PET using 18F-2-fluoro-2-deoxy-D-glucose (FDG-PET) has been gradually introduced in the diagnostic clinical criteria of the most prevalent
neurodegenerative diseases. Moreover, an increasing amount of literature has shown that the information provided by FDG-PET enhances the
sensitivity of standard imaging biomarkers in less frequent disorders in which an early differential diagnosis can be of paramount relevance for
patient management and outcome. Therefore emerging uses of FDG-PET may be important in prion diseases, autoimmune encephalitis (AE) and
amyotrophic lateral sclerosis. Interestingly, FDG-PET findings can also be observed in the early phases of these conditions, even in the presence
of normal magnetic resonance imaging scans. Thalamic hypometabolism is a common finding in sporadic Creutzfeldt-Jacob disease and fatal
familiar insomnia patients, with further cortical synaptic dysfunction in the former. Limbic and extra-limbic metabolic abnormalities (more often
hypermetabolism) can be observed in AE, although specific patterns may be seen within different syndromes associated with antibodies that
target neuronal surface or synaptic antigens. FDG-PET shows its usefulness by discriminating patients with amyotrophic lateral sclerosis associated
to upper motor neuron onset that evolve to frontotemporal dementia. Besides visual and voxel based image analysis, multivariate analysis as
interregional correlation analysis and independent/principal component analysis have been successfully implemented to PET images increasing
the accuracy of the discrimination of neurodegenerative diseases. The clinical presentation and current diagnostic criteria of these neurologic
disorders as well as the emerging usefulness of FDG-PET in the diagnostic workup are presented and discussed in this review.
