80
Glossopharyngeal, vagus and accessory nerves
Muscles which move the cords are supplied by the recurrent laryngeal nerve (X). Making the noise intelligible: articulation The pharyngeal muscles (X), the tongue (XII), the muscles of facial expression (VII), mandibular movements (Vc) and the palate (X, V) all modify the crude noise produced by the larynx to create speech. Pitch Pitch is modulated principally by tensing (cricothyroid) and relaxing (vocalis) the vocal cords. All movements of the vocal cords are controlled by the nucleus ambiguus through the superior and recurrent laryngeal nerves (X). It is unnecessary to learn individual laryngeal muscles or their attachments; it is enough to know that they are all innervated by the nucleus ambiguus. Lesions affecting the nucleus ambiguus lead to profound swallowing and speech disorders: bulbar and pseudobulbar palsies.
13.3
Bulbar palsy: ipsilateral lower motor neuron lesion
This is caused by a lesion of the medulla (e.g. vascular, multiple sclerosis, motor neuron disease) which involves the nucleus ambiguus and the hypoglossal nucleus. There would be an ipsilateral lower motor neuron lesion of the muscles of the tongue and pharynx. Chewing, swallowing and speaking would be affected. Because the nuclei concerned are in the medulla or bulb, this is called a bulbar palsy.