Use of an epidural blood patch to treat spinal headache after accidental dural puncture is well recognized. The high success rate associated with this practice has been questioned and it is not uncommon for patients to suffer recurring headaches after a supposedly successful blood patch. We describe a patient in labour who suffered accidental dural puncture, and whose headache was treated twice with an epidural blood patch. Despite this, the headache persisted. The case highlights the difficulty in the diagnosis of headache in the postnatal period in patients who have had regional analgesia and the importance of considering an alternative pathology, even if epidural blood patching has been successful. In this case, a diagnosis of cortical vein thrombosis was made. The incidence, presentation, aetiology and treatment of this rare condition is described.