ABSTRACT
A progressive and debilitating neurodegenerative process, Parkinson’s disease
(PD) is characterized by systemic degeneration of dopaminergic neurons, with
selective loss in the brain’s basal ganglia-a bundle of neuron fibers consisting
of the corpus striatum, subthalamic nucleus (STN), and substantia nigra. Overt
PD symptomatology typically emerges after 70% of dopaminergic reduction in
the nigrostriatal regions (1). Primary behavioral manifestations of the disorder
include resting tremor, bradykinesia, postural instability, and rigidity. As
such, PD is regarded primarily as a movement disorder. However, various
secondary “nonmotor” disturbances are common in PD, likely due to disruption
of noradrenergic and serotonergic neurotransmitter systems, as well as systemic
disruption of the dopaminergic system. These nonmotor symptoms include
psychiatric and cognitive changes, as well as autonomic, sleep, and sensory dis-
orders. Changes in mood and cognition are common in the advanced stages of
PD, though they may antedate the onset of obvious motor symptoms. Psychia-
tric complications of PD include anxiety, depression, apathy, hypersexuality,
and other neuropsychiatric symptoms ranging from vivid dreams to psychosis
and delirium. Changes in cognitive functioning are common and may range
from none or slight impairment of cognitive abilities to frank dementia.
