22. Cranial Nerves Flashcards
1
Q
Label the diagram.
A
NB system is symmetrical, so there are two of each cranial nerve
2
Q
Label the diagram.
A
3
Q
Label the diagram.
A
4
Q
Describe the features of CN I
A
- Name: Olfactory nerve
- Function: Sensory - sense of smell, receptors in the olfactory/nasal mucosa
- Origin: Caudal surface of the olfactory bulbs
- Emergence from CNS: Not identifiable on the brain, but olfactory bulbs can be seen on the rostral and ventral surface of the brain (above the cribriform plate of the ethmoid bone)
- Extracranial course: Receptors lie in the nasal mucosa and send small unmyelinated axons through the cribriform plate to enter the cranial cavity
- Intracranial course: Small unmyelinated axons travel through the cribriform plate and to the olfactory bulbs, where second order neurons then form the olfactory tract (still considered part of the CN)
- Peripheral distribution: Nasal mucosa
- Testing of function: One nostril is compressed and then patients are asked to identify different substances through smelling them with the open nostril
- Consequences of lesions: Damage to the nerves results in anosmia (loss of sense of smell), but the cells are constantly regenerated from stem cells in the olfactory epithelium, so the loss is often only transient
- [EXTRA] Interest in use of these olfactory stem cells and specialised glial cells as potential neural stem cells
- [EXTRA] The nerve fibres are particularly prone to damage if head is subjected to violent movement, particularly if the ethmoid bone is damaged
- Control and interrelations of cranial nerve nucleus: Olfactory bulb in the forebrain, links to the anterior perforated substance aka olfactory trigone. There are also eventual inputs into the limbic system.
5
Q
What is Kallmann’s syndrome?
[EXTRA]
A
A condition characterised by delayed or absent puberty and an impaired sense of smell - is a genetic condition, and inheritance is determined by the specific mutation. Hypogonadotrophic hypogonadism.
Anosmia/hyposmia (and other features) are due to a failure of GnRH neurons to migrate during development, from the nasal mucosa into the brain.
6
Q
Describe the features of CN II
A
- Name: Optic nerve
- Function: Sensory - allows vision from the retina
- Origin: Arises from retinal output, the retinal ganglion cells
- Emergence from CNS: Optic tracts/optic chiasm is visible on the ventral surface of the brain
- Extracranial course: Optical nerve head is where the optic nerve leaves the retina, with fibres passing through the lamina cribrosa (collagen lattice). Enters the skull through the optic canal, a passageway through the sphenoid bone.
- Intracranial course: Optic nerves pass via the canal to the base of the brain where they meet to form the optic chiasm. Axons from temporal retina remain ipsilateral, axons from nasal retina decussate. Fibres will then travel to the lateral geniculate nucleus (LGN) and then on to visual areas.
- Peripheral distribution: The eye.
- Testing of function: Raised intraocular and raised intercranial pressure can affect the optic nerve. Ophthalmoscope can visualise the retina and optic nerve head, so is used to detect these two issues. Visual acuity and fields can be tested, using Snellen’s chart and testing vision in the periphery of the 4 quadrants respectively
- Consequences of lesions: See diagram.
- Control and interrelations of cranial nerve nucleus: Lateral geniculate nucleus.
7
Q
Describe the features of CN III
A
- Name: Oculomotor nerve
- Function: Motor and parasympathetic
- Motor to 4 of the eye muscles (superior rectus, inferior rectus, medial rectus and inferior oblique), and levator palpabrae muscle of the eyelid
- Parasympathetic to the eye, innervates the ciliary ganglion to control the ciliary (lens) and iris (pupil) muscles.
- Sympathetic nerves also innervate the iris muscles for dilation of the pupil
- Origin: Oculomotor nucleus found in the midbrain of the brainstem, ventral to the cerebral aqueduct, parasympathetic supply arises from the Edinger-Westphal nucleus
- Emergence from CNS: Junction of the midbrain and the pons (anterior midbrain)
- Intracranial course: After emergence, found on rostral border of pons and emerges into the interpeduncular fossa, passing inferiorly to the posterior cerebral artery and superiorly to the superior cerebellar artery. Leaves the skull via the superior orbital fissure.
- Extracranial course: Superior and inferior branches, which innervate the superior and inferior regions of the eye respectively
- Superior branch: to superior rectus and levatory palpabrae
- Inferior branch: to inferior rectus, medial rectus, inferior oblique and parasympathetic innervation
- Parasympathetic innervation (post-ganglionic) branches into the short ciliary nerves
- Peripheral distribution: To the eye and muscles surrounding the eye
- Testing of function: Ocular movements are tested through asking the patient to follow an object with their eyes, without moving their head. Accomodation reflex is tested (pupils should constrict as object of focus is moved towards the nose). Pupillary light reflex is tested (both pupils should constrict in response to bright light). Extraocular movements are tested for through looking for ptosis and eye positioning.
- Consequences of lesions: Eye deviates downwards and laterally due to unopposed action of lateral rectus and superior oblique muscles. Pupils dilate and eyelid droops (ptosis, due to loss of levator palpebrae).
- Control and interrelations of cranial nerve nucleus: Oculomotor nucleus in the midbrain, associated with the pre-ganglionic parasympathetic Edinger-Westphal nucleus. Links to CN IV and VI.
