Introduction: The accumulation of intracranial air introduces a potential confounder in deep brain stimulation (DBS). Previous literature indicates lack of consensus between intracranial air and eventual clinical outcome. Here we qualify the relationship between the volume of intracranial air and the need for subsequent electrode repositioning and characterize the MRI signal changes after DBS for movement disorders.
Methods: We performed a retrospective review of 510 consecutive operative cases from our tertiary movement disorders center with particular attention to MRI findings. MR series were analyzed using a specialized software program to track the volume of the intracranial air. Statistical analysis was undertaken with one-way anova test and Pearson r statistic.
Results: 510 patients were evaluated. MRI signal changes after DBS procedure showed 32 cases (6.31%) with edema, 20 cases with hemorrhage (3.96%), 10 cases with infarction (1.99%), and 4 cases (0.79%) with midline shift, and 177 cases (35%) with intracranial air of various volumes. Only 12 patients (2.35%) from the above MRI signal changes were symptomatic.
A subset of patients with intracranial air was analyzed. The average number of electrode trajectories was 1.9 ± 1.2. Average volume of intracranial air was 12.1 ± 8.8 cm3. No correlation between the number of electrode trajectories and the amount of intracranial air was found. 27% of patients required repositioning of their electrode. There was no correlation between volume of intracranial air and repositioning of electrode. Furthermore, there was no statistically significant difference between the air volume of repositioned and randomly selected non-repositioned electrodes (p=0.55).
Conclusions: Our analysis indicates that there is no direct and systematic association between the amount of intracranial air and repositioning of electrode and majority of the MRI signal changes observed after DBS are benign. Brain shift secondary to intracranial air is clinically insignificant and is not implicated in suboptimal achievement of DBS targets.
Patient Care: It will help optimize DBS outcome. It allows accurate estimates of adverse events to better inform patients and caregivers about potential risks and benefits of surgery and provide normative data for process improvement.
Learning Objectives: 1) Identify relationship between intracranial air and repositioning of electrodes
2) Identify five common MRI findings post-DBS and its clinical significance
3) Identify the critical threshold of MRI air volume and DBS repositioning