Cranial nerves Flashcards
Cranial nerve 0
Nervus terminalis
Function of nervus terminalis
Lies alongside the olfactory bulb.
Serves as a conduit along which a population of neurones migrates from the olfactory placode into the pre-optic area and hypothalamus.
These neurones are essential for reproductive function in both sexes
Components of the nuclei for CNs innervating the extraocular muscles.
Contain both motor neurones and internuclear neurones, with axons that contact the motor neurons for muscles that move the opposite eye in the same direction.
Location of oculomotor nucleus
Periaquedctal grey matter of the midbrain, ventral to the aqueduct at the level of the superior colliculus.
Passage of oculomotor nerve fibres within the midbrain.
Myelinated axons from each nucleus curve ventrally through the tegmentum and emerge from the medial side of the cerebral peduncle in the interpeduncular fossa.
Passage of oculomotor fibres after leaving the midbrain
Pass in the subarachnoid space, the lateral wall of cavernous sinus and the SOF.
What happens to the oculomotor nerve in the orbit?
Superior divison:
SR, LPS
Inferior division:
MR, IR, IO, Ciliary ganglion via short ciliary nerves
Arrangement of motor units in the oculomotor nucleus
The motor neurones for individual muscles are localised in distinct subnuclei.
The small sizes of the motor units (6 muscle fibres supplied by one neurone) indicate the level of precision required for co-ordinated eye movement in binocular vision
Location of the EW nucleus?
Situated dorsal to the main oculomotor nucleus.
Function of the EW nucleus
Preganglionic parasympathetic
Passage of EW neurones
Accompany the other oculomotor neurones into the orbit where they terminate in the ciliary ganglion behind the eye.
How do post-ganglionic parasympathetic fibres of the EW reach their targets
Pass through the short ciliary nerves to the eyeball where they supply the sphincter pupllae muscle of the iris and ciliary muscle
Through which structure do oculomotor and EW fibres run in the tegmentum of the midbrain?
Pass through the red nucleus.
Location of the trochlear nucleus
Immediately caudal to the oculomotor nucleus at the level of the inferior colliculus.
Passage of the trochlear nerve fibres after leaving their nucleus.
Small bundles of fibres curve around the periaqueductal grey matter with a caudal slope and decussate in the superior medullary velum.
Where do trochlear nerve fibres leave the brainstem?
The only nerve to emerge from the dorsum.
The slender nerve emerges immediately caudal to the inferior colliculus.
Function of SO
Depress, inwardly rotate and abduct the eyeball.
Location of the abducens nerve
Situated beneath the facial colliculus in the pons in the floor of the fourth ventricle.
What is the relationship of the facial nerve to the abducens nucleus?
A bundle of facial nerve fibres known as the internal genu curves over the nucleus, contributing to the facial colliculus.
Passage of motor neurones of the abducens
Gives rise to axons that pass through the pons in a ventrocaudal direction, emerging from the brainstem at the junction of the pons and the pyramid.
Interneurons of the abducens
Axons cross into the contralateral MLF and travel rostrally to the oculomotor subnucleus that supplies the contralateral rectus muscle.
Saccadic eye movements
Quick movements of the eyes in altering direction of gaze
Fr. saccader- to jerk
Optokinetic movements
Frequent saccades, made when the image on the retina is continuously changing.
Vergence movements
Both eyes looking medially to look at a near object or laterally to look into the distance.
Vestibular eye movements
Those driven by sensory input from the vestibular apparatus of the inner ear.
Concomitant squint
Both eyes can move through a full range of positions. Not caused by paralysis or weakness of the muscles. If one eye is covered the other will be able to move through the full range.
Why does diplopia disappear overtime
Diplopia is caused by misalignment of the image on the fovea of each eye. Over time the brain suppresses the false image.
What are the two golden rules in the diagnosis of diplopia?
The separation of the images increases with the amount of movement in the direction of pull of the weak muscle.
The flase image is displaced in the direction of action of weakness (i.e. the outside image is from the weakned eye).
Droppin of upper eyelid.
Lateral strabismus caused by unopposed action of LR
Inability to direct the eye medially or vertically.
