Since 2002, deep brain stimulation (DBS), the surgical implantation of a pacemaker-like device that sends electrical impulses to targeted parts of the brain, has been used as a treatment for motor symptoms of Parkinson’s disease (PD). But are patients trading part of their sense of self in exchange for improved mobility?
In the last decade, a growing number of published articles have raised the concern of personality changes in PD patients as a result of DBS, and tried to discern if the concern is real or overblown. At Thursday’s International Neuroethics Society (INS) meeting discussion “DBS: Continuity of Self,” panelists aimed to add clarity to the debate. “Speculation shouldn’t be divorced from clinical reality,” said panel moderator and ethicist Hannah Maslen, who introduced the session.
The speakers, philosopher and neuroethicist Frederic Gilbert, neuropsychologist Cynthia Kubu, behavioral neurologist Winston Chiong, and ethics researcher Jonathan Pugh, offered a range of perspectives. They largely focused on the state of the evidence and why it’s so difficult to assess personality changes in patients.
There isn’t much empirical data available, Gilbert said. In a review paper he authored, he found that of 1,535 articles from the 30 top bioethics journals he found on the topic, only 64 qualified as first-hand studies, and forty-three of those did not support a direct link between DBS and changes in personality, identity, agency, authenticity, autonomy, and self. [Contribute to new research on the subject by submitting a paper to Neuroethics by February 1!]
But what does the existing primary research say?
In his own work, Gilbert and colleagues conducted interviews with 17 Australian patients implanted with DBS, focusing on their self-experience through the process. The researchers found a correlation between patients who already felt alienated by the disease and those who felt post-operative feelings of estrangement.
One patient who met this criterion told them, “[Parkinson’s disease] really takes over. … I couldn’t work, which was a big part of my identity. … If I didn’t have the device I’d probably be dead right now,” and later states “I think that [DBS] does change you as a person.”
Feelings of estrangement could be qualified as deteriorative, reflecting loss of control, for example, or restorative, reflecting , such as increased confidence and/or strength, he reported. The majority of the 17 people he studied reported the latter.
Kubu, who was awarded a grant from the National Institute of Health last year to study how DBS affects PD patients, documents patient and care-partner perspectives and experiences before and after DBS. She uses standard personality measures and personal narrative to inform her research, asking questions such as “What words best describe you?” and “What characteristics are you most afraid of losing?”
Her preliminary observations note that how you ask a question shapes the answer. PD changes personality from both the patient and family perspective, and existing personality measures do not capture all characteristics that patients and family members value.
On the second point, it’s important to recognize that the disease itself carries cognitive and behavioral symptoms that can affect personality. Kubu listed several examples, including depression, anxiety, apathy, hallucinations, delusions, and impulse control. [In scenarios where DBS is used to treat mental health conditions such as depression, this issue only becomes even more complicated. DBS pioneer Helen Mayberg discusses her work with DBS and depression in our article, “What is Well?”]
“There’s an overabundance of competing explanations” for personality changes, said Chiong, who pointed to the external environmental, such as a death in the family, as another potential cause.
But, when does the reward outweigh the risk? The wide-scope view is that DBS does change personality/identity/self, said Pugh, but almost all successful medical procedures lead to some change in the patient. He pointed to the need to consider both the costs and the benefits of the health outcomes, and to adequately inform patients of the full range of potential issues related to DBS.
Stay tuned for our coverage of the INS public program, “My Brain Made Me Buy It.”
–Ann L. Whitman