Introduction: Occurrence of brain shift during deep brain stimulation (DBS) may lead to deviation in electrode placement, which may reduce clinical benefit. Intracranial air (ICA) has been cited as one potential factor influencing the amount of shift. We analyzed a series of patients with ICA after DBS to better understand the impact on electrode position and clinical outcomes.

Methods: We performed a retrospective review of patients treated at our institution for refractory PD who underwent bilateral STN DBS. The immediate post-operative CT was fused with the 4-week follow-up CT, and deviation of the electrode was determined. Amounts of ICA were calculated and correlated to various parameters. Patients were grouped according to amount of ICA, and clinical outcomes were assessed for each of these groups.

Results: ICA had resolved fully at follow-up. In 60 total leads, average deviation at the tip was 1.14 ± 0.72 mm. The proximal lead deviated anteriorly an average of 2.97 ± 1.81 mm. Mean ICA was 20.7 ± 13.5 cm3, and did not significantly correlate to duration of disease, but did correlate to patient age and total number of passes (p < .05). There was a statistically significant correlation of ICA to proximal lead deviation (Pearson’s test, r=.356, p = .03), but not to tip deviation. Patients in group 4 with ICA greater than 30 cm3 had worse scores on the MDS-UPDRS part 3 at 6 and 12 months, while those with <30 cm3 had scores that were comparable and stable across time.

Conclusions: Regardless of the amount of ICA introduced during surgery, electrode deviation at the tip is minimal. With ICA <30 cm3, there appears to be a negligible effect on clinical outcome scores, however, ICA greater than this may play a role in DBS success. Further studies with larger numbers of patients are needed to fully examine this.

Patient Care: This research will improve patient care by helping elucidate the role of intracranial air in DBS electrode deviation and its clinical impact.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Identify factors that may lead to brain shift during stereotactic surgery, 2) Discuss the role of intracranial air on targeting accuracy, and 3) Discuss the effect of ICA on clinical outcome after DBS.

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