Cerebral microbleed distribution following cardiac surgery can mimic cerebral amyloid angiopathy

Abstract

Background and aimsHaving anecdotally noted a high frequency of lobar-restricted cerebral microbleeds (CMBs) mimicking cerebral amyloid angiopathy (CAA) in patients with previous cardiac surgery (especially valve replacement) presenting to our transient ischaemic attack (TIA) clinic, we set out to objectively determine the frequency and distribution of microbleeds in this population.MethodsWe performed a retrospective comparative cohort study in consecutive patients presenting to two TIA clinics with either: (1) previous coronary artery bypass grafting (CABG) (n=41); (2) previous valve replacement (n=41) or (3) probable CAA (n=41), as per the Modified Boston Criteria, without prior cardiac surgery. Microbleed number and distribution was determined and compared.ResultsAt least one lobar-restricted microbleed was found in the majority of cardiac surgery patients (65%) and 32/82 (39%) met diagnostic criteria for CAA. Valve replacement patients had a higher microbleed prevalence (90 vs 51%, p<0.01) and lobar-restricted microbleed count (2.6±2.7 vs 1.0±1.4, p<0.01) than post-CABG patients; lobar-restricted microbleed count in both groups was substantially less than in CAA patients (15.5±20.4, p<0.01). In postcardiac surgery patients, subcortical white matter (SWM) microbleeds were proportionally more frequent compared with CAA patients. Receiver operator curve analysis of a ‘location-based’ ratio (calculated as SWM/SWM+strictly-cortical CMBs), revealed an optimal ratio of 0.45 in distinguishing cardiac surgery-associated microbleeds from CAA (sensitivity 0.56, specificity 0.93, area under the curve 0.71).ConclusionLobar-restricted microbleeds are common in patients with past cardiac surgery, however a higher proportion of these CMBs involve the SWM than in patients with CAA.

MRI versus CT in the detection of brain lesions in patients with infective endocarditis before or after cardiac surgery

“…Our experience also confirms that CMBs are more common after cardiac surgery. In addition, also cerebral amyloid angiopathy is associated with CMBs that have the same distribution as the one following cardiac surgery, further complicating the picture [ 13 ]. Interestingly, it is worth noting that in our sample CT showed CMBs in 2 patients, while there is no literature data supporting the detectability of such lesions on CT [ 11 , 12 ].…”

Cerebral amyloid angiopathy: clinical presentations and management challenges in the Australian context

“…There are also other causes of microhaemorrhages such as cardiac bypass-associated lobar microbleeds. 10 CAA-related microhaemorrhages are associated with APOE ε4 and correlated with areas of concentrated amyloid-β deposition on PET imaging. In the Rotterdam study, lobar and non-lobar microhaemorrhages were found on imaging in up to 35.7% of patients over 80 years and were associated with regions of amyloid-positive vessels.…”

“…The presence of microhaemorrhages is also associated with age. There are also other causes of microhaemorrhages such as cardiac bypass‐associated lobar microbleeds 10 . CAA‐related microhaemorrhages are associated with APOE ε4 and correlated with areas of concentrated amyloid‐β deposition on PET imaging.…”

Not all cortical cerebral microbleeds are due to cerebral amyloid angiopathy

“…Investigators from Adelaide report in this volume of BMJ Neurology Open a pattern of CMBs consistent with CAA according to the modified Boston criteria but occurring following cardiac surgery, either coronary artery graft surgery or cardiac valve replacement in patients referred to their two TIA clinics. 2 Clinical and radiological criteria for probable CAA were met in 39% of their post cardiac surgery cases. They found that subcortical white matter (SWM) CMBs rather than purely cortical CMBs were more common in the cardiac surgery patients than in the probable CAA patient subset without a history of cardiac surgery.…”