8
Q
Describe the features of CN IV
A
- Name: Trochlear nerve
- Function: Motor - motor to eye muscles (superior oblique, extraocular, turns eye down and out))
- Origin: Trochlear nuclei (paired) within the medial midbrain at the level of the inferior colliculus
- Emergence from CNS: Emerges dorsally and decussates before emerging just behind the inferior colliculus - only nerve to emerge posteriorly/dorsally
- Intracranial course: From origin, course dorsally and decussate dorsal to PAG before exiting the brainstem directly below the inferior colliculus. Courses towards the lateral wall of the cavernous sinus and the superior orbital fissure.
- Extracranial course: Passes out of the CNS via the middle cranial fossa (cavernous sinus is part of this structure, see image), and enters the orbit through the superior orbital fissure
- Peripheral distribution: Nerve only innervates the single muscle in the eye
- Testing of function: Extraocular muscles are synergistic, so it is difficult to isolate the single muscle, so patient is asked to look downwards and inwards, as this is the movement the muscle contributes towards most. Can use Bielschowsky’s head tilt test (isolates superior oblique muscle)
- Often tested in conjunction with the oculomotor and abducens nerves (see other flashcards)
- Consequences of lesions: Affects superior oblique muscle, causing difficulties in looking down - difficult to detect
- Control and interrelations of cranial nerve nucleus: Somewhat associated with the oculomotor and abducens nerves due to synergistic actions of muscle.
9
Q
Describe the features of CN V
A
- Name: Trigeminal nerve
- Function: Sensory, motor - sensory to face and mouth, motor to jaw muscles, has 3 main branches:
- Ophthalmic (supplies forehead and nose)
- Purely sensory, innervating the skin of the forehead, front of the eyeball and front of nose
- 3 main branches, frontal (forehead), lacrimal (eyelid) and nasociliary (front of eye and nose)
- Maxillary (supplies uppre jaw and maxillary facial region)
- Sensory only, innervating the middle part of the face and teeth of the upper jaw
- 4 main branches, infraorbital (maxilla and upper lip), alveolar (upper teeth), zygomatic (lateral face), palatine (nasal cavity and palate)
- Mandibular (supplies lower jaw and face)
- Both sensory and motor
- Motor supply from motor neurons in brainstem, innervating muscles of mastication (temporalis, masseter, medial and lateral pterygoid, anterior belly of digastric)
- Two main branches of the sensory nerve, inferior alveolar (lower teeth), lingual nerve (common sensation to the anterior 2/3s of the tongue)
- Ophthalmic (supplies forehead and nose)
- Origin: 3 sensory nuclei (mesencephalic, principal sensory, spinal nuclei of trigeminal nerve) and one motor nucleus (motor nucleus of the trigeminal nerve), which extend from the midbrain to the medulla
- Emergence from CNS: Trigeminal ganglion arises at the level of the pons (this is the sensory root), then splits into 3 branches. Motor nucleus originates from the pons and also forms a root - these are analogous to the dorsal and ventral roots of the spinal cord
- Trigeminal ganglion has a peripheral (associated with special sensory receptors) and central process, lying in a small depression on the petrous temporal bone (trigeminal/Meckel’s cave, lies in the medial cranial fossa)
- Motor root passes inferiorly to the trigeminal ganglion and fuses with the mandibular branch
- Intracranial course:
- Ophthalmic nerve: Enters via superior orbital fissure, travels along the cavernous sinus and then medially to the trigeminal ganglion
- Gives rise to the recurrent tentorial branch, which innervates the tentorium cerebelli
- This supplies sensation to the dura mater
- Maxillary nerve: Enters via foramen rotundum, passes through the lateral wall of the cavernous sinus and the reaches the trigeminal ganglion
- Mandibular nerve:
- Motor root runs inferior to the sensory root/along the floor of the trigeminal/Meckel’s cave, joining with the mandibular nerve after the ganglion and then leaving the skull via the foramen ovale
- Sensory root therefore follows same path
- Ophthalmic nerve: Enters via superior orbital fissure, travels along the cavernous sinus and then medially to the trigeminal ganglion
- Extracranial course:
- Ophthalmic nerve: Innervates the upper face, afferent pathway therefore enters skull via superior oblique fissure (three pathways fuse before entry)
- Maxillary nerve: Innervates regions around the maxilla, passes from the maxilla through the foramen rotundum to the maxilla (afferent)
- Mandibular nerve: Afferent and efferent fibres, innervates the lower face and mandible, pathway to and from the skull is via the foramen ovale, but also passes through the infratemporal fossa extracranially, where it splits into the 4 tributaries
- Peripheral distribution: Covers most of the face and jaw, muscles of mastication
- Testing of function:
- Jaw jerk reflex (tests both efferent and afferent fibres, e.g. both motor and sensory, which are linked by the proprioceptive nucleus - stretch reflex of masseter muscle
- Check sense of touch on cornea (corneal reflex) and face
- Check to see whether the jaw is symmetrical when closed
- [EXTRA] Jaw will deviate towards side of paralysis when opened
- Consequences of lesions: Toothache, headache, migraine, facial pain, can alter eating behaviour and cause substantial pain. Lateral medullary syndrome may occur if PICA is occluded.
