV-associated white matter lesions of the brain in 18 AIDS patients at autopsy; it includes a time-controlled correlation of neuropathology to clinical staging of the AIDS dementia complex. Three distinct lesion types can be delineated: 1 Vacuolar myelin damage (n = 15) in the hemispheric and interhemispheric white matter, in projection fibre tracts, and in intracerebral segments of cranial nerves III, VII, and VIII; 2 Angiocentric foci (n = 14), disseminated randomly in the white matter; 3 HIV leukoencephalopathy (n = 14), as previously defined, seen predominantly in the hemispheric white matter. As a sole lesion type, HIV leukoencephalopathy is found in two cases, while vacuolar myelin damage and angiocentric foci always occur in combination with one or both other types of pathology. Patients with advanced AIDS-dementia complex consistently show severe and combined white matter pathologies at autopsy. We conclude that, in addition to the previously defined features of diffuse HIV leukoencephalopathy, vacuolar myelin damage and angiocentric foci are significant and frequent components of white matter pathology in AIDS autopsies. This reflects the multitude of pathogenetic factors which co-operate in damaging the brain in AIDS. The advanced AIDS dementia complex correlates with the combined and severe white matter lesions.

Subacute diencephalic angioencephalopathy: an entity similar to angiodysgenetic necrotizing encephalopathy and Foix-Alajouanine disease

A previously healthy 58-year-old man developed neurological illness with progressive dementia, hallucinations, central motor and vegetative impairment which led to death in 14 weeks. Autopsy revealed lesions in a symmetrical centrencephalic distribution. Inner cerebral veins and arteries were surrounded by extravasation of plasma and perivascular haemorrhage and were thickened by fibrous scarring and muscle fibre proliferation. Necrotized blood vessels were also found. The parenchyma was damaged by incomplete to complete necrosis. The age and sex of the patient, the progressive clinical course, the increase of cerebrospinal fluid protein, and the histopathology of the lesion show some similarities to angiodysgenetic necrotizing encephalopathy and spinal Foix-Alajouanine disease.

Presence, distribution and spread of productive varicella zoster virus infection in nervous tissues

Nervous tissue lesions were retrospectively studied for detection of productive varicella zoster virus (VZV) infection in 33 autopsied cases, including 19 herpes zoster (HZ) (10 trigeminal, nine spinal) and 14 cases of nodular brainstem encephalitis without HZ. Immunocytochemistry for VZV antigens and in situ hybridization with a biotinylated VZV DNA probe were used on formol-fixed paraffin sections. Peripheral and central nervous system, skin and striated muscle were investigated in serial sections; available tissue blocks, however, varied between cases. Varicella zoster virus production (both antigen and DNA) in nervous tissue was found in HZ cases but only of short survival after a rash of up to 7 wks (eight out of 12 patients). Varicella zoster virus was visualized in nerve cells, glial cells, Schwann cells and blood vessels. In the central nervous system (CNS), VZV was detected in trigeminal nuclei (one out of 10 brains) or disseminated nodular brainstem lesions (one out of 10 brains), in subependymal microvessels (one out of 10 brains) or vasculitic arteries (two out of 19 brains or spinal cords). In the peripheral nervous system (PNS), VZV (DNA and antigen) was found in neurons and satellite cells of sensory ganglia (four out of seven cases with sampling of ganglia), and in damaged nerve fibres including a muscle nerve in one case; myositis with VZV in affected muscle fibres was found in the latter case. In nodular brainstem encephalitis, one case contained VZV within nodular lesions. We conclude that (i) VZV neural spread is suggested by detectable virus in ganglia, nerve fibres and CNS target nuclei; (ii) haematogenous spread of VZV is suggested by detection of virus in CNS microvessels and in disseminated brainstem encephalitis; (iii) VZV myositis may occur in zosteric myotomes; and (iv) VZV is a possible agent in nodular brainstem encephalitis.

