The brain is slightly elastic, so you'd want to advance a needle glacially slowly (microns/second) into it so it ends up at the right position. The injection itself is also done slowly (microliters/minute) so you don't cause pressure damage.
They might also do some intraoperative imaging (some ORs have MRI or CT machines), which slows things down, and of course there's tons of cleaning and repair work afterward.
The brain is slightly elastic, so you'd want to advance a needle glacially slowly (microns/second) into it so it ends up at the right position. The injection itself is also done slowly (microliters/minute) so you don't cause pressure damage.
They might also do some intraoperative imaging (some ORs have MRI or CT machines), which slows things down, and of course there's tons of cleaning and repair work afterward.