Unveiling autonomic failure in synucleinopathies: Significance in diagnosis and treatment

Autonomic failure is frequently encountered in synucleinopathies such as multiple system atrophy (MSA), Parkinson's disease (PD), Lewy body disease, and pure autonomic failure (PAF). Cardiovascular autonomic failure affects quality of life and can be life threatening due to the risk of falls and the increased incidence of myocardial infarction, stroke, and heart failure. In PD and PAF, pathogenic involvement is mainly post-ganglionic, while in MSA, the involvement is mainly pre-ganglionic. Cardiovascular tests exploring the autonomic nervous system (ANS) are based on the analysis of continuous, non-invasive recordings of heart rate and digital blood pressure (BP). They assess facets of sympathetic and parasympathetic activities and provide indications on the integrity of the baroreflex arc. The tilt test is widely used in clinical practice. It can be combined with catecholamine level measurement and analysis of baroreflex activity and cardiac variability for a detailed analysis of cardiovascular damage. MIBG myocardial scintigraphy is the most sensitive test for early detection of autonomic dysfunction. It provides a useful measure of post-ganglionic sympathetic fiber integrity and function and is therefore an effective tool for distinguishing PD from other parkinsonian syndromes such as MSA. Autonomic cardiovascular investigations differentiate between certain parkinsonian syndromes that would otherwise be difficult to segregate, particularly in the early stages of the disease. Exploring autonomic failure by gathering information about residual sympathetic tone, low plasma norepinephrine levels, and supine hypertension can guide therapeutic management of orthostatic hypotension (OH).

Autoimmune limbic encephalopathy and anti-Hu antibodies in children without cancer

OBJECTIVE

The aim of this study was to describe the clinical presentation of children and adolescents with anti-Hu antibodies (Hu-Abs).

METHODS

This was a retrospective study of children and adolescents with Hu-Abs collected by the French Paraneoplastic Neurological Syndrome (PNS) Reference Center between January 1, 2000 and December 31, 2011.

RESULTS

The center identified 251 patients with Hu-Abs. Only 8 patients were younger than 18 years. All of the 243 adult patients had PNS. In contrast, of the 8 children, only 2 (25%, Fisher exact test p = 0.0003) had neuroblastoma and opsoclonus-myoclonus. The other 6 children (5 female and 1 male) presented with limbic encephalitis (progressive personality changes, memory loss, and seizure) and were free of cancer (mean follow-up time: 50 months; range: 34-72 months). Brain MRI scans were abnormal in 4 of the 6 patients, with left, right, or bitemporal T2/fluid-attenuated inversion recovery hyperintensity. Protein levels and cell counts in the CSF were normal in all patients, but numerous oligoclonal bands were observed in 4 patients. All 6 patients received antiepileptic drugs and immunotherapy, but management of epilepsy was difficult in all of them. Five of the children developed cognitive impairments.

CONCLUSION

In children, as in adults, Hu-Abs can be a marker of PNS. However, in contrast to adults, Hu-Abs in children are also associated with an aggressive form of autoimmune nonparaneoplastic limbic encephalitis. Future studies should be conducted to determine the incidence of this syndrome and whether earlier diagnosis and T-cell-directed immunotherapies may improve its prognosis.

Brain immunohistopathological study in a patient with anti-NMDAR encephalitis

BACKGROUND AND PURPOSE

Anti-N-methyl-D-asparate (NMDA) receptor encephalitis is thought to be antibody-mediated. To perform an immunohistopathological study of the inflammatory reaction in a brain biopsy performed before immunomodulatory treatments in a patient with anti-NMDA receptor encephalitis.

METHODS

An immunohistochemical study was performed using CD3, CD68, CD20, CD138 and CD1a antibodies.

RESULTS

Prominent B-cell cuffing was present around brain vessels accompanied by some plasma cells, while macrophages and T cells were scattered throughout the brain parenchyma.

CONCLUSION

These findings suggest that the B cells interact with the T cells and are involved in antibody secretion by the plasma cells.

Bone marrow CD34+/B220+ progenitors target the inflamed brain and display in vitro differentiation potential toward microglia

Recent evidence indicates that microglial cells may not derive from blood circulating mature monocytes as they express features of myeloid progenitors. Here, we observed that a subpopulation of microglial cells expressed CD34 and B220 antigens during brain development. We thus hypothesized that microglia, or a subset of microglial cells, originate from blood circulating CD34+/B220+ myeloid progenitors, which could target the brain under developmental or neuroinflammatory conditions. Using experimental allergic encephalomyelitis (EAE) as a model of chronic neuroinflammation, we found that a discrete population of CD34+/B220+ cells expands in both blood and brain of diseased animals. In EAE mice, intravenous transfer experiments showed that macrophage-colony stimulating factor (M-CSF) -expanded CD34+ myeloid progenitors target the inflamed central nervous system (CNS) while keeping their immature phenotype. Based on these results, we then assessed whether CD34+/B220+ cells display in vitro differentiation potential toward microglia. For this purpose, CD34+/B220+ cells were sorted from M-CSF-stimulated bone marrow (BM) cultures and exposed to a glial cell conditioned medium. Under these experimental conditions, CD34+/B220+ cells were able to differentiate into microglial-like cells showing the morphological and phenotypic features of native microglia. Overall, our data suggest that under developmental or neuroinflammatory conditions, a subpopulation of microglial cells derive from CNS-invading CD34+/B220+ myeloid progenitors.

Brain and bone damage in KARAP/DAP12 loss-of-function mice correlate with alterations in microglia and osteoclast lineages

Human polycystic lipomembraneous osteodysplasia with sclerosing leukoencephalopathy, also known as Nasu-Hakola disease, has been described to be associated with mutations affecting the immunoreceptor tyrosine-based activation motif-bearing KARAP/DAP12 immunoreceptor gene. Patients present bone fragilities and severe neurological alterations leading to presenile dementia. Here we investigated whether the absence of KARAP/DAP12-mediated signals in loss-of-function (KDelta75) mice also leads to bone and central nervous system pathological features. Histological analysis of adult KDelta75 mice brains revealed a diffuse hypomyelination predominating in anterior brain regions. As this was not accompanied by oligodendrocyte degeneration or microglial cell activation it suggests a developmental defect of myelin formation. Interestingly, in postnatal KDelta75 mice, we observed a dramatic reduction in microglial cell numbers similar to in vitro microglial cell differentiation impairment. Our results raise the intriguing possibility that defective microglial cell differentiation might be responsible for abnormal myelin development. Histomorphometry revealed that bone remodeling is also altered, because of a resorption defect, associated with a severe block of in vitro osteoclast differentiation. In addition, we show that, among monocytic lineages, KARAP/DAP12 specifically controls microglial and osteoclast differentiation. Our results confirm that KARAP/DAP12-mediated signals play an important role in the regulation of both brain and bone homeostasis. Yet, important differences exist between the symptoms observed in Nasu-Hakola patients and KDelta75 mice.