Radionuclide shunt studies have been used for decades to evaluate intracranial shunt patency (SP); however, the methodology is neither standardized nor well validated. The purpose of this study was to determine the clinical utility of radionuclide ventriculoatrial (VA) SP study for diagnosis of suspected shunt malfunction.
A retrospective review was undertaken of all patients who had a VA radionuclide SP study between 2001 and 2009. All had a 20-minute gamma camera acquisition (1 min/frame) immediately following injection of 99mTc DTPA into the shunt reservoir. Time-activity curves were generated and a half-time (T½) of emptying quantified. The results were correlated with the final clinical diagnoses.
Forty-nine studies in 40 adult patients with a minimum of 6 months’ follow-up were analyzed. Thirteen shunt studies had a T½ of 3.9 to 8.0 minutes, had final diagnosis of normal functioning shunt, and did not need revision surgery for a mean follow-up of 15.1 months. Fourteen patient studies had a T½ of less than 3.9 minutes; 13 had final diagnosis of overdraining shunts, and 1 required revision surgery. Twenty-two had a T½ longer than 8 minutes: 13 had final diagnosis of shunt obstruction, 4 had overdrainage, and 5 had underdrainage.
The radionuclide SP study is valuable for evaluation of VA SP. Results can be interpreted using a single variable (T½). T½ of 3.9 to 8 minutes indicates a patent shunt; T½ less than 3.9 minutes is consistent with overdrainage. T½ of >8 requires further evaluation to differentiate between obstruction and overdrainage/underdrainage.
From the *Department of Radiology, Mercy Catholic Medical Center, Drexel University, Philadelphia, PA; †Russell H. Morgan Department of Radiological Sciences; and ‡Department of Neurosurgery, The Johns Hopkins University, Baltimore, MD.
Received for publication July 1, 2012; revision accepted February 12, 2013.
Conflicts of interest and sources of funding: none declared.
Reprints: Beril Gok, MD, Department of Radiology, Mercy Catholic Medical Center, 1500 Lansdowne Ave, Darby, PA 19023. E-mail: firstname.lastname@example.org.
Author contributions: B.G.: substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; S.B.: substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; H.E.: drafting or revising of the manuscript critically for important intellectual content; D.R.: final manuscript approval for submission and publication; H.Z.: final manuscript approval for submission and publication.