Role of magnetic resonance imaging and 18‑fluorodeoxyglucose positron emission tomography‑computed tomography in identifying pain generators in patients with chronic low back pain

Introduction: Identification of the pain generators in low back pain is sometimes difficult with the conventional modalities such as magnetic resonance imaging (MRI), computed tomography (CT), or X‑ray. Single‑photon emission CT or fluorodeoxyglucose (FDG) positron emission tomography‑CT (PET‑CT) have
emerged as an adjuvant tool in these cases. In this study, we evaluated and analyzed the role of 18‑FDG PET‑CT in identifying active pain
generators and the outcomes of interventions based on that compared to MRI

Methods: All patients who fell under inclusion criteria . VAS and ODI scores were calculated. All the patients underwent MRI lumbosacral spine with sacroiliac (SI) joint and 18‑FDG PET‑CT whole spine. Patients in whom PET‑CT was positive and active pain generator was identified were managed for the specific level or pain generator responsible by appropriate modalities, i.e.surgery, interfacetal injections, transforaminal epidural injections, and SI joint injections. Patients in whom PET‑CT was negative were managed according to the pain generator identified on the basis of MRI and clinical correlation. Follow‑up was done after 1 week and 1 month with VAS and ODI assessments.

Results: Out of 20 , twelve patients had multiple level pathology without any significant pain generator and eight patients’ symptoms did not correlate with the MRI findings. 18‑FDG PET‑CT was done in all patients. 10% (2/20) patients were identified with active pain generators on PET‑CT which were not identified on MRI. Eleven out of twenty patients underwent intervention in the form of surgery or pain injections. The mean VAS and ODI score in the patients intervened on the basis of 18‑FDG PET‑CT improved by 70.59% and 50%, respectively, whereas in patients who underwent intervention on the basis of MRI had improvement in mean VAS and ODI score by 58.57% and 30.81%, respectively

Conclusion : Inflammation and associated degenerative process in the spine is a continuous process and affects multiple levels and might
not be easily picked up on MRI or other conventional modalities. Thus,18‑FDG PET‑CT is useful in identifying these active inflammatory
processes and thereby helping in the localization of active pain generators thus has a better outcome in patients after intervention in terms of pain relief.