Point
9
Intro
A
unilateral lesion of nucleus ambiguus will result in
atrophy and paralysis of all palatine muscles
ipsilateral to the lesion, except the tensor veli
palatini (C.N. V). Because of the palate paralysis, the
patient's speech may be nasal. This is because air is
allowed to escape into the nose during speaking. Normally,
the soft palate elevates in order to reduce the
nasopharyngeal aperture during speaking. This elevation of
the soft palate detours the air through the mouth, the path
of least resistance. Due to the hemiplegic palate the
patient may complain of nasal regurgitation of
liquids since he/she is unable to shut off completely the
nasopharynx from the buccal cavity. Moreover, during
phonation (say ahhh!) the soft palate is elevated on the
normal side and the UVULA DEVIATES TOWARDS THE NORMAL
SIDE (contralateral to the lesion; contrast this with
lesions of the hypoglossal nucleus). Remember from Gross
Anatomy that the levator veli palatini raises the soft
palate and, in doing so, also pulls it backward. Also, some
awkwardness of swallowing, called dysphagia, may
occur due to the unilateral paralysis of the constrictors of
the pharynx. Due to paralysis of the laryngeal muscles, the
patient exhibits dysphonia, his/her voice being
husky or hoarse (speech requires phonation by
the vocal cords; phono=voice, sound).
Bilateral lesions of nucleus ambiguus
increase the difficulties I have just described following
ipsilateral lesions. Nasal regurgitation is more distressing
and permanent. Dysphagia is more pronounced and speech and
respiratory disorders may be profound. Respiratory
disorders, induced by the paralysis of the abductor muscles
(of the larynx) bilaterally may lead to suffocation unless
treated by intubation.