Tympanic displacement analysis in healthy volunteers after indomethacin administration

The aim of this study was to investigate whether a tympanic displacement analyser could detect decreases in cerebral blood flow and intracranial pressure after administration of indomethacin in healthy volunteers. In a double-blind crossover study involving 14 healthy volunteers all subjects first underwent a test-retest evaluation to investigate reproducibility followed by tests performed in sitting and supine positions to confirm intracranial-cochlear pressure transfer. In two further sessions tests were performed before and 90 min after subjects were blindly administered a suppository containing either 100 mg of indomethacin or placebo. It was found that tympanic membrane analysis performed 90 min after administration of such a suppository did not mirror the induced reduction in cerebral blood flow after administration of active drug. After administration of indomethacin eight of the subjects experienced discomfort and dizziness; after placebo none experienced subjective symptoms. After administration of indomethacin a statistically significant decrease in heart rate was demonstrated. The exponential form of the intracranial pressure-volume curve may explain why a decrease in intracranial pressure was not detected using the tympanic membrane displacement method, because the measurements were made in subjects with normal intracranial pressure. More significant findings may be found in patients with elevated intracranial pressure.