To characterize clinical and imaging findings using 18F-FDG PET scans in patients with subacute neurocognitive decline, which demonstrate similar patterns of multifocal cortical hypometabolism.

Reversible neurocognitive disorders remain poorly understood, underdiagnosed, and undertreated. These disorders are often characterized by variable neuropsychiatric presentations, grossly normal magnetic resonance imaging, nonspecific findings on cerebrospinal fluid analysis, and electroencephalography that may reveal nonspecific generalized slowing. As a result, they remain controversial with unclear pathogenesis and limited objective biomarkers. Herein, we report on patients with subacute neurocognitive decline and a novel constellation of findings characterized by a regional pattern of multifocal cortical hypometabolism on brain FDG-PET in addition to consistent blood biomarkers.

This retrospective case series includes seven patients presenting with subacute neurocognitive decline and elevated thyroid antibodies. Results of brain 18F-FDG PET were compared to identify shared features of metabolic patterns.

Mean age 47 ±6.52, 6 female, 1 male. All presented with neurocognitive syndrome with elevation of thyroglobulin or thyroid peroxidase antibodies or both. Three were initially diagnosed with functional neurological disorders. All showed relative hypometabolism on FDG-PET: temporal (100%), parietal (57%), prefrontal (43%), cingulate (14%), precuneus (14%), and occipital (14%) cortices. Often, radiology interpreted the findings as consistent with Alzheimer’s disease pattern. Following immunomodulation (steroids, intravenous immunoglobulins, or rituximab), all patients clinically improved, and 2/2 patients who had repeated FDG-PET showed improved metabolism.

We describe a novel subset of patients with consistent clinical and radiological patterns with response to immunomodulation. We propose calling this subset CHANT Syndrome: Cortical Hypometabolism Associated with Neurocognitive disorder and Thyroid antibodies. Our findings highlight the importance of utilizing brain FDG-PET as a biomarker to detect multifocal cortical hypometabolism in patients presenting with subacute neurocognitive syndrome. Recognition of this pattern may facilitate earlier diagnosis and treatment. Future studies are needed to understand the pathophysiology of this neuroinflammatory disorder.