CAA or not? When cerebral microbleeds are not enough.

Lobar cerebral microbleeds (CMBs) are significant indicators of cerebral amyloid angiopathy (CAA) and are increasingly recognized in both clinical and population studies. Although CMBs are common incidental findings, their progression in CAA patients underscores their diagnostic relevance. Recent criteria highlight additional markers of small vessel disease (SVD), such as white matter hyperintensities (WMHs) and enlarged perivascular spaces (EPVSs), yet the current diagnostic framework does not fully address the implications of multiple SVD markers. This case report discusses a 55-year-old man with a history of acute lymphoblastic leukemia who presented with recurrent vertigo and was initially suspected of having CAA due to MRI findings of CMBs. However, the absence of cortical CMBs, WMHs, and EPVSs, coupled with his history of whole brain radiotherapy (WBRT), led to the conclusion that the observed CMBs were likely long-term effects of WBRT. Follow-up MRI demonstrated the emergence of new CMBs, reinforcing the need for careful consideration of differential diagnoses in patients with a history of radiation therapy.