Effect of Eye Opening on Single-Unit Activity and Local Field Potentials in the Subthalamic Nucleus.

BACKGROUND: Subthalamic nucleus deep brain stimulation (STN DBS) is an established treatment in Parkinson's disease (PD). We investigate the effect of eye opening on neuronal activity and local field potentials (LFPs) in the STN. METHODS: We prospectively enrolled 25 PD patients undergoing STN DBS in our institution. During DBS, single-unit activity (SUA) and LFPs were measured when eyes were open and closed. As movement is known to result in changes in LFPs, we tested response to eye opening in the presence and absence of movement. RESULTS: Neither eye state nor arm movement has a significant influence on SUA recordings. There is a statistically significant interaction between eye state and arm movement (p < 0.05). In the presence of movement, STN SUA increase when eyes open (p < 0.05). When eyes are closed, STN SUA decrease with movement (p < 0.05). STN theta LFP oscillations decrease when eyes are open compared to closed, irrespective of movement status (p < 0.05). DISCUSSION: STN activity is influenced by eye state and arm movement. It is unclear whether this is attributed to a change in the STN's role in oculomotor control or from a change in attentional state. Understanding how physiologic normal activity alters neural activity is critical for the optimization of DBS therapy, particularly in closed-loop neuromodulation.

The Impact of Peripheral Nerve Stimulation on Disability and Depression.

BACKGROUND: Peripheral nerve stimulation (PNS) of the named nerves of the head has been shown to be effective in reducing pain levels in patients with chronic pain refractory to other treatments. However, the impact of cranial PNS on depression and disability has not been well documented. OBJECTIVES: We prospectively examine the impact of PNS on quality of life via validated survey scores which assess symptoms of depression and daily functional capacities within patients. METHODS: Patients who underwent permanent PNS implantation completed five validated questionnaires: Oswestry Disability Index (ODI), the Beck's Depression Inventory (BDI), the Pain Catastrophizing Scale (PCS), McGill Pain Questionnaire (MPQ), and the visual analog scale (VAS) score. These were completed at baseline, six months, and one year to assess changes in functioning levels. Results were analyzed via repeated measures ANOVA and bivariate analysis. RESULTS: Compared with baseline, at six months patients showed significantly less depression on BDI (F = 7.9, p = 0.021), and at one year, a significant decrease in disability was observed on the ODI (F = 6.1, p = 0.036). At both six months and one year, patients showed a significant decrease in pain on VAS (F = 16.5, p = 0.012). We noted a trend for ODI to correlate with BDI at six months (R = 0.616, p = 0.077). DISCUSSION: Our prospective data show PNS to be an effective modality in improving overall life quality by limiting depression and disability as well as pain.