Angiopathie amyloïde cérébrale révélée par une leptoméningite : aspect IRM évocateur

Cerebral amyloid angiopathy (CAA) is a frequent pathology of the demented and non-demented elderly. Its expression is mainly hemorrhagic - lobar intracerebral hemorrhage, brain microbleeds, superficial hemosiderosis - but also ischemic - white matter changes, small cortical infarcts. It can also be revealed by transient focal neurological symptoms and/or cognitive impairment. We report the case of a 64-year-old woman who presented brief stereotypic episodes of left brachio-facial numbness. The cerebral MRI showed focal pial FLAIR hyperintensities enhanced by gadolinium and a superficial hemosiderosis of the right central sulcus. The etiological investigation of leptomeningitis found no evidence for a neoplastic, infectious or inflammatory cause. Because of the clinical worsening and the MRI progression of the pial lesions, a cortico-meningeal biopsy was obtained and revealed CAA associated with intense microglial activation, which did not match the usual aspect of the inflammatory forms of CAA. This is an atypical presentation of CAA characterized by isolated and rapidly progressive leptomeningeal abnormalities. This case report highlights the heterogeneous spectrum of the clinical and neuroradiological CAA presentations and highlights the need to update current diagnostic criteria.