SPECT and MR imaging in herpes simplex encephalitis

Two cases of necrotizing herpes simplex encephalitis (HSE) were investigated with 99mTc-hexamethylpropyleneamineoxime (HMPAO) SPECT and MR. The clinical course was compared with the neuroimaging results. In the acute stage, the increased HMPAO uptake matched the MR hyperintense signal in the limbic temporal lobe and in the basal ganglia. Protracted inflammation was accompanied by persistently high HMPAO uptake. The sequelae of HSE were characterized by decreased HMPAO uptake and postnecrotic widening of the temporal horns. The "limbic" pattern recognized in both SPECT and MR reflects the basic pathophysiology and neuropathology of HSE. Both methods may be useful in the diagnosis and follow-up of HSE.

Atypical vertebral artery in a patient with an intra-and extraspinal cervical neurenteric cyst

A 15 year old girl experienced Horner's syndrome on the right side, paraesthesia of the right arm and meningitis. CT and MRI showed a cystic lesion on the right side of the cervical spine at C3/C4 which descended with an extraspinal portion down to C6. Histology revealed a complex neurenteric cyst. The ipsilateral vertebral artery showed an atypical course. This abnormal artery besides a partial fusion of the vertebrae C2/C3/C4 suggest a complex malformation at the site of the cyst. Disturbed developmental relationships in this case indicate that pathological blood vessels may represent a risk factor in the surgical treatment of neurenteric cysts.

Misinterpretation of neuroradiological appearances of an epidermoid cyst

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Multifocal vacuolar leucoencephalopathy: a distinct HIV-associated lesion of the brain

A 20-year-old male AIDS patient developed rapidly progressive dementia for more than 3 months prior to death. Autopsy showed, in addition to adrenal cytomegalovirus (CMV) infection and focal cerebral necrosis due to toxoplasmosis, multifocal subcortical white matter lesions of the brain which were strikingly similar to the histopathology of vacuolar myelopathy in AIDS. These distinct lesions contained macrophages which were rarely multinucleated and expressed HIV antigens by immunocytochemistry. The distribution of lesions mimics extrapontine myelinolysis and progressive multifocal leucoencephalopathy (PML); PML was excluded by the absence of papovaviruses by immunocytochemistry and by in situ DNA hybridization. Tissue damage in multifocal vacuolar leucoencephalopathy is different from hitherto characterized HIV-specific neuropathology such as HIV encephalitis and HIV leucoencephalopathy, and should be included in the list of conditions with damage of the brain white matter in AIDS.

Progressive multifocal leukoencephalopathy (PML) in AIDS and in the pre-AIDS era. A neuropathological comparison using immunocytochemistry and in situ DNA hybridization for virus detection

Twenty-five brains with definite, and three brains with possible, progressive multifocal leukoencephalopathy (PML), including six brains of AIDS patients, were studied with special regard to the detection of papovaviruses. Formalin-fixed serial paraffin sections were immunostained with monospecific anti-JC virus (JCV) and genus-specific anti-simian virus (SV) 40 antisera, and hybridized in situ with DNA probes for JCV and SV 40, respectively. Immunocytochemistry (ICC) and in situ hybridization (ISH) were similarly sensitive in detecting virus in classical PML lesions. In all but one definite PML cases at least one method detected virus (96%). Possible PML tissue was never labeled. Labeling patterns were generally similar in ICC and ISH: mainly oligodendroglia and, less frequently, astroglia harbored virus, whereas labeling of neurons and endothelia was absent. Bizarre giant astrocytes were occasionally labeled by ICC and ISH. Burnt-out lesions harbored JCV DNA but not virus antigens. SV 40 DNA was never detectable. PML morphology in AIDS cases did not usually differ from the disease process seen in the pre-AIDS era. However, two AIDS brains presented extremely extended and, in one case, unusually necrotizing PML damage; in the latter case, PML lesions contained large amounts not only of JCV, but also of human immunodeficiency virus (HIV) antigens. We conclude that ICC and ISH are methods of comparable sensitivity for detection of papovavirus in fluorishing PML lesions. In burnt-out PML lesions only ISH may detect virus. The possibility of an exceptional non-JCV (e.g., SV 40) etiology of PML could be neither confirmed nor disproved. In AIDS, massive coinfection by HIV of PML lesions may increase damage to tissue, resulting in unusually extended and necrotizing PML.