Applied Anatomy Of The Cranial Nerves Flashcards
Where does the oculomotor nerve originate from and which two arteries does it run between?
Anterior aspect of the midbrain
Moves anteriorly, passing below the posterior cerebral artery and above the superior cerebellar artery
Where does the oculomotor nerve go after the two arteries?
Pierces the dura mater
Enters the lateral aspect of the cavernous sinus
Receives sympathetic fibres from the internal carotid plexus which travel in its sheath but don’t combine
Through which fissure does the oculomotor nerve leave the cranial cavity? What happens to it?
Superior orbital fissure
Divides into superior and inferior fibres
What does the superior branch of the oculomotor nerve do?
Motor innervation to superior rectus and levator palpebrae superioris
Sympathetic fibres running with it to innervate the superior tarsal muscle
What does the inferior branch of the oculomotor nerve supply?
Motor innervation to the inferior and medial rectus and inferior oblique
Parasympathetic fibres to the ciliary ganglion - sphincter pupillae and ciliary muscles
What are the causes of a lesion to the oculomotor nerve?
Increase intracranial pressure, compressing it against the temporal bone
Aneurysm of the posterior cerebral artery
Cavernous sinus infection or trauma
Clinical signs of oculomotor nerve lesion?
Ptosis due to paralysis of LPS
Eyeball is down and out - paralysis of superior rectus, medial rectus and inferior oblique.
Unable to elevate, depress or adduct the eye
Dilated pupil due to unopposed action of the dilator pupillae
If proximal to the ciliary ganglion, loss of accommodation
If distal to ciliary ganglion, pupils of both eyes will be equal
Which is the largest cranial nerve?
Trigeminal nerve
What is the trigeminal nerve associated with?
Derivatives of the first pharyngeal arch
What is a nucleus?
A collection of nerve cell bodies within the CNS
Where does the trigeminal nerve originate from?
Three sensory nuclei -mesencephalic -principle sensory sensory -spinal nuclei of trigeminal nerve
They merge at the level of the pons to form a sensory root
And one motor nucleus (motor nucleus of the trigeminal nerve) extending from the midbrain to the medulla which forms a motor root
What is a ganglion?
A collection of nerve cell bodies outside of the CNS
What happens to the roots of the trigeminal nerve at the middle cranial fossa?
Sensory root expands into the trigeminal ganglion which is lateral to the cavernous sinus in a depression of the temporal bone called the trigeminal cave
What branches does the peripheral aspect of the trigeminal ganglion give rise to?
Ophthalmic (V1)
Maxillary (V2)
Mandibular (V3)
What do the divisions of the trigeminal nerve exit the cranium via?
Ophthalmic - superior orbital fissure
Maxillary - foramen rotundum
Mandibular - foramen ovale, entering the infratemporal fossa
What are the terminal branches of the ophthalmic nerve?
Frontal
Lacrimal
Nasociliary
What does the ophthalmic nerve innervate?
Skin and mucous membranes of derivatives of the frontonasal prominence: -forehead and scalp -cornea -frontal and ethmoidal sinuses -dorsum of nose -upper eyelid and conjunctiva
Where is parasympathetic innervation to the lacrimal gland derived from?
Postganglionic fibres from the pterygopalatine ganglion travel with the zygomatic branch of V2 (maxillary) and then join the lacrimal branch of V1
What is an absence of the corneal reflex a sign of?
Damage to the trigeminal, ophthalmic or facial nerve
What is the route for the corneal reflex?
Stimulation of cornea detected by ophthalmic nerve
Trigeminal ganglion
Trigeminal nerve nucleus in brainstem
Right/left facial nerve via inter-neurones
Orbicularis oculi contracts
Bilateral blinking
How many terminal branches does the maxillary nerve have?
14
What does the maxillary nerve innervate?
Skin, mucous membranes and sinuses of derivatives of the maxillary prominence of the first pharyngeal arch -lower eyelid and conjucntiva -cheeks and maxillary sinus -nasal cavity and lateral nose -upper lip -superior palate -upper molar, incisor and canine teeth and associated gingiva
Where is the parasympathetic supply of the nasal glands derived from?
Post-ganglionic fibres travel with the nasopalatine and greater palatine nerves (branches of V2)
What are the terminal branches of the mandibular nerve?
Buccal nerve
Inferior alveolar nerve
Auricotemporal nerve
Lingual nerve
Where do the terminal branches of the mandibular nerve arise?