- Trigeminal neuralgia is chronic inflammation of the trigeminal nerve, resulting in allodynia
- Control and interrelations of cranial nerve nucleus:
- Spinal trigeminal nucleus - pain and temperature fibres synapse here, second order axons project across the midline to the contralateral brainstem and thalamus
- Nucleus has structure like the dorsal horn of the spinal cord, with a marginal zone, substantia gelatinosa and a nucleus proprius
- Principle sensory nucleus: touch fibres relay here, second order axons cross the midline to ascend to the thalamus with the medial lemniscus
- Mesencephalic nucleus spans the length of the midbrain, and proprioceptive neurons of the trigeminal system arise here (not the trigeminal ganglion), they are central afferent neurons with projections into the periphery
- Nerve branches take on some autonomic functions, namely the facial and glossopharyngeal nerves (parasympathetic secretory/motor function)
- Provides sensory information for the face, so contributes to the somatotrophic map
- Spinal trigeminal nucleus - pain and temperature fibres synapse here, second order axons project across the midline to the contralateral brainstem and thalamus
10
Q
Describe the function and course of the ophthalmic branch of CN V
A
- Function:
- Ophthalmic (supplies forehead and nose)
- Purely sensory, innervating the skin of the forehead, front of the eyeball and front of nose
- 3 main branches, frontal (forehead), lacrimal (eyelid) and nasociliary (front of eye and nose)
- Intracranial course:
- Enters via superior orbital fissure, travels along the cavernous sinus and then medially to the trigeminal ganglion
- Gives rise to the recurrent tentorial branch, which innervates the tentorium cerebelli
- This provides sensation to the dura mater
- Extracranial course:
- Ophthalmic nerve: Innervates the upper face, afferent pathway therefore enters skull via superior oblique fissure (three pathways fuse before entry)
11
Q
Describe the function and course of the maxillary branch of CN V
A
- Function:
- Maxillary (supplies uppre jaw and maxillary facial region)
- Sensory only, innervating the middle part of the face and teeth of the upper jaw
- 4 main branches, infraorbital (maxilla and upper lip), alveolar (upper teeth), zygomatic (lateral face), palatine (nasal cavity and palate)
- Intracranial course:
- Enters via foramen rotundum, passes through the lateral wall of the cavernous sinus and the reaches the trigeminal ganglion
- Extracranial course:
- Innervates regions around the maxilla, passes from the maxilla through the foramen rotundum to the maxilla (afferent)
12
Q
Describe the function and course of the mandibular branch of CN V
A
- Function:
- Mandibular (supplies lower jaw and face)
- Both sensory and motor
- Motor supply from motor neurons in brainstem, innervating muscles of mastication (temporalis, masseter, medial and lateral pterygoid, anterior belly of digastric)
- Two main branches of the sensory nerve, inferior alveolar (lower teeth), lingual nerve (common sensation to the anterior 2/3s of the tongue)
- Intracranial course:
- Motor root runs inferior to the sensory root/along the floor of the trigeminal/Meckel’s cave, joining with the mandibular nerve after the ganglion and then leaving the skull via the foramen ovale
- Sensory root therefore follows same path
- Extracranial course:
- Afferent and efferent fibres, innervates the lower face and mandible, pathway to and from the skull is via the foramen ovale, but also passes through the infratemporal fossa extracranially, where it splits into the 4 tributaries
13
Q
What are the effects of damage to CNs III, IV and VI?
A
CN III: Oculomotor nerve:
- Loss of upward, downward and medial movement of the eye
- Ptosis (drooping of eyelid)
- Pupillary dilation (paralysis of sphincter pupillae)
- Diplopia (double vision)
CN IV: Trochlear nerve:
- Diplopia upon looking downwards or medially
CN VI: Abducens nerve:
- Loss of lateral movement of the eye
- Diplopia upon looking to the affected side
14
Q
What is lateral medullary syndrome?
A
- AKA Wallenburg syndrome
- This is the loss of pain and temperature sensation from the ipsilateral face and contralateral body
- Caused by ischaemia in the lateral part of the medulla oblongata
- Face affected as it involves the spinal trigeminal nucleus
15
Q
Summarise the different nuclei of the trigeminal nerve
A
- Spinal trigeminal nucleus - pain and temperature fibres synapse here, second order axons project across the midline to the contralateral brainstem and thalamus
- Nucleus has structure like the dorsal horn of the spinal cord, with a marginal zone, substantia gelatinosa and a nucleus proprius
- Principle sensory nucleus: touch fibres relay here, second order axons cross the midline to ascend to the thalamus with the medial lemniscus
- Mesencephalic nucleus spans the length of the midbrain, and proprioceptive neurons of the trigeminal system arise here (not the trigeminal ganglion), they are central afferent neurons with projections into the periphery
16
Q
What afferents of CN V are involved in coughing and sneezing?
