Cranial nerve nuclei : summarized lecture notes

Cranial nerve nuclei

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The cranial nerve nuclei are aggregate of cells (collection of cell bodies). Attached to these cell bodies are fibers called cranial nerves (bundles of axons). These nuclei are either sensory or motor but never both. However, cranial nerves can be sensory, motor or mixed nerves (when they have both sensory and motor functions).

The cranial nerve nuclei are a series of bilateral grey matter motor and sensory nuclei located in the midbrain, pons and medulla that are the collections of afferent and efferent cell bodies for many of the cranial nerves.

Some nuclei are small and contribute to a single cranial nerve, such as some of th motor nuclei.

 Other nuclei, however, are long and span several regions of the brainstem contributing to several cranial nerves.

 Several motor and sensory nuclei form longitudinal columns in the brainstem, leading to some authors describing them as single discontinuous longitudinal nuclear columns rather than the more numerous individual separate nuclei.

Three long discontinuous efferent columns have been described: somatic, brachiomotor and parasympathetic.

Extensive interconnections exist between many of these nuclei, as well as with other brainstem nuclei and white matter tracts such as the medial lemniscus and medial longitudinal fasciculus.

1. oculomotor nucleus: somatic motor nucleus for the oculomotor nerve
2. Edinger-Westphal nucleus: general visceral motor (parasympathetic) nucleus for the oculomotor nerve,
3. trochlear nucleus: somatic motor nucleus for the trochlear nerve
4. motor nucleus of CN V: somatic motor nucleus for the trigeminal nerve
5. ​mesencephalic nucleus of CN V: somatic sensory nucleus for the trigeminal nerve
6. main sensory nucleus of CN V: somatic sensory nucleus for the trigeminal, facial, glossopharyngeal and vagus nerves
7. spinal nucleus of CN V: somatic sensory nucleus for the trigeminal nerve
8. abducent nucleus: somatic motor nucleus for the abducens nerve
9. facial nucleus: special visceral motor (branchial) nucleus for the facial nerve
10. superior salivatory nucleus: general visceral motor (parasympathetic) nucleus for the facial nerve
11. cochlear nuclei: group of two special sensory nuclei for the cochlear branch of the vestibulocochlear nerve
12. vestibular nuclei: group of four special sensory  nuclei for the superior and inferior vestibular branches of the vestibulocochlear nerve
13. inferior salivatory nucleus: general visceral motor (parasympathetic) nucleus for the glossopharyngeal nerve

14.    solitary tract nucleus: special visceral sensory nucleus for the facial, glossopharyngeal and vagus nerves

15.    ambiguus nucleus: special visceral motor (branchial) nucleus for the glossopharyngeal and vagus nerves

16.    dorsal motor nucleus: general visceral motor (parasympathetic) nucleus for the vagus nerve

17.    hypoglossal nucleus: somatic motor nucleus for the hypoglossal nerve

18.     the gracile and cuneate nuclei

the cranial nerve nuclei with motor functions can be grouped according to the following functional components to which their fibers belong:

·         General Somatic Efferents (GSE)

·         Special Visceral Efferents (SVE)

·         General Visceral Efferents (GVE)

Similarly, the cranial nerve sensory nuclei are grouped according to the information they receive, which constitutes the functional components to which their attached nerves belong. These functional components are:

·         General Somatic Afferents (GSA)

·         Special Somatic Afferents (SSA)

·         General Visceral Afferents (GVA)

·         Special Visceral Afferents (SVA)

In the brainstem, there are about 18 cranial nerve nuclei comprising of 10 motor cranial nerve nuclei and 8 sensory cranial nerve nuclei. 

 

General somatic efferent nuclei	Oculomotor, trochlear, abducens, hypoglossal
Special visceral efferent nuclei	Motor nucleus of trigeminal nerve, nucleus of facial nerve, nucleus ambiguus
General visceral efferent nuclei	Accessory oculomotor nucleus (Edinger-Westphal nucleus), salivatory nuclei, dorsal vagal nucleus
General and special visceral afferent nuclei	Nucleus of the solitary tract, commissural nucleus of the vagus, gustatory nucleus
General somatic afferent nuclei	Principal sensory nucleus of the trigeminal nerve, spinal nucleus of the trigeminal nerve, mesencephalic nucleus of the trigeminal nerve
Special somatic afferent nuclei	Cochlear and vestibular nuclei