Symmetry of cerebral microbleeds and cortical superficial siderosis in cerebral amyloid angiopathy.

Abstract

Background: Susceptibility- weighted MRI imaging (SWI) is important in the diagnosis of cerebral amyloid angiopathy (CAA). As well as cerebral microbleeds (CMBs), SWI is sensitive to cerebral convexity subarachnoid haemosiderin, cortical superficial siderosis (cSS), which can be symptomatic or asymptomatic, and may be more specific for CAA than CMBs. Whether these two haemosiderin deposition consequences of CAA progress uniformly and symmetrically throughout the brain and its coverings has not been determined. Methods: MRI scans of patients with probable CAA as defined by the Modified Boston Criteria were graded for cSS presence and CMB count in each hemisphere. Patients presented to Epworth Hospital Richmond between 1 January 2011 and 31 December 2015 with Strike found to be ICH, or transient focal neurological symptoms (TFNS) found o be due convexity subarachnoid haemorrhage (cSAH), the acute forerunner of cSS. We compared CMB counts and cSS distribution by hemisphere. Asymmetry was defined as a cerebral hemisphere having 65% or more of the total CMB or cSS burden. Result: 50 patients had probable CAA with SWI MRI scans available for analysis. CMBs were present in all patients and cSS was present in 26 (52%) (95% confidence interval 29.9% - 70.1%). The distribution of CBMs was asymmetrical in 64.0% (95% ci 49.2%-77.1%) of cases. Fifteen (30%) (95% ci 17.9%-44.6%) had CMBs in one hemisphere only. In patients with cSS the distribution was asymmetrical in 65.4% (95% ci 44.3%-82.8%.) Thirteen patients (50%) (95% ci 29.9%-70.0%) had cSS in one hemisphere only. Conclusion: In CAA the pathology may not be uniform in its distribution across the brain. This may have implications for the pathogenesis of CAA and its mode of progression.