Jeremy D. W. Greenlee

The subthalamic nucleus (STN) of the basal ganglia is key to the inhibitory control of movement. Consequently, it is a primary target for the neurosurgical treatment of movement disorders like Parkinson’s Disease, where modulating the STN via deep-brain stimulation (DBS) can release excess inhibition of thalamo-cortical motor circuits. However, the STN is also anatomically connected to other thalamo-cortical circuits, including those underlying cognitive processes like attention. Notably, STN-DBS can also affect these processes. This suggests that the STN may also contribute to the inhibition of non-motor activity, and that STN-DBS may cause changes to this inhibition. We here tested this hypothesis in humans. We used a novel, wireless outpatient method to record intracranial local field potentials (LFP) from STN DBS implants during a visual attention task (Experiment 1, N=12). These outpatient measurements allowed the simultaneous recording of high-density EEG, which we used to derive the steady-state visual evoked potential (SSVEP), a well-established neural index of visual attentional engagement. By relating STN activity to this neural marker of attention (instead of overt behavior), we avoided possible confounds resulting from STN’s motor role. We aimed to test whether the STN contributes to the momentary inhibition of the SSVEP caused by unexpected, distracting sounds. Furthermore, we causally tested this association in a second experiment, where we modulated STN via DBS across two sessions of the task, spaced at least one week apart (N=21, no sample overlap with Experiment 1). The LFP recordings in Experiment 1 showed that reductions of the SSVEP after distracting sounds were preceded by sound-related γ-frequency (>60Hz) activity in the STN. Trial-to-trial modeling further showed that this STN activity statistically mediated the sounds’ suppressive effect on the SSVEP. In Experiment 2, modulating STN activity via DBS significantly reduced these sound-related SSVEP reductions. This provides causal evidence for the role of the STN in the surprise-related inhibition of attention. These findings suggest that the human STN contributes to the inhibition of attention, a non-motor process. This supports a domain-general view of the inhibitory role of the STN. Furthermore, these findings also suggest a potential mechanism underlying some of the known cognitive side-effects of STN-DBS treatment, especially on attentional processes. Finally, our newly-established outpatient LFP recording technique facilitates the testing of the role of subcortical nuclei in complex cognitive tasks, alongside recordings from the rest of the brain, and in much shorter time than perisurgical recordings.

Objective Endoscopic repair of skull base defects is required following resection of intracranial pathology via the endoscopic endonasal approach (EEA). Many closure techniques have been described, but choosing between techniques remains controversial. We report outcomes of 560 EEA procedures of skull base reconstruction performed on 508 patients over a 15‐year‐period. Halfway through this period, we adopted the use of a rigid, bioabsorbable extrasellar plate for reconstruction, enabling a comparison between this technique and those used previously. Methods All patients undergoing EEA from 2005 to 2019 at our institution were retrospectively reviewed. Demographic information, surgical pathology, tumor dimensions and radiographic features, reconstructive technique, and patient‐related outcomes were collected and analyzed with univariate and multivariate statistical modeling. Results Five‐hundred sixty procedures were performed on 508 patients. The series complication rate was 8.2%. Overall, cerebrospinal fluid (CSF) leak rate was 5.0% but varied significantly across closure techniques ( p < 0.001). Critically, the CSF leak rate in the 272 cases prior to our 2013 adoption of the Resorb‐X Plate (RXP) was 8.5%, whereas leak rate in the subsequent 288 cases was 1.7%. RXP was protective against CSF leak ( p = 0.001), whereas gross total resection (GTR) correlated with increased leak rate ( p = 0.001). Patient BMI was significantly associated with risk of leak ( p = 0.047). Other variables did not impact leak risk. Conclusion Reconstructive technique, extent of resection, and patient BMI significantly contributed to CSF leak rate. GTR was associated with increased leak risk while the RXP was protective. The bioabsorbable RXP is an effective option for rigid skull base repair with comparatively few complications. Level of Evidence 3 Laryngoscope , 133:1092–1098, 2023