MHD instabilities like the Neoclassical Tearing Modes (NTM) constitute an important issue for ITER. In this device, NTMs are predicted to limit drastically the operational bN = b%aB/IpMA. Thus it is essential to understand better the physics of those modes. Simulations have been already carried out with the XTOR code with a simplified model.We present here the implementation of a more complete formulation based on the viscous stress tensor that is directly linked to the pressure anisotropy. It allows one to recover the neoclassical equilibrium and thus to treat the evolution of NTMs in a consistent manner.