The outcome of spontaneous intracranial hypotension (SIH) years after onset is largely unknown. The objective of our study was to describe our clinical experience and long-term outcomes in a case series of patients with SIH. From March 2007 to March 2022, demographic variables, clinical symptoms, neuroimaging findings, and response to treatment were retrospectively analyzed in patients with confirmed SIH and in a subgroup of patients with clinical symptoms but not confirmed by MR or LP, probable SIH (pSIH). We have included 37 SIH and 13 pSIH patients. The average age at onset was 44 years, and 59% (pSIH 46%) were women. All patients presented with a new-onset orthostatic headache. In the SIH group, brain MRI showed signs of intracranial hypotension in all patients, spinal MR was performed in 70%, and pathological findings were identified in 73%. The range of EBP was 1-8 (average 2.2). Good outcome after single or 2 EBPs had 42% (pSIH 46%) of patients. At follow-up, 81% (pSIH 54%) of patients had a favorable outcome. Relapse occurred in 16% of patients in the SIH group and none in the pSIH group. The mean follow-up time was 60 months. EBP is an effective and minimally invasive treatment, and efficacy seems independent of disease duration. The long-term prognosis is favorable in 80% of SIH patients and in half of pSIH patients. Despite the lack of MRI signs of low intracranial pressure on neuroimaging, pSIH patients should also be offered EBP, and more awareness of SIH is needed. [ABSTRACT FROM AUTHOR]