In this brief note, we consider the variation of the entanglement entropy of
a region as the shape of the entangling surface is changed. We show that the
variation satisfies a Wess-Zumino like integrability condition in field
theories which can be consistently coupled to gravity. In this case the
"anomaly" is localized on the entangling surface. The solution of the
integrability condition should give all the nontrivial finite local terms which
can appear in the variation of the entanglement entropy.Comment: 14 pages, presentation improve