Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dēmentĭo, īre, 4, v. n. [demetior], to be out of one’s senses, to be mad, to rave (anteand post-class.): dementit deliraque fatur, * Lucr. 3, 464: sese mea magia in amorem inductam dementire, App. Mag. p. 324, 9: aliquis instinctu daemonis percitus dementit, effertur, insanit, Lact. 4, 27 med.