Indium 111 Diethylenetriamine Pentaacetic Acid Scintigraphy in the Identification and Management of Intrathecal Pump Malfunction

Background: Intrathecal drug-delivery systems have become widely used tools in the management of refractory chronic pain and spasticity. Because increasing numbers of patients are using these systems, rehabilitation specialists frequently are the initial care providers who identify clinical signs and symptoms indicating possible complications elating to the implanted system. Identification of a pump malfunction often presents a diagnostic challenge. Distinguishing among progression of disease, new organic problems, and/or drug-device complications is critical. The use of nuclear medicine indium 111diethylenetriamine pentaacetic acid (DTPA) studies represents a highly effective, straightforward, minimally invasive way to assess implant function and drug distribution. Objective: To identify patients with suspected intrathecal pump malfunction and todetermine whether the use of indium 111 DTPA is effective in identifying the source of failure. Design: A retrospective review was performed from 2011 to 2012. Setting: The study was performed at Georgia Health Sciences University. Patients: The 23 selected patients had implanted devices for either spasticity or pain and were experiencing symptoms of a possible pump malfunction despite normal radiographic imaging. Twenty-four scintigraphic studies were performed, with malfunction documented in 19 patients. Methods: A standard refill technique was used to inject 0.3 mL of indium 111 DTPA into the pump reservoir. Radionuclide images were reviewed at varying time points up to 48 hours after injection. The extent of radionuclide progression from the pump reservoir to the intrathecal space was evaluated. In cases in which a problem with the implant was identified, correlation with operative findings is described. Results: Normal results of studies ultimately correlated with other clinical issues and confirmed an alternative etiology for the clinical changes noted. In studies with abnormal results, several patterns of failure were identified: restriction of the radionuclide to the pump reservoir, extravasations of tracer into the pump subcutaneous pocket, failure of the tracer to migrate from the subcutaneous catheter to the intrathecal space, and pooling of the tracer in the subcutaneous tissues. In all cases, surgical findings confirmed the suspected mechanism of malfunction as determined by the study. Conclusions: Indium 111 DTPA scintigraphy is a safe, straightforward way to identify and characterize clinical changes associated with intrathecal drug-delivery systems and to guide appropriate and clinical surgical management.