Functional imaging of non-motor signs in Parkinson's disease.

Non-motor signs encountered in Parkinson's disease consist in a heterogeneous group of manifestations including hyposmia, pain, fatigue, sleep disorders, neuropsychic disorders. Functional imaging techniques provide an invaluable method to understand their pathophysiology, allowing us to study the abnormalities of brain metabolism or perfusion associated with these manifestations or the underlying dysfunction of different neurotransmission systems. The present paper covers the recent advances provided by functional imaging in this area.