[TA] the small canal opening found lateral to the pyramidal eminence in the posterior wall of the middle ear cavity from which the chorda tympani nerve emerges to pass anteriorly between the ossicles accompanied by a branch of the stylomastoid artery. SYN: apertura tympanica canaliculi chordae tympani [TA], tympanic opening of canaliculus for chorda tympani.