Dilation of the pupil due to unopposed action of the dilator pupillae muscle in the iris
CN3 palsy
What happens to the pupil and lens in CN3 palsy
The pupil no longer constricts either in response to an increase in light intensity nor accommodation.
The ciliary muscle does not contract to allow the lens to increase in thickness for focussing on near objects.
What is the first sign of CN3 compression and why?
Slowness of pupillary response to light.
Preganlionic parasympathetic fibres run on the external surface of the oculomotor nerve.
Vertical diplopia maximal when eye directed downwards and inwards
Difficulty walking down stairs
Due to SO weakness
CN4 palsy
Causes of CN IV palsy
Peripheral neuropathy e.g. DM
A persistent complication of head injury
Tiny vascular lesions in the midbrain may be the most common cause of isolated non-traumatic oculomotor and trochlear palsies in the elderly
Medial squint with the inability to direct affected eye laterally.
CN VI palsy
The manifestation of CN VI nuclear damage
LR and contralateral MR paralysis.
The patient cannot direct gaze to the side of the lesion.
A nuclear lesion may also involve the nearby nucleus or axons of the facial nerve (remember close relation to internal genu) causing paralysis of all the ipsilateral facial muscles.
Which portion of the cortex controls voluntary eye movements
Frontal eye field
Location of frontal eye field
Anterior to general motor cortex
Brodman’s area 8
Consequence of stimulation of the frontal eye field
Conjugate deviation of the eyes to the opposite side.
Regions involved in voluntary eye movements
Prefrontal cortex
FEF
Superior colliculus
Extraocular CN nuclei.
Various areas of brainstem (pretectal, superior colliculus, PPRF, nucleus prepositus hypoglossi, rostral interstitial nucleus of the MLF, interstitial nucleus of Cajal). These regions are involved in maintiang the position of the eyes, genrating saccades and determining whether the eyes will move in the horizontal or vertical plane
What is the function of the paramedian pontine reticular formation
Centre for lateral gaze
Receives afferents from the contralateral cerebral cortex, contralateral superior colliculus and ipsilateral vestibular nuclei.
Action of the PPRF?
Sends bursts of impulses to the motor and internuclear neurones causing rapid contraction of the lateral rectus and contralateral medial rectus.
Slower tonic stimulation of the ocular motor neurones comes from the nucleus propositus hypoglossi which is rostral to the hypoglossal nucleus in the medulla.
Control of visual fixation
Slow eye movements
Posterior parietal eye field, adjacent to the visual association cortex of the lateral aspect of the occipital lobe.
Neural circuity involves the cerebellum and vestibular nuclei.
Neural pathways for convergence
Similar to those of visual fixation.
Requires the integrity of the occipital cortex but not that of the PPRF or the frontal eye field.
Afferent limb of pupillary response to light
Retina
Optic nerve
Olivary pretectal nucleus (in the pretectal area)
Efferent limb of pupillary light reflex
Fibres project from pretectal nucleus to EW.
Some pretectal neurones send their axons across the midline in the posterior commissure to the contralateral EW nucleus.
What are the reasons for consensual light reflex?
Each optic tract contains fibres from both retinas
The pretectal area projects to both sides.
Afferent limb of accommodation
Triggered by signals that originate in the retina and in the occipital cortex that are relayed through the superior colliculus to the EW nucleus
Efferent limb of accommodation reflex?
EW nucleus to the ciliary ganglion.
Action of the ciliary muscle?
On contraction allows the lens to increase in thickness and increases the refractive power
Action of sphincter pupillae
Sharpens the image by decreasing the diameter of the pupil and reducing spherical aberration in the refractive media of the eye.
Consequence of destruction of the frontal eye field?
Causes deviation of both eyes towards the side of the lesion.
Voluntary saccadic movements of the eyes away from the side of the cortical lesion cannot be made.
Commonly caused by ischaemic damage which is associated with damage to the premotor and motor areas due to its close relation.
Consequent paralysis of the limbs and lower half of the face on the contralateral side with the deviated eyes looking away from the paralysed side of the body.
What is the impact of a destructive lesion of the posterior parietal lobe on eye movements?
Impair the ability to make smooth pursuit movements away from the side of the lesion.
Voluntary saccades are unaffected.
The attempt to puruse a target in the visual field becomes a series of small, rapid movements of the eyes.
