«

»

KREST INTERNATIONAL WEBINARS. IMAGING IN NEURO – INFLAMMATION Dr Joga Rao C , FRANZCR,MD,DNB,PHD



Neuroinflammation and Blood Brain Barrier:
Neuroinflammation plays a crucial role in the multiple neurological disorders. Multiple sclerosis, HIV, connective tissue disorders, illicit drugs, malignant CNS neoplasms, Stroke, dementic illnesses and traumatic brain injury were all known to induce neuroinflammation contributing to the neural injury.

I will cover the Imaging characteristics of few select conditions for the first 30 mts and then discuss the imaging methods to identify the neuroinflammation

Pathogenesis:

The resident immune cells in the brain, microglia play a key role in the brain surveillance and homeostasis. Whilst these cells play a neuroprotective role in physiological conditions, sustained neural injury appears to evoke a large repertoire of local and distant responses leading to an inflammatory cascade with production and release of inflammatory cytokines and resultant proinflammatory response leading to oxidative injury and neuronal death. Thus, the protector response of the neural injury depending on the inducing pathological mechanism, contribute to the disease process itself

A singularly defining response of nervous system to this neuroinflammation is increased permeability of blood brain barrier. Blood brain barrier comprises of a barrier of endothelium of brain microvasculature endothelial cells (BMECs) and underlying the BMECS is the basal lamina in apposition with multiple neural cell types, the chief of which are Astrocytes, Pericytes that maintain the integrity the BBB. A more recent evidence points to an alternative convection system: Glymphatic system, which is a macroscopic system of convective fluid fluxes with rapid interchange of CSF and interstitial fluid facilitated by influx of CSF along the periarterial space

Multiple Sclerosis:

Multiple sclerosis (MS) is a chronic inflammatory disease, an autoimmune-mediated disorder that affects the central nervous system (CNS) that can lead to severe physical or cognitive disability as well as neurological defects. Multifocal zones of inflammation due to focal T-lymphocytic and macrophage infiltrations, and oligodendrocyte death are the primary causes of myelin sheath destruction that result in the formation of plaques composed of inflammatory cells in both white and gray matter.

Three areas of interest in MS: Tumefactive Demyelination, Active MS and Variants of MS.

Autoimmune encephalitis:

Autoimmune encephalitis is immune-mediated disease involving the central nervous system that characteristically demonstrate neurocognitive impairment, altered mental status and seizures. This antibody-mediated attack on neuronal structures results in a localized inflammatory response. Depending on the antibody response to the antigenic trigger, they are subdivided into three classes.

Para neoplastic that attack the intracellular neuronal antigens and Cytotoxic (Anti Hu), whilst Non-neoplastic are those which attack the cell surface antigens and often humoral or B cell dependent and more malleable to treatment (N-methyl D-aspartate receptor (NMDAr) encephalitis) and mixed variants.

While limbic dysfunction is the single most consistent finding in autoimmune encephalitis, varying degrees of involvement are seen within the neocortex, striatum, hindbrain, spine, and peripheral nervous system based on the unique antibody profile.

Points of discussion: Characteristic imaging findings in Limbic encephalitis and examples

Stroke and Stroke mimics:

Neuroinflammation as a result of stroke and tumours is well established.

For want of time we will discuss just two clinical scenarios

PRESS/ RCVS: The increased vascular permeability is the underlying causal principle and discuss imaging characteristics.

If time permits I will present one multiparametric MRI of the tumour addressing the role of APT imaging

Neuroinfections and inflammation:

Neuroinflammation associated with infections is often not a well-considered entity. Whilst the cerebral abscesses and encephalitis are often have characteristic features, many mimics can masquerade these rather common presentations and we will try to address them

Imaging Points of discussion: Cerebral abscess what to look for. How to differentiate the Opportunistic infections in HIV disease and understanding the Immune mediated reactivation.

Alzheimer’s Disease and Neurodegenerative disorders:

The inflammation induced by intracellular neurofibrillary tangles and extracellular amyloid-beta (Aβ) plaques in Alzheimer’s disease leads to volume loss in the select areas of the brain and I will briefly discuss the nuances of this volume loss and MRS and ASL role.

Imaging the Neuroinflammation:

MRS: High Choline and Myoinositol and glutamatergic (Excitotoxic Injury)

BBB: Dynamic contrast enhanced Perfusion imaging derived metric: Ktrans.

ASL: Perfusion imaging to show altered blood flow.

Joga Rao Chaganti