Deep brain stimulation is an established therapy for multiple brain disorders, with rapidly expanding potential indications. Neuroimaging has advanced the field of deep brain stimulation through improvements in delineation of anatomy, and, more recently, application of brain connectomics. Older lesion-derived, localizationist theories of these conditions have evolved to newer, network-based "circuitopathies," aided by the ability to directly assess these brain circuits in vivo through the use of advanced neuroimaging techniques, such as diffusion tractography and fMRI. In this review, we use a combination of ultra-high-field MR imaging and diffusion tractography to highlight relevant anatomy for the currently approved indications for deep brain stimulation in the United States: essential tremor, Parkinson disease, drug-resistant epilepsy, dystonia, and obsessive-compulsive disorder. We also review the literature regarding the use of fMRI and diffusion tractography in understanding the role of deep brain stimulation in these disorders, as well as their potential use in both surgical targeting and device programming. ABBREVIATIONS: AL ¼ ansa lenticularis; ALIC ¼ anterior limb of the internal capsule; ANT ¼ anterior nucleus of the thalamus; AS ¼ ansa subthalamica; ATR ¼ anterior thalamic radiations; DBS ¼ deep brain stimulation; DRTT ¼ dentatorubrothalamic tract; ET ¼ essential tremor; FGATIR ¼ fast gray matter acquisition T1 inversion recovery; FL ¼ fasciculus lenticularis; FS ¼ fasciculus subthalamicus; GPe ¼ globus pallidus externus; GPi ¼ globus pallidus internus; MFB ¼ medial forebrain bundle; MMT ¼ mammillothalamic tract; OCD ¼ obsessive-compulsive disorder; PD ¼ Parkinson disease; slMFB ¼ superolateral branch of the medial forebrain bundle; STN ¼ subthalamic; TF ¼ thalamic fasciculus; VIM ¼ ventral intermedius nucleus; VO ¼ ventralis oralis; ZI ¼ zona incerta

OBJECTIVE The authors’ goal was to use a multicenter, observational cohort study to determine whether supramarginal resection (SMR) of FLAIR-hyperintense tumor beyond the contrast-enhanced (CE) area influences the overall survival (OS) of patients with isocitrate dehydrogenase–wild-type (IDH-wt) glioblastoma after gross-total resection (GTR). METHODS The medical records of 888 patients aged ≥ 18 years who underwent resection of GBM between January 2011 and December 2017 were reviewed. Volumetric measurements of the CE tumor and surrounding FLAIR-hyperintense tumor were performed, clinical variables were obtained, and associations with OS were analyzed. RESULTS In total, 101 patients with newly diagnosed IDH-wt GBM who underwent GTR of the CE tumor met the inclusion criteria. In multivariate analysis, age ≥ 65 years (HR 1.97; 95% CI 1.01–2.56; p < 0.001) and contact with the lateral ventricles (HR 1.59; 95% CI 1.13–1.78; p = 0.025) were associated with shorter OS, but preoperative Karnofsky Performance Status ≥ 70 (HR 0.47; 95% CI 0.27–0.89; p = 0.006), MGMT promotor methylation (HR 0.63; 95% CI 0.52–0.99; p = 0.044), and increased percentage of SMR (HR 0.99; 95% CI 0.98–0.99; p = 0.02) were associated with longer OS. Finally, 20% SMR was the minimum percentage associated with beneficial OS (HR 0.56; 95% CI 0.35–0.89; p = 0.01), but > 60% SMR had no significant influence (HR 0.74; 95% CI 0.45–1.21; p = 0.234). CONCLUSIONS SMR is associated with improved OS in patients with IDH-wt GBM who undergo GTR of CE tumor. At least 20% SMR of the CE tumor was associated with beneficial OS, but greater than 60% SMR had no significant influence on OS.

Treatment of non-saccular aneurysms of the posterior circulation poses a great challenge with unpredictable outcomes due to the absence of a true aneurysm neck and the presence of perforating vessels. In this article, we aim to compare endovascular treatment of unruptured posterior circulation non-saccular aneurysms with stent-assisted coiling (SAC) and flow diversion (FD) in terms of occlusion rate and clinical outcomes. A systematic search of electronic databases from inception to August 2019 identified 484 articles for screening. After proper inclusion/exclusion criteria, 15 articles were included and data were extracted and analyzed using meta-analysis of proportions. The pooled cohort consisted of 430 aneurysms: 128 (29.7%) treated with SAC in 5 studies and 302 (70.3%) treated with FD in 11 studies. Complete/near-complete occlusion was achieved in 83% after FD (95% CI 0.75 to 0.90; I2=45%) and 84% after SAC (95% CI 0.72 to 0.91; I2=22%), with no significant difference between techniques (p=0.95). Periprocedural complications were observed in 18% after FD (95% CI 0.14 to 0.23; I2=0%) and 6% after SAC (95% CI 0.02 to 0.13; I2=0%); the subgroup analysis was statistically significant (p=0.008). Furthermore, no statistically significant difference was observed in favorable clinical outcomes between groups. These results suggest similar efficacy in occlusion rate and favorable clinical outcome for posterior circulation non-saccular aneurysms treated with SAC and FD. Stroke was the most common complication regardless of treatment modality, and a lower periprocedural complication rate was noted with SAC. Further studies are needed with the primary focus of reducing the risk of stroke with either modality.

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