SPECT and PET imaging of apathy

Abstract

Apathy is a frequent behavioural syndrome which is now characterised by precise criteria. It can be found in various neurological diseases. In Alzheimer’s disease in particular, it is present at all stages and, in MCI patients, is a risk factor for conversion. Anterior cingulate-subcortical circuit which originates from the anterior cingulate cortex in Brodmann’s areas (BA) 24 and 32 and projects to the limbic striatum, globus pallidus and thalamus is the anatomical support of motivated behaviour. Lesions of this cortico-subcortical circuit are responsible for apathetic syndromes. SPECT perfusion studies fi rst demonstrated in vivo the relationships between apathy and lesions of this circuit. FDG PET studies confi rmed these fi ndings in particular in AD. In degenerative diseases, apathy is generally related to anterior cingulate hypoperfusion or hypometabolism. This is a recognisable pattern for image interpretation. In post-stroke patients, the situation is different, apathy being mostly due to lesions located at the subcortical levels of the circuit. More neurotransmission imaging studies are necessary to complete the understanding of the pathophysiology of this syndrome and to participate to specifi c treatment developments.