Infratemporal fossa
Sensory supply of the mandibular nerve?
Mucous membranes and floor of the oral cavity
External ear
Lower lip
Chin
Anterior two thirds of tongue (general sensation)
Lower molar, incisor, canine teeth and associated gingiva
What motor supply does the mandibular nerve do?
Muscles of mastication
Anterior belly of digastric muscle
Tensor vali palatini
Tensor tympani
Parasympathetic innervation of the submandibular and sublingual glands?
Post-ganglionic fibres from the submandibular ganglion derived from the facial nerve, travel with lingual nerve to innervate these glands
Parasympathetic supply of the parotid gland?
Post-ganglion fibres from the otic ganglion (derived from glossopharyngeal nerve) travel with the auricotemporal branch to innervate the parotid
What is the facial nerve associated with?
Derivatives of the second pharyngeal arch
From where and what does the facial nerve begin as?
Arises in the pons
Begins as a large motor root and a small sensory root (the branch from the sensory root known as the intermediate nerve)
Where do the two roots of the facial nerve travel?
Through the internal acoustic meatus, an opening in the petrous part of the bone, in very close proximity to the inner ear
Within the temporal bone, then enter the facial canal which is Z shaped.
What happens within the facial canal?
The motor root and sensory root fuse to form the facial nerve which forms the geniculate ganglion
Gives rise to the greater petrosal nerve, nerve to stapedius and chorda tympani
Then exits the facial canal and cranium via the stylomastoid foramen, just posterior to the styloid process
What does the chorda tympani supply?
Taste to anterior two thirds of the tongue
What is the first extracranial branch of the facial nerve and what does it innervate? Then where do the next branches go to?
Posterior auricular nerve
Motor innervation to some muscles around the ear
More branches go to the posterior belly of the digastric and the stylohyoid muscle
Where does the facial nerve travel extracranially?
Exits skull, turns superiorly to run anterior to the outer ear
Continues to parotid gland where it terminates and splits into branches
Name the terminal branches of the temporal nerve What do they innervate?
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical
Muscles of facial expression
What does the posterior auricular nerve innervate?
Intrinsic and extrinsic muscles of the outer ear
Occipital part of the occipitofrontalis muscle
What does the temporal branch of the facial nerve innervate?
Frontalis Orbicularis oculi Corrugator supercillii
What does the zygomatic branch of the facial nerve innervate?
Orbicularis oculi
What does the buccal branch of the facial nerve innervate?
Orbicularis oris Buccinator Zygomaticus
What does the marginal mandibular branch of the facial nerve innervate?
Mentalis muscle
What does the cervical branch of the facial nerve innervate?
Platysma muscle
Which nerve does the chorda tympani hitchhike on?
Lingual nerve
What does the greater petrosal nerve do?
Arises in the facial canal Exits temporal bone via middle cranial fossa Through foramen lacerum to pterygopalatine fossa Forms the pterygopalatine ganglion Branches do parasympathetic innervation to -mucous glands of oral cavity, nose and pharynx -lacrimal gland
What forms the submandibular ganglion? What does it innervate?
Chorda tympani fibres which combine with the lingual nerve (branch of the trigeminal)
Branches travel to the submandibular and sublingual salivary glands
What can cause intracranial lesions of the facial nerve?
Middle ear pathology such as a tumour or infection
How can you tell if a lesion to the cranial nerve is intracranial or extracranial?
Intracranial: muscles of facial expression are paralysed or weakened and can get other symptoms Extracranial: only get loss of facial muscles
What can cause an extracranial lesion of the facial nerve?
Parotid gland pathology eg tumour Infection of the nerve, especially herpes virus Compression from forceps delivery Idiopathic - Bell’s palsy
Why can compression of the facial nerve happen in a forceps delivery?
Neonatal mastoid process is not fully developed so doesn’t provide complete protection of the nerve
What does the oculomotor nerve do? (CN III)
Motor and parasympathetic innervation Motor -extra-ocular muscles (except lateral rectus and superior oblique) Parasympathetic -sphincter pupillae and ciliary muscles of the eye
Signs/symptoms of damage to the chorda tympani?
Reduced salivation and loss of taste on ipsilateral two thirds of tongue
Signs/symptoms if nerve to stapedius is damaged?
Ipsilateral hyperacusis
Signs/symptoms of greater petrosal nerve damage?
Ipsilateral reduced lacrimal fluid production
