  We investigate spin-$0$ and spin-$\frac{1}{2}$ perturbations for non-extremal
and extremal Reissner-Nordstr\"om backgrounds using the isomonodromic method.
We calculate the fundamental quasinormal modes (QNMs) associated with each
perturbation as a function of the electromagnetic coupling $qQ$ and ratio
$Q/M$. After corroborating the literature values for generic $qQ$ and $Q/M$, we
turn to study the near-extremal limit. In parallel with the study of QNMs for
the Kerr geometry, we find the existence of "non-damping" modes for $qQ$ above
a spin-dependent critical value, and locate the bifurcation point in the $q-Q$
parameter space.

General Relativity and Quantum Cosmology;High Energy Physics - Theory