932 - Complication of lower extremity paraplegia measured by Spinal Cord Stimulator impedance following SCS implantation: A Case Report

67 year old female with chronic low back pain and bilateral lower extremity radiculopathy presented for a T10/T11 laminectomy for T8/T9 Dorsal Column Stimulator (DCS) paddle implant. In the operating room DCS implantation was successful without any complications however upon arrival in PACU patient started experiencing new onset weakness in bilateral lower extremities. Upon examination patient was noted to have 0/5 strength consistent with findings of T8 paraplegia. It was then noticed that the impedances which were previously normal in the operating room were slowly increasing reaching over 16,600 ohms. There was concern of device failure and patient was immediately returned to operating room where  patient was found to have a severely stenotic spinal canal at T8/T9 leading to thecal sac indentation.  It was decided to go forward with decompressive laminectomy at T8/T9 after which neurological symptoms resolved with post-op physical examination demonstrating 5/5 strength in bilateral lower extremities. 

Discussions: Spinal cord stimulation (SCS) is a treatment used for back pain that has failed other modalities such as therapy, medications, or injections. To properly understand SCS it is essential to understand the components of current, voltage, and impedance. Lead impedance represents tissue resistance to the changes in voltage that travels as a current through the electrodes.  Changes in impedance can be acute or chronic. Acute impedance changes can result from lead migration, spine positional alterations, or abrupt CSF changes. As with any treatment monitoring for postoperative complications is essential.

Conclusions: This case highlights an example of an acute elevation in SCS impedance. Up till now there are not many studies correlating acutely elevated SCS impedance to postoperative complications. In the future this may warrant postoperative monitoring of SCS impedance as a measuring tool to effectively predict any further neurological evaluation.