1410. Non-invasive Thermal Transcutaneous Diffusion Technology in the Assessment of Shunt Function in Patients with Normal Pressure Hydrocephalus

Authors: Cassie Poole, PA-C; Diem Kieu Tran, MD; Diviya Gupta, BS; Daniel Kim, BS; Jordan Xu, MD; Jefferson Chen, MD (Orange, CA)

Introduction: Ventriculoperitoneal shunts (VPS) for idiopathic normal pressure hydrocephalus (iNPH) are becoming more common as iNPH is increasingly recognized with the expanding elderly population. iNPH is typically believed to be a low pressure/low flow state, so demonstrating patency and adequate CSF flow through shunts has been challenging. The FDA has approved a device utilizing non-invasive thermal transcutaneous diffusion technology to measure temperature gradients generated by VPS CSF flow. We demonstrate the utility of using this device in an outpatient clinic and the surprising but robust CSF flow in the iNPH shunts. Methods: This retrospective case series was performed in a neurosurgery clinic at a tertiary medical center. We included shunted patients with iNPH whose shunts were interrogated with the non-invasive thermal transcutaneous diffusion system. The rationale for the tests included obtaining baseline studies as well as patient symptomatology. This device was installed on a mobile workstation in the clinic. These studies were done from January 2015 to January 2018. Results: We identified 20 patients with iNPH who underwent shunt evaluations using this device. The female:male = 0.9:1.0. The average age was 76.62 (St. Dev.=6.4; range 66-86). Five different shunt brands were encountered, and anti-siphon valves did not seem to affect the measurements. All patients demonstrated shunt flow. Testing can be completed within 15 minutes by a single PA. Provocative testing with positioning or valve re-programming may also elicit enhanced flow. Conclusion: Symptoms of iNPH shunt malfunction are frequently insidious and mimicked by common medical ailments (i.e. urinary tract infections). The thermal transcutaneous system we examined is non-invasive, low cost and easily deployed in the clinic to garner information about shunt flow in patients with iNPH. This can obviate the need for more costly, time-consuming radiographic tests and enhance patient confidence in their care.