Rethinking Temporopolar White-Matter Hyperintensity in CADASIL: A Context-Dependent Biomarker

Temporopolar white-matter hyperintensity (WMH) has long been regarded as a characteristic MRI feature of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).¹,² In clinical practice, its presence often raises strong suspicion of NOTCH3-related small-vessel disease (SVD) and frequently prompts genetic testing.¹,² However, emerging evidence supports a more-nuanced interpretation of whether temporopolar WMH is truly a disease-specific biomarker.³,⁴,⁵

A recent study addressed this issue in a large cohort of patients with genetically confirmed CADASIL alongside a comparison group with sporadic cerebral SVD.⁵ A notable strength of that study was the application of NOTCH3 epidermal-growth-factor-like repeat (EGFr) risk stratification, reflecting the increasing recognition of genetic and clinical heterogeneity in NOTCH3-associated SVD.³ This framework challenges the traditional view that all CADASIL-causing variants behave uniformly and highlights that the variant location influences imaging phenotypes, clinical manifestations, and disease severity.⁵

The diagnostic value of temporopolar WMH varies between patients, with this being strongly influenced by the location of the NOTCH3 variant: temporopolar WMH was observed in 94.7% of individuals with high-risk EGFr variants, compared with only 54.4% and 33.3% in those with medium- and low-risk variants, respectively.⁵ Notably, the prevalence was similar (31.9%) in patients with sporadic SVD. These findings underscore that while temporopolar WMH remains a powerful imaging clue in patients harboring high-risk variants, its specificity is substantially lower in other genetic contexts.⁵ Thus, temporopolar WMH should not be regarded as a fixed hallmark of CADASIL, but rather as a context-dependent biomarker that is influenced by the genotype and broader clinicoradiological profile.³,⁵,⁶

The study also extends the role of temporopolar WMH beyond diagnosis, with the findings suggesting that it can serve as an indicator of the disease burden and functional impairment, rather than merely indicating the presence of CADASIL.⁵ This perspective is consistent with the broader shift in the field from binary classification toward quantitative assessments of disease severity and progression.³,⁶ Within this evolving framework, temporopolar WMH may contribute to staging paradigms, such as the proposed NOTCH3-SVD classification, and offer additional insight into the continuum of cerebral SVD across hereditary and sporadic forms.⁵

The findings raise a specific mechanistic question: why should high-risk EGFr variants produce disproportionate temporopolar involvement when NOTCH3 expression itself is not obviously regional? The high prevalence of temporopolar WMH in carriers of high-risk EGFr variants supports a potential link between variant location and regional vulnerability within the brain.⁵ Elucidating the biological basis of this predilection may provide deeper insight into NOTCH3-related vascular pathology and its interaction with regional white-matter susceptibility.⁵ However, caution is also warranted. The study population was confined to an Asian cohort, and so the generalizability of these findings to other racial groups remains uncertain. This limitation indicates the need for validation in diverse populations and supports the importance of integrating imaging, genetic, and clinical data in a comprehensive diagnostic framework.

Finally, the work should be viewed within the broader evolution of biomarker research in CADASIL.⁵ Beyond imaging, recent studies have explored the roles of the gut microbiota and metabolic signatures as potential modifiers of disease expression, pointing toward a more-complex, systems-level understanding of disease heterogeneity.⁷ In this context, the present study shows that even well-established imaging biomarkers must be reinterpreted in light of the genetic context and disease biology.

Temporopolar WMH is not a universally reliable diagnostic hallmark of CADASIL,⁵ with its significance instead depending critically on the location of the NOTCH3 variant and the overall disease context. However, it may provide valuable information regarding the disease burden and functional status.⁵ These insights support a more-refined and integrative interpretation of MRI findings in NOTCH3-associated SVD.

Availability of Data and Material

Data sharing not applicable to this article as no datasets were generated or analyzed during the study.