Disorders Of The Lower Cranial Nerves

TENTH (VAGUS) CRANIAL NERVE

This is a mixed nerve with motor, sensory and parasympathetic functions. The central connections are complex though similar to those of the glossopharyngeal nerve.

1. Motor fibres supplying the pharynx, soft palate and larynx arise in the nucleus ambiguus.

2. Preganglionic parasympathetic fibres arise in the dorsal motor nucleus. Postganglionic fibres supply the thoracic and abdominal viscera.

3. Afferent fibres from the pharynx, larynx and external auditory meatus have cell bodies in the jugular ganglion and end in the nucleus and tract of the trigeminal nerve.

4. Afferent fibres from abdominal and thoracic viscera have cell bodies in the nodose ganglion and end in the nucleus solitarius. Taste perception in the pharynx ends similarly.

The nerve emerges from the brain stem as a series of converging rootlets. It exits from the cranial cavity by the jugular foramen where both ganglia lie.

Extracranial branches:

Motor and sensory supply to the pharynx---

Superior laryngeal branch to the laryngeal muscles-

Supply to thoracic and abdominal viscera ----^

Medulla

Dorsal nucleus Nucleus solitarius •-

Jugular -ganglion

Nodose ganglion /

Nucleus ambiguus

Jugular foramen

Jugular foramen

Disorders of the vagus nerve cause: Palatal zueakness

Unilateral - minimal symptoms.

Bilateral - nasal regurgitation of fluid, nasal quality of speech. Pharyngeal weakness

Pharyngeal muscles are represented by the middle part of the nucleus ambiguus.----------*

Unilateral - pharyngeal wall droops on the affected side. Bilateral - marked dysphagia. Laryngeal weakness /

Motor fibres arise in the lowest part of the nucleus ambiguus. Fibres to tensors of the vocal cords pass in superior laryngeal nerves.

Fibres to adductors and abductors of the vocal cords are supplied by the recurrent laryngeal nerves.

Stylopharyngeus Pharynx

Larynx

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