The pedunculopontine nucleus and its relationship to the pathophysiology of Parkinson's disease

Several decades of neuropathological and imagenologic investigations have provided sufficient evidences about alterations in cholinergic neurotransmission that go together with the dopaminergic dysfunction in Parkinson's Disease (PD). The laterodorsal segmental Pedunculopontine nucleus (PPN) represents one of the main sources of cholinergic projections into the brain and at the same time the origin of the only cholinergic projection that substantia nigra pars compacta (SNPC) receives. at present, the study of the PPN participation as part of the physiopathology of PD has two notions: the impact of the lack of pontine excitatory influence on SNPC, associated to the early degeneration of PPN as well as the low frequency stimulation in the PPN as a beneficial surgical treatment for the axial symptoms of pd. PPN has emerged as an essential structure in the comprehension of PD physiopathology, given by its relation with the basal ganglia nuclei, thalamus, motor cortex and the spinal cord. The degeneration of some of its neuronal populations in PD pre symptomatic steps, has suggested a cause and effect relation on this finding and the death of nigral dopaminergic cells. On the other hand, PPN stimulation has favorable results on postural and gait disorders, which present themselves in late PD stages and are refractory to other pharmacological and surgical treatments.