A
Ophthalmic and maxillary
17
Q
Describe the features of CN VI
A
- Name: Abducens nerve
- Function: Motor - motor to eye muscle, lateral rectus (abduction of eye in opposition to the medial rectus)
- Origin: Abducens nucleus in the pons
- Emergence from CNS: Through the superior orbital fissue, arises at level of the pons
- Intracranial course: Exits the brainstem at the level of the pons and medulla, enters the subarachnoid space and pierces the dura mater to travel through Dorello’s canal, leaving this to enter the cavernous sinus at the tip of the petrous temporal bone, where it will then enter the orbit via the superior orbital fissure
- Extracranial course: Exits the skull through the superior orbital fissure, goes on to innervate the lateral rectus muscle in the orbit
- Peripheral distribution: Only to the eye
- Testing of function: Tests of the pupillary reflex (constriction of both pupils upon introduction to bright light) and accomodation reflex (ability to focus/dilation of pupils as an object is brought closer) are tests used to determine the function of the oculomotor system (CNs III, IV and VI)
- Consequences of lesions: Deviation of the eye (medially due to unopposed action of medial rectus) and loss of coordinated movements of the two eyes
- A left abducens lesion causes left esotropia (form of strabismus/medial misaligment of eye), with major limitation of abduction (increases upon looking to the left)
- Control and interrelations of cranial nerve nucleus: Associated with synergistic functions of CNs III and IV
18
Q
Describe the features of CN VII
A
- Name: Facial nerve
- Function: Motor, parasympathetic and sensory - motor to the face/muscles of facial expression (NOT mastication), parasympathetic to the lacrimal and salivary glands, sensory to the anterior 2/3rds of the tongue for taste
-
Motor: Innervates muscles from the second branchial arch (muscles of facial expression) and the stapedius muscle of the inner ear
- Main branches are the temporal, zygomatic, buccal, mandibular and posterior auricular
- Sensory: Taste for the anterior 2/3rds of the tongue, and sensation to the external ear (reflects embryonic origin)
- Parasympathetic: Innervates the pterygopalatine ganglion (tear production and mucus secretion) and the submandibular ganglion (salivary secretion from submandibular and sublingual glands)
-
Motor: Innervates muscles from the second branchial arch (muscles of facial expression) and the stapedius muscle of the inner ear
- Origin: Arises from the brainstem at the cerebellar pontine angle
- Motor supply: facial nucleus
- Sensory supply: terminates in the nucleus solitarius (medulla)
- Pre-ganglionic parasympathetic fibres: superior salivary nucleus
- Emergence from CNS: Arises at the cerebellar pontine angle, leaves the skull through the stylomastoid foramen
- Intracranial course:
- Motor supply: Fibres from the nucleus course around the abducens nucleis before emerging at the cerebellar pontine angle (forms slight elevation in the fourth ventricle, the facial colliculus), then passes into the internal acoustic meatus and turns 90* to enter the facial canal (where the two roots fuse and form the geniculate ganglion). Emerges from the stylomastoid foramen.
- Sensory supply: Smaller root, does not loop, passes into the internal acoustic meatus and then the facial canal, exiting the cranium at the stylomastoid foramen
- Parasympathetic supply: Pre-ganglionic fibres arise from the superior salivatory nucleus and synpase in the pterygopalatine and submandubular ganglia. Greater petrosal nerve is given off in the early stages of the facial canal.
- Extracranial course: After exit from the cranium, runs just anterior to the external ear
- Posterior auricular nerve branches off first
- Main trunk then carries on anteriorly and inferiorly into the parotid gland (NB this is not innervated by the facial nerve)
- Nerve then terminates by splitting into the other 5 main branches
- Peripheral distribution: Innervates much of the face (2nd branchial arch)
- Testing of function:
- Motor: check for facial asymmetry and involuntary movements through a series of motions: raising eyebrows, frown, close both eyes tightly and resist them being opened, show both upper and lower teeth, smile, puff out both cheeks
- Sensory: test taste
- Consequences of lesions: Bell’s palsy, characterised by loss of expression, dry eyes, altered taste, ptosis and uncontrolled salivation/dribbling
- Hyperacusis can also occur (hyper-sensitivity to sound) due to paralysis of the stapedius muscle
- Control and interrelations of cranial nerve nucleus:
- Solitary nucleus has connections with the glossopharyngeal and vagus nerves, and projects to other regions related to autonomic control, such as the thalamus and hypothalamus
19
Q
Describe the motor supply of CN VII
A
- Facial nerve: Innervates muscles from the second branchial arch (muscles of facial expression) and the stapedius muscle of the inner ear
- Main branches are the temporal, zygomatic, buccal, mandibular and posterior auricular
- Arises from the facial motor nucleus
20
Q
Describe the sensory supply of CN VII
A
- Facial nerve: Taste for the anterior 2/3rds of the tongue, and sensation to the external ear (reflects embryonic origin)
- Sensory innervation is achieved through the chorda tympani
- Connections to the geniculate ganglion and origins at the nucleus solitarius
21
Q
Describe the parasympathetic supply of CN VII
A
- Facial nerve: Innervates the pterygopalatine ganglion (tear production and mucus secretion) and the submandibular ganglion (salivary secretion from submandibular and sublingual glands)
- Supply to lacrimal glands and nose via pterygopalatine ganglion
