Spontaneous intracranial hypotension (SIH) is a rare disorder that occurs secondary to acquired cerebrospinal fluid (CSF) leaks in the spine. Treatment involves either an epidural blood patch or surgical ligation. Essential to the selecting the optimal management strategy is classifying the type of leak and accurate localization of its level. Hitherto, this has been achieved using conventional imaging methods such as static CT or MR myelography which are adequate for the demonstration of only high flow leaks. Digital subtraction myelography (DSM) is a novel technique which provides superior temporal and spatial resolution in the localization of more challenging slow flow leaks. However, DSM may also be initially non-diagnostic. We report a case of SIH in which repeat DSM revealed a type 3 CSF-venous fistula and demonstrate a possible mechanism of transient CSF leak block resulting in the initial false negative findings based on morphological changes in the culprit nerve sheath diverticulum-pseudomeningocoele complex. The patient underwent successful surgical ligation with clinicoradiological resolution of SIH.