A 52-year-old man with poorly controlled hypertension (BP 210/130 mmHg) presents with headache, blurred vision, and dyspnea. On funduscopy, multiple retinal findings are noted including flame-shaped hemorrhages, hard exudates, and arteriolar changes. The structure marked **B** in the diagram appears as a white, fluffy lesion in the nerve fiber layer. Which of the following best describes the pathophysiological basis of this finding?
A. Axonal swelling and cytoplasmic stasis in the superficial retinal nerve fiber layer
B. Ischemic infarction of the nerve fiber layer due to arteriolar narrowing and hypoperfusion
C. Lipid and protein extravasation into Henle's layer from blood-retinal barrier breakdown
Fibrinoid necrosis of the arteriolar wall with acute endothelial damage
D.
Explanation
Why "Ischemic infarction of the nerve fiber layer due to arteriolar narrowing and hypoperfusion" is right
Cotton-wool spots (marked B) represent areas of ischemic infarction within the nerve fiber layer caused by chronic arteriolar vasoconstriction and reduced perfusion pressure in hypertensive retinopathy. The SME anchor explicitly states: "COTTON-WOOL SPOTS (areas of nerve fiber layer infarction representing axoplasmic stasis)." These lesions appear as white, fluffy opacities because infarcted axons accumulate cytoplasmic material (axoplasmic stasis) that scatters light. In the Keith-Wagener-Barker Grade 3 classification, cotton-wool spots indicate moderate hypertensive end-organ damage and correlate with systemic complications including left ventricular hypertrophy and hypertensive nephropathy. The ischemic mechanism is the direct result of sustained arteriolar narrowing and endothelial damage from chronic hypertension.
Why each distractor is wrong
Lipid and protein extravasation into Henle's layer from blood-retinal barrier breakdown: This describes hard exudates (not cotton-wool spots). Hard exudates form a macular star pattern and represent lipid/protein deposits in the outer plexiform layer (Henle's layer), not nerve fiber layer infarction.
Fibrinoid necrosis of the arteriolar wall with acute endothelial damage: While fibrinoid necrosis does occur in severe hypertension (particularly in Grade 4 / malignant hypertension), it affects the vessel wall itself, not the nerve fiber layer. This is the pathological basis of acute endothelial injury, not cotton-wool spot formation.
Axonal swelling and cytoplasmic stasis in the superficial retinal nerve fiber layer: Although axoplasmic stasis is mentioned in the anchor as a feature of cotton-wool spots, the PRIMARY pathophysiological mechanism is ischemic infarction; axoplasmic stasis is the consequence, not the cause. The question asks for the basis of the finding, which is ischemia.
