Shade
Monster Junkie
This suggests to me that you can use somatic components; after all, your arms aren't pinned.
Agreed. Although, we could just go for the simplification of the similar-themed choker...
Constrict (Ex): A choker deals 1d3+3 points of damage with a successful grapple check against a Large or smaller creature. Because it seizes its victim by the neck, a creature in the choker’s grasp cannot speak or cast spells with verbal components.