I didn't used to send a lot of critics but here i wanna give you my oinion on this one.
First, the whole picture have a nice impact, we have a character at the center of interessest you did well. We have a nice facial expression for the pain feeling with in this view eyes a little curved down and mouth open. Maybe add a little tears on her right cheek and make the eyesmore wet could enhanced this feeling. For the whole picture you should try to add more colours in this one, we can see you use some greenish value in the left top part of the picture as well. To come back to the character, her mouth is really open so we should see her tonsils coming to the front in her mouth. While you open the mouth for pain feeling often, the tongue is a little curved to the top of the mouth. As some people told it in comments under, maybe some more work on the ears would be nice. In all case i really like the whole pictures and here are just some details wich i think could improve the final image rendering.
I'm not good at character drawing so here is just my personal opinion and so does my tastes
I'm not sure about what the reference to "Vulcan" is (my first thought was that of the Star Trek Vulcans but a closer look to her ears suggest otherwise. Is it from some particular piece of fiction or a theme of your own? Also, is she showing pleasure or pain? It's a bit ambivalent to me (or maybe that's the point?)
Anyway, this is a good picture with lots of impact. Certainly made me stop and ponder! . Griatch
I can say the core is from roman mythology, but I translate it into my own complex at that moment. I don't really understand what I said myself either, but I think, thats about it. Pleasure and pain... are they really different? Hehe