Sex-specific effects of subthalamic nucleus stimulation on pain in Parkinson's disease

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is known to reduce motor symptoms of Parkinson's disease (PD). The effects of DBS on various nonmotor symptoms often differ from patient to patient. The factors that determine whether or not a patient will respond to treatment have not been elucidated. Here, the authors evaluated sex differences in pain relief after DBS for PD.

The authors prospectively evaluated 20 patients preoperatively and postoperatively after bilateral STN DBS with the validated numeric rating scale (NRS), Revised Oswestry Disability Index for low-back pain (RODI), and King's Parkinson's Disease Pain Scale (KPDPS) and assessed the impact of sex as a biological variable.

The cohort consisted of 6 female and 14 male patients with a mean duration of 11.8 ± 2.0 months since DBS surgery. Females were significantly older (p = 0.02). Covariate analysis, however, showed no effect of age, stimulation settings, or other confounding variables. KPDPS total scores statistically significantly improved only among males (p < 0.001). Males improved more than females in musculoskeletal and chronic subsets of the KPDPS (p = 0.03 and p = 0.01, respectively). RODI scores significantly improved in males but not in females (p = 0.03 and p = 0.30, respectively). Regarding the NRS score, the improvements seen in both sexes in NRS were not significant.

Although it is well recognized that pain complaints in PD are different between men and women, this study is unique in that it examines the sex-specific DBS effects on this symptom. Considering sex as a biological variable may have important implications for DBS pain outcome studies moving forward.