Cognition and mood predict life quality after deep-brain stimulation
medwireNews: Measures of cognition and depression, rather than motor outcomes, predict the quality of life (QoL) of patients undergoing subthalamic nucleus deep-brain stimulation (DBS) for Parkinson’s disease (PD), research shows.
Single-trial learning performance and depressive symptoms, as well as QoL prior to surgery predicted QoL at follow-up, report Darlene Floden (Cleveland Clinic, Ohio, USA) and team.
The three variables together correctly classified 70% of patients according to whether or not their QoL improved after surgery.
“The focus of prior DBS research has been on predicting motor improvements after surgery, which reflects the success of DBS from the clinician’s perspective”, they write in Neurology. “The recent interest in QoL outcomes signals a shift to understanding the patient characteristics and disease variables that underlie success from the patient’s perspective.”
The 85 patients in the study reported their QoL before and an average of 8.2 months after surgery, and, overall, it significantly improved in that time. Patients reported a significant improvement on the 39-item Parkinson’s Disease Questionnaire (PDQ-39) overall and in every subdomain except cognition and communication.
In all, 51% of the patients reported improved QoL after surgery, 47% had unchanged QoL and 2% had poorer QoL.
The strongest predictor of improved QoL was single-trial learning on the Rey Auditory Verbal Learning Test, with each additional word remembered associated with a 58% increase in the likelihood of QoL improvement.
The researchers say that single-trial learning “is sensitive to dysfunction in distributed frontal and temporal circuits”, indicating that poorer performance may reflect greater degeneration outside the midbrain and subcortical regions.
“In that case, our model would suggest that patients with more preserved function in cortical regions before surgery report greater increases in QoL after surgery”, say Floden et al.
In addition, postoperative QoL increased with increasing preoperative PDQ-39 score and fell with increasing symptoms on the 2nd edition of the Beck Depression Inventory, which “underscores the importance of psychiatric care accompanying surgical care”, note the researchers.
They also highlight three variables expected to predict QoL improvement, which in fact did not. The first was reduced medication use, despite many patients stating this as a goal preoperatively; and the second was the effectiveness of stimulation, suggesting that time in off state rather than severity of symptoms affects QoL.
The third variable was change in verbal fluency “which indicates that the most frequently reported cognitive decline after DBS implantation does not have a negative impact on outcome from the patient’s perspective”, says the team.
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By Eleanor McDermid, Senior medwireNews Reporter