- Supply to submandibular and sublingual salivary glands via chorda tympani and submandibular ganglion
22
Q
Describe the features of CN VIII
A
- Name: Vestibulocochlear nerve
- Function: Sensory - supplies the vestibulocochlear region for hearing and balance, dual sensory nerve
- Conveys auditory information from the inner ear to the auditory relays of the brainstem (in the auditory/cochlear nerve)
- Vestibular portion of the nerve conveys information about head position to regulate posture
- Origin: Sensory receptors in the inner ear and vestibular systems respectively
- Nuclei are the cochlear (junction of the pons and the medulla) and vestibular (lower pons and upper medulla) nuclei
- Both are complexes, made up of several subnuclei
- Vestibular portion from 4 subnuclei
- Cochlear portion from the ventral and dorsal cochlear nuclei
- Emergence from CNS: The two roots emerge from the junction of the pons and medulla (cerebellopontine angle) behind the facial nerve (CN VII) and then combine to form the nerve, exits the cranium via the internal acoustic meatus in the temporal lobe
- Intracranial course: Nerve emerges at the cerebellopontine angle and travels to the internal acoustic meatus in the temporal bone to exit the cranium
- Extracranial course: Nerve splits in the distal aspect of the internal acoustic meatus
- Vestibular portion goes to the vestibular system and semicircular canals in the inner ear
- Cochlear portion has cell bodies in the spiral ganglion and innervates the sensory hair cells of the cochlear (inner ear)
- Peripheral distribution: Innervates the inner ear and balance organs/semi-circular canals in the vestibular system
- Testing of function: Hearing is tested through whispering numbers into one ear (other is covered), and the patient is asked to repeat them
- Or, sounds can be played from either the left or the right side, and the patient must correctly identify which side the sound is coming from
- Rinne and Weber tests can be conducted
- Rinne: place tuning fork on mastoid bone, compare hearing through the bone and through air (positive if louder through air, indicates sensorineurial hearing loss)
- Weber: tuning fork placed in middle of head, used to unilateral hearing loss of either type (sensorineurial or conductive)
- Vestibular system: moving the patient’s head to 45* or lying them down may result in nystagmus (rapid eye movements) if lesion is present
- Consequences of lesions: Deafness and issues with balance
- Control and interrelations of cranial nerve nucleus:
- Balance is linked to many different systems, including proprioception and extraocular movements
- Also links to the thalamus for the concious perception of gravity
- Balance is linked to many different systems, including proprioception and extraocular movements
23
Q
What is acoustic neuroma?
A
- Benign tumour on the either/or the cochlear and vestibular branches of the vestibulocochlear nerve
- Compression can lead to hearing and/or balance loss
24
Q
Describe the features of CN IX
A
- Name: Glossopharyngeal nerve
- Function: Motor, sensory, parasympathetic
- Motor: to pharynx, supplies the stylopharyngeus muscle
- Sensory: posterior 1/3rd of the tongue, both sensation and taste, also to the skin of the external ear and Eustachian tube (middle ear)
- Sensation to the oropharynx
- Also provides innervation of the carotid bodies
- Parasympathetic: parotid gland (main salivary gland)
- Origin: Emerges at the lateral medulla, originates from 5 nuclei:
- Solitary nucleus (sensory fibres terminate here along with CN VII)
- Spinal nucleus of the trigeminal nerve
- Lateral nucleus of the vagal trigone
- Nucleus ambiguus
- Inferior salivatory nucleus
- Associated with the third pharyngeal arch
- Emergence from CNS: Emerges at the lateral medulla just in front of the vagus nerve rootlets, exits the skull via the jugular foramen
- Intracranial course: Originates at the medulla oblongata, emerging from the anterior aspect and moves laterally in the posterior cranial fossa, exiting the skull via the jugular foramen
- Extracranial course: Once it has exited the skull via the jugular foramen, tympanic nerve arises (mixed sensory and parasympathetic function)
- Immediately outside of the jugular foramen are the superior and inferior/petrous ganglia, which contain the cell bodies of sensory neurons in CN IX
- CN IX descends down the neck (anterolateral to internal carotid artery), with motor branches separating at the inferior margin of stylopharyngeus - this is also where the carotid sinus nerve splits off to innervate the carotid sinus and body
- Nerve enters the pharynx through passing between the superior and middle pharyngeal constrictors, terminating in three branches (lingual, tonsil and pharyngeal)
- Peripheral distribution: Passes down the neck and innervates the pharynx, alongside some internal structures. Also provides some sensation to the tongue, oropharynx and ear.
- Testing of function: Tested along with the vagus nerve
- Gag reflex
- Can visualise deviation of the uvula on the affected side when articulating ‘AHH’ (use tongue depressor)
- Palatal articulation: ‘KA’ sound
- Guttural articulation: ‘GO’ sound
- Consequences of lesions: Impairment of swallowing and palate control, impairment of taste over a third of the tongue, impairment of sensation over same third of tongue, palate and pharynx, absent gag reflex, dysfunction of the parotid gland
- Neuralgia of nerve is caused often by blood vessels impinging and pressing on the nerves as they exit the brainstem
- Control and interrelations of cranial nerve nucleus:
- Solitary nucleus has links to facial nerve, vagus and glossopharyngeal - coordinates taste afferents and is a site of initiation and integration of a variety of reflexes. Principle visceral sensory nucleus.
