Peri-lead edema and local field potential correlation in post-surgery subthalamic nucleus deep brain stimulation patients

Regression-based thresholds to detect clinical changes in verbal fluency after STN-DBS in Parkinson's disease

INTRODUCTION

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor functions in patients with Parkinson's disease (PD) but may cause a decline in specific cognitive domains including executive processes and language. The aim of this study was to derive standardized regression-based (SRB) reliable change indices (RCIs) in an Italian cohort of Parkinson's patients undergoing STN-DBS to detect clinically meaningful variations in verbal fluency (VF) one year after surgery define.

METHODS

Before (T0) and 12 months after (T1) surgery, 36 PD patients who underwent bilateral STN-DBS were evaluated with the Alternate Verbal Fluency Battery (AVFB), including phonemic (PVF), semantic (SVF) and alternate VF tests (AVF) and a composite shifting index (CSI). At T0, motor status was assessed using the Unified Parkinson's Disease Rating Scale-III (UPDRS-III) and L-dopa equivalent daily dose was recorded.

RESULTS

Group-level declines were limited to PVF and SVF scores. Applications of these RCIs revealed idiosyncratic patterns of longitudinal trends that differed from those at the group level. Indeed, when looking at individual performances, no clustered pattern of decline or improvement could be visibly detected. The UPDRS-III predicted T1 AVF and CSI scores.

CONCLUSION

Our study provides Italian practitioners and researchers with SRB-RCIs to detect meaningful differences in the VF performance of PD patients undergoing STN-DBS one year after surgery. Variables associated with postoperative cognitive changes can be used in future studies to develop multivariable predictive models to support clinical decision making and patient counselling.

Preventing Shift from Pneumocephalus During Deep Brain Stimulation Surgery: Don't Give Up the 'Fork in the Brain'

Clinical vignette

We present the case of a patient who developed intra-operative pneumocephalus during left globus pallidus internus deep brain stimulation (DBS) placement for Parkinson's disease (PD). Microelectrode recording (MER) revealed that we were anterior and lateral to the intended target.

Clinical dilemma

Clinically, we suspected brain shift from pneumocephalus. Removal of the guide-tube for readjustment of the brain target would have resulted in the introduction of movement resulting from brain shift and from displacement from the planned trajectory.

Clinical solution

We elected to leave the guide-tube cannula in place and to pass the final DBS lead into a channel that was located posterior-medially from the center microelectrode pass.

Gap in knowledge

Surgical techniques which can be employed to minimize brain shift in the operating room setting are critical for reduction in variation of the final DBS lead placement. Pneumocephalus after dural opening is one potential cause of brain shift. The recognition that the removal of a guide-tube cannula could worsen brain shift creates an opportunity for an intraoperative team to maintain the advantage of the 'fork' in the brain provided by the initial procedure's requirement of guide-tube placement.