Chapter 20: Central Nervous System Pathology

Central Nervous System Pathology begins by distinguishing between the types of meningitis, contrasting the cerebrospinal fluid profiles and clinical presentations of acute aseptic viral meningitis against acute purulent bacterial meningitis caused by pathogens such as Streptococcus pneumoniae and Neisseria meningitidis. The discussion expands to include meningoencephalitis caused by tuberculosis, fungi like Cryptococcus, and viral agents including Herpes simplex and HIV, as well as the spongiform encephalopathy observed in prion disorders like Creutzfeldt-Jakob disease. A significant portion of the text is dedicated to cerebrovascular disease, breaking down the pathophysiology of global ischemia, transient ischemic attacks, and the distinct mechanisms behind thrombotic and embolic strokes, alongside the life-threatening consequences of berry aneurysm rupture and subarachnoid hemorrhage. The chapter details the spectrum of central nervous system trauma, from concussions and contusions to catastrophic epidural and subdural hematomas, diffuse axonal injury, and the long-term effects of chronic traumatic encephalopathy. It further explains the mechanical dynamics of brain herniations, including subfalcine, transtentorial, and tonsillar types. Developmental and perinatal neuropathology is explored through neural tube defects like spina bifida and anencephaly, cerebellar malformations including Arnold-Chiari and Dandy-Walker, and injuries such as germinal matrix hemorrhage. The summary covers demyelinating conditions, specifically focusing on the autoimmune nature of Multiple Sclerosis and the risks of central pontine myelinolysis. A major section addresses degenerative and dementing disorders, differentiating the pathophysiology of Parkinson disease, Huntington disease, and Amyotrophic Lateral Sclerosis from the cortical atrophy and protein accumulations seen in Alzheimer disease and Lewy body dementia. Finally, the chapter categorizes central nervous system tumors, distinguishing between pediatric posterior fossa neoplasms like medulloblastomas and adult supratentorial malignancies such as glioblastoma multiforme, while also reviewing meningiomas, schwannomas, and metastatic lesions.