[Google Scholar] 2. evidence of infections. CSF 14-3-3 and tau protein assay results were pending during hospitalization. Admission diffusion-weighted image (DWI) brain MRI demonstrated hyperintense cortical ribboning throughout the left hemisphere with corresponding hypointensity on apparent diffusion coefficient (ADC) mapping, sparing bilateral caudate nuclei and putamen (figure, A and B). Admission EEG was low voltage with slight left hemispheric slowing in the delta/theta range, without periodic sharp-wave complexes commonly associated with prion disease. Open in a separate window Figure MRI and fluorodeoxyglucose-PET imaging(A) Diffusion-weighted image shows hyperintense cortical ribboning throughout the left hemisphere with (B) corresponding restricted diffusion on apparent diffusion coefficient map, better seen in the left precuneus (large arrow) and cortical gray matter (small arrows) sparing the Anethol bilateral caudate nuclei and putamen. (C) On fluid-attenuated inversion recovery, no conspicuous hyperintense signal is noted in the left cerebral cortex. (DCF) In a separate study, FDG-PET showed increased uptake in the left posterior cingulate gyrus, left posterior frontal cortex, left occipital cortex, left thalamus, and left precuneus. On day 6 the patient followed no commands, and had right facial myoclonus, right hemineglect, and severe ataxia. Antithyroperoxidase antibody level was 528 WHO units/mL blood. CT demonstrated a thyroid nodule and a 4-mm right upper lung nodule with 1 prominent hilar lymph node. Whole-body FDG-PET on COL18A1 day 8 demonstrated increased uptake in the left posterior cingulate gyrus, posterior frontal cortex, occipital cortex, thalamus, and precuneus (figure, DCF). EEG 9 days after admission again showed low voltage without an alpha Anethol rhythm. On day 9, treatment with high-dose IV steroids and IV immunoglobulins was initiated for a 5-day course. By day 13, the patient was fully orientated with improved memory, was able to follow commands, had fluent speech, and walked unassisted. The myoclonus and hemineglect resolved. Three days after hospital discharge, the autoantibody assays showed raised neuronal voltage-gated potassium channel (VGKC) antibody and P/Q-type calcium channel antibody titers (0.05 nmol/L and 0.07 nmol/L, respectively; normal 0.02 nmol/L). CSF 14-3-3 protein was detected and tau protein was 1,152 pg/mL (normal 1,150 pg/mL). Thyroid nodule and hilar lymph node biopsies were unremarkable. DISCUSSION This patient with RPD met clinical criteria for probable and proposed MRI criteria for definite sCJD, contrary to prior reports of AE mimicking sCJD.1,C3 Autoimmune conditions are common and potentially treatable nonprion RPD etiologies.4 His smoking history, hyponatremia, pulmonary and thyroid nodules, and prominent hilar lymph node raised concern for an AE. In addition, CSF protein is not typically elevated in sCJD.1,4 A similar presentation has been Anethol reported in 2 cases with VGKC autoimmunity.5 Both asymmetric DWI/fluid-attenuated inversion recovery (FLAIR) hyperintensities and hypointense ADC maps in the cingulate, striatum, or cortex have been cited in differentiating sCJD from nonprion RPD, with DWI hyperintensities reportedly more sensitive than FLAIR abnormalities in sCJD.1,2,4 Conversely, cortical DWI hyperintensity with normal ADC mapping has been described in VGKC autoimmunity, a point of distinction of AE from sCJD.4,5 The AE case presented here contradicts these descriptions. Of note, qualitative and quantitative evaluation of ADC maps for changes in cortical gray matter signal is challenging due to close proximity to hyperintense subarachnoid CSF signal, especially in the absence of associated abnormal subcortical signal.2 Brain FDG-PET was obtained to distinguish sCJD from AE, with cerebral hypermetabolism suggesting an autoimmune process.6,7 In the absence of evidence of an infectious or primary malignant process, the brain FDG-PET findings prompted the initiation of first-line immunomodulatory therapy, suggesting further utility of this modality beyond occult malignancy screening in the evaluation of RPD.4 Confirmatory serum autoantibody results.