neurosthenia

From New Latin, from Ancient Greek νεῦρον (neûron) + Ancient Greek σθένος (sthénos); by surface analysis, neuro +‎ sthenia.

neurosthenia (uncountable)

1. (medicine, archaic) Strong reaction or overreaction of a nerve to a stimulus.

From mistaken rebracketing of neurasthenia (whose valid surface analysis is neur- +‎ asthenia) as if it were prefixed with neuro-, by false analogy with most other ISV compounds beginning with the syllable neur- + /ə/ (which are thus prefixed). The error is not rare, but it invites proscription because the -a- syllable in neurasthenia corresponds to the negation of strength, that is, to weakness (of constitution or affect); by surface analysis, it is equivalent to a- ("without"/"opposite"), the difference between strength and weakness.

neurosthenia (uncountable)

1. (medicine, proscribed) Misconstruction of neurasthenia.

Because the error makes the word neurosthenia nearly contranymic and may suggest (to a careful reader) either carelessness or ignorance on the writer's part, replacing it with the intended word, neurasthenia, is a good way to avoid any reproach.