The effect of extrinsic laryngeal muscles on the position of the paral
yzed vocal fold (VF) was analyzed in 13 adult human larynges. Fresh sp
ecimens were suspended within a specially constructed frame designed t
o reproduce the three-dimensional position of the VF, and to allow for
simulation of laryngeal muscle action, in five successive experiments
resembling: 1) complete vagal paralysis and contralateral adduction,
2) laryngeal elevation added, 3) vocal fold stretching added, 4) contr
alateral laryngeal tilting added, and 5) ipsilateral cricothyroid musc
le activation added. We observed an incremental narrowing of the middl
e and posterior glottic gaps from 3.9 mm and 6.8 mm respectively in ex
periment 1 to 1.1 mm and 1.9 mm in experiment 5. Glottic closure in th
e final experiment was associated with rotation of the glottis to the
''paralyzed'' side in the axial plane, and contralateral laryngeal til
ting in the coronal plane. We show that extrinsic laryngeal muscles ca
n help to close a paralytic gap; crossing of the contralateral VF past
the midline was not observed in any of the experiments.