Neuronal loss, demyelination and volume change in the multiple sclerosis neocortex.

AIMS: Indices of brain volume [grey matter, white matter (WM), lesions] are being used as outcomes in clinical trials of patients with multiple sclerosis (MS). We investigated the relationship between cortical volume, the number of neocortical neurons estimated using stereology and demyelination. METHODS: Nine MS and seven control hemispheres were dissected into coronal slices. On sections stained for Giemsa, the cortex was outlined and optical disectors applied using systematic uniform random sampling. Neurons were counted using an oil immersion objective (× 60) following stereological principles. Grey and WM demyelination was outlined on myelin basic protein immunostained sections, and expressed as percentages of cortex and WM respectively. RESULTS: In MS, the mean number of neurons was 14.9 ± 1.9 billion vs. 24.4 ± 2.4 billion in controls (P < 0.011), a 39% difference. The density of neurons was smaller by 28% (P < 0.001) and cortical volume by 26% (P = 0.1). Strong association was detected between number of neurons and cortical volume (P < 0.0001). Demyelination affected 40 ± 13% of the MS neocortex and 9 ± 12% of the WM, however, neither correlated with neuronal loss. Only weak association was detected between number of neurons and WM volume. CONCLUSION: Neocortical neuronal loss in MS is massive and strongly predicted by cortical volume. Cortical volume decline detected in vivo may be similarly indicative of neuronal loss. Lack of association between neuronal density and demyelination suggests these features are partially independent, at least in chronic MS.

Neuronal and glial cerebrospinal fluid protein biomarkers are elevated after West Nile virus infection.

Neurotrophic West Nile virus (WNV) disease is a severe arbovirus infection in which neuronal loss is the likely anatomical substrate for the high morbidity and mortality. We investigated whether cerebrospinal fluid (CSF) protein biomarkers were elevated in vivo and related to disease severity in patients with WNV infection. This exploratory study included 114 patients (24 acute WNV, 77 noninflammatory controls, six peripheral neuropathies, seven aseptic meningoencephalitis). CSF levels of neuronal (neurofilaments, NfH-SMI35) and glial (glial fibrillary acidic protein, GFAP, S100B) biomarkers were measured by enzyme-linked immunosorbent assay (ELISA). Immunocytochemistry was performed in two fatal WNV cases. A significant proportion of patients with WNV had pathological CSF levels for NfH-SMI35 (58%, median concentration 1.01 ng/mL), GFAP (58%, 10 pg/mL), and S100B (90%, 1.29 ng/mL). The results were consistent with postmortem evidence for neuronal death and astrogliosis. Surprisingly, CSF protein biomarker levels were also found to be pathological in a considerable proportion of patients who presented with WNV fever only (100% for GFAP and S100B and 43% for NfH-SMI35). Elevated CSF protein biomarker levels are suggestive of neuronal death and glial pathology in human WNV infection. The results indicate the presence of neuroinvasive disease across the spectrum of WNV disease, including WNV fever.

Neurotrophin-3 administration alters neurotrophin, neurotrophin receptor and nestin mRNA expression in rat dorsal root ganglia following axotomy.

In the months following transection of adult rat peripheral nerve some sensory neurons undergo apoptosis. Two weeks after sciatic nerve transection some neurons in the L4 and L5 dorsal root ganglia begin to show immunoreactivity for nestin, a filament protein expressed by neuronal precursors and immature neurons, which is stimulated by neurotrophin-3 (NT-3) administration. The aim of this study was to examine whether NT-3 administration could be compensating for decreased production of neurotrophins or their receptors after axotomy, and to determine the effect on nestin synthesis. The levels of mRNA in the ipsilateral and contralateral L4 and L5 dorsal root ganglia were analyzed using real-time polymerase chain reaction, 1 day, 1, 2 and 4 weeks after unilateral sciatic nerve transection and NT-3 or vehicle administration via s.c. micro-osmotic pumps. In situ hybridization was used to identify which cells and neurons expressed mRNAs of interest, and the expression of full-length trkC and p75NTR protein was investigated using immunohistochemistry. Systemic NT-3 treatment increased the expression of brain-derived neurotrophic factor, nestin, trkA, trkB and trkC mRNA in ipsilateral ganglia compared with vehicle-treated animals. Some satellite cells surrounding neurons expressed trkA and trkC mRNA and trkC immunoreactivity. NT-3 administration did not affect neurotrophin mRNA levels in the contralateral ganglia, but decreased the expression of trkA mRNA and increased the expression of trkB mRNA and p75NTR mRNA and protein. These data suggest that systemically administered NT-3 may counteract the decrease, or even increase, neurotrophin responsiveness in both ipsi- and contralateral ganglia after nerve injury.

