A 36-year-old woman presented with transient diplopia and right-sided paresthesia. MR scan of the brain showed multiple chronic ischaemic lesions in the white matter, linear hyperdensities along sulci and reduced visibility of the middle cerebral arteries (figure 1A– B). Angiography identified progressive narrowing of the internal carotid arteries, with tiny and tortuous lenticulostriate arteries giving a ‘puff of smoke’ appearance, leptomeningeal collaterals from the posterior cerebral arteries and transdural anastomosis (figure 1C– F).