1. Cranial Nerve VII & VIII

2. Lecture Objectives
Follow up the course of facial nerve from its point of central connections, exit and down to its target areas.
Follow up the central connections of the facial nerve.
Discuss the various modalities of its fibers.
Review your knowledge of its target organs.
Follow the course of the VIII nerve down to its point of entry to the brain.
Follow up the central connections of the VIII nerve.

3. Facial Nerve (VII) Mixed cranial nerve Motor Modalities
Motor fibers (SVE) originate from the pons and innervate facial, scalp muscles
Parasympathetic innervation (GVE) (via the pterygopalatine and submandibular ganglia) to various glands in the head
Major motor functions are regulating muscles of facial expression and secretion of saliva and tears

4. Facial Nerve (VII) Sensory Modalities
Sensory fibers (SVA) from the taste buds of the anterior ⅔ of the tongue
Sensory fibers (GVA) from soft palate
Sensory fibers (GSA) from external ear
All sensory fibers go to the geniculate ganglion (in facial canal)

5. Facial Nerve Nuclei Main motor nucleus (SVE) Location Connection
Cortex*
Upper muscles – both sides
Lower muscles – contralateral innervation
*upper motor neuron lesion would affect lower muscles only
Fibers course
Colliculus facialis

6. Facial Nerve Nuclei Parasympathetic nuclei (GVE) Superior salivatory
Connections
Hypothalamus
Lacrimal
Sensory nuclei of V
Corneal irritation

7. Facial Nerve: Sensory Nucleus
1st order neuron – geniculate ganglion
2nd order neuron –Nucleus of the tractus solitarius (SVA, GVA)
Taste and sensation from palate
Location
Axons cross midline
3rd order neuron – PVM of thalamus
Axons → internal capsule → corona radiata → cortex (postcentral gyrus)

8. Facial Nerve (VII): Course
Facial nerve (motor root (SVE) & nervus intermedius (GVE,SVA,GVA,GSA))
Pons (cerebellopontine angle)
Internal acuastic meatus
Facial canal
Stylomastoid foramen

9. Facial Nerve (VII): Branches
Nerve to the stapidius muscle (SVE)
Posterior auricular n. (SVE)
Stylohyoid & posterior belly of digastric
Five terminal branches (SVE)

10. Facial Nerve (VII): Branches
Greater petrosal nerve (GVE, GVA)↔ hiatus of the facial canal ↔ pterygoid canal ↔ pterygpalatine ganglion

11. Facial Nerve (VII): Branches
Chorda tympani n. (GVE, SVA,GVA) ↔ canal in the tympanic cavity ↔ canal in the petrotympanic fissure ↔ foramen at the spine of sphenoid ↔ lingual nerve (V3)

13. Facial Nerve (VII): Lesion
Bell’s palsy: paralysis of facial expression mm.
Unable to show teeth and close eye
Loss of corneal reflex (efferent limb)
Loss of taste from the anterior
⅔ of tongue (corda tympani)
Unable to distinguish taste sensations (sweet, bitter, sour & salt)
Decrease salivation (corda tympani)

14. UMN Vs LMN Lesions of Facial Nerve

15. Vestibulocochlear Nerve (VIII)
Formerly called the acoustic or auditory nerve
Brainstem (between pons & medulla) → Internal acoustic meatus
Mainly a sensory nerve
Consists of two branches:
Cochlear branch
Associated with hearing
Receptors in the spiral organ in the cochlea
The cell bodies in the spiral ganglion
Axons travel to nuclei in the medulla
if damaged deafness or tinnitus (ringing) is produced

16. Auditory Nuclei/Pathway
1st order neuron – spiral ganglion
2nd order neurons
Cochlear nuclei
Anterior & posterior
Location
Relations – inferior cerebellar peduncles
Axons cross and uncross midline

17. Auditory Nuclei/Pathway
3rd order neurons
Posterior nucleus of trapezoid body & superior olivary nucleus
Axons – lateral lemniscus
4th order neurons
Inferior colliculus
Medial geniculate body (5th) → internal capsule → auditory cortex (superior temporal gyrus)

18. Vestibulocochlear Nerve (VIII)
Vestibular branch
Associated with equilibrium
Receptors in the semicircular canals; saccule, and utricle
The cell bodies in vestibular ganglion
Axons travel to nuclei in the thalamus; some fibers also travel to the cerebellum
Lesion results in disequilibrium, vertigo, nystagmus, ataxia

19. The Vestibular Nuclei/Pathway
Location – 4th ventricle
Vestibular nuclei (2nd order neurons)
Lateral → vistibulospinal tract
Superior
Medial
Inferior
Inputs from cerebellum
Axons
To spinal cord
To eye muscles nerves (III, IV, VI)
To thalamus (VP) → vestibular area in cerebral cortex (postcentral gyrus)