Radioactive tracers are frequently used in the detection and localization of CSF leaks in pa tients with rhinorrhea. However, little data are available concerning normal levels of nasal se cretion of intrathecally injected â€oe11n-DTPA. We propose a technique which compares the ac tivity in nasal pledgets to plasma activity in 16 patients without any known abnormalities. The ratio of pledget activity to plasma activity per 0.5 ml did not exceed 1 .3. In a proven case of occult CSF rhinorrhea

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... ratio was 6.2. The combined technique of visualization by cister nography and localization by quantitative study of pledgets may offer an improved method for the detection and localization of occult CSF leaks in patients with either CSF rhinorrhea or recurrent meningitis even in the absence of CSF rhinorrhea.