Striking lack of visualization of striatum on ¹⁸F-FDG brain PET in chorea-acanthocytosis

Excerpt

A 52-year-old man presented choreic movement disorder, orofacial tics with tongue dystonia, and increasing disinhibition, without cognitive impairment. Repeat blood tests had shown spiked red blood cells (acanthocytes). Because of clinical features and blood analyses suspicious of chorea-acanthocytosis, genetic testing was conducted, which detected mutations of the VPS13A gene, a gene that encodes chorein. Deficits of this protein lead to neuronal death in the striatum [1, 2]. Therefore, the diagnosis of chorea-acanthocytosis was confirmed. An ¹⁸F-FDG PET brain scan showed a severe bilateral striatal (caudate nuclei and putamen) hypometabolism (a), without other cortical metabolic changes [2, 3]. In contrast, the MRI was initially interpreted as normal, but in a second look after the clinical diagnosis and the ¹⁸F-FDG PET findings, a mild loss of volume in the striatum was identified (b). This image highlights the striking pattern shown on ¹⁸F-FDG PET scans in the assessment of chorea-acanthocytosis, as the main neuropathological process takes place in the striatum, with alterations of glucose metabolism at such level, even before the structural changes become apparent (c; fused PET-MRI). ¹⁸F-FDG PET brain scan can be also considered as a potential supportive biomarker to monitor and evaluate possible cortical metabolic changes relative to cognitive decline, as in advance stages of the disease patients can developed dementia due to degeneration [4].

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