Pain Physician. 2016 Jul;19(5):E775-80.

High-Resolution Three-Dimensional Computed Tomography for Assessing Complications Related to Intrathecal Drug Delivery.

Morgalla M, Fortunato M, Azam A, Tatagiba M, Lepski G.

University of Tuebingen, University Hospital, Dept. of Neurosurgery, Tuebingen, Germany.

 

ABSTRACT

Background: The assessment of the functionality of intrathecal drug delivery (IDD) systems remains difficult and time-consuming. Catheter-related problems are still very common, and sometimes difficult to diagnose.

Objectives: The aim of the present study is to investigate the accuracy of high-resolution three-dimensional computed tomography in order to detect catheter-related pump dysfunction.

Study design: An observational, retrospective investigation.

Setting: Academic medical center.

Methods: We used high-resolution 3D computed tomography with volume rendering technique (VRT) or fluoroscopy and conventional axial-CT to assess IDD-related complications in 51 patients from our institution who had IDD systems implanted for the treatment of chronic pain or spasticity.

Results: Twelve patients (23.5%) presented a total of 22 complications. The main type of complication in our series was catheter-related (50%), followed by pump failure, infection and inappropriate refilling. Fluoroscopy and conventional CT were used in 12 cases. High-resolution 3D CT (VRT) scan was used in 35 instances with suspected yet unclear complications.

Using 3D-CT (VRT) the sensitivity was 58.93 %-100% (CI 95%) and the specifity 87.54%-100% (CI 95%).The positive predictive value was 58.93%-100% (CI 95%) and the negative predictive value: 87.54%-100% (CI 95%).

Flouroscopy and axial CT as a combined diagnostic tool had a sensitivity of 8.3%-91.7% (CI 95%) and a specifity of 62.9%-100% (CI 95%). The positive predictive value was 19.29%-100% (CI 95%) and the negative predictive value: 44.43 – 96.89% (CI 95%).

Limitations: This study is limited by its observational design and the small number of cases.

Conclusion: High-resolution 3D computed tomography (VRT) is a non- invasive method that can identify IDD-related complications with more precision than axial CT and fluoroscopy.

Key words: volume rendering technique (VRT), intrathecal drug delivery systems, high-resolution 3D computed tomography, complications, spasticity, chronic pain, cost effectiveness, fluoroscopy.

 

 

SUPPLEMENT

Intrathecal drug administration is considered efficacious for the treatment of severe spasticity and pain (1-3). In spite of the clinical efficacy, a high level of adverse events (AE) is reported during chronic intrathecal therapy (4-7). Although several publications have addressed complications related to intrathecal therapy (8-10), a better diagnostic workflow is highly desirable. Here, we investigated the role of CT with the aid of 3D volumetric rendering techniques (VRT) for the diagnosis of catheter-related complications after pump implantation (11,12).

In all patients, an IDD system was implanted using a standardized surgical protocol. The implanted systems were purchased from different companies: Medtronic Synchromed® II (n=31), Tricumed® (n=14), Medstream® Codman (n=8), Medtronic Isomed® (n=4), Infusaid® Fa. Bitzer (n=2) and Archimed-Typ® (n=1).

If we suspected a catheter-related problem such as a disconnection, kink, stricture or catheter dislocation, we routinely performed an abdomen CT with volume rendering technique (VRT) reconstruction (SOMATOM® Definition Flash Scanner, Siemens). First, the medication was aspirated from the catheter via the access port of the pump, and a contrast agent was injected prior to CT-scan acquisition of the abdomen. Next, the images were reconstructed using VRT. Specifically, we used maximum intensity projection (MIP), which is a data visualization method that enables the detection of structures that give off high intensity signals, probably suitable for visualization of IDD systems (11,12). With MIP, the pump and the associated catheter were visualized continuously in a three dimensional fashion. Additionally, a perception of rotation was created in order to permit pump visualization from different angles.

 

This retrospective observational study was conducted on patients treated between 2003 and 2013 at the Neurosurgical Clinic of the University Hospital of Tuebingen, Germany.

We enrolled in this study 51 patients, 24 women (47%) and 27 men (53%). The median age was 54 years (18-78 years). The main indications for surgery were as follows: 28 patients for spastic disease (54.9%), 2 for generalized dystonia (3.9%) and 21 for chronic pain (41.2%). A total of 60 pumps were implanted, including those used in re-operations due to complications. Of those 60 pumps, 36 were used for baclofen delivery and 24 for morphine. We detected a total of 22 complications, half of which were catheter-related. Among the catheter-related problems, one case (9.1%) was a pump disconnection, 3 were spinal catheter disconnections (27.3%), three were intrathecal catheter dislocations (27.3%), one was a minor catheter leak (9.1%) and two were strictures or obstruction of the catheter (18.2%).

