ABSTRACT
BACKGROUND: In orthostatic headache (OH) associated with low cerebrospinal fluid (CSF) pressure, loss of CSF vol-ume reflected by pachymeningeal enhancement (PCE) on brain magnetic resonance image (MRI) has been suggested as a pathogenenesis according to Monro-Kellie rule. We attempted to test the following hypotheses; 1) OH is caused by loss of CSF volume, 2) CSF volume loss in OH is caused by hyperabsorption of CSF or 3) by decreased production of CSF. METHODS: Nineteen patients with OH were recruited. Lumbar puncture, brain MRI and radioisotope cisternogra-phy (RIC) were performed in all of them. We evaluated duration of headache from onset to first evaluation, presence of PCE on MRI and CSF leakage (CSFL) on RIC. Firstly, we compared duration of headache between patients with and without PCE. Secondly, between those with and without PCE, we analyzed presence of CSF fistula and demonstration of CSFL on RIC. RESULTS: Mean duration (16.1 +/-19.6) of headache in 13 patients with PCE (66.7%) was significantly longer than in those without PCE (P=0.036). Among 19 patients, CSF fistula was detected in 13 patients (72%) and CSFL in 16 patients (88.9%). There was no significant difference in CSF fistula presence (P=0.114) and in demonstra-tion of CSFL between those with and without PCE. In 16 patients, delayed appearance of radioisotope along cerebral interhemispheric and sylvian regions was shown on RIC. CONCLUSIONS: Pain in OH may be caused by CSF volume loss, however, whether CSF volume loss is caused by CSF hyperabsorption or decreased production remains to be clarified.