Usefulness of Imaging for Intrathecal Drug Delivery Systems: An update

Abstract

Intrathecal Drug Delivery Systems are invasive pain treatment techniques that require bypassing the blood-brain barrier in order to implant a catheter inside the CSF. Imaging is a key element before and during implantation as well as in the diagnosis of complications. The understanding of delivery mechanisms has been greatly improved using MRI. Drug diffusion can now be modeled according to infusion level and flow rate for each individual patient. MRI and CT are useful in diagnosing the patient, targeting spinal level, and accurately evaluating implantation concerns or contraindications. Imaging is a key tool during the implantation of the device. Catheter positioning is essential as the treatment diffusion is limited, and the tip of the catheter must be set behind the spinal cord. Currently, fluoroscopy is the gold standard for catheter placement. Biplane Interventional Imaging and surgical CT scan will soon be able to help with more accurate positioning. An ultrasoundguided technique is helpful to localize a recessed septum in challenging pump refill procedures where pumps are deeply situated. Imaging is also essential for device malfunction diagnosis. Plain radiology is currently limited as new catheters have a poor opacity, but it remains useful for confirming motor stall of the peristaltic pump and is appropriate for the diagnosis of pump rotation. High-resolution threedimensional Computer Tomography reconstruction allows accurate control of catheter positioning and the diagnosis of dislodgment, kinking, and breaking. MRI is the most accurate imagery to diagnose spinal cord injuries following implantation or as an adverse effect of IT treatment such as granuloma. Diffusion control requires dynamic imaging which can be performed by TC99 scintigraphy. This allows for the visualization of drug diffusion and velocity. In the near future, novel techniques such as PET-CT scan could be useful for testing the distribution of intrathecal drugs