Picture Quiz: An unusual cause of headache.

A sixty-six year old lady was admitted after describing two 'vacant' episodes with collapse. She had also complained of chronic fronto-occipital headache and more than 10kg weight loss over the preceding three month period. She denied any gastrointestinal, respiratory or cardiac symptoms. She was a non-smoker and did not drink alcohol regularly. She had a past history of hypertension and hypothyroidism for which she was taking ramipril and thyroxine. On examination she appeared cachexic, but no other abnormality was detected.