Incremental value of whole-body 18 F-fluorodeoxyglucose PET/computed tomography in cavernous sinus syndrome: guiding...

Cavernous sinus syndrome (CSS) has diverse causes and correctly identifying the underlying pathology is difficult. The study aimed to determine the incremental value of whole-body 18 F-fluorodeoxyglucose (FDG)-PET/computed tomography (CT) in detecting extra-cranial involvement in CSS, to guide biopsy sites; and characterizing cavernous sinus pathologies based on metabolic activity.

Participants with treatment-naive CSS after clinical assessment and MRI brain were recruited prospectively from July 2022 to December 2023. All the participants underwent whole-body 18 F-FDG-PET/CT, and images were analyzed for the presence, site, extent, and standardized uptake value (SUV max ) and feasibility of biopsy from cavernous sinus and extracranial lesions. Reference standards were histopathology, definite MRI findings, or established diagnostic criteria for immunoglobulin G 4 -related disease, neurosarcoidosis and Tolosa-Hunt syndrome.

Data of 54 patients (mean age: 44.8 years) was analyzed. Cavernous sinus lesion was detected in all 54 patients, and 26 (48.1%) patients had extra-cranial lesions. PET-directed biopsies were done from the local extension of FDG-avid cavernous sinus lesions in 20 (37%) and extra-cranial lesions in 12 (22.2%) patients. The final etiological diagnoses were infection in 18 (33.3%), inflammatory disorders in 18 (33.3%), benign neoplasms in 11 (20.5%), and malignancy in seven (12.9%) cases. PET/CT demonstrated significantly lower FDG-avidity in benign cavernous sinus neoplasms (median SUV max : 5.5, IQR: 4.5-8.0) as compared to the infective, inflammatory, and malignant conditions involving the cavernous sinus (median: 15.0, IQR: 10.7-22.4; P  < 0.001). Bony erosions and contiguous paranasal involvement were more frequently associated with infective CSS ( P  < 0.001).

Whole-body 18 F-FDG-PET/CT effectively identifies extracranial disease in CSS, enables less invasive biopsy site selection, and enhances diagnostic yield while minimizing high-risk intracranial biopsies. 18 F-FDG-PET/CT should be considered in imaging of CSS, especially when definite diagnosis is not established with conventional workup.