Isotopic scintigraphy combined with computed tomography: a useful method for investigating inefficiency of intrathecal baclofen

Isotopic Scintigraphy in Intrathecal Drug Delivery Failure: A Single-Institution Case Series

Background

The aim of this study was to assess the feasibility and diagnostic accuracy of an optimized ¹¹¹Indium‐diethylenetriamine‐penta‐acetic‐acid single‐photon‐emission computed tomography (CT) (¹¹¹In‐DTPA SPECT‐CT) examination in patients with suspected intrathecal drug delivery (ITDD) failure.

Materials and Methods

Retrospective analysis of routinely collected observational data from a case series of patients in the setting of the academic Center for Pain Medicine, Departments of Radiology and Nuclear Medicine and Neurosurgery. Twenty‐seven patients participated between January 2014 and January 2019. Thirty‐six optimized examinations including standardized pump flow rate with additional SPECT‐CT imaging and a stepwise standardized analysis were performed. A 10 mL mixture of medication and 20 MBq 111In‐DTPA was injected into the pump reservoir. Planar and SPECT‐CT images were acquired at 24, 48, and 72 hours (h) after injection and at 96 hours and/or seven days, if needed. All images were reassessed by the first two authors using an optimized procedure.

Results and Conclusions

Twenty‐two abnormalities were identified in 21 examinations, with these abnormalities consisting of leakage (n = 7), spinal catheter obstruction (n = 7), and cerebrospinal fluid flow obstruction (n = 8). Interventions (n = 19) confirmed the cause of ITDD failure. A false‐positive finding at follow‐up (n = 1) and a false‐negative finding (n = 1) were encountered. Sensitivity was 95% (20/21) and the specificity 93% (14/15). A significant difference (p < 0.001) was found between the accuracy of the conventical and the optimized analysis. The optimized ¹¹¹In‐DTPA SPECT‐CT examination is a powerful diagnostic tool for detecting the cause of ITDD failure.

Catheter Access Port (Computed Tomography) Myelography in Intrathecal Drug Delivery Troubleshooting: A Case Series of 70 Procedures

Objectives

Intrathecal drug delivery is used for the treatment of intractable spasticity, dystonia, and pain. When the symptomatology fails to respond to therapy, the cause could be failure of the medication infusion. The purpose of this study is to assess pump catheter access port (CAP)‐myelography and CAP‐CT‐myelography as advanced imaging methods in treatment failure.

Materials and Methods

We analyzed observational routinely collected data of 70 CAP procedures with 2D/3D reconstructions and additional imaging of 53 adult patients where the cause of treatment was unclear between November 2013 and November 2018. CAP‐myelography and CAP‐CT myelography were performed with postprocessing 2D/3D reconstructions. When myelography could not be obtained or when the result did not reveal the cause of the treatment failure, additional procedures, such as noncontrast CT, MRI, lumbar puncture CT, and 111Indium‐DTPA SPECT‐CT, were performed.

Results

CAP fluid aspiration prior to contrast medium injection was not possible (N = 17). In one case, contrast was injected into the pump pocket unintentionally (N = 1). Of 70 procedures, 24% were unaspiratable. The remaining CAP myelography examinations (N = 52) had limited value for the diagnosis. CAP‐CT myelography (N = 50) was normal (N = 31). The abnormal results (N = 19) were dorsal dural leak (N = 5), subdural catheter position (N = 2), limited rostral flow of contrast material (N = 4), limited and abnormal contrast distribution (N = 3), obstruction of rostral flow (N = 2), a leak at the pump‐catheter connection (N = 1), and a sheared catheter localized in the pump pocket (N = 2). Limited contrast distributions were found to be false positive findings (N = 2). Four normal CT‐CAP myelographic procedures were false negatives, as the reference tests revealed a cause of intrathecal drug delivery (ITDD) failure. The CAP‐CT procedures resulted in a sensitivity of 81% (17/21) and a specificity of 93% (27/29).

Conclusions

CAP‐CT myelography with 2D/3D reconstructions is an essential step in the diagnostic algorithm for cases involving ITDD failure.

Plain radiography in patients treated with intrathecal drug delivery using an implantable pump device

OBJECTIVES

Intrathecal drug administration using an implanted pump system is well established in intractable spasticity and pain. However, despite continuous advancements in manufacturing technology, adverse events related to the pump and catheter still occur. Most of them, such as migration, damage, disconnection and occlusion, are related to the spinal catheter. The aim of this overview is to update radiologists on how plain radiography of the implanted delivery system for intrathecal drug administration should be interpreted and to increase awareness for the need of urgent and timely multidisciplinary troubleshooting.

METHODS

Plain radiographic images of patients treated with intrathecal drug administration using an implantable drug delivery system were analysed in a multidisciplinary setting at our (university) referral centre for complications in intrathecal drug administration.

RESULTS

Examples of catheter-related adverse events are described and a proposal is made for stepwise interpretation of standard plain radiographic images.

CONCLUSIONS

Plain radiological images are the mainstay for the diagnosis of catheter-related adverse events in intrathecal drug delivery. Radiologists play an important role in an early diagnosis. An awareness of abnormal radiological findings seems important to avoid a life-threatening withdrawal syndrome.

TEACHING POINTS

• Untimely cessation of intrathecal drug delivery can lead to a life-threatening withdrawal syndrome. • Initially mild symptoms can lead to an exacerbation of a withdrawal syndrome. • Most intrathecal catheter-related problems are visible on plain radiography. • Common causes of catheter problems are migration, lacerations, occlusion and disconnection. • Knowledge on implanted intrathecal catheters is crucial for interpretation of plain radiography.

Isotopic Scintigraphy Coupled With Computed Tomography for the Investigation of Intrathecal Baclofen Device Malfunction

OBJECTIVE

To assess the potential use of indium-111 diethylenetriamine pentaacetic acid ((111)In-DTPA) scintigraphy coupled with computed tomography (CT) for the investigation of intrathecal baclofen (ITB) device malfunction.

DESIGN

Retrospective study of a case series of patients.

SETTING

Neurosurgical and physical and rehabilitation medicine departments.

PARTICIPANTS

Patients (N=7) with reduced ITB effectiveness in whom prior conventional radiographs were inconclusive.

INTERVENTION

Nine (111)In-DTPA scintigraphic studies and 8 CT scans. Planar acquisitions were followed by tomoscintigraphy combined with CT.

MAIN OUTCOME MEASURE

Progression of the radiotracer in the pump, catheters, and in the subarachnoid space.

RESULTS

In 7 cases, scintigraphy coupled with CT showed leakage behind the pump, lack of activity outside the pump reservoir, abrupt interruption of activity in the catheter, or abnormal distribution of the radiotracer, thus demonstrating that the drug did not reach its target. Surgical revision confirmed these findings in 5 cases. In 1 case, combined imagery ruled out device dysfunction. In the remaining case, only planar acquisitions were performed, showing correct diffusion of the radiotracer.

CONCLUSIONS

The combination of scintigraphy and CT provides simultaneous functional and anatomic imagery of the device. The slow infusion of the radioisotope mimics the diffusion of baclofen, and this could be a useful method to explore intrathecal device malfunction. Further studies are required to compare scintigraphy coupled with CT, to radiopaque injection followed by fluoroscopy or CT.