Cervical catheter placement leads to improved rostral distribution of a radiolabeled 18F-baclofen analog in cynomolgus monkeys

Abstract

Background: Intrathecal (IT) catheter delivery of baclofen via continuous infusion using an implantable pump is an important means of treating patients with severe spasticity. We evaluated the impact of IT catheter tip placement (upper vs. lower) on brain and spine distribution of a radioactive tracer molecule. Methods: Cynomolgus monkeys were implanted with an IT catheter, with the distal tip located at either C1 or T10 and attached to an implanted continuous infusion pump. A radioactive tracer molecule, an 18F-baclofen analog, and PET imaging were utilized to observe tracer distribution and quantitate levels of tracer in both the brain and spine according to catheter tip location. Results: It was consistently determined that a high cervical (C1) catheter tip placement resulted in both more rapid distribution and higher concentrations of radiotracer in the brain and upper spine compared with lower thoracic (T10) during the first 6 hours of infusion. Conclusions: These results indicate that delivery of 18F-baclofen by IT catheter results in repeatable proportional distribution within regions of the brain and spine. The data also suggest that the greatest exposure to the brain and cervical spinal cord occurs when the catheter tip is located at the first cervical vertebra.