Incoming ethical issues for deep brain stimulation: when long-term treatment leads to a 'new form of the disease'

Deep brain stimulation (DBS) has been regarded as an efficient and safe treatment for Parkinson's disease (PD) since being approved by the Food and Drug Administration (FDA) in 1997. It is estimated that more than 150 000 patients have been implanted, with a forecasted rapid increase in uptake with population ageing. Recent longitudinal follow-up studies have reported a significant increase in postoperative survival rates of patients with PD implanted with DBS as compared with those not implanted with DBS. Although DBS tends to increase life expectancy for most patients with PD, this medical benefit does not come without attendant negative consequences. For example, emerging forms of iatrogenic harms are sometimes induced-harms which were not initially expected when clinicians proposed neurosurgery and patients or their guardians consented to the treatment. We report and discuss the clinical case of a patient who was implanted with DBS more than 20 years ago (at the time of writing) and is now experiencing unexpected stages of PD. This case illustrates how extending the life span without improving quality of life may introduce a burden of harms for patients and families. As well, this case shows why we should prepare for the expanding numbers of PD-implanted patients experiencing a gain of longevity but with severe stages of disease leading to diminution in quality of life. This newly observed effect of DBS treatment requires us to explore ethical questions related to iatrogenic harms, informed consent, end of life and caregivers' burden.