- Spinal trigeminal nucleus is responsible for conveying ipsilateral sensations, including deep/crude touch, pain and temperature - CN IX has some sensory function, and so is integrated here
- Nucleus ambiguus is the common nucleus for efferent fibres of IX and X, providing fibres to innervate the somatic muscles of the pharynx, larynx and soft palate (coordinate action)
25
Q
Describe the features of CN X
A
- Name: Vagus nerve
- Function: Parasympathetic, sensory, motor
- Parasympathetic to heart and viscera - outflow from dorsal nucleus of vagus, supplies all thoracic and abdominal organs (heart, lungs, alimentary canal), derivatives of the fore- and midgut
- Organs in the pelvis are instead supplied by the sacral plexus
- Sensory to the aorta, viscera (fore- and midgut derivatives) and epiglottis (gag reflex), alonside innervating the pinna, auditory canal and tympanic membrane
- Stimulation of the external auditory meatus can therefore cause initiation of the gag reflex
- There is a large corresponding visceral sensory component for the thoracic and abdominal viscera, including aortic body (chemo- and stretch receptors) and epiglottic taste buds
- Also associated with the cranial portion of the accessory nerve (CN XI)
- Motor to the larynxand pharynx
- To larynx, regulates the position and tension of the vocal cords
- Innervates one of the extrinsic muscles of the tongue, palatoglossus
- Parasympathetic to heart and viscera - outflow from dorsal nucleus of vagus, supplies all thoracic and abdominal organs (heart, lungs, alimentary canal), derivatives of the fore- and midgut
- Origin: Emerges from the medulla as a series of rootlets, originates from 4 different nuclei
- Nucleus ambiguus (motor neurons)
- Solitary nucleus
- Spinal trigeminal nucleus
- Dorsal nucleus of vagus nerve
- Emergence from CNS: Arises from the medulla as a series of rootlets, passes from the skull via the jugular foramen
- Intracranial course: Originates from the medulla of the brainstem, motor branches from the nucleus ambiguus, parasympathetic from the dorsal nucleus of vagus nerve, sensory from the solitary and spinal trigeminal nuclei
- Exits the cranium via the jugular foramen, along with CN IX and XI
- Auricular branch arises withint the cranium, supplying sensation to the posterior part of the external auditory canal and external ear
- Extracranial course:
- In the neck:
- Vagus nerve passes into the carotid sheath, travelling inferior to the internal jugular vein and common carotid artery
- At the base of the neck, R and L vagus nerves have differing pathways, but both enter the thorax
- Pharyngeal (motor to muscles of pharynx), superior laryngeal (cricothyroid and sensory innervation of laryngopharynx and superior part of the larynx) and recurrent laryngeal (right side only, innervates majority of internal muscles of the larynx) nerves arise in the neck
- In the thorax:
- Right vagus forms the posterior vagal trunk, left forms the anterior vagal trunk, with both contributing to the formation of the oesophageal plexus
- Left recurrent laryngeal nerve arises in this compartment, as well as the cardiac branches (regulated HR and provide visceral sensation)
- In the abdomen:
- Vagal trunks terminate by dividing into branches to supply the oesophagus, stomach, small and large bowel (up until the splenic flexure)
- In the neck:
- Peripheral distribution: The ‘wandering’ nerve, innervates much of the region and structures between the throat and the pelvis
- Testing of function: Same tests as with glossopharyngeal nerve
- Gag response
- Visualizing uvula deviation away from affected side on articulating “AHH” with tongue depressor.
- Palatal articulation “KA”
- Guttural articulation “GO”
- Consequences of lesions: palatal and pharyngeal paralysis, laryngeal paralysis (causes a hoarse voice), and a series of autonomic dysfunctions (difficulty controlling HR, gastric secretions, oesophageal motility, gallbladder emptying)
- Control and interrelations of cranial nerve nucleus:
- Solitary nucleus has links to facial nerve, vagus and glossopharyngeal - coordinates taste afferents and is a site of initiation and integration of a variety of reflexes. Principle visceral sensory nucleus.
- Spinal trigeminal nucleus is responsible for conveying ipsilateral sensations, including deep/crude touch, pain and temperature - CN IX has some sensory function, and so is integrated here
- Nucleus ambiguus is the common nucleus for efferent fibres of IX and X, providing fibres to innervate the somatic muscles of the pharynx, larynx and soft palate (coordinate action)
26
Q
Describe the features of CN XI
A
- Name: Spinal accessory
- Function: Motor - to the trapezius and sternomastoid
- This nerve innervates the somatic neck muscles, function is to shrug shoulders
- Origin: Emerge as a series of rootlets from C1-6, passing up into the skull at the foramen magnum, then exiting from the jugular foramen. Small cranial portion arises from the lateral aspect of the medulla oblongata. Nuclei include:
- Spinal accessory nucleus
- Nucleus ambiguus
- Emergence from CNS: Spinal component passes up into the skull through the foramen magnum, cranial component arises from medulla oblongata, both leave via the jugular foramen
- Intracranial course: Fibres from C1-C5/6 coalesce to form the nerve and enter the cranial cavity via the foramen magnum, then traverses the posterior cranial fossa to reach the jugular foramen just after briefly associating with the cranial component of the nerve. Exits with CN IX and X
- Extracranial course:
- Spinal component: descends along the interal carotid artery to innervate sternocleidomastoid, then moves across the posterior triangle of the neck to supply motor fibres to the trapezius
- NB this is relatively superficial, therefore vulnerable
- Cranial component: combines with the vagus nerve immediately after leaving the skull at the inferior ganglion of the vagus nerve, then are distributed throughout the vagus nerve. Therefore associated with CN X.
