Branch retinal vein occlusion as a manifestation of systemic vasculopathy in CADASIL: a multimodal imaging case report

Background: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small vessel disease caused by mutations in the NOTCH3 gene. While it predominantly affects cerebral arterioles, emerging evidence indicates systemic vascular involvement. Ocular manifestations, particularly venous abnormalities such as branch retinal vein occlusion (BRVO), are exceedingly rare and not well characterized in CADASIL. Case Presentation: We report a case of a 63-year-old male presenting with decreased vision and floaters in the left eye. Multimodal imaging revealed macular edema, intraretinal hemorrhages, and superior temporal BRVO. Systemic risk factors were excluded. Genetic testing confirmed heterozygous pathogenic NOTCH3 variant c.317G>A (p.Cys106Tyr) and a variant of uncertain significance c.1774C>A (p.Arg592Ser). Based on this diagnosis, family members were referred for genetic counseling. The patient received intravitreal bevacizumab followed by dexamethasone implants due to recurrent cerebrovascular events and concerns regarding anti-VEGF systemic safety. Conclusion: This case underscores that CADASIL-related vasculopathy may extend to the retinal venous system. Detailed ocular imaging can support early recognition of systemic microvascular disease. BRVO in CADASIL patients may represent an underrecognized manifestation, supporting the need for regular ophthalmic evaluation and interdisciplinary management.