  In the past decade, the precise measurement of the lastly known neutrino
mixing angle $\theta_{13}$ has enabled the resolution of neutrino mass
hierarchy (MH) at medium-baseline reactor neutrino oscillation (MBRO)
experiments. On the other hand, recent calculations of the reactor neutrino
flux predict percent-level sub-structures in the $\bar\nu_e$ spectrum due to
Coulomb effects in beta decay. Such fine structure in the reactor spectrum
could be an important issue for the determination of neutrino MH for the MBRO
approach since they could affect the sub-dominant oscillation pattern used to
discriminate different hierarchies. Inconveniently, the energy resolutions of
current reactor experiments are not sufficient to measure such fine structure,
and therefore the size and location in energy of these predicted
discontinuities has not been confirmed experimentally. There has been
speculation that a near detector is required with sufficient energy resolution
to resolve the fine structure such that it can be accounted for in any analysis
which attempts to discriminate the MH. This article studies the impact of fine
structure on the resolution of MH, based on the predicted reactor neutrino
spectra, using the measured spectrum from Daya Bay as a reference. We also
investigate whether a near detector could improve the sensitivity of neutrino
MH resolution using various assumptions of near detector energy resolution.