- Spinal component: descends along the interal carotid artery to innervate sternocleidomastoid, then moves across the posterior triangle of the neck to supply motor fibres to the trapezius
- Peripheral distribution: Runs down the head and neck, terminates at the upper part of the trapezius muscle
- Testing of function: Shrug shoulders and turn head from side to side
- Consequences of lesions: Shoulder pain, winging of the scapula, weakness in the trapezius muscle
- Control and interrelations of cranial nerve nucleus:
- Nucleus ambiguus is the common nucleus for efferent fibres of IX and X, providing fibres to innervate the somatic muscles of the pharynx, larynx and soft palate (coordinate action)
27
Q
Describe the features of CN XII
A
- Name: Hypoglossal nerve
- Function: Motor - to the tongue, purely motor nerve that innervates muscles derived from cranial somites
- Innervates all intrinsic muscles of the tongue, and three of the extrinsic muscles:
- Styloglossus
- Genioglossus
- Hyoglossus
- NB NOT palatoglossus (CN X)
- Innervates all intrinsic muscles of the tongue, and three of the extrinsic muscles:
- Origin: Emerges from the caudal brainstem (medulla), between the pyramids and the medulla, only associated with the hypoglossal nucleus
- Emergence from CNS: Passes through the hypoglossal canal to reach the tongue
- Intracranial course: Arises from the hypoglossal nucleus in the medulla oblongata, passing laterally across the posterior cranial fossa within the subarachnoid space. Nerve exits the cranium via the hypoglossal canal.
- Extracranial course: Nerve receives a branch from the cervical plexus (C1-2), but they do not combine and merely travel in the same sheath. Nerve passes inferiorly to the angle of the mandible, corssing the internal and external carotid arteries to enter the tongue in an anterior direction
- Peripheral distribution: Innervation only occurs at the tongue
- Testing of function: Stick tongue and move it from side to side, then inspect tongue for atrophy, fasciculations (twitches) or asymmetry in movement/appearance
- Consequences of lesions: Results in deviation of the tongue and atrophy on the side of the lesion
- Control and interrelations of cranial nerve nucleus: Coordinates with the actions of CN IX, X and XI to regulate swallowing, nucleus has connections with the cerebellum, solitary nucleus and trigeminal sensory nucleus
28
Q
What cranial nerves are involved in the control of swallowing?
A
- CN V: Trigeminal
- CN VII: Facial
- CN IX: Glossopharyngeal
- CN X: Vagus
- (CN XI: Spinal accessory)
- CN XII: Hypoglossal
29
Q
What is medial medullary syndrome?
A
- Aka hypoglossal alternating hemiplegia, as affects the hypoglossal nerve
- Type of alternating hemiplegia (unilateral paralysis, alternating means that episodes are recurrent)
- This is due to occlusion of the anterior spinal artery
- Presents as a deviation of tongue to side of infarct on attempted protrusion, limb weakness on contralateral side of infarct, loss of discriminative touch and conscious perception on the contralateral side below the infarct
- Syndrome rises due to an infarction of the medial part of the medulla oblongata
35
Q
What is the mnemonic for the cranial nerves?
A
36
Q
What is the mnemonic for the modalities of the cranial nerves?
A
38
Q
Where does CN I exit the cranium?
A
Olfactory nerve exits via the cribriform plate
39
Q
Where does CN II exit the cranium?
A
Optic nerve exits via the optic canal
40
Q
Where does CN III exit the cranium?
A
Oculomotor nerve exits via the superior orbital fissure
41
Q
Where does CN IV exit the cranium?
A
The trochlear nerve exits via the superior orbital fissure
42
Q
Where does the ophthalmic branch of CN V exit the cranium?
A
This branch of the trigeminal nerve exits via the superior orbital fissure
43
Q
Where does the maxillary branch of CN V exit the cranium?
A
This branch of the trigeminal nerve exits via the foramen rotundum
44
Q
Where does the mandibular branch of CN V exit the cranium?
A
This branch of the trigeminal nerve exits via the foramen ovale
45
Q
Where does CN VI exit the cranium?
A
The abducens nerve exits via the superior orbital fissure
46
Q
Where does CN VII exit the cranium?
A
The facial nerve exits via the internal auditory meatus
47
Q
Where does CN VIII exit the cranium?
A
The vestibulocochlear/auditory nerve exits via the internal auditory meatus
48
Q
Where does CN IX exit the cranium?
A
The glossopharyngeal nerve exits via the jugular foramen
49
Q
Where does CN X exit the cranium?
A
The vagus nerve exits via the jugular foramen
50
Q
Where does CN XI exit the cranium?
A
The accessory nerve exits via the jugular foramen
51
Q
Where does CN XII exit the cranium?
A
The hypoglossal nerve exits via the hypoglossal canal
52
Q
Which nerve(s) exit the cranium via the cribriform plate?
A
CN I, the olfactory nerve
53
Q
Which nerve(s) exit the cranium via the optic canal?
A
CN II, the optic nerve
54
Q
Which nerve(s) exit the cranium via the superior orbital fissure?
A
- CN III - oculomotor nerve
- CN IV - trochlear nerve
- Ophthalmic branch of CN V - trigeminal nerve
- CN VI - abducens nerve
55
Q
Which nerve(s) exit the cranium via the foramen rotundum?
