Also known as Parkinson disease, Parkinson's, idiopathic parkinsonism, primary parkinsonism, PD, or paralysis agitans - is a degenerative disorder of the central nervous system resulting from the death of dopamine-containing cells in the substantia nigra, a region of the midbrain. Despite more than a century of intensive scientific research, the cause of the cell-death is unknown.
In addition, mystery surrounds a therapeutic neurosurgical procedure for PD known asDeep Brain Stimulation (DBS) which was introduced in 1987:
“Despite its remarkable clinical efficacy in many patients with Parkinson’s disease – the exact mechanism of Deep Brain Stimulation (DBS) is as yet unknown.”
source:Clinical Neurosurgery, March 2016, Volume 127, Issue 3, Page e25