Foville’s syndrome
Caused by a dorsally located infarction in the caudal part of the pons, compromises ipsilateral nuclear CN6 an LMN facial palsy with contralateral hemiplegia and conjugate gaze palsy.
The limb paralysis recovers because most of the descending motor fibres are ventral to the infarct.
What is the difference between a nuclear and a nerve CN6 lesion?
Nerve- loss of LR
Nuclear- loss of LR and contralateral MR due to involvement of fibres to the MLF or the MLF itself
Internuclear ophthalmoplegia
Caused by a lesion inthe MLF (usually demyelination).
Interruption of the fibres going from abducens of the opposite to the oculomotor nucleus of the same side causes an inability to adduct the eye on the side of the lesion.
There will also be nystagmus of the abducting eye.
These abnormalities are present only when the patient is asked to gaze to the side opposite to that of the lesion.
Normal medial rectus function with convergence.
Where is the lesion in INO if the right eye cannot adduct.
Right sided MLF lesion.
Would expect the left eye to be able to abduct and there to be nystagmus.
https://www.youtube.com/watch?v=_rXQmDZva8Y
Destruction of the PPRF
Prevents saccadic contractions of the LR and the contralateral medial rectus muscles.
Pursuit and vergence movemnts are preserved.
Causes of paralysis of vertical gaze
Caused by lesion in the rostral midbrain.
Pressure from nearby tumour
Isolated lesions of various diseases
Parinaud’s syndrome
Pineal gland tumour compressing the posterior commissure and nearby structures causes paralysis of upward gaze
Compression of which structure causes paralysis of vertical gaze?
Posterior commisssure in the rostral midbrain.
Marcus Gunn Pupil
Paradoxical dilatation of the pupil on swinging light test.
Seen particularly in patients with optic neuritis.
No pupillary reflexes can be elicited by light shone into an eye that is blind for any reason.
https://www.youtube.com/watch?v=WrNYqNH3b3A
What is the most common cause of impaired pupillary light reflex?
Head injury.
Compression of the oculomotor nerve by the uncus which is forced over the free edge of the tentorium cerebelli as a result of raised ICP.
Aneurysms of which vessels can cause CN3 palsy
PComm
PCA
SCA
Holmes Adie pupil
Responds more slowly than the other pupil to both light and accommodation
Attributed to the death of neurones in the ciliary ganglion.
May be associated with sluggish stretch reflexes throughout the body (Holmes Adie Syndrome)
Argyll Robertson pupil
Accommodates
Does not react to light.
Pupil typically smaller and irregular.
Associated with CNS syphillis.
https://www.youtube.com/watch?v=IbBYxGk1pUw
Classification of cranial nerve pathways
Supranuclear (above brainstem)
Nuclear (brainstem)
Infranuclear (fascicle/nerve)
Common pathway for horizontal and vertical gaze pathway
PPRF/ CNVI
Location of vertical gaze centre
Thalamomesencephalic junction
Location of horizontal gaze centre
Pons
Supranuclear input on gaze pathways.
FEF- contralateral saccades
Parieto-occipitotemporal- ipsilateral smooth pursuit
How to differentiate between a supranuclear gaze palsy and a nuclear gaze palsy
In a supranuclear gaze palsy the VOR will be intact i.e. Doll’s head
Why is upgaze palsy more common than downgaze palsy
Upgaze is unilateral and crosses at the level of the posterior commissure where it is vulnerable to compression or damage by a single lesion (e.g. by pineal body tumour)
Downgaze is bilateral so later
1.5 syndrome
Horizontal gaze palsy (PPRF/VI)
+
INO (MLF)
One eye will have no horizontal movement (loss of abduction due to PPRF/VI lesion, loss of adduction due to MLF involvement)
Contralateral eye will have loss of adduction only (no contralateral signal)
Subarachnoid course of CN6
What is the significance of this?
Exits the root exit zone of the pons where it is tethered and ascends the clivus, turns 90 degrees at the superior aspect of the pons at the petroclinoid ligament.
Means that anything causing increased ICP affecting this subarachnoid portion will cause false localising sign.
In which portion of the cavernous sinus does CN6 lie
In the substance, in contrast to the other CN which lie in the wall
What are the 6 CN6 syndromes?