Brain biopsy in dementia.

Brain biopsy has an uncertain role in the diagnosis of dementia. Here we report a retrospective analysis of 90 consecutive cerebral biopsies undertaken for the investigation of dementia in adults at a tertiary referral centre between 1989 and 2003. In most cases (90%), biopsy consisted of a right frontal full thickness resection of cortex, white matter and overlying leptomeninges. Fifty-seven per cent of biopsies were diagnostic: the most frequent diagnoses were Alzheimer's disease (18%), Creutzfeldt-Jakob disease (12%) and inflammatory disorders (9%). Other diagnoses in individual patients included Pick's disease, corticobasal degeneration and other tauopathies, Lewy body dementia, multiple sclerosis, Whipple's disease, progressive multifocal leucoencephalopathy, cerebral autosomal dominant arteriopathy with subcortical ischaemic leucoencephalopathy, vasculopathies and paraneoplastic encephalopathy. The most frequent biopsy finding in the non-diagnostic group and for the series as a whole (37%) was non-specific gliosis variably affecting both cortex and white matter. Complications (11%) included seizures, intracranial and wound infections, and intracranial haemorrhage; there were no deaths or lasting neurological sequelae attributable to the procedure. No trends in diagnostic yield or complication rate over the course of the series were identified. Information obtained at biopsy determined treatment in 11%. A raised cerebrospinal fluid cell count was the only robust predictor of a potentially treatable (inflammatory) process at biopsy. The constellation of behavioural change, raised CSF protein and matched oligoclonal bands in CSF and serum was associated with non-specific gliosis at biopsy. This series underlines the value of cerebral biopsy in the diagnosis of dementia, and suggests that certain clinical and laboratory features may be useful in guiding the decision to proceed to brain biopsy where a treatable disease cannot be excluded by other means.

Detection of HIV proviral DNA in cortex and white matter of AIDS brains by non-isotopic polymerase chain reaction: correlation with diffuse poliodystrophy.

OBJECTIVE: (1) To determine whether detection of HIV proviral DNA sequences in the cerebral cortex correlates with the presence of pathological changes in this region, believed to contribute to the HIV-associated cognitive/motor complex. (2) To compare the frequency with which HIV infects cortical and subcortical regions of the brain. DESIGN: In vitro studies on HIV neurotoxicity suggest that HIV may be involved in the pathogenesis of cortical damage, recently defined as diffuse poliodystrophy (DPD) in AIDS. Previous detection of HIV antigen has localized HIV more frequently to subcortical than to cortical regions. It is not known whether HIV preferentially infects subcortical tissues or if viral expression varies in these two regions. METHODS: HIV antigen and proviral DNA sequences were detected in anterior frontal lobe tissues using immunohistochemistry (IHC) and the polymerase chain reaction (PCR), respectively. DPD was assessed by staining with antibodies against astrocytes (GFAP) and microglia/macrophages (HAM 56). RESULTS: HIV proviral DNA was detected in nine out of 15 cortical samples and in 10 out of 15 white matter samples, whilst HIV p24 antigen was localized to the cortex in three out of 15 and to the white matter in seven out of 15 cases. DPD was found in 10 cases, although in five a different aetiology may have been involved. However, DPD was present in eight out of the nine cases in which HIV proviral DNA was detected in the cortex. CONCLUSIONS: Using a non-isotopic PCR method, HIV was detected in the brains of more cases than would be expected on the basis of IHC detection, and was present in the cortex as frequently as in the white matter. HIV, together with other factors, may contribute to the pathogenesis of DPD.

