22.1 Specific Cranial Nerves Flashcards
CN III
Oculomotor nerve
CN IV
Trochlear nerve
CN VI
Abducens nerve
How can oculomotor, trochlear and abducens nerves be tested to see if they are functional? (Give 2 tests)
Examine
1) pupillary reflexes
2) eye movements
What are the signs of damage to the oculomotor nerve (III)?
- Diplopia (double vision)
- Ptosis
- Pupil dilation
- DOWN and OUT movement of eye (bc unopposed left superior oblique and lateral rectus muscles)
What are the signs of damage to the trochlear nerve (IV)?
Diplopia when looking downward and medially
bc affected eye cannot move in and down
What are the signs of damage to the abducens nerve (VI)?
Loss of lateral movement of eye –> diplopia when looking to affected side
bc lateral rectus paralysed
CN V
Trigeminal nerve
What are the three branches of the trigeminal nerve?
V1: opthalmic
V2: maxillary
V3: mandibular
Where do the three trigeminal branches split off from?
The trigeminal ganglion
Role of CNV1 (ophthalmic)?
Sensory supply to forehead and eyes
Role of CNV2 (maxillary)?
Sensory supply to maxilla and upper teeth
Roles of CNV3 (mandibular)?
- Sensory supply to anterior 2/3 of tongue, jaw, lateral sides of face, dura, tympanic membrane
- Motor supply to tensor tympani and muscles of mastication
What is a good visual way to remember the innervation of the three trigeminal branches?
Knight’s helmet
Where does the opthalmic branch pass through the cranium?
Superior orbital fissure
Where does the maxillary branch pass through the cranium?
Foramen rotundum
Where does the mandibular branch pass through the cranium?
Foramen ovale
How can the ophthalmic and maxillary afferents be unusually involved in coughing and sneezing reflexes?
As they join the trigeminal ganglion along with the mandibular branch, which innervates the muscles of mastication involved in these reflexes
What are the two sensory nuclei in the brainstem next to the trigeminal ganglion that the fibres may travel to?
Primary
Spinal
(Extra: mesencephalic, = proprioceptive)
What are the roles of the primary and spinal sensory nuclei?
Primary: touch
Spinal: nociceptive
Which nucleus do the mandibular motor fibres travel to?
Motor nucleus
What is lateral medullary syndrome?
Acute ischaemic infarct of the lateral medulla, due to occlusion of PICA (posterior inferior cerebellar artery)
What symptoms does lateral medullary syndrome cause? Why?
Loss of pain and temp sensation (bc trigeminal nuclei affected) from ipsilateral face and contralateral body (bc spinothalamic tracts have decussated before this, in the spinal cord)
What are three tests for CN V?
- Touch cornea to induce blink reflex
- Test sensation in face
- Check that jaw closes symmetrically
CN VII
Facial nerve
What are the roles of CN VII (facial)?
- Special sensory: taste to anterior 2/3 of tongue
- Motor: muscles of facial expression and stapedius
- Parasympathetic: supply to salivary glands
Via which nerve and ganglion does CN VII parasympathetically innervate the submandibular and siblingual glands?
Chorda tympani
Submandibular ganglion
Via which ganglion does CN VII parasympathetically innervate the lacrimal glands?
Pterygopalatine ganglion
Which nerve innervates the stapedius?
Facial nerve VII
Via which ganglion and nerve does the facial nerve provide taste sensation to the anterior 2/3 of the tongue?
Geniculate ganglion
Chorda tympani
Where does the motor supply of the facial nerve originate in the brainstem?
In the motor nucleus
Where does the sensory supply of the facial nerve originate in the brainstem?
Nucleus solitarius
Where does the parasympathetic supply of the facial nerve originate in the brainstem?
Superior salivatory nucleus
How is the facial nerve tested?
Examine control of facial muscles
Check symmetry of expression
What are two things that can occur with a facial nerve lesion?
Bell’s palsy
Hyperacusis
What is Bell’s palsy characterised by?
characterised by loss of expression, dry eyes, altered taste, ptosis and uncontrolled salivation/dribbling
What is hyperacusis?
Increased sensitivity to everyday sounds that causes an intolerance
Which number cranial nerve is the vestibulocochlear nerve?
VIII
State a mnemonic to remember if the cranial nerves are sensory, motor or mixed (both)? What is the vestibuloochlear nerve?
Some say money matters, but my brother says big brains matter most
Sensory (CN I)
Sensory (CN II)
Motor (CN III)
Motor (CN IV)
Both (CN V)
Motor (CN VI)
Both (CN VII)
Sensory (CN VIII)
Both (CN IX)
Both (CN X)
Motor (CN XI)
Motor (CN XII)
‘says’ = sensory
Vestibulocochelar carries sensory information
Where is the origin of the vestibulocochlear nerve?
