Researchers are currently developing a new robotic device that can reach remote regions of the brain through the cheek.

The new device being developed is less invasive or complicated but does require certain adjustments as it is difficult to reach the hippocampus even from below. The device makes use of a steerable needle, made of nitinol, that can be used to navigate to the required region without damaging the surrounding tissue.
Researchers hope to being testing on cadavers and then move to clinical trials with the final product at least a decade away.
Source-Medindia