HIV-associated brain pathology in the United Kingdom: an epidemiological study.

OBJECTIVES: To examine the epidemiology of HIV-associated neuropathology in the United Kingdom and to investigate whether the prevalence of different forms of HIV-associated brain pathology varies with exposure category. DESIGN: The study was a cross-sectional survey; data was analysed from the Medical Research Council National AIDS Neuropathology database. SETTING: Information was gathered from throughout England, Scotland and Wales. SUBJECTS: Individuals who died from AIDS in the United Kingdom and had a postmortem examination. The database comprised 7% of all AIDS deaths in the United Kingdom between 1982 and 1993. MAIN OUTCOME: Neuropathological diagnoses based on internationally accepted neuropathological terminology of AIDS-related brain lesions. RESULTS: HIV encephalitis was the most prevalent pathological diagnosis, occurring in 25.3% [95% confidence interval (CI), 21.0-29.6] of the study sample. Statistically significant independent associations for the occurrence of HIV encephalitis were found for injecting drug use (odds ratio, 6.86; 95% CI, 2.91-16.17), and age less than 30 years at death (odds ratio, 3.58; 95% CI, 1.99-6.44). Vascular lesions were significantly higher among blood product recipients, 95% of whom were haemophiliacs. CONCLUSIONS: This was the first epidemiological investigation of HIV-associated brain pathology in the United Kingdom. HIV encephalitis appeared to occur more frequently in injecting drug users and those who died younger. Whereas the findings must be interpreted cautiously, one hypothesis was that differences in the route of transmission may have affected the manifestation of HIV-associated brain damage.

Granular cell tumor of the fifth cranial nerve: further evidence for Schwann cell origin.

Granular cell tumors arising from the cranial nerves are rare. We describe a granular cell neoplasm of the fifth cranial nerve in a 66-year-old male. Light microscopic appearances included rows and clusters of cells with small peripheral nuclei and abundant eosinophilic cytoplasm. Ultrastructurally the cytoplasm of these cells contained numerous dense bodies, multivesicular bodies and vacuoles. In some areas tumor cells were intermingled with myelinated and unmyelinated nerve fibers showing the same relationships as do Schwann cells and nerve fibers. The association between tumor cells and axon seen in this case lends further support to the putative Schwann cell origin of this neoplasm.

Immunohistochemical changes and PCR detection of HIV provirus DNA in brains of asymptomatic HIV-positive patients.

The stage of HIV infection at which the virus enters the nervous system remains poorly understood. Examination of brains of HIV-positive non-AIDS patients often shows lymphocytic meningitis, myelin pallor and gliosis, but no immunohistochemical (IHC) evidence of the virus. In this study we have examined a number of brains from HIV-positive patients with (23) and without (8) AIDS as well as brains from 5 HIV-negative controls by morphological, morphometric, IHC and polymerase chain reaction (PCR) methods in an attempt to establish at what stage of the infection HIV can be detected in the brain and to correlate its presence with the pathological changes in the cortex. HIV-1 proviral DNA was found by PCR in the cortex of the majority of AIDS and in 2 out of 8 non-AIDS cases. Astroglial reaction was observed in the cortex of the majority of AIDS brains but not in most of the non-AIDS brains which showed, in addition, a dramatic reduction of glial fibrillary acidic protein staining around blood vessels; moreover, in this group the density of microglial cells was higher than in the AIDS group. These results show that: 1) HIV proviral DNA can be found in the brains of HIV-positive non-AIDS patients; 2) in the same group there is an increase in density of microglial cells which 3) appears to be transient, since AIDS brains without neuropathology show a lower density of these cells. They also suggest that the status of 'immune reaction' existing in AIDS may predate this period.(ABSTRACT TRUNCATED AT 250 WORDS)

Early entry and widespread cellular involvement of HIV-1 DNA in brains of HIV-1 positive asymptomatic individuals.

