  Within the type-I seesaw and in the basis where charged lepton and heavy
neutrino mass matrices are real and diagonal, $\mu\tau$ symmetric four and
three zero neutrino Yukawa textures are perturbed by lowest order $\mu\tau$
symmetry breaking terms. These perturbations are taken to be the {\it most
general ones for those textures}. For quite small values of those symmetry
breaking parameters, permitting a lowest order analysis, current best-fit
ranges of neutrino mass squared differences and mixing angles are shown to be
accommodable, including a value of $\theta_{13}$ in the observed range,
provided all the light neutrinos have an inverted mass ordering.