A
The maxillary branch of CN V - trigeminal nerve
56
Q
Which nerve(s) exit the cranium via the foramen ovale?
A
The mandibular branch of CN V - trigeminal nerve
57
Q
Which nerve(s) exit the cranium via the internal auditory meatus?
A
- CN VII - facial nerve
- CN VIII - auditory/vestibulocochlear nerve
58
Q
Which nerve(s) exit the cranium via the jugular foramen?
A
- CN IX - glossopharyngeal nerve
- CN X - vagus nerve
- CN XI - accessory nerve
59
Q
Which nerve(s) exit the cranium via the hypoglossal canal?
A
CN XII - hypoglossal nerve
60
Q
What is label 1 pointing at and what structures pass through here?
A
- Structure: Foramina of the cribriform plate
- Olfactory nerve bundles pass through here
61
Q
What is label 2 pointing at and what structures pass through here?
A
- Structure: Optic canal
- CN II (Optic nerve) and Ophthalmic artery pass through here
62
Q
What is label 3 pointing at and what structures pass through here?
A
- Structure: Superior orbital fissure
- CN III (Oculomotor), CN IV (Trochlear), branches of CN V (ophthalmic division of the trigeminal nerve), CN VI (Abducens), Superior ophthalmic vein [EXTRA] all pass through here
63
Q
What is label 4 pointing at and what structures pass through here?
A
- Structure: Foramen Rotundum
- Division of CN V (Maxillary branch of Trigeminal nerve) passes through here
64
Q
What is label 5 pointing at and what structures pass through here?
A
- Structure: Foramen ovale
- Division of CN V (Mandibular branch of the Trigeminal nerve), Accessory meningeal artery [EXTRA], Lesser petrosal nerve [EXTRA] all pass through here
65
Q
What is label 6 pointing at and what structures pass through here?
A
- Structure: Foramen spinosum
- Middle meningeal artery and vein, Meningeal branch of the mandibular division of CN V [EXTRA] pass through here
66
Q
What is label 7 pointing at and what structures pass through here?
A
- Structure: Foramen lacerum
- Internal carotid artery passes over(?) it, Greater petrosal nerve [EXTRA] passes over this space
67
Q
What is label 8 pointing at and what structures pass through here?
A
- Structure: Carotid canal
- Internal carotid artery, Internal carotid nerve plexus [EXTRA] pass through here
68
Q
What is label 9 pointing at and what structures pass through here?
A
- Structure: Internal acoustic meatus
- CN VII (Facial), CN VIII (Vestibulocochlear), Labyrinthe artery pass through here
69
Q
What is label 10 pointing at and what structures pass through here?
A
- Structure: Jugular foramen
- Internal jugular vein, CN IX (Glossopharyngeal), CN X (Vagus), CN XI (Accessory), Sigmoid venous sinus [EXTRA], Posterior meningeal artery [EXTRA], Inferior petrosal venous sinus [EXTRA] pass through here
70
Q
What is label 11 pointing at and what structures pass through here?
A
- Structure: Hypoglossal canal
- CN XII (Hypoglossal) passes through here
71
Q
What is label 12 pointing at and what structures pass through here?
A
- Structure: Foramen magnum
- Vertebral arteries, Spine, Medulla oblongata [EXTRA], Meninges [EXTRA], Meningeal branches of vertebral arteries [EXTRA], Spinal roots of accessory nerves [EXTRA] all pass through here
72
Q
Label this diagram, including all of the structures passing through each structure.
A
- Structure: Foramina of the cribriform plate
- Olfactory nerve bundles pass through here
- Structure: Optic canal
- CN II (Optic nerve) and Ophthalmic artery pass through here
- Structure: Superior orbital fissure
- CN III (Oculomotor), CN IV (Trochlear), branches of CN V (lacrimal, frontal, nasociliary branches of the ophthalmic division of the trigeminal nerve), CN VI (Abducens), Superior ophthalmic vein all pass through here
- Structure: Foramen Rotundum
- Division of CN V (Maxillary branch of Trigeminal nerve) passes through here
- Structure: Foramen ovale
- Division of CN V (Mandibular branch of the Trigeminal nerve), Accessory meningeal artery, Lesser petrosal nerve (occasionally) all pass through here
- Structure: Foramen spinosum
- Middle meningeal artery and vein, Meningeal branch of the mandibular division of CN V pass through here
- Structure: Foramen lacerum
- Greater petrosal nerve passes over this space
- Structure: Carotid canal
- Internal carotid artery and internal carotid nerve plexus pass through here
- Structure: Internal acoustic meatus
- CN VII (Facial), CN VIII (Vestibulocochlear), Labyrinthe artery pass through here
- Structure: Jugular foramen
- Inferior petrosal venous sinus, CN IX (Glossopharyngeal), CN X (Vagus), CN XI (Accessory), Sigmoid venous sinus, Posterior meningeal artery pass through here
- Structure: Hypoglossal canal
- CN XII (Hypoglossal) passes through here
- Structure: Foramen magnum
- Medulla oblongata, Meninges, Vertebral arteries, Meningeal branches of vertebral arteries, Spinal roots of accessory nerves all pass through here
73
Q
What foramen is this and what passes through it?
A
- Stylomastoid foramen
- CN VII (facial) passes through it
