Cerebral vascular malformation screening in hereditary hemorrhagic telangiectasia: Balancing low diagnostic yield against high-risk hemorrhage

BACKGROUND: Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disorder predisposed to cerebral vascular malformations (CVMs). With conflicting international guidelines on systematic CVM screening in adults, we evaluated the prevalence, clinical relevance, and risks of screening in a national Danish HHT cohort. METHODS: This combined prospective and retrospective study analyzed data from the Danish HHT Registry. The prospective arm involved systematic non-contrast brain MRI in 202 HHT patients (aged 18-65, no MRI in previous 5 years). The retrospective arm included 119 patients who underwent opportunistic MRI. Primary outcomes were CVM prevalence and characteristics; secondary outcomes included incidental findings and their clinical consequences. RESULTS: Systematic screening (n = 202) showed a low CVM yield (2.0 %), none required intervention, but a high rate of incidental findings (36.1 %), of which 41.1 % were clinically actionable. In a unified analysis of all CVM patients from both cohorts, all 8 spontaneous hemorrhages occurred in HHT Type 1 (ENG) patients. CVM prevalence was markedly higher in HHT Type 1 (ENG) (13.6 %) than HHT Type 2 (ACVRL1) (1.5 %). CONCLUSION: Systematic CVM screening in an unselected adult HHT cohort has a low diagnostic yield for immediately actionable CVMs, but a high rate of incidental findings. However, hemorrhage from undiagnosed CVMs, while devastating, was exclusively observed in HHT Type 1 (ENG) patients in our cohort. Consequently, our findings suggest that a risk-stratified approach, prioritizing HHT Type 1 (ENG), may offer a pragmatic strategy, while acknowledging that the high rate of incidental findings necessitates careful shared decision-making for other genotypes.