Characterization of regional brain metabolic changes in metastatic melanoma using 18F-FDG PET/CT imaging: A case report.

Brain metastases occur in 40%-60% of melanoma patients and represent a major clinical challenge with historically poor prognosis. While conventional neuroimaging modalities such as magnetic resonance imaging (MRI) delineate metastases with high specificity, they cannot capture the widespread cerebral metabolic disruptions that underlie neurological impairment associated with infiltrative lesions. This case report demonstrates the utility of fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) in characterizing regional brain metabolic changes in metastatic melanoma. We present a case of a 78-year-old female diagnosed with metastatic melanoma who underwent 18F-FDG PET/CT restaging. The imaging findings revealed hypometabolism in regions adjacent to hypoattenuation in the left occipital area, which was subsequently confirmed as a discrete parietal lobe metastasis on MRI. Quantitative assessment using MIMneuro software across 84 brain regions revealed diffuse metabolic disturbances extending beyond the focal lesion. The most pronounced hypometabolism was observed in the cingulate gyri (z=-4.47), cerebellum (z=-2.29), pons (z=-2.22), and temporal regions (z=-2.18). In contrast, marked hypermetabolism was noted in occipital and parietal regions (z=5.71). These widespread patterns support the concept that brain metastases can result in systemic neurological defects, disrupting mechanisms related to diaschisis, vascular regulation, and immune-mediated pathways. These findings highlight the utility of 18F-FDG PET/CT in uncovering functional brain alterations not visible on conventional imaging, offering potential value in clinical decision making and disease assessment of melanoma patients with brain metastases.