We reconsider decays of pseudoscalar mesons (P) to neutrino pairs and possibly additional photons in presence of (light) Majorana neutrinos. For this purpose we derive a model-independent general parametrization of neutrino mass matrices with physically interpretable and irreducible set of parameters. The parametrization is valid for any number of neutrinos and interpolates smoothly between the heavy Majorana and the (pseudo)Dirac neutrino limits. We apply the new parametrization to the study of P rightarrow nu nu and P rightarrow nu nu gamma decays within the SM extended by additional singlet fermions. We update the SM predictions for the branching ratios of B_{s,d} rightarrow nu nu gamma and discuss the sensitivity of the B_{s,d} rightarrow E_{mathrm{miss}} (gamma ) decays to neutrino mass and mixing parameters.