Individuals with Parkinon’s disease who have worse quality of life due to their disease-related impairments may benefit most from treatment with deep-brain stimulation.
The study with that finding, “Quality of life predicts outcome of deep brain stimulation in early Parkinson disease,” was published by the journal Neurology.
Deep-brain stimulation (DBS) is an invasive surgical technique in which thin wires are implanted in the brain to deliver electric pulses to specific areas, such as the subthalamic nucleus (STN), to ease motor symptoms in patients for whom standard medications are not effective.
In a previous Phase 4 clinical trial (NCT00354133) called the EARLYSTIM study, researchers evaluated the long-term impact of STN-DBS as an add-on to best medical treatment regarding quality of life in patients with Parkinson’s disease for a period of more than two years.
The study enrolled patients younger than 61 who had a good response to levodopa therapy, but who still had developed motor complications. Among the participants, 124 were treated with DBS-STN and best medical treatment, while 127 patients received the best medical treatment only.
In the most recent study researchers reviewed the trial data to understand which factors contributed to the detectable changes in disease-specific quality of life, as measured using the 39-item Parkinson’s Disease Questionnaire summary index (PDQ-39-SI). The self-reported questionnaire assesses Parkinson’s-specific health across eight quality-of-life dimensions.
The analysis revealed that quality of life over the two years of follow-up correlated with the initial value of the PDQ-39-SI in both treatment groups. Still, this association was more pronounced among patients who were treated with STN-DBS.
Patients with very mild impairment due to Parkinson’s, corresponding to PDQ-39-SI values lower than 15, were found not to benefit from STN-DBS as compared to patients treated with standard care alone. In contrast, patients treated with STN-DBS who had PDQ-39-SI sores higher than 15 (worse quality of life) at the beginning of the study experienced better quality of life changes.
“In patients with very low baseline ratings on the PDQ-39-SI, the natural progression of impairment of [quality of life] may outweigh the improvement achieved by STN-DBS,” researchers wrote. “On the other hand, some patients with very modest impairment of their [quality of life] seem to have less to gain from STN-DBS,” they added.
Patients’ cognitive status before the treatment, as determined by the Mattis Dementia Rating Scale (MDRS), was not predictive of change in quality of life in either treatment group. However, higher scores for depression and poorer mood correlated with larger improvements in quality of life among patients in the STN-DBS group.
These findings “may indicate that these patients have a potential for nonmotor improvement to gain from surgery,” researchers suggested.
Changes in quality of life during the two years of follow-up were independent of patient age, disease duration, duration of motor complications, severity of parkinsonian motor manifestation under levopoda therapy, or treatment complications.
Supported by these findings, the team believes that “baseline impairment of quality of life is (…) a reasonable aspect to consider for the decision to treat with STN-DBS.”
“The subjective individual suffering as measured with the PDQ-39-SI should be taken into account as a predictive factor for outcome when selecting patients with early motor complications for STN-DBS,” researchers concluded.