Non-motor Symptoms Determine Quality of Life After DBS
“Postoperative QOL was associated with non-motor symptoms … rather than motor symptoms,” the researchers found, specifically noting that patients with worse impulsivity pre-surgery had a lower quality of life following the procedure than those without such issues.
Importantly, the findings also show that, three years after DBS, patients reported significant depression and problems with verbal fluency.
The study, “Neuropsychiatric Symptoms in Parkinson’s Disease After Subthalamic Nucleus Deep Brain Stimulation,” was published in Frontiers in Neurology.
Deep brain stimulation, known as DBS, is a surgical treatment for Parkinson’s that involves implanting a device to stimulate specific parts of the brain with electricity. The effectiveness of DBS to treat motor symptoms of Parkinson’s is well-established.
However, compared with the effect on motor symptoms, the impact of DBS on a person’s quality of life tends to be fairly small. In the new study, a team of researchers in Japan hypothesized that this discrepancy could be due to non-motor symptoms affecting the patients’ quality of life after surgery.
To test this idea, the team evaluated 61 people with Parkinson’s who underwent DBS at Chiba University Hospital, in Japan. The patients were on average 65.3 years old, and had been living with Parkinson’s for an average of 11.9 years.
Assessments of the study participants were done before surgery, then at three months, one year, and three years after the procedure. Of note, fewer participants were assessed at the later timepoints — specifically, 54 participants were evaluated after three months, as compared with 23 after three years — which the researchers acknowledged as a major limitation of the study.
A battery of different assessments were used, including the Unified Parkinson’s Disease Rating Scale or UPDRS, which measures both motor and non-motor symptoms, as well as appraisals of depression, impulsivity, and cognition. The participants’ QOL was measured with the 39-item Parkinson’s disease questionnaire, called PDQ-39.
Following surgery, motor symptoms substantially eased, consistent with the known effects of DBS.
Using statistical analyses, the researchers looked for connections between these various measures over time.
The team found that, prior to DBS surgery, motor symptoms — as assessed by the UPDRS — were major determinants of life quality. This finding was reasonable, according to the researchers, since DBS is usually given to people who have substantial motor symptoms that are impairing their daily life.
In contrast, after surgery, motor symptoms were not significantly associated with QOL, as measured by PDQ-39. Instead, at three months and three years after surgery, significant associations were found between PDQ-39 and the UPDRS part I — the part of the UPDRS that assesses non-motor symptoms.
“Because UPDRS part I includes questions on cognitive functions, hallucination, depression, and motivation, we might say that non-motor symptoms partially contribute to QOL after [DBS] in [Parkinson’s] patients,” the researchers wrote.
Another noteworthy finding from the analysis is that people who scored higher on assessments of impulsivity tended to report worse life quality, both before and after surgery.
The researchers speculated that this association could be because more impulsive people feel more confined by the limitations imposed by their disease. However, the team noted a need for more research on the impact of impulsivity on quality of life in people with Parkinson’s.
Also of note, patients reported significantly worsening of depression three years after surgery.
“We do not know the exact reason why the depression score worsened significantly only at 3 years after [DBS], nor whether the worsening of depression scores is attributed to the effect of [DBS] or is a natural disease progression,” the researchers wrote.
While UPDRS part I scores were significantly predictive of life quality after surgery, other measures of cognition and apathy showed no such association.
“One possible explanation for this discrepancy might be that the [other measures] are not specific scales for PD [Parkinson’s] patients, whereas UPDRS part I is specific” for these patients, the researchers wrote.
Nonetheless, the team noted the need for further studies with larger groups of patients to further assess what affects life quality after DBS, which could help in directing care for these patients.