Precise Delivery Into Chronic Spinal Cord Injury Syringomyelic Cysts with Magnetic Nanoparticles MRI Visualization

Background Traumatic spinal cord injury (SCI) often results in the deficiency of glia and neurons in cystic cavities. These syringomyelic cysts can prevent axonal regeneration and sprouting. Details of the mechanism of syringomyelic cyst formation are unknown and an effective treatment for overcoming syringomyelic cysts is not available. Material/Methods Ten adult female Wistar rats underwent contusion SCI modeling resulting in syringomyelic cyst formation. A novel method for locating the cysts was developed and employed. MRI safe silver needles were inserted through the erector spinae of anesthetized rats to create a stable reference point. MRI images of the rodent spine were taken with the needles in situ. This information was used to accurately locate the cyst and determine the 3-dimensional entry point coordinates for nanoparticle delivery. Nanoparticles were injected into the cyst during a primary injection of 8 ul and a secondary injection of 8 ul, to prove the procedure can be accurately repeated. Results None of the rats died intra- or post-operatively. The syringomyelic cysts were accurately located with the 3-dimensional entry point coordinates. After nanoparticle delivery twice into each rat, the visualized syringomyelic cyst volume significantly decreased from 5.71±0.21 mm3 to 3.23±0.364 mm3 and to 1.48±0.722 mm3. Conclusions The present study describes a novel strategy for precise nanoparticle delivery into a syringomyelic cyst, using measurements obtained from MRI images. This strategy may aid in developing a new method for studying chronic spinal cord injury and a novel treatment for syringomyelic cysts.