We present the first measurements of the fast dynamics of cationic wormlike micelles (WLM) using neutron spin echo (NSE). The comparison with theory [Zilman, A.; Granek, R. Phys. Rev. Lett. 1996, 77, 4788. Granek, R. J. Phys. II 1997, 7, 1761](1,2) enables coarse grained parameters to be identified. We propose and validate a calibration procedure to extract the bending constant kappa from NSE measurements.