Nuclear
Fascicle
Subarachnoid portion i.e. false localising
Clivus syndrome from meningioma
Cavernous sinus syndrome
SOF syndrome
Raymond syndrome
Ventral pontine syndrome
Ipsilateral LR paresis due to CNVI involvement
Contralateral hemiplegia sparing the face due to pyramid tract involvement
CN6 fascicle involved
Etymology of clivus
Means slope
Millard Gubler Syndrome
Ventral pontine syndrome
Basis pontis and fsacicles of CN VI and VII affected.
Contralateral hemiplegia sparing the face due to pyramidal tract involvement
Ipsilateral LR palsy, accentuated when the the patient looks towards the lesion.
Ipsilateral peripheral facial paresis due to CN VII involvement
Why is the trigeminal so named?
Because it branches intracranially into three divisions
Where are the cell bodies of most of the primary sensory neurones of the trigeminal located?
Trigeminal ganglion in Meckel’s cave
The remainder are located in the mesencephalic trigeminal nucleus.
Extent of the sensory innervation of the trigeminal
Skin of the face and forehead, scalp as far back as the vertex of the forehead
Mucosa of the oral and nasal cavities and paranasal sinuses and the teeth.
Also innervates most of the dura and the cerebral arteries
Where do the central processes of the trigeminal ganglion cells terminate?
In the pontine and spinal ncueli.
Location of the pontine trigeminal nucleus?
(AKa chief, principal, or superior sensory nucleus)
Located in the dorsolateral area of the tegmentum at the level of entry of the sensory axons.
Components of the trigeminal nucleus?
Mesencephalic nucleus
Pontine trigeminal nucleus (principle nucleus)
Spinal trigeminal nucleus
Motor nucleus
Parts of the spinal trigeminal nucleus?
Pars oralis
Pars interpolaris
Pars caudalis
Where do discriminative fibres for touch sensation from nerves in the trigeminal field terminate?
In the pontine trigeminal nucleus
What forms the spinal trigeminal tract?
Large numbers of sensory root fibres turn caudally on entering the pons.
Contains innervation for light touch, pain and temperature.
Form the spinal trigeminal tract.
It also acquires fibres from the facial, glossopharyngeal and vagus nerves.
Extent of the spinal trigeminal tract
Form the lower pons to the upper third cervical segment of the spinal cord where they intermingle with axons on the dorsolateral tract of Lissauer
Where do axons in the spinal trigeminal tract terminate?
In the subjacent spinal trigeminal nucleus
Extent of the spinal trigeminal nucleus
Pontine trigeminal nucleus to the caudal limit of the medulla where it blendswith the dorsal horn of the spinal grey matter
Extent of pars caudalis of the
Extends from the level of the pyramidal decussation to spinal segment C3
Modality received by pars caudalis of the trigeminal nucleus
Pain and temperature
Ipsilateral for the head
Extent of the pars interpolaris
From the keel of the rostral third of the inferior olivary nucleus to the pyramidal decussation
Extent of the pars oralis of the spinal trigeminal nucleus
Extends from the pars interpolaris rostrally to the pontine trigeminal nucleus.
Involved in tactile stimulation
Corneal reflex
Afferent- ophthalmic branch of trigeminal
Terminates in the motor nucleus of facial
Efferent: facial nerve
Normal corneal reflex
Bilateral closure of eyelid.
Sneezing reflex
Afferent- maxillary branch of trigmeinal
Motor nucleus of trigeminal and facial nerves, nucleus ambiguus and hypoglossal nucleus, phrenic nucleus and motor cells in the spinal cord.
What is the pathway from the pontine and spinal trigmeninal nuclei to the thalamus?
Crossed ventral trigeminothalamic tract which ascends close to the medial lemnisucus.
Smaller number of fibres crosssed and uncrossed proceed from the pontine trigeminal nuclues to the thalamus in the dorsal trigeminothalamic tract.
What is the trigeminal lemniscus?
Combined ventral and dorsal trigeminothalamic tract
Where do fibres of the trigeminal lemnsicus terminate?
Ventral posterior medial nucleus of the thalamus
What is unusual about the mesencephalic trigeminal nucleus?
