A 45-year-old man with poorly controlled hypertension (BP 220/130 mmHg) presents with headache and blurred vision. Fundoscopy reveals diffuse arteriolar narrowing, AV nicking, flame-shaped hemorrhages, and a macular star of hard exudates. The structure marked **B** in the diagram is noted to be multiple in number and scattered across the retina. What is the pathophysiological basis for the appearance of the structures marked **B**?
A. Leakage of plasma proteins from damaged retinal vessels into the interstitium
B. Microaneurysms arising from weakened capillary walls due to loss of pericyte support
C. Focal infarcts of the nerve fiber layer from precapillary arteriolar occlusion with accumulated axoplasmic debris in ganglion cell axons
D. Fibrinoid necrosis of arteriolar walls causing direct rupture of the vessel lumen
Explanation
Why option 1 is right
Cotton wool spots (marked B) represent focal infarcts of the nerve fiber layer caused by precapillary arteriolar occlusion in the setting of severe hypertension overwhelming retinal autoregulation. The white appearance is due to accumulated axoplasmic debris within infarcted ganglion cell axons. This is the pathognomonic finding of Grade 3 hypertensive retinopathy and reflects acute ischemic injury to the nerve fiber layer. (Harrison's 21e Ch 277; Keith-Wagener-Barker classification)
Why each distractor is wrong
Option 2 (Microaneurysms from pericyte loss): While pericyte loss does occur in chronic hypertension and diabetes, microaneurysms are not the pathology of cotton wool spots. Microaneurysms appear as small red dots and are more characteristic of diabetic retinopathy. Cotton wool spots are infarcts, not microaneurysms.
Option 3 (Plasma protein leakage): This mechanism accounts for hard exudates (marked D in the diagram), which form a macular star radiating from the fovea. Hard exudates are lipid and protein deposits, not cotton wool spots. Cotton wool spots are ischemic infarcts, not exudative lesions.
Option 4 (Fibrinoid necrosis causing rupture): Fibrinoid necrosis of arteriolar walls is indeed the underlying pathology in malignant hypertension, but it directly causes flame-shaped hemorrhages (marked A), not cotton wool spots. Hemorrhages result from vessel rupture; cotton wool spots result from arteriolar occlusion and ischemia.
High-YieldNEET PG
Cotton wool spots = nerve fiber layer infarcts from arteriolar occlusion; hard exudates = protein leakage; flame hemorrhages = vessel rupture. Each lesion in hypertensive retinopathy has a distinct pathophysiology.
