Ethan Taub

Deep brain stimulation of different targets has been shown to drastically improve symptoms of a variety of neurological conditions. However, the occurrence of disabling side effects may limit the ability to deliver adequate amounts of current necessary to reach the maximal benefit. Computed models have suggested that reduction in electrode size and the ability to provide directional stimulation could increase the efficacy of such therapies. This has never been demonstrated in humans. In the present study, we assess the effect of directional stimulation compared to omnidirectional stimulation. Three different directions of stimulation as well as omnidirectional stimulation were tested intraoperatively in the subthalamic nucleus of 11 patients with Parkinson's disease and in the nucleus ventralis intermedius of two other subjects with essential tremor. At the trajectory chosen for implantation of the definitive electrode, we assessed the current threshold window between positive and side effects, defined as the therapeutic window. A computed finite element model was used to compare the volume of tissue activated when one directional electrode was stimulated, or in case of omnidirectional stimulation. All but one patient showed a benefit of directional stimulation compared to omnidirectional. A best direction of stimulation was observed in all the patients. The therapeutic window in the best direction was wider than the second best direction (P = 0.003) and wider than the third best direction (P = 0.002). Compared to omnidirectional direction, the therapeutic window in the best direction was 41.3% wider (P = 0.037). The current threshold producing meaningful therapeutic effect in the best direction was 0.67 mA (0.3-1.0 mA) and was 43% lower than in omnidirectional stimulation (P = 0.002). No complication as a result of insertion of the directional electrode or during testing was encountered. The computed model revealed a volume of tissue activated of 10.5 mm(3) in omnidirectional mode, compared with 4.2 mm(3) when only one electrode was used. Directional deep brain stimulation with a reduced electrode size applied intraoperatively in the subthalamic nucleus as well as in the nucleus ventralis intermedius of the thalamus significantly widened the therapeutic window and lowered the current needed for beneficial effects, compared to omnidirectional stimulation. The observed side effects related to direction of stimulation were consistent with the anatomical location of surrounding structures. This new approach opens the door to an improved deep brain stimulation therapy. Chronic implantation is further needed to confirm these findings.

BACKGROUND: To date, no civilian studies have demonstrated that pre-hospital (PH) tourniquets improve survival. We hypothesized that late, trauma center (TC) tourniquet use would increase death from hemorrhagic shock compared to early (PH) placement. METHODS: All patients arriving to a Level 1, urban TC between October 2008 and January 2016 with a tourniquet placed before (T-PH) or after arrival to the TC (T-TC) were evaluated. Cases were assigned the following designations: indicated (absolute indication [vascular injury requiring repair/ligation, operation within 2 hours for extremity injury, or traumatic amputation] or relative indication [major musculoskeletal/soft tissue injury requiring operation 2-8 hours after arrival, documented large blood loss]) or non-indicated. Outcomes were death from hemorrhagic shock, physiology upon arrival to the TC, and massive transfusion requirements. After univariate analysis, logistic regression was carried out to assess independent predictors of death from hemorrhagic shock. RESULTS: A total of 306 patients received 326 tourniquets for injuries to 157 upper and 147 lower extremities. Two hundred eighty-one (92%) had an indication for placement. Seventy percent of patients had a blunt mechanism of injury. T-TC patients arrived with a lower systolic blood pressure (SBP, 101 [86, 123] vs. 125 [100, 145] mm Hg, p < 0.001), received more transfusions in the first hour of arrival (55% vs. 34%, p = 0.02), and had a greater mortality from hemorrhagic shock (14% vs. 3.0%, p = 0.01). When controlling for year of admission, mechanism of injury and shock upon arrival (SBP ≤90 mm Hg or HR ≥120 bpm or base deficit ≤ 4) indicated T-TC had a 4.5-fold increased odds of death compared to T-PH (OR 4.5, 95% CI 1.23-16.4, p = 0.02). CONCLUSIONS: Waiting until TC arrival to control hemorrhage with a tourniquet was associated with worsened blood pressure and increased transfusion within the first hour of arrival. In routine civilian trauma patients, delaying to T-TC was associated with 4.5-fold increased odds of mortality from hemorrhagic shock. LEVEL OF EVIDENCE: Level IV.

The supracerebellar transtentorial (SCTT) approach, a modification of the infratentorial supracerebellar approach, facilitates simple and minimally invasive access to posterior temporomedial structures without requiring retraction of the temporal or occipital lobe. The SCTT approach was used in 16 patients over a 3-year period. Eleven patients harbored tumors confined to, or located mainly within, the posterior hippocampal formation, three patients harbored aneurysms (one ruptured posterior cerebral artery [PCA] aneurysm at the P2-P3 junction, one ruptured giant PCA [P2] aneurysm, and one giant basilar artery-superior cerebellar artery aneurysm), one patient had juvenile-type moyamoya disease, and one patient suffered from medically intractable epilepsy. In these patients, the SCTT approach enabled tumor removal, aneurysm clipping, and vascular bypass procedures. The authors' experience suggests that this approach can be used routinely in treating lesions in the posterior temporomedial region.