Strand of large unipolar neurones extending from the pontine trigeminal nucleus of the midbrain.
Primary sensory neurones- the only to be within the CNS rather than ganglia
What is the mesencephalic tract
Myelinated axons of the primary sensory neurones from the mesencephalic nucleus
What is the principle function of neurones from the mesencephalic nucleus
Their fibres end in deep proprioceptive receptors adjacent to the teeth.
They run to the motor nucleus of the trigeminal.
Involved in the control of forces of the bite
Location of the trigeminal motor nucleus?
Medial to the pontine trigeminal nucleus
What are the muscles of mastication?
Temporalis
Masseter
Medial + lateral pterygoid
What are the additional muscles innervated by the motor nucleus of the trigeminal
Tensor veli palatani
Tensor tympani
Anterior belly of digastric
Mylohyoid.
How does the motor nucleus of the trigeminal nerve receive descending efferents from the cortex?
By way of the corticobulbar tract
Jaw reflex
Mandibular nerve
Mesencephalic and motor trigeminal nucleus
Back down the mandibular.
What is the jaw-opening reflex
Contractions of the masseter, temporalis and medial pterygoid muscles are inhibited as a result of painful pressure applied to teeth.
Action of the tensor tympani
Receives acoustic fibres from the superior olivary nucleus.
Reflex contraction checks excessive movement of the tympanic membrane caused by loud sound
Pathophysiology of trigeminal neuralgia
Demyelination of neurones in the sensory root caused in most cases by pressure of a small aberrant artery.
Which branch of the trigeminal nerve is most frequently involved in trigeminal neuralgia?
Maxillary
Then mandibular
Then ophthalmic
To which side does the mandible deviate in atrophy of the muscles of mastication
To the affected side becuase of the unopposed action of the contralateral pterygoid muscle which protrudes the jaw.
Cranial nerve fascicle
Portion of cranial nerve fibres that are within the brainstem.
Sensory component of the facial nerve?
Taste anterior 2/3rds of the tongue
Cutaneous fibres to the external ear
Facial nerve is parasympathetic to which glands?
Lacrimal
Submandibular
Sublingual
Glands of nasal mucosa
Where do the sensory and parasympathetic components of the facial nerve arise?
Nervus intermedius which is located between the motor root and the vestibulocochlear nerve
WIth which pharyngeal arch is the mandibular branch of trigeminal associated?
First pharyngeal arch
With which pharyngeal arch is the facial nerve associated?
Second
Intracranial portion of the facial nerve
Divided into subarachnoid portion and then facial canal portion
Origin of the facial nerve
Motor portion from facial nerve nucleus in the pons
Sensory and parasympathetic from nervus intermedius
Where are the cell bodies for the afferent nerves of the facial nerve found?
Geniculate ganglion
Where are the cell bodies for the efferent nerves of the facial nerve found?
Facial motor nucleus
Where are the cell bodies for the parasympathetic efferent component of the facial nerve found?
Superior salivary nucleus
What nerve leaves the facial nerve in he facial canal at the level of the geniculate ganglion
Greater petrosal nerve
How does the chorda tympani leave the middle ear?
Through a tiny canal in hte tymapnic part o the temporal bone to the infratemporal fossa
What are the branches of the facial nerve within the facial canal
Greater petrosal
Nerve to stapedius
Chorda tympani
What is the sensory branch of the facial nerve just prior to exiting the stylomastoid foramen
Somatic afferent fibres which merge with the IX and X to supply a small portion of the concha
What are the motor branches of the facial nerve after it exits hte stylomastoid formaen (extracranial)
Posterior auricular
Branch to posterior belly of digastric
Branch to stylohyoid
What are the terminal branches of the facial nerve
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical
Where is the geniculate ganglion found?
In the petrous temporal bone
What is the relationship of the facial nerve to abduences
Facscile arises ventral to VI in the pons, passes dorsally around the abducens nucleus at the facial colliculus as the facial genu before passing ventrally again to leave the brainstem ventrally.
What happens to teh axons of geniculate ganglin cells carrying taste from the anterior 2/3rds of te tongue after entering the brainstem?
Enter the brainstem in the nervus intermedius and turn caudally in the solitary tract.
