Abnormal [18F]FDG PET/MRI Findings in Paraspinal Muscles of Patients with Suspected Cerebrospinal Fluid Leak

Objectives: The symptoms resulting from cerebrospinal fluid (CSF) leaks vary widely, but the pain usually manifests as orthostatic headaches and/or nonspecific spine and body pain. Magnetic resonance imaging (MRI), MR or CT myelography, radionuclide cisternogram and CSF pressure measurement are currently the tools for confirming a suspected CSF leak, but no one diagnostic tool can rule out CSF leak with high sensitivity or are able to accurately localize the actual site of leakage (1). Since extradural CSF fluid is potentially inflammatory outside of the nervous system, we are conducting an [18F]FDG PET/MRI clinical study that aims to localize sites of increased spinal/paraspinal inflammation related CSF leaks (2,3). In this abstract, we present the abnormal imaging findings in the patients with suspected CSF leaks. Methods: IRB approval was obtained for this study. Patients included in the study were those suspected of suffering from CSF leak. Six patients suffering from chronic pain suspected to be the result of a CSF leak and six asymptomatic controls were recruited for the study. Subjects were imaged using a GE SIGNA PET/MRI system (time-of-flight PET; 3.0T bore; 4-8 min/bed position) from the head through the feet. All patients underwent imaging one hour after a single 10 mCi injection of [18F]FDG. MRI sequences obtained include an axial and coronal DESS, coronal PSIF (isotropic), axial LAVA FLEX (with water/fat separation), axial T2W FSE with fat-saturation, and axial MSDE CUBE-FLEX Radiologic review and [18F]FDG uptake measurements were conducted using image analysis software (OsiriX v.8.0 64-bit). Results: Focal increased uptake of [18F]FDG in the paraspinal muscles in all six patients (see Table1, Figures 1 & 2), significantly greater than in the corresponding areas of [18F]FDG uptake in asymptomatic controls (two-tailed t-test, p = 0.01). Asymptomatic controls did not show areas of focal increased tracer uptake. Two patients have been treated with local injections (epidural blood patches) based on PET/MRI findings and have reported significant improvement in symptoms. While all studied patients showed abnormalities with [18F]FDG PET, none of the patients showed MR abnormalities on conventional MR imaging that were obtained during routine workup of the patient at least 2 weeks prior to PET/MR imaging. In 3 out of 6 patients, increased signal (T2 or DESS) was observed in the same region of the PET abnormality using our high-resolution MR approaches