ABSTRACT
Most forms of neurological or psychiatric dysfunction can now be associated with specific disruptions of structural integrity or specific disturbances in chemical processes localised to defined regions in the CNS. At the cellular level, structural degeneration capable of causing neurological dysfunction can involve both neurones and glia. The types of changes that can affect neurones include outright neuronal cell death, neuronal atrophy (e.g., shrinkage of the cell body and dendrites, retraction of processes, and loss of synapses), subcellular abnormalities (e.g., neurofibrillary tangles), and aberrant growth (e.g., hypertrophy
of the cell body and dendrites, growth of inappropriate or dystrophic neurites, and formation of neuritic plaques). Glial cell changes include cell loss, demyelination, gliosis, and glial scarring. Molecular disturbances that can lead to CNS malfunction in the absence of obvious structural abnormalities are less well characterised, but include metabolic disturbances, dysfunction of transmitter associated enzymes, and effects mediated via specific receptors either by exposure to exogenous ligands such as drugs or other environmentally derived substances, or by exposure to inappropriate levels of endogenous ligands. It is not known whether prolonged dysfunction of this type can occur in the absence of eventual structural changes. Here we will focus on events that lead to detectable degenerative changes in neural tissues.
