Anatomy of CNVII Flashcards
What are the different modalities of CNVII
Motor division - the facial nerve
Sensory division - nervus intermedius
Autonomic division - part of the nervus intermedius and the greater petrosal nerve
Visceral sensory division - chorda tympani
Where does CNVII become the facial nerve?
Once it has passed the sylomastoid foramen
Where is the facial nucleus and what fibres does it give rise to?
Facial nucleus of the pons houses cell bodies of motor fibres of CNVII. These fibres are branchiomotor fibres to muscles.
What is the facial colliculus?
Fibres from the facial nucleus of the pons circle around the abducens nerve, creating the facial colliculus which has both of these nuclei.
Where is the superior salivatory nucleus and what fibres does it give rise to?
Superior salivatory nucleus of the pons
Gives rise to the preganglionic parasympathetic fibres that travel as part of CNVII. Also gives some axon fibres contributing to the chorda tympani.
Where is the spinal nucleus of cranial nerve V and what fibres is it supplied by?
Spinal nucleus of cranial nerve V from the medulla
A nuclear complex involved in general sensation. Trigeminal nerve also processes information from CNVII. Only small contribution from CNVII of general sensation: sensation to pinna and tympanic membrane (so do not need own nucleus to process these signals).
Somatic sensory component
Where is the solitary tract nucleus (nucleus solitarius) and what fibres supply it?
Solitary tract nucleus of the medulla
Processes special taste sensation signals arising from the anterior 2/3 of the tongue. It receives sensations that are carried by the chorda tympani, (and some palatine tastebud sensation from the greater petrosal).
Where are the cell bodies of the chorda tympani?
Chorda tympani has its cell bodies in the geniculate ganglion in the petrous part of the temporal bone. It’s axons access the brain and signals are processed by the nucleus solitarius.
What does the greater petrosal nerve innervate and what fibres is it made from?
Lacrimal gland
Made from fibres of superior salivatory nucleus and nucleus solitarius
Purely autonomic nerve. Forms part of the vidian nerve. Synapses in the pterygopalatine ganglion.
What does the chorda tympani supply?
Taste to the anterior 2/3 of the tongue
The submandibular and sublingual glands by synapsing in the submandibular ganglion
What is the course of CNVII before it passes through the stylomastoid foramen?
CNVII axons constitute 2 unequal roots (larger motor smaller sensory). These roots then pass through the internal acoustic meatus to enter the petrous part of the temporal bone and through the facial canal. Eventually the facial nerve itself exits via the stylomastoid foramen.
What travels with CNVII through the internal acoustic meatus?
Vestibulocochlear nerve CNVIII, labyrinthine artery
How is the geniculate ganglion relevant to CNVII?
Sensory fibres synapse in the geniculate ganglion but motor fibres pass straight through
What happens to the nervus intermedius after it passes through the internal acoustic meatus?
Fibres from the sensory nucleus of CNV leave to supply cutaneous sensation to the tympanic cavity, membrane, EAM and back of the ear.
Half of the fibres from the superior salivatory nucleus will for the greater petrosal nerve, which will exit the petrous temporal and travel through the foramen lacerum with the deep petrosal nerve. Enters the vidian canal and synapses in the pterygopalatine ganglion to supply the lacrimal glands.
Other half of fibres from SSN and fibres from nucleus solitarius will form the chorda tympani. Travel out of skull by petrotympanic fissure into the infratemporal fossa. Joins with the lingual nerve. The GVE fibres will synapse at the submandibular ganglion to supply the 2 salivary glands. The SVA fibres will remain with the lingual nerve and distribute fibres to the tastebuds on the anterior 2/3 of the tongue.
What happens to the motor component of CNVII after it passes through the internal acoustic meatus?
Fibres from the motor nucleus give off the nerve to stapedius and then it travels through the stylomastoid foramen. Gives off the posterior auricular branch, then a branch to the posterior belly of digastric and stylohyoid, before piercing the parotid gland to terminate into the final TZBMC.
How ones the chorda tympani enter the skull?
Passes between the malleus and incus bones of the ear entering the skull separately, which is why state is often spared even though other branches of the facial nerve are affected in Bell’s Palsy.
What happens in damage to the chorda tympani?
Special taste sensation is lost s well as functionality in relation to preganglionic parasympathetic fibres.
What side of the body does the facial nerve innervate (motor component)?
Majorit of muscles on the same side of the body as that of the cell bodies of neurones of the facial motor nucleus, except the forehead.
Describe innervation of the forehead
Muscles of expression of the forehead, frontalis, receives bilateral innervation from both motor divisions of CNVII.
Can can damage to the facial nerve lead to?
Loss of facial expression
Loss of sphincter function
Loss of naso-labial fold
Hyperacusis - sensitivity to sounds due to damage of stapedius
Forehead sparing
What does the autonomic division of CNVII innervate?
Lacrimal, submandibular, sublingual glands
Mucous membranes of Nasopharynx, paranasal sinuses, hard and soft palates
What might damage within the posterior wall of the tympanic cavity affect?
Affects taste to the anterior 2/3 of the tongue and salivation and lacrimation
What might surgery on the middle ear cause?
Might damage the facial nerve within the labyrinthine wall of the tympanic cavity
What tumour could affect the facial nerve?
Tumours within petrous part of temporal bone
Tumours of the parotid gland will lead to congestion within parotid sheath and palsy of the motor branches
