Microbleeds as a Causative Factor in Diffusion-weighted Imaging-Negative Acute Brainstem Stroke Syndrome: A Report of Three Cases.

A significant number of patients with acute stroke syndrome present with negative diffusion-weighted imaging (DWI) findings on brain magnetic resonance imaging (MRI). Cerebral microbleeds (CMBs), a marker of small vessel disease, are rarely considered a cause of acute neurological deficits and are often excluded from the differential diagnosis of stroke syndrome. Three cases of acute-onset brainstem syndrome were identified, each presenting with diplopia; two cases had abducens palsy, and one had oculomotor palsy upon assessment. Two patients also experienced dizziness and ataxia, while one presented with peripheral facial palsy. All cases showed negative DWI findings. CMBs were found in regions corresponding to the patients' neurological deficits. All patients recovered from their major symptoms within 7 days. These cases highlight the potential role of CMBs in DWI-negative acute brainstem syndrome, emphasizing the need to consider CMBs in the differential diagnosis of posterior circulation stroke syndromes. Future research is needed to better understand long-term outcomes and inform targeted management strategies for CMB-related acute neurological deficits. Microbleeds need to be considered as the causal lesion in patients presenting with acute stroke syndrome but DWI negative on brain MRI, particularly in those with brainstem syndrome.