There is overwhelming evidence that invasion of the central nervous system (CNS) by HIV-1 takes place at an early stage of the infection. It has been demonstrated that HIV-1 DNA is present in brains of asymptomatic individuals. Evidence of immune activation and increased expression of cytokines suggested that neuropathological changes and neuronal and axonal damage could be the effect of the presence of the virus. The purpose of the study is to ascertain whether target cells for HIV-1 in brain of patients at early stage of the infection are the same as those found in AIDS sufferers or if the distribution seen in AIDS patients results from the late spreading of the infection from cells considered traditionally the reservoir of the virus, i.e. microglial cells. Eighteen brains, all HIV-1 DNA positive, as shown by nested polymerase chain reaction (PCR), were selected among the group of HIV-1 positive asymptomatic cases. In 6 of them, HIV-1 DNA was detected by PCR in situ. Positive cells included astrocytes and endothelial cells, in addition to microglial cells. We conclude that astrocytes and endothelial cells are already infected at an early (asymptomatic) stage of the infection and suggest that they might contribute to the damage of the CNS.

Axonal damage revealed by accumulation of beta-APP in HIV-positive individuals without AIDS.

The presence of neuropsychological disturbances in HIV-positive, pre-symptomatic individuals is a controversial issue. Neuroimaging studies have not shown brain atrophy or hyperintensity in the white matter, whereas proton magnetic resonance spectroscopy has revealed some abnormality of cerebral biochemistry. Using an antibody to beta-amyloid precursor protein (beta-APP), we previously demonstrated frequent and widespread axonal changes in the brains of AIDS patients. In this study, we extended the use of beta-APP to asymptomatic patients in order to establish a possible morphological correlation with neuropsychological disorders. Brain samples from 29 patients were examined. Results showed bundles of beta-APP-positive axons in 8/29 cases (27%). The changes, seen in both superficial and deep white matter, were either focal or diffuse, could not be visualized by silver or ubiquitin stains, and did not coexist with any change in distribution or morphology of astrocytes and microglial cells. We conclude that in HIV-positive asymptomatic individuals, axonal changes: (a) may be related to the state of immune activation with consequent presence of toxic substances, including cytokines, observed in these patients; (b) may represent mild changes that could undergo repair, unless other pathological events, such as the supervening of the AIDS stage and the specific encephalitis, make them permanent.

Trypanosomiasis.

African (sleeping sickness) and American (Chagas' disease) trypanosomiasis, caused by protozoa of the family Trypanosomatidae, are diseases that are endemic in parts of Africa and Latin America, respectively. Physicians in developed countries may occasionally see cases because of extensive travel and immigration from endemic countries. Although neurological involvement is common in both, its incidence and clinical presentation differ considerably. African trypanosomiasis, caused by subspecies of Trypanosoma brucei (T b rhodesiense, T b gambiense), is transmitted by the tsetse fly and causes meningoencephalitis, in which somnolence is a prominent feature. Parasites may reach the brain parenchyma through the choroid plexus or the Virchow Robin spaces. American trypanosomiasis, caused by Trypanosoma cruzi is transmitted by reduviid bugs. While lesions in the central nervous system are not prominent, except in the reactivated forms which occur in immunodeficient patients, the peripheral nerve, mainly the autonomic nervous system, is frequently involved, leading to the cardiomegaly and the digestive megaviscera. Congenital infections may also occur. In this paper we give an account of the epidemiology, clinical presentation and pathological features of these two protozoal infections based on human and experimental studies of both the central and peripheral nervous system.

The neuropathology of paraneoplastic syndromes.