 

We performed conventional X-rays in all cases with possible malfunction of the system. In 35 instances with suspected but uncertain complications after conventional diagnosis, high-resolution 3D CT (VRT) was used.  In 7 of these cases, catheter-related problems were detected and needed further surgical treatment (fig. 1A-C). In all cases, where the high-resolution 3D CT (VRT) scans revealed a cause for the dysfunction, the diagnosis was confirmed intra-operatively. In 28 cases in which high-resolution 3D CT (VRT) was used, no abnormalities were detected and surgical revision was avoided.

This method rendered a sensitivity of 58.93 %-100% (CI 95%) and a specificity of 87.54%-100% (CI 95%).The positive predictive value was 58.93%-100% (CI 95%) and the negative predictive value: 87.54%-100% (CI 95%).

Taken together, the investigation of IDD-malfunctioning with 3D CT (VRT) scans allowed higher sensitivity and specificity in comparison with the standard methods (conventional X-ray and fluoroscopy). With this strategy, even small catheter leaks, minimal kinking or obstruction can be easily identified.

 

The evaluation of complications related to intrathecal drug delivery systems is difficult, time-consuming and dependent on ample clinical experience (13-14, 15-16). Obvious signs such as a fluid collection around the pump or a swelling near the wound are less common. Plain X-rays may only reveal gross abnormalities and often do not allow the visualization of the catheter behind the pump. An ordinary axial CT of the abdomen can improve visualization somewhat, but a high-resolution 3D CT of the abdomen using VRT reconstruction provides visualization of the full length of the catheter at crucial locations: the connection at the pump, the area behind the pump, the connection of the catheter at the spine, as well as its intrathecal course. This technique can be performed quickly on an outpatient basis.  In the beginning we used multiplanar imaging (coronal, sagittal and axial reconstructions). But now we hardly use these reconstructions any more. High resolution surface rendered 3D computed tomography using VRT has the advantage to view the pump and its catheters as a whole in different rotational projections. Other tissues than bone are not visualized. We think that possible problems regarding the catheters can be identified thoroughly that way. VRT reconstructions are currently not yet a routine method in most of the imaging departments.

In the literature, there is only one case report describing the utility of this method for identification of a small leak (17). Here, we strengthen the value of this technique for the diagnosis of pump dysfunctions when simple diagnostic tests fail to demonstrate the underlying cause.

 

Our data suggest that high-resolution 3D CT (VRT) seems to be superior to the current standard diagnostic techniques for diagnosing catheter-related complications.

However, our study is an observational study. It lacks the direct comparison of fluoroscopy and 3D-CT on the same patient. The number of comparable complications is also small in order to perform statistical comparisons between the different methods. Therefore, prospective studies which address these needs are still necessary.

The evaluation of complications associated with the use of IDD systems remains challenging. High-resolution 3D computed tomography (VRT) improves the identification of catheter-related complications. Slow catheter leaks can also be located more accurately using this technique than with fluoroscopy. Therefore, we recommend high-resolution 3D computed tomography (VRT) as a first line examination method whenever catheter-related IDD system complications are suspected.

 

 

 

 

 

A patient with an intrathecal drug delivery device (IDD) suffered a severe fall with a subsequent marked increase in pain. A catheter-related complication of his pump was suspected and different diagnostic examinations were undertaken:

A) A plain X-ray revealed no abnormalities.

B) A 3D CT with VRT reconstruction of the anterior posterior view detected no abnormalities.

C) Only after rotation of the pump using the same 3D CT with VRT reconstruction it was possible to view the catheter behind the pump. Here, a stricture of the catheter close to one of the fixation sutures of the fascia was identified. The patient underwent surgery and the stricture was released.

 

MH Morgalla MD PhD FCS/SA

Professor of Neurosurgery

Head of Neurosurgical Pain Clinic

Department of Neurosurgery

University of Tuebingen

Hoppe-Seyler-Str. 3

D-72076 Tuebingen

Germany

Tel.: 0049-7071-2986679

Fax.: 0049-7071-295621

Email: matthias.morgalla@med.uni-tuebingen.de

Web: www.neurochirurgische-schmerztherapie-tuebingen.de

 

 

 

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