Combined direct and indirect revascularization is associated with low rates of recurrent ischemic and hemorrhagic stroke in adult moyamoya disease.

ity. Afterdischarges were less likely to be induced by direct hippocampal stimulation during periods when the hippocampal LFP had already been suppressed with preceding preparatory stimulation. Evoked potentials produced in the hippocampus by thalamic stimulation were also suppressed when preparatory direct hippocampal stimulation was provided. The authors were also able to demonstrate 2 novel closed-loop control stimulation paradigms whereby the ambient theta band power recorded in the hippocampus was used to trigger deep brain stimulation, leading to suppression of power in this band pass. In the first paradigm, hippocampal theta band power at a specified threshold was used to control the delivery of short 10-second bursts of direct hippocampal stimulation (0.9 V, 300 microseconds, 50 Hz) that successfully produced LFP suppression and maintained this suppression over extended periods of time (Figure). The second closed-loop system demonstrated instead used continuous thalamic stimulation at a frequency of 40 Hz. Changes in recorded hippocampal theta band activity were used to modulate the amplitude of the continuous thalamic stimulation, and by this means, hippocampal activity was suppressed, which was also sustained over a period of time. In summary, Stypulkowski et al have now demonstrated (in awake behaving animals) that both local and remote deep brain stimulation can produce specific effects on hippocampal excitability. Two novel closed-loop control paradigms were demonstrated in which each successfully depressed hippocampal activity within a desired range. This kind of closedloop deep brain stimulation paradigm is currently actively undergoing investigation with the hope that it can be applied to many different disease states, and because neuromodulation is delivered only when necessary, it is thought that this can be used to minimize possible side effects of stimulation and to increase battery lifetime while also maximizing therapeutic benefit.