--the lips are considered to be part of the trigeminal nerve distribution, and therefore symptoms with them are more likely to be of the small-fiber rather than cervical compression variety.

Having said that, though, not everyone has the same dermatomal distribution as the maps. There is considerable variation, and not all follow the typical patterns. It's possible, for example, to get some sensation in the upper chest from the C6 and C7 levels, which you won't find on most dermatomal maps. This is due to some crossing of nerve pathways in the brachial plexus. And there have been reports of some people having upper cervical pathways--the C2/C3/C4 levels--into parts of the face as well as the more typical back of the head/ears distribution one sees on dermatomal images.

My neurologist even says that the dermatomal images are just a starting point; people are more varied in their nerve root patterns than the images portray.