CSF Shuntogram results and intra-operative shunt functional testing in patients with suspected shunt malfunction

Objectives To determine if cerebrospinal fluid (CSF) shuntogram findings predict intra-operative shunt functional testing in patients with suspected shunt malfunction.

Methods A retrospective chart review was completed on adult patients who presented to the nuclear medicine clinic who had ventricular CSF shuntograms completed between June 2005 and September 2009 for suspected shunt malfunction.

Results A total of 148 shuntograms were evaluated in 104 patients for suspected shunt malfunction with a CSF shuntogram. Of these, 30 patients were found to have scintigraphic evidence of shunt obstruction. The sensitivity of the shuntogram was found to be 75% and the specificity 84.8 %. The positive predictive value was 42.9 % and the negative predictive value was 94.6 %. There were 37 (24.7%) shunts with shuntogram evidence of positional dysfunction that did not drain spontaneously in the supine position, but drained with additional maneuvers. Of these 37 patients, 6 went to surgery and had their shunts replaced, of which 4 were obstructed (11.4% of the positional, non-obstructed shuntograms were found to be obstructed at surgery). A total of twenty nine patients who had shuntograms (20.0%) went for shunt revision surgery for suspected shunt malfunction. Fifteen patients were found to have obstructed shuntograms who did not go to surgery.

Conclusions In patients who went on to surgery, there is good correlation with respect to testing shunt function at the time of revision, however, PPV for post surgical obstruction was low, (42.9%), primarily due to the fact that half of these patients did not go to surgery. No patient who had a completely normally functioning shunt by shuntogram, went to surgery (NPV =94.6%)