Neuropsychological and 18FDG-PET studies in a family with idiopathic basal ganglia calcifications

Idiopathic basal ganglia calcification (FIBGC) is a rare autosomal dominant neurodegenerative disease, the main clinical signs of which are parkinsonism, cognitive deterioration and/or psychiatric troubles. Familial forms are rare. The underlying basis is not known. We performed detailed neurological, neuropsychological, brain CT scans and MRI evaluations in 15 patients of a large FIBGC family. Three patients also underwent a 18FDG-PET scan study not previously performed in patients with FIBGC. Basal ganglia calcifications were present in 8 individuals, 3 of which had schizophrenia-like psychosis, cognitive and/or extrapyramidal signs. The mean age at disease onset was 34.0 ± 3.6 years. Two patients had moderate executive dysfunction, whereas the proband had more severe dementia. 18FDG uptake was significantly reduced in striatal or cortical areas, including the precuneus, posterior cingulate and superior temporal gyri. This study shows that calcifications and striatal neuronal degeneration can occur independently, and that functional changes in cortical areas can be observed early in FIBGC. Hypometabolism in the precuneus and posterior cingulate gyrus, which are involved in episodic memory processing, could be responsible for the episodic memory deficit found in the patients. Whether the underlying mechanism involves a neuronal loss or a functional alteration remains to be elucidated.