A 50-year-old woman presented with recurrent episodes of headache, nausea and disturbed consciousness that were fully reversible within a few days. Clinical and radiological findings suggested raised intracranial pressure, which on one occasion was confirmed by intracranial pressure monitoring. Magnetic resonance imaging performed in the asymptomatic interval disclosed a diffuse leukoencephalopathy. Brain biopsy surprisingly revealed the typical vascular changes of CADASIL and subtle endothelial alterations. The white matter showed edematous changes and reactive gliosis. Mutational analysis of the Notch3 gene revealed a previously unreported mutation. We suggest that a transient disturbance of the blood-brain barrier related to the underlying vascular pathology may have caused this unusual presentation of CADASIL.