Vestibular area of the Rhomboid fossa of the brainstem (vestibular and cochlear nuclei
What are the two components of the vestibulocochlear nerve? What are their functions?
Vestibular component = balance
Cochlear component = hearing
What is the functional categorisation of the vestibulocochlear nerve?
Special somatic afferent
Describe the course taken by the vestibulocochlear nerve from where it emerges to where it terminates
Emerges from the vestibular and cochlear root
Leaves the brain through the internal acoustic meatus in the posterior cranial fossa
In here it splits into two roots: vestibular cochlear
The vestibular root connects to the vestibular ganglion
The cochlear root reaches the spiral canal of the modlolus where the spiral ganglion is located
What is an acoustic neuroma? How may it cause sensorineural hearing loss? What other symptoms may it cause?
Benign tumuor compressing CN VIII leading to auditory loss, nausea, vertigo and motion sickness (sometimes facial numbness)
Give some causes of conductive hearing loss
Cerumen (wax) occluding external auditory meatus
Perforated eardrum
Infections producing fluid in tympanic cavity
Immobilisation of the ossciles
Where does cranial nerve IX originate from?
Laterally from the medulla oblongata
Which nerve is shown below?
Cranial nerve IX
Which embryological strucutres are generally innervated by the glossopharyngeal nerve? List them
Third branchial arch:
Senory innervation to (afferents from)
-Carotid bodies and sinus
-Tympanic membrane and tube
-oropharynx
-mucosa of middle ear
-Mastoid air cells
-General sensation for posterior 1/3 tongue
-Taste sensation for posterior 1/3 tongue
Parasymapthetic:
-innervate salivary parotid gland
Motor:
-Stylopharygeus muscle
-Superior pharyngeal contrictor
What does cranial nerve IX provide motor input to?
Stylopharyngeus muscle
Which nuclei do motor afferents for cranial nerve IX, X and XI come from?
Nucelus ambiguous
Which branch of the glossopharyngeal nerve gives taste to the posterior 1/3 tongue?
Lingual branch
How can the glossopharyngeal nerve and vagus nerve be tested for?
Test the gag reflex on posterior part of tongue
(glossopahryngeal nerve innervates mucosa of pharynx and anastomoses with the vagus)
What is the function of the stylopharygenus muscle?
Elevates the pharynx and larynx so plays an important role in swallowing and speaking
What is the origin of the vagus nerve?
Lateral medulla oblongata of the brainstem
Which nuclei provide parasympathetic supply from the vagus nerve? What is this to?
Dorsal motor nucelus - parasymapthetic motor innervation to pharynx, larynx and all of GI tract derived from foregut and midgut
Nucelus ambiguus - (as well as efferent motor) parasympathetic fibres to the heart
What is supplied by the vagus nerve? What type of innervation is each one?
SENSORY:
-Larynx
-External acoustic meatus
-Aortic chemoreceptors and baroreceptors
-Epiglottis taste buds
PARASYMPATHETIC:
-Heart (nucelus ambiguus)
-Smooth muscle of phaynx, larynx, thorax and GI tract
MOTOR:
-Pharyngeal muscles (excluding stylopharyngeal)
-Laynx
-Palatoglossus
Which cranial nerve is this?
Spinal accessory nerve (XI)
What is the origin of the accessory nerve?
Posterior border of the olive below the level of the vagus nerve
What foramen does the glossopharyngeal, vagus and accessory nerves pass through?
Jugular foramen
Which muscles are innervated by the spinal accessory nerve?
Pharyngeal constrictors
Larynx and muscles of soft palate
Trapezius
Sterncelidomastoid
Why is spinal accessory nerve not a ‘true’ cranial nerve
Does not necessarily originate in the cranium
Has a cranial division from the medulla at the level of the nucelus ambiguus (cranial nucelus) emerging at posterior border of the olive leaving at jugular foramen where it briefly contacts spinal part of accessory nerve
Roots emerge from C1-6 and pass into the cranium via foramen magnum
What type of innervation does CN XII supply?
MOTOR
What is innervated by the hypoglossal nerve?
ALL intrinsic muscles of the tongue
All extrinisc muscles of the tongue but palatoglossus (vagus)
Geniohyoid muscle (one of the suprahyoid muscles between madible and hyoid bone)
Where does the hypoglossal nerve leave the cranium?
Hypoglossal canal
What causes medial medullary syndrome?
Occlusion/Lesion of the anterior spinal artery causing infarction of the medial part of the medulla oblongata
What are the characteristics of medial medullary syndrome?
-a deviation of the tongue to the side of the infarct on attempted protrusion, caused by ipsilateral muscle weakness (hypoglossal)
-loss of discriminative touch, proprioception and vibration on contralateral side (medial lemniscus)
-limb weakness on contralateral side (medullary pyramid and corticospinal tract)