The facial nerve fibres in this fasciulus are joined more caudally by gustatory axons rfrom the GPA and X.
Fibres from all three soruces terminate in the solitary nucleus. A column of cells adjacent to and partly surrounding the tract.
Only the large celled rostral part of the solitary nucleus recieves taste fibres.
What is the function of the rostral nucleus of the solitary tract?
Receives taste receptors from VII, IX and X
What is the area postrema?
Region of the medulla that controls vomiting.
What happens to ascending fibres for taste?
Run rostrally in the ipsilateral central tegmental tract, through the midbrain and subthalamic region tom their site of termination in the VPN of the thalamus.
Which thalamic nucleus receives taste fibres?
Ventral posterior nucleus
Where is the cortical area for taste?
Adjacent to the general sensory area for the tongue and extends onto the insula and forward to the frontal operculum.
Location of the facial motor nucleus
Caudal one third of the ventrolateral part of the pontine tegmentum.
What is the name for the configuration of facial nerve fibres running around abduenes?
The internal genu of the facial nerve
What is the function of stapedius
Reflex contraction in response to loud sounds prevents excessive movement of the stapes
What afferents input onto the facial motor nucelus?
Tectobulbar fibres from the superior colliculus- closure of the eyelids in response to bright light
Fibres from the trigeminal ssensory nucleus- corneal reflex, sucking and chewing repsonsel
Fibres fromt he superior olivary nucleus (part of the auditory pathway)- permits reflex stapedius conraction
How do parasympathetic fibres to the lacrimal glands reach their destination?
Preganglionic pass into the greater petrosal nerve and terminate in the pterygopalatine ganglion.
Post gangionic reach the lacrimal gland via the zygomatic branch of the maxillary nerve.
How do preganglionic fibres get to the submandibular ganglion?
Leave the facial nerve in the chorda tympani and are carried in the lingual branch of V3
Corticobulbar afferents to the muscles supplied by the facial nerve?
Are crossed, except for those supplying frontalis and orbicularis oculi which receive both uncrossed and crossed fibres.
Contralateral voluntary paralysis of only the lower facial muscles is therefore only a feature of UMN lesions
Forehead sparing right facial nerve weakness
Left UMN lesion
Featuresn of Bell’s palsy
Ipsilateral paralysis of the face
Ageusia of the anterior 2/3rds of te gonue.
Hyperacusis
(dependent on where int he canal the nerve is affected)
Ageusia
Loss of taste
Causs of multiple cranial nerve lesions
NP carcinoma
Chronic meningitis e.g. CA, haematological malignancy, TB, sarcoid
GBS (motor only)
Brainstem lesions
Arnold-Chirari
Trauma
Paget’s
Mononeuritis multiplex
Common causes of CNIII lesion
Idiopathic
Trauma
Central causes of CNIII lesion
Brainstem vascular lesions
Tumour
Demyleination
Peripheral causes of CNIII palsy
Compressive:
PComm anuerysm
Tumour
Basal meningitis
Nasopharyngeal carcinoma or orbital lesions
Ischaemia or infarciton in GCA, DM
complete ptosis (partial ptosis may occur with an incomplete lesion)
divergent strabismus (eye ‘down and out’)
dilated pupil
unreactive to direct light (the consensual reaction in the opposite normal eye is intact)
unreactive to accommodation.
CNIII
How can CN4 lesions be ruled out in a patient with CN3 palsy?
Always try to exclude a fourth (trochlear) nerve lesion when a third nerve lesion is present.
Tilt the head to the same side as the lesion.
The affected eye will intort if the fourth nerve is intact (remember SIN-the superior oblique intorts the eye).
Causes of CN IV palsy
Idiopathic
Trauma
Cerebral peduncle lesions
Failure to intort the eye
The patient may walk around with his or her head tilted away from the lesion – that is, to the opposite shoulder (this allows the patient to maintain binocular vision)
CN IV
Causes of bilatearl VI palsy
Trauma
Wernicke
Mononeuritis
Raised ICP
Causes of unilateral CN VI palsy
idiopathic
trauma
central (e.g. vascular lesion or tumour)
peripheral (e.g. raised intracranial pressure or diabetes mellitus)
Cause of central CN IX and X palsy?
