Pathologic Basis of Disease Neuropathology - 1

Major cells of the CNS Neurons Glial cells: -astrocytes -oligodendrocytes -ependymal cells -microglial cells

Supporting structures Meninges: arachnoid cells Choroid plexus Blood vessels: blood-brain barrier

Organization of the CNS and disease Not all cells in the CNS are ‘equal’: while some disease processes affect some groups of cells more than others (‘selective vulnerability’), other disease processes could affect other areas more. Not all areas in the brain are equal: most areas in the brain have specific functions: a same disease process in two different areas of the brain, often give different symptoms. Some disease processes are the same in the brain as elsewhere in the body, while others are unique to the brain (eg demyelinative disease, neurodegenerations)

NEURON Maturity: G0 phase Great metabolic activity requiring a continuous supply of O 2 and glucose

Neuron cell death Phagocytosis by macrophages: acute neuronal death, viral infections Apoptosis ‘simple atrophy’: loss of cell volume and ultimately cell death due to metabolic derangement (often in neurodegeneration).

Protection of neurons from the bad outside world Blood brain barrier: capillaries with endothelial cells with tight junctions (only active transport possible), astrocytic footplates Brain CSF barrier: ependymal cells with tight junctions, and astrocytic footplates.

WHY BBB & BCB Controlled external milieu of neurons – needed for excitability of neurons Protection against infections Protection against autoimmune responses Protection against cerebral oedema (skull is a closed box-no volume increase possible)

CEREBRAL EDEMA Abnormal accumulation of fluids with increase in cerebral tissue volume Normal Edema Grey matter 800mg/g 820mg/g White matter 680mg/g 760mg/g

Topography of edema Localized edema Generalized edema

Types of edema Vasogenic edema: rupture of the blood- brain barrier Cytotoxic edema: pump failure Interstitial edema: passage through the ependymal lining of the ventricles