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

With great interest we read the article of Frémondière et al and were pleased that your journal offered the opportunity to publish this article. Rehabilitation physicians are often involved in the aftercare of intrathecal baclofen (ITB) devices, and for this, their knowledge on troubleshooting is a prerequisite. In our experience, because sophisticated imaging examinations are not often performed, patients are often unjustifiably regarded as tolerant to ITB treatment. As a referral center for ITB troubleshooting, we have used indium-111 diethylenetriamine pentaacetic acid scintigraphy in treatment failures for many years. In the last 2 years we have also extended the standard planar investigations with tomoscintigraphy combined with single-photon emission computed tomography (SPECT-CT). Using these dynamic imaging techniques, we are able to follow the delivery of infusion and also localize a problem in the delivery tract. As a result, SPECT-CT represents an important improvement in our diagnostic procedures. The drawbacks are the high costs and the repeated visits to the nuclear medicine department. An important question to be addressed is: When should we perform an indium-111 diethylenetriamine pentaacetic acid scintigraphic examination including SPECT-CT? Frémondière et al prefer not to use an access port investigation by injecting a radiopaque contrast solution in advance; we are not in agreement with this. As they stated, the technique involves aspiration of fluid from the accessory pump port to avoid acute baclofen overdose due to an injection of contrast medium. To prevent obstruction caused by the high-viscosity dye solution, the small diameter catheter should also be rinsed with saline, and after that, to prevent a withdrawal syndrome, a calculated baclofen bolus (in accordance with the spinal catheter dead space) should be delivered with the pump. As this technique often reveals the cause of the problem, we only use scintigraphy when cerebral spinal fluid cannot be aspirated from the access port or when we have no explanation for the cause. The problems present in patients 1, 2, 3a, 4a, 4b, and 5 could probably have been discovered with an access port examination. The conclusion of a device failure in patients 3b and 5 with activity outside the pump, indicating pump fluid delivery, is not clear to us. Correct interpretation of the obtained images is sometimes difficult and may need a multidisciplinary approach. Figure 1B shows a mixture of delivered radioactivity by the pump and cerebral spinal fluid leaking from the catheter and an accumulation around the pump. With the available information, we would have concluded a pump-catheter disconnection problem as the most likely cause and not pump dysfunction.