Vascular lesions (e.g. Wallenberg’s)
Tumouir
Syringobulbia
MND
Causes of peripheral CN IX X palsies
Aneurysms at base of skull
TUmours
Chronic meningitis
GBS
Which way is the uvula drawn in a unilatearl CN X palsy?
Towards the normal side
Cuases of unilateral CN XI palsy
trauma involving the neck or the base of the skull
poliomyelitis
basilar invagination (platybasia)
syringomyelia
tumours near the jugular foramen
Bilateral causes of CN XI palsy
MND
Polio
GBS
Causes of bilatearl CN XII palsy
Vascular
MND
Tumours
Causes of central unilateral LMN CN XII palsy
Vascular
MND
Syrinrgobulbia
Causes of peripheral unilateral CN XII palsy
Posterior fossa: aneuryssms or tumours, chronic meningitis, trauma
Tumours of lymphadenopathy
Arnold-Chiari malformation
Why is there usually no deviation of the tongue with a unilateral UMN lesion of CN XII
The tongue like the upper forehead as bilateral UMN innervation
What is the largest avascular organ in the body?
Intervertebral disc
What is a zygapophyseal joint
Another name for spinal facet joint
What is the most common dermatome syndrome seen with craniocervical disease
C2
Where does the pyramidal decussation begin and where does it complete?
Just below the obex and is not completed until below the exit of the first ceerbical nerve root
Which spinal tract is compromised in a foramen magnum tumour presenting with hand weakness?
Corticospinal tract
What is the significance of an enlarged intervetrebral foramen on radiology?
May represent a tumour
What ligament is important to divide for proper visulaisation of .a ventral spinal tumour after dural opening in a posterior approach?
Dentate ligament
Hyoid bone cervical level
C3
Thyroid cartilage cervical level
C4-5
Cervical level cricoid
C6
Perioral tingling and numbness in syringobulbia is due to compression of which tract?
Spinal trigeminal tract
At what level is the line drawn from one scapula tip to another when the patient is positioned prone?
T7
What is a possible neuranatomical reason why a dorsal rhiotomy may fail to relieve pain and why a dorsal root ganglionectomy may be more effective
There may be a few nociceptive fibres that come into the horn via the ventral honr to terminate on the superifical layers of the dorsal horn.
These aberrant fibres do not traverse dorsal root but do no synapse in DRG
What is a dorsal rhizotomy?
Neurosurgical procedure that selectively destroys dorsal . erve roots
Which ligament is the priamry restraint against atlantoaxial AP transolcation?
Transverse ligament
What is the caudalis portion of the spinal trigeminal tract?
An extension of the dorsal root entry zone and substantia gelatinosa of the trigeminal system into the lower meudllary and high cervical regions
What supplies sympathetic innervation to the arm?
T2 and 3 nerve roots
What is the spinal homologoue of the spinal trigeminal nucleus?
Spinal dorsal horn
What is the other name of the dosal ramus of the C1 nerve root?
Suboccipital nerve
What innervates the cervi al disk?
Plexus formed by the sinuvertebral nerve dorsally and the cervical sympathetic trunk ventrally.
Nocicpetive information from cervical disks enters the trigeminothalamic tract in the upper cervical spine and may be a contributory factor in patietns with cervicogenic headaches
Level of aortic bifurcation
L4
Loss of sensation of the first dorsal webspace of the foot is indicative of injury to which nerve?
Deep peroneal
Nerve root affected with loss of Achilles reflex?
S1
What nerve roots mediate biceps reflex?
C5/6
Which reflex is associated with L5 nerve root?
None
Where do pain and temperature 1o neurones synpase in the spinal cord?
Small, finely myelinated axons with bodies in the DRG.
The afferents enter the cord at the dorsolateral tract (zone of Lissauer) and synapse in the substantia gelatinosa ( II)
What are the radiographic findings in acute transverse myelitis?
Usually normal, possibly with increased T2 signal
What is Pott’s?
Tuberculous vertebral osteomyelitis
How does tuberculous osteomyelitis of the spine differ from other bacterial infections
Affects the vertebral body rather than the disks primarily.
To which part of the brain are the olfactory nerves attached
Telencephalon of prosