Originally named "aliquorrhea" by Schaltenbrand 1 in 1938, spontaneous intracranial hypotension (SIH) is an increasingly recognized syndrome characterized by a triad of low CSF pressure, postural headache, and magnetic resonance imaging (MRI) abnormalities. 2 The classic MRI finding of diffuse pachymeningeal enhancement, 3 with leptomeningeal sparing, is thought to be a result of engorgement of dural bridging veins secondary to decreased CSF pressure.4 This is such a hallmark feature that its absence has been suggested to exclude the diagnosis. 2 There have been only a few reported cases of SIH with absent MRI findings. 5 We report four cases of SIH that presented to our institution ABSTRACT: Background: Spontaneous intracranial hypotension (SIH) is a neurologic syndrome of unknown etiology, characterized by features of low cerebral spinal fluid (CSF) pressure, postural headache and magnetic resonance imaging (MRI) abnormalities. Methods: Four symptomatic cases of SIH presented to our institution over a six-month period. Magnetic resonance imaging studies were performed in all four cases. Diagnostic lumbar puncture was done in all except one case. Results: All of the patients on whom lumbar punctures were performed demonstrated low CSF pressure and CSF protein elevation with negative cultures and cytology. Three out of the four patients exhibited MRI findings of diffuse spinal and intracranial pachymeningeal gadolinium enhancement and extradural or subdural fluid collections. One patient had no MRI abnormalities despite prominent postural headache and reduced CSF pressure at lumbar puncture. All patients recovered with intravenous fluids and conservative treatment. Conclusions: Magnetic resonance imaging abnormalities are found in most, but not all patients, with SIH. Cerebral spinal fluid abnormalities can be detected even in patients with normal MRI studies. It is important to recognize the variability of imaging results in this usually benign disorder.