Deep brain stimulation
In 1983, designer drug users took MPTP, which created a Parkinsonian syndrome. Later that same year, researchers reproduced the effect in non-human primates. Over the next seven years, the brain areas that were over- and under-active in Parkinson's were mapped out in normal and MPTP-treated macaque monkeys using metabolic labelling and microelectrode studies. In 1990, deep brain lesions were shown to treat Parkinsonian symptoms in macaque monkeys treated with MPTP, and these were followed by pallidotomy operations in humans with similar efficacy. By 1993, it was shown that deep brain stimulation could effect the same treatment without causing a permanent lesion of the same magnitude. Deep brain stimulation has largely replaced pallidotomy for treatment of Parkinson's patients that require neurosurgical intervention. Current estimates are that 20,000 Parkinson's patients have received this treatment.