New Intraspinal cause of physiological FDG uptake

Physiological distribution of 18F-FDG in the spinal cord: A systematic review

Context: The importance of physiologic distribution of ¹⁸F-FDG in the spinal cord.Objective: The recognition of the physiologic distribution of ¹⁸F-FDG in the spinal cord is pivotal for accurate PET/CT imaging interpretation, especially in oncologic patients. Therefore, we performed a systematic review to investigate the normal distribution of ¹⁸F-FDG throughout the spinal cord.Methods: Data sources: We carried out a comprehensive search of the literature on the physiologic patterns of ¹⁸F-FDG distribution in the spinal cord. PubMed and Scopus databases were searched using the following keywords: "spinal cord" AND "FDG". Data extraction: Findings of the selected articles were described.Results: Thirteen studies comprising 24,125 patients entered the systematic review. These investigations showed discrepancies in location, size, number, and intensity of ¹⁸F-FDG uptake throughout the spinal cord. However, cumulative results showed that ¹⁸F-FDG uptake was higher in the lower thoracic portion of spinal cord (T11-T12). Moreover, a decreasing trend in ¹⁸F-FDG uptake was observed from cervical to lumbar levels. Low maximal standardized uptake values, female sex, and higher body weight seem to be related to the physiological spinal cord ¹⁸F-FDG uptake.Conclusions: On ¹⁸F-FDG PET/CT imaging, focal hypermetabolism of the spinal cord at the level of lower thoracic and lower cervical vertebrae should be considered physiological until proven otherwise.

Evaluation of Avulsion-Induced Neuropathology in Rat Spinal Cords with 18F-FDG Micro-PET/CT

Brachial plexus root avulsion (BPRA) leads to dramatic motoneuron death and glial reactions in the corresponding spinal segments at the late stage of injury. To protect spinal motoneurons, assessment of the affected spinal segments should be done at an earlier stage of the injury. In this study, we employed ¹⁸F-FDG small-animal PET/CT to assess the severity of BPRA-induced cervical spinal cord injuries. Adult Sprague-Dawley rats were randomly treated and divided into three groups: Av+NS (brachial plexus root avulsion (Av) treated with normal saline), Av+GM1 (treated with monosialoganglioside), and control. At time points of 3 day (d), 1 week (w), 2 w, 4 w and 8 w post-injury, ¹⁸F-FDG micro-PET/CT scans and neuropathology assessments of the injured spinal roots, as well as the spinal cord, were performed. The outcomes of the different treatments were compared. The results showed that BPRA induced local bleeding and typical Wallerian degeneration of the avulsed roots accompanied by ¹⁸F-FDG accumulations at the ipsilateral cervical intervertebral foramen. BPRA-induced astrocyte reactions and overexpression of neuronal nitric oxide synthase in the motoneurons correlated with higher ¹⁸F-FDG uptake in the ipsilateral cervical spinal cord during the first 2 w post-injury. The GM1 treatment reduced BPRA-induced astrocyte reactions and inhibited the de novo nNOS expressions in spinal motoneurons. The GM1 treatment also protected spinal motoneurons from avulsion within the first 4 w post-injury. The data from this study suggest that ¹⁸F-FDG PET/CT could be used to assess the severity of BPRA-induced primary and secondary injuries in the spinal cord. Furthermore, GM1 is an effective drug for reducing primary and secondary spinal cord injuries following BPRA.

The normal variant (18)F FDG uptake in the lower thoracic spinal cord segments in cancer patients without CNS malignancy

Focal increased lower thoracic spinal cord (18)F FDG uptake is not infrequently observed as a normal physiological finding and may be confused for spinal cord metastases. This study was conducted to evaluate a possible correlation between the lower thoracic (T11-T12) spinal uptake and lower limb movements/ambulatory status of the patients as a surrogate. The primary endpoint was to identify the possible cause(s) of the normal variant focal increased thoracic spinal cord (T11-T12) (18)F FDG activity and correlate it with the lower limb movements/ambulatory status of the patients. This was a retrospective analysis of PET-CT scans of 200 patients with solid and hematological malignancies. The focal relatively increased (18)F FDG activity in the lower thoracic spinal cord correlated strongly with the (18)F FDG intensity of the liver, bowel, C3-C5 cervical cord activity, weight of the patient and injected dose of (18)F FDG. With regard to the primary endpoint, no significant correlation was found between the ambulatory status of patients in any of the groups and thoracic spine SUVmax. This could be further assessed by performing dual studies in the same patient with and without moderate to excessive leg motion. Identifying this variant focal increased (18)F FDG activity can minimize errors of misdiagnosis and unnecessary further investigation.