Physiological ¹⁸F-FDG uptake by the spinal cord: is it a point of consideration for cancer patients?

It is essential to be familiar with normal patterns of (18)F FDG distribution in the whole body for accurate PET interpretation. We assessed FDG uptake by the spinal cord to evaluate its characteristics in cancer patients. For 101 cancer patients who underwent (18)F FDG PET/CT the spinal cord along its segments was visually assessed for FDG uptake, regarding MaxSUV-measurement ≥1 as cut-off point. This assessment was correlated with the patient's database variables. MRI and FDG PET-CT follow-up were included in the evaluation of positive subjects with FDG cord uptake. Forty-nine (48.5%) were positive for FDG cord uptake. The most encountered sites were the eleventh and twelfth dorsal vertebrae (36/49; 73.5%), all cervical (24/49; 49%), and the first lumbar segments (19/49; 38.7%). 38/49 (77.6%) and 11/49 (22.4%) were detected in the winter and summer, respectively (P = 0.007). MRI was available for 25 of the positive FDG cord uptake patients and showed no cord abnormalities, and in follow-up FDG PET-CT studies within 3-6 months 41/49 (83.7%) faded completely, while stationary or reduced uptake was observed for the remainder (8/49; 16.3%). FDG uptake in multiple consecutive segments of the spinal cord is not uncommon in cancer patients. This must be recognized as physiological, to avoid misdiagnosis as malignant involvement. Such physiological uptake is mostly encountered in the cervical, last two dorsal, and first lumbar levels, and quite frequently in winter.