How does human brain stimulation result in lasting changes in cortical excitability? Uncertainty on this question hinders the development of personalized brain stimulation therapies. To characterize how cortical excitability is altered by stimulation, we applied repetitive direct electrical stimulation in eight human subjects (male and female) undergoing intracranial monitoring. We evaluated single-pulse corticocortical-evoked potentials (CCEPs) before and after repetitive stimulation across prefrontal ( = 4), temporal ( = 1), and motor ( = 3) cortices. We asked whether a single session of repetitive stimulation was sufficient to induce excitability changes across distributed cortical sites. We found a subset of regions at which 10 Hz prefrontal repetitive stimulation resulted in both potentiation and suppression of excitability that persisted for at least 10 min. We then asked whether these dynamics could be modeled by the prestimulation connectivity profile of each subject. We found that cortical regions (1) anatomically close to the stimulated site and (2) exhibiting high-amplitude CCEPs underwent changes in excitability following repetitive stimulation. We demonstrate high accuracy (72-95%) and discriminability (81-99%) in predicting regions exhibiting changes using individual subjects' prestimulation connectivity profile, and show that adding prestimulation connectivity features significantly improved model performance. The same features predicted regions of modulation following motor and temporal cortices stimulation in an independent dataset. Together, baseline connectivity profile can be used to predict regions susceptible to brain changes and provides a basis for personalizing brain stimulation. Brain stimulation is increasingly used to treat neuropsychiatric disorders by inducing excitability changes at specific brain regions. However, our understanding of how, when, and where these changes are induced is critically lacking. We inferred plasticity in the human brain after applying electrical stimulation to the brain's surface and measuring changes in excitability. We observed excitability changes in regions anatomically and functionally closer to the stimulation site. Those in responsive regions were accurately predicted using a classifier trained on baseline brain network characteristics. Finally, we showed that the excitability changes can potentially be monitored in real-time. These results begin to fill basic gaps in our understanding of stimulation-induced brain dynamics in humans and offer pathways to optimize stimulation protocols.

This study demonstrates the feasibility of utilizing the 3D 4K-HD EX system and highlights potential technical assets of this novel technology in regard to optics, ergonomics, and maneuverability. Further clinical research is needed to examine the clinical effectiveness of the EX system for different surgical approaches through quantitative methodology.

Successful treatment of hypothalamic hamartoma (HH) can result in the resolution of its sequelae including epilepsy and rage attacks. Risks and morbidity of open surgical management of this lesion have motivated the development of laser interstitial thermal therapy (LITT) as a less invasive treatment approach to the disease. Although overall morbidity and risk would appear to be lower, complications related to LITT therapy have been reported, and the longer-term follow-up that is now possible after initial experience helps address the question of whether LITT provides equivalent efficacy compared to other treatment options. We conducted a retrospective analysis of clinical outcomes in eight patients undergoing LITT for HH at our center using the Visualase/Medtronic device. Five patients had refractory epilepsy, one had rage attacks, and two had both. We also compared the published seizure-free outcomes over time and the complication rates for different interventional approaches to the treatment of epilepsy due to HH including open craniotomy, neuroendoscopic, radiosurgical, and radiofrequency approaches. With a mean follow-up of 19.1 months in our series of eight patients, six of seven epilepsy patients achieved seizure freedom, whereas the one patient with rage attacks only did not have improvement of his symptoms. A length of hospital stay of 2.6 days reflects low morbidity and rapid postoperative recuperation with LITT. Considering other reported series and case reports, the overall published seizure freedom rate of 21 of 25 patients is superior to published outcomes of HH cases treated by stereotactic radiosurgery (SRS), craniotomy, or neuroendoscopy, and comparable to radiofrequency ablation. The cumulative experience of our center with other published series supports relatively lower operative morbidity than more invasive approaches and efficacy that is as good or better than open craniotomy procedures and SRS. Although morbidity appears to be lower than other open approaches, complications related to LITT and their avoidance should be considered carefully.

BACKGROUND Cerebral bypass operation is a technically challenging operation that requires excellent surgical visibility and efficient ergonomics to minimize complications and maximize successful revascularization. Despite the operative microscope's utilization for the past two generations, there remains a need for continued improvement in operative visualization and surgical ergonomics. OBJECTIVE To report the positives and negatives of our initial experience using a novel 4 K high-definition (4K-HD) 3-dimensional (3D) exoscope (EX) for cranial bypass surgery. METHODS A retrospective review over 6 mo was performed of all patients who have undergone cerebral bypass surgery at a single institution using the 4K-HD 3D EX. Advantages and disadvantages of the EX and clinical outcome of the patients were assessed. RESULTS A total of 5 patients underwent cerebral EC-IC bypass surgery with no EX-related complications and successful revascularization. The lightweight design of the EX allowed for easy instrument maneuverability as well as uncomplicated surgical set up in the operating room. The assistance of the cosurgeon was significantly more efficient compared to that of the operating microscope. The large monitor allowed for an immersive, collaborative, and valuable educational surgical experience. CONCLUSION Using the EX for cerebral bypass surgery, with 3D ultra-high-definition optics, enhancements of ergonomics, and improved training, we believe that the 3D 4K-HD EX may represent the next generation of operative scopes in microneurosurgery.

ObjectiveDisconnection of the cerebral hemispheres by corpus callosotomy (CC) is an established means to palliate refractory generalized epilepsy. Laser interstitial thermal therapy (LITT) is gaining acceptance as a minimally invasive approach to treating epilepsy, but this method has not been evaluated in clinical series using established methodologies to assess connectivity. The goal in this study was to demonstrate the safety and feasibility of MRI-guided LITT for CC and to assess disconnection by using electrophysiology- and imaging-based methods.MethodsRetrospective chart and imaging review was performed in 5 patients undergoing LITT callosotomy at a single center. Diffusion tensor imaging and resting functional MRI were performed in all patients to assess anatomical and functional connectivity. In 3 patients undergoing simultaneous intracranial electroencephalography monitoring, corticocortical evoked potentials and resting electrocorticography were used to assess electrophysiological correlates.ResultsAll patients had generalized or multifocal seizure onsets. Three patients with preoperative evidence for possible lateralization underwent stereoelectroencephalography depth electrode implantation during the perioperative period. LITT ablation of the anterior corpus callosum was completed in a single procedure in 4 patients. One complication involving misplaced devices required a second procedure. Adequacy of the anterior callosotomy was confirmed using contrast-enhanced MRI and diffusion tensor imaging. Resting functional MRI, corticocortical evoked potentials, and resting electrocorticography demonstrated functional disconnection of the hemispheres. Postcallosotomy monitoring revealed lateralization of the seizures in all 3 patients with preoperatively suspected occult lateralization. Four of 5 patients experienced > 80% reduction in generalized seizure frequency. Two patients undergoing subsequent focal resection are free of clinical seizures at 2 years. One patient developed a 9-mm intraparenchymal hematoma at the site of entry and continued to have seizures after the procedure.ConclusionsMRI-guided LITT provides an effective minimally invasive alternative method for CC in the treatment of seizures associated with drop attacks, bilaterally synchronous onset, and rapid secondary generalization. The disconnection is confirmed using anatomical and functional neuroimaging and electrophysiological measures.