Here are a couple of pictures to help with shot placement for a 'brain" shot on a whitetail.
I've shot a lot of deer, perhaps a hundred of them while hunting but I've shot many hundreds for crop damage. A head shot is a good shot but some folks have zero knowledge of deer anatomy and equate a head shot to any shot to the 'head' of a deer; the objective of a 'head' shot is to hit the brain and not just a mass of soft tissue and bone such as the nose or jaw.
As you can see in the images below (I made these some years back for another post on this subject) the brain on a deer is not too large, maybe 4" x 2.5" x 3". The easiest and best shots are those that give a bullet direct access to the brain with as little soft tissue interferance as possible, straight from behind while the deers' head is erect or straight from the front (top of the head) while the deer is head down as in feeding or drinking. Trying to pass a round 'up the nose' into the brain is a poor option, there is a lot of tissue and bone to deflect a bullet in a shot like this.
Small light caliber shots to the lungs (broadside presentation) will kill deer fairly quickly, I usually shoot for the heart area (low chest) rather than the upper lung area.
A lot of deer have been killed with a .22 Rimfire and the .22 Rimfire Magnum but it would be for a skilled shooter in my opinion.
An "X" would indicate to me a good shot placement area on a deer head..