Kinsey Rowe Pillsbury MD, Presenter: Nothing to Disclose

David Paul Chason MD, Abstract Co-Author: Nothing to Disclose

Dana Mathews MD, PhD, Abstract Co-Author: Nothing to Disclose

Radionuclide cisternography (RNC) may be used to evaluate patients with suspected cerebrospinal fluid (CSF) leaks when the source is not obvious. The presence of radioactivity greater than plasma background on pledgets placed in the nose or ears is crucial as the leaks are seldom visualized. This study evaluates the plasma to pledget ratio (PPR) needed to reliably indentify a CSF leak.

Medical reports and records were reviewed for patients undergoing RNC for suspected CSF leak from 1995-2010. The majority had prior sinus surgery. Pledgets were placed in the nose or ears and ≈1.3 mCi (48MBq) of 111In DTPA was injected into the CSF via lumbar puncture. 24 hour brain images were obtained and then pledgets removed, counted and compared to similar sized pledget soaked in the patient’s plasma. The historical value of a PPR >1.3 was considered positive for a leak. RNC ratios were correlated with results of B-transferrin (2) and operative findings (15). For the purposes of this study, a positive result on B-transferrin or a leak seen at surgery was considered substantiation for a true CSF leak.

26/54 patients (48%) had RNC ratios of ≥1.3. Only 7 (27%) of these were subsequently found to have CSF leaks (6 at surgery, 1 by B-transferrin); the average ratio (AR) was 125.6. Three patients underwent surgery and no leak was found (AR 4.4). One had a cervical spine CSF leak (ratio 1.7). 15/26 patients never required surgery (AR: 2.6). Of the remaining 28/54 patients with ratios <1.3 only 2 (7%) were found to have CSF leak at surgery (AR: 0.8).

Patients with documented CSF leaks at surgery had a PPR greater than the accepted value of 1.3, by at least an order of magnitude. Those who went to surgery with lower ratios were not reliably found to have leaks. Our data brings into question the clinical utility of current guidelines.

RNC can be useful for the work up of occult CSF leaks. However, the current recommended PPR >1.3 for a positive scan results in excessive false positives and needs revision.

Pillsbury, K, Chason, D, Mathews, D, Radionuclide Cisternography in the Management of Cerebrospinal Fluid Leak.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11002659.html