Intracranial hypotension is characterized by diffuse gadolinium enhancement of the dura on magnetic resonance imaging (MRI). 1 Awareness of the significance of dural enhancement has led to increased recognition of spontaneous intracranial hypotension. 2 However, failure to diagnose this condition is still a problem and may have serious consequences. 3,4 The clinical manifestations are varied 2,3,5 and the diagnosis of spontaneous intracranial hypotension may not be obvious in patients with headache.We treated three patients with spontaneous intracranial hypotension, two of whom were referred to our hospital with incorrect diagnoses. All three patients had subdural fluid ABSTRACT: Background: Misdiagnosis of spontaneous intracranial hypotension remains a problem, despite increasing recognition. Methods: Three patients with spontaneous intracranial hypotension presented with typical findings on lumbar puncture, magnetic resonance (MR) imaging, and radioisotope cisternography. All patients showed subdural effusions in the posterior fossa on axial T2-weighted MR imaging. Axial MR images of 112 patients with other conditions were also screened for this finding. Results: One of three patients had typical orthostatic headache, and the other two had continuous headache. The finding of subdural effusions in the posterior fossa on axial T2-weighted MR imaging disappeared after treatment. Similar findings were found in 14 of 112 patients with other conditions. Most of the patients were over 60 years old or had dementia or previous radiation therapy. Conclusions: Subdural effusions in the posterior fossa can be identified by T2-weighted axial MR imaging, and are useful for the diagnosis of spontaneous intracranial hypotension and for verifying the effectiveness of treatment.RÉSUMÉ: Épanchements sous-duraux de la fosse cérébrale postérieure associés à l'hypotension intracrânienne spontanée. Contexte: Bien que l'hypotension intra-crânienne spontanée soit diagnostiquée correctement de plus en plus fréquemment, cette pathologie est demeure souvent mal diagnostiquée. Méthodes: Chez trois patients atteints d'hypotension intracrânienne spontanée la ponction lombaire, l'imagerie par résonance magnétique (IRM) et la cisternographie radio-isotopique montraient des signes typique de cette pathologie. Tous les patients avaient un épanchement dans la fosse cérébrale postérieure à l'IRM axiale pondérée en T2. L'IRM axiale de 112 patients atteints d'autres pathologies a également été examinée à cet effet. Résultats: Un des trois patients atteints d'hypotension intracrânienne spontanée avait une céphalée orthostatique typique et les deux autres avaient une céphalée continue. Les signes d'épanchement sous-dural de la fosse cérébrale postérieure à l'IRM axiale pondérée en T2 sont disparus sous traitement. 14 des 112 patients témoins présentaient des signes de cette pathologie à l'IRM. La plupart avaient plus de 60 ans, étaient atteints de démence ou avaient été traités par radiothérapie. Conclusions: Les épanchements sous-duraux de la fosse ...