The term "paraneoplastic neurological syndromes" encompasses a number of uncommon disorders associated with systemic malignancies. In order to be classified a paraneoplastic neurological syndrome, the malignancies must not invade, compress, or metastasize to the nervous system. They can either focally or diffusely involve the central and peripheral nervous system or the neuromuscular junction. This paper reviews the neuropathology of the syndrome. It will first describe the clinical presentation and give an account of the systemic tumors most commonly associated with the various types of disorders. Then it will review the general pathological features that consist of an inflammatory process predominantly affecting the gray matter. Finally, it will describe in detail the main clinico-pathological types, including 1) encephalomyelitis, 2) cortical cerebellar degeneration, 3) peripheral neuropathy, 4) opsoclonus-myoclonus and 5) retinopathy. The Lambert-Eaton myasthenic syndrome will be dealt with separately in another paper in this symposium.

Neuropathology of early HIV-1 infection.

Early HIV-1 invasion of the central nervous system has been demonstrated by many cerebrospinal fluid studies; however, most HIV-1 carriers remain neurologically unimpaired during the so called "asymptomatic" period lasting from seroconversion to symptomatic AIDS. Therefore, neuropathological studies in the early pre-AIDS stages are very few, and the natural history of central nervous system changes in HIV-1 infection remains poorly understood. Examination of brains of asymptomatic HIV-1 positive individuals who died accidentally and of rare cases with acute fatal encephalopathy revealing HIV infection, and comparison with experimental simian immunodeficiency virus and feline immunodeficiency virus infections suggest that, invasion of the CNS by HIV-1 occurs at the time of primary infection and induces an immunological process in the central nervous system. This includes an inflammatory T-cell reaction with vasculitis and leptomeningitis, and immune activation of brain parenchyma with increased number of microglial cells, upregulation of major histocompatibility complex class II antigens and local production of cytokines. Myelin pallor and gliosis of the white matter are usually found and are likely to be the consequence of opening of the blood brain barrier due to vasculitis; direct damage to oligodendrocytes by cytokines may also interfere. These white matter changes may explain, at least partly, the early cerebral atrophy observed, by magnetic resonance imaging, in asymptomatic HIV-1 carriers. In contrast, cortical damage seems to be a late event in the course of HIV-1 infection. There is no significant neuronal loss at the early stages of the disease, no accompanying increase in glial fibrillary acid protein staining in the cortex, and only exceptional neuronal apoptosis. Although HIV-1 proviral DNA may be demonstrated in a number of brains, viral replication remains very low during the asymptomatic stage of HIV-1 infection. This makes it likely that, although opening of the blood brain barrier may facilitate viral entry into the brain, specific immune responses including both neutralising antibodies and cytotoxic T-lymphocytes, continuously inhibits viral replication at that stage.

Fulminating multiple sclerosis-like leukoencephalopathy revealing human immunodeficiency virus infection.

A 66-year-old French homosexual man and a 42-year-old Brazilian man with no known risk factors for HIV infection developed headaches, asthenia, and neurologic episodes of abrupt onset. CT showed multiple hypodense, nonenhancing lesions. Serology for HIV was positive. They died respectively 2 months and 1 month after onset of the illnesses. Autopsy in both cases showed multiple, well-demarcated, demyelinating foci in the white matter of the cerebral hemispheres, brainstem, and cerebellum with histologic features characteristic of recent plaques of multiple sclerosis. There were no multinucleated giant cells or microglial nodules. Immunostaining for HIV was negative. Although a random coincidence of MS and HIV infection cannot be ruled out, the close temporal relationship between the 2 disorders suggests a possible etiologic association.

Nigral degeneration in neuroacanthocytosis.

We counted nerve cells in different subregions of the substantia nigra in three patients with neuroacanthocytosis and compared the results with those of age-matched Parkinson's disease and control patients. Two patients with neuroacanthocytosis and clinical parkinsonism in life had a reduced neuronal density in the substantia nigra, while in a third patient without parkinsonism, this number was at the lower limit of the control range. In neuroacanthocytosis with parkinsonism and in Parkinson's disease, the ventrolateral region of the substantia nigra was most severely affected, although in neuroacanthocytosis cases, nigral neuronal loss was more widespread.

Cortical dysplasia with angiodysgenesis and chronic inflammation in multifocal partial epilepsy.

A 25-year-old man with a long history of temporal lobe epilepsy developed right occipital lobe seizures and a progressive right homonymous hemianopia. MRI showed diffuse enhancement of the left temporoparieto-occipital white matter and cortical thickening of the left medial temporal lobe. The resected temporal lobe revealed cortical dysplasia and angiodysplasia with foci of more recent ischemic necrosis and chronic inflammation as an explanation for the clinical deterioration.

Bilateral isolated hippocampal malformation in temporal lobe epilepsy.

Hippocampal malformations in patients with epilepsy usually are reported in the context of widespread cortical malformations. Isolated hippocampal malformations are more rarely identified in MRI studies with little documentation of their pathologic appearance. Postmortem examination revealed abnormal position and complex convolutional malformations isolated to the hippocampal formation in an adult with temporal lobe epilepsy in whom MRI demonstrated bilateral hippocampal abnormalities.

Chronic encephalitis and epilepsy in adults and adolescents: a variant of Rasmussen's syndrome?

Chronic encephalitis and epilepsy (Rasmussen's encephalitis) is a rare progressive disorder of uncertain etiology that usually occurs in children, producing focal epilepsy, hemiparesis, and intellectual deterioration. We identified 13 patients in whom seizures developed in adolescence or adulthood with a pathologic picture of chronic encephalitis. The clinical characteristics were more variable than those occurring in children, with the patients falling into three groups: five patients developed seizures in adulthood, but otherwise showed many resemblances to the childhood form; five developed seizures in adolescence, with similar presentation but rather more benign course than in the younger patients; and three presented with clinical features initially suggestive of a tumor. Occipital onset to the seizures appeared to be more common than in the childhood form, and bilateral disease also occurred.

The development of the gracile nucleus in the rat: the time of ingrowth of ascending primary sensory fibres and effect of early deafferentation.

An investigation was carried out of the time of ingrowth of primary sensory fibres in the medulla and of their penetration into the gracile nucleus, and of the effect of an early loss of these fibres upon the development of the nucleus in rats. After injection of the conjugate horseradish peroxidase-wheat germ agglutinin in the hind limbs of fetuses, a bundle of labelled fibres was seen in close proximity of the gracile nucleus at embryonic day 17. However, fibres did not appear to leave the bundle until embryonic day 19, when they were seen to project ventrally and penetrate the nucleus which, on embryonic day 20 and thereafter, contained an increasing number of labelled fibres. Synaptic contacts within the gracile nucleus were found at all stages of the observation; the presynaptic processes consisted of an electron-lucent matrix which contained round vesicles. Although no mature glomeruli were observed, an occasional terminal appeared to be presynaptic to more than one process. After transection of the primary sensory afferents at embryonic day 18 and 19, no degeneration was seen within the gracile nucleus; degenerated boutons were occasionally seen after deafferentation at embryonic day 20 and became more numerous thereafter; nerve cells in various stages of degeneration could also be seen. Removal of primary afferents to the gracile nucleus at the time they reach the nucleus or soon after was followed by a severe loss of nerve cells and a reduced increment in size of the remaining ones. Moreover, the results of the present investigation show that penetration of primary sensory fibres into the gracile nucleus takes place approximately 2 days after they have been seen in the medulla and are in keeping with observations made in other pathways of the nervous system of the rat as well as in other animals. The findings that mature glomeruli, previously described in 1-day-old rats, are not present shortly before birth, suggest a fast rate of maturation of these synapses.

Orbital optic nerve glioma in adult life.

In seven cases, optic nerve glioma presented as an expanding orbital mass in previously asymptomatic adults. Clinically and histologically, these tumors were similar to the orbital optic nerve gliomas of childhood; in contrast to the rapidly progressive malignant gliomas of the chiasm well described in adults, the patients with these tumors had a more benign clinical course. Management of optic nerve glioma in adulthood should be conservative in the presence of useful vision.