Non-motor dysfunction in Parkinson's disease

In the field of neurology, Parkinson's disease (PD) is commonly perceived to be a disorder affecting only the (extrapyramidal) motor system, characteristically manifesting as bradykinesia, rigidity, tremor and postural instability. Although non-motor symptoms such as behavioural abnormalities, dysautonomia, sleep disturbances and sensory dysfunctions are also common and quite disabling manifestations of the disease, they are often not formally assessed and thus are frequently misdiagnosed and/or under diagnosed. For this reason, in this review we have concentrated on the pathophysiological and clinical basis of non-motor involvement such as olfactory dysfunction, depression, dementia, dysautonomia and sleep disorders in PD. The early recognition of these symptoms may well perhaps lead to an earlier diagnosis of PD, but in any case should lead to more prompt and effective treatment of the relatively unrecognized non-motor problems associated with PD.