Background Postdural puncture headache (PDPH) is a relatively common acute complication that occurs following regional anesthesia and is among the clinical features of secondary intracranial hypotension syndrome (IHS).

The aim of this study was to document the radiological findings specific to PDPH with brain MRI and to determine whether these findings differed from those described in the third edition of the International Headache Society’s International Classification of Headache Disorders (ICHD-3).

Methods Thirty patients who were diagnosed with PDPH based on the ICHD-3 clinical criteria were enrolled in the study and signed the informed consent form approved by our hospital ethics committee. Their symptoms were recorded and they underwent brain MRI before and after the administration of a gadolinium-based contrast agent within 48–72 hours after the onset of their orthostatic headache.

Results All patients with PDPH presented with MRI features of pachymeningeal enhancement. The thickness of the pachymeningeal enhancement varied from 0.6 mm to 4.1 mm, with a mean of 1.6 mm+0.8.

No cases of brain sagging were observed. 4 of the 30 patients presented with intracranial subdural fluid collections, 7 presented with pneumocephalus and 7 pituitary gland enlargement.

Conclusions The radiological characteristics of IHS and PDPH are most likely the result of compensatory mechanisms in response to decreased cerebrospinal fluid pressure. The acute nature of PDPH probably causes its radiological MRI characteristics to differ from those of IHS, given that no brain sagging could be demonstrated.