A 63-year-old woman presented with headache, progressive somnolence, neurocognitive decline and urinary incontinence through a year. Medical history was unremarkable except for hypertension and hypercholesterolaemia. Neurological examination was normal. Brain MRI showed findings typical for spontaneous intracranial hypotension (subdural fluid collection, pachymeningeal enhancement, brain sagging) and pituitary tumour. The patient's complaints improved dramatically but temporarily after treatment with each of repeated targeted as well as non-targeted blood patches and a trial with continuous intrathecal saline infusion. Extensive work up including repeated MRI-scans, radioisotope cisternographies, CT and T2-weighted MR myelography could not localise the leakage, but showed minor root-cysts at three levels. Finally, lateral decubitus digital subtraction dynamic myelography with subsequent CT myelography identified a tiny dural venous fistula at the fourth thoracic level. After surgical venous ligation, the patient fully recovered. Awareness of spontaneous dural leaks and their heterogeneous clinical picture are important and demands an extensive workup.