Relevant General Pathology for the Neuropathologist
Systemic disease in the nervous system
Neuropathology questions often hinge on general pathology principles applied to the CNS.
Concepts to master:
- Vascular pathology: atherosclerosis, hypertensive small vessel disease (lacunes, microbleeds), amyloid angiopathy, and vasculitis. Cerebral amyloid angiopathy causes lobar hemorrhage.
- Thrombosis and embolism: cardioembolic vs atherothrombotic infarcts; hemorrhagic transformation.
- Inflammation: granulomatous disease, autoimmune conditions, and infection patterns.
- Neoplasia principles: grading, staging, margins, and metastasis patterns - the brain is a common site for lung, breast, and melanoma metastases.
- Metabolic and toxic injury: hypoglycemia, hepatic encephalopathy (Alzheimer type II astrocytes), and osmotic demyelination.
Traps:
- Confusing hypertensive hemorrhage (basal ganglia, thalamus, pons, cerebellum) with amyloid angiopathy hemorrhage (lobar, cortical).
- Missing that metastatic tumors often outnumber primary brain tumors in adults.
- Overlooking systemic causes of neuropathy (diabetes, paraproteinemia, vasculitis).
Rule of thumb: For any CNS lesion, ask whether it is primary or secondary to systemic disease. Location plus systemic history often answers the question before histology.
Worked example: An elderly patient with lobar hemorrhage and no hypertension - think cerebral amyloid angiopathy, not hypertensive small vessel disease. The location (lobar/cortical) is the key discriminator.