A 50 year old man, with known Marfan’s syndrome, was admitted with a one week history of severe headaches over the top of his skull, neck pain, and daily vomiting. His symptoms were greatly aggravated by standing, but they disappeared when he lay flat. He was systemically well and had no history of trauma. He had undergone an aortic root and metallic valve replacement 13 months previously and was on lifelong warfarin.

On examination he had morphological features consistent with Marfan’s syndrome, including tall stature, pectus carinatum, arachnodactyly, joint hypermobility, and high arch palate. He did not have a fever. He had no neurological deficit, photophobia, or signs of meningism. His blood investigations were unremarkable except for an international normalised ratio of 3.8. Magnetic resonance imaging of the brain and lumbosacral spine was performed (figs 1-3⇓ ⇓ ⇓).