A prospective pilot study of the effects of deep brain stimulation on olfaction and constipation in Parkinson's disease

Background: Previous studies suggest deep brain stimulation of the subthalamic nucleus (STN-DBS) may improve olfaction and constipation in PD, using subjective measures. Objective: To utilize objective measures to assess olfaction and constipation in PD following STN-DBS. Methods: In this prospective pilot study, olfaction (University of Pennsylvania Smell Identification Test [UPSIT]), bowel symptoms (ROME III questionnaires, daily bowel diaries, 100 mm visual analog scales for satisfaction with treatment and bowel habits), and motor manifestations of PD were evaluated before and after STN-DBS. Levo-dopa equivalent daily dose (LEDD) was calculated. Results: Ten patients (8 men, mean age 67.4 +/- 6.0 years) with mean PD duration of 7.5 +/- 3.7 years underwent bilateral STN-DBS, with mean follow-up of 3 months for all measures, except 7 months follow-up for bowel diaries. There was improvement in the Unified Parkinson's Disease Rating Scale motor "off" scores (33.7 +/- 6.7 before and 16.1 +/- 10.8 after, P = 0.001). Mean UPSIT scores (20.0 +/- 6.6 versus 17.5 +/- 5.7, P = 0.03) worsened from severe to total hyposmia. Seven patients had baseline constipation and completed bowel diaries. There was improvement in number of complete spontaneous bowel motions (CBSM) per week (2.2 +/- 1.9 before versus 4.7 +/- 2.4 after, P = 0.04), satisfaction with treatment of constipation (44 +/- 27 before versus 64 +/- 25 after, P = 0.02), and with bowel motions (33 +/- 22 before and 48 +/- 20 after, P = 0.2). However, laxative use (P = 0.15) and LEDD (P = 0.15) were unchanged. Conclusion: Olfaction worsened while symptoms of constipation improved but did not resolve after STN-DBS.