LAS VEGAS – , according to a small study presented at the annual meeting of the North American Neuromodulation Society. DBS of the subthalamic nucleus (STN), however, does not significantly improve these symptoms.
“Further work will be needed to confirm whether DBS needs to be bilateral ... and whether demographic differences are significant,” said Michael Gillogly, RN, clinical research nurse in the department of neurosurgery at Albany (New York) Medical Center. “The pilot data suggest that, if all else is equal, and the patient has significant urinary dysfunction as a major complaint, GPI DBS may be preferentially considered.”
The benefits of DBS on motor symptoms in Parkinson’s disease are well documented in the literature, but the technique’s effects on nonmotor symptoms are less clear. Nonmotor symptoms – such as cognitive deficits, gastrointestinal dysfunction, genitourinary dysfunction, and sleep disturbance – are common in all stages of Parkinson’s disease and significantly impair quality of life. Data indicate that speech and neuropsychological symptoms worsen with DBS of the STN, but research into the effect of DBS of the GPI on nonmotor symptoms is limited.
Mr. Gillogly and his colleagues considered all surgical candidates at their facility for enrollment into a study evaluating nonmotor outcomes in Parkinson’s disease at baseline, before implantation, and at 6 months after DBS. Study outcomes were patient perception of urinary, swallowing, and gastrointestinal function at 6 months after DBS of the GPI, compared with DBS of the STN.
The researchers chose two tools each to measure sialorrhea, dysphagia, and genitourinary dysfunction. These tools included the Drooling Severity and Frequency Scale (DSFS), the Swallowing Disturbance Questionnaire, and the International Prostate Symptom Score (IPSS). The investigators also collected demographic information, including sex, age at the time of surgery, duration of illness, neuropsychological profile, and medication inventory.
In all, 34 patients (12 women) were enrolled in the study and completed each outcome measure preoperatively and at 6 months postoperatively. The mean age of our subjects at the time of surgery was 64 years. Eight received DBS of the GPI, and 26 received DBS of the STN. Mr. Gillogly and his colleagues observed a significant 31% improvement in DSFS score and a significant 24% improvement on the IPSS among GPI-targeted patients. They found no significant improvements among patients who had STN targeting. When the investigators compared patients with unilateral lead placement and those with bilateral lead placement, they observed that all of the significant improvement among patients with GPI targeting occurred when treatment was bilateral.
The small sample size is a notable limitation of the study, and subset analyses were limited, said Mr. Gillogly. In addition, it was difficult to determine whether the symptoms studied were directly related to Parkinson’s disease, because they often arise as part of the natural aging process. “Other limitations of the study include lack of objective measurements, as these are all patient perception, and the innate limitations of self-reported questionnaires,” said Mr. Gillogly.
Two of the researchers reported having consulted for Medtronic, which markets a DBS system. One author received grant funding and consulting fees from Boston Scientific, Medtronic, and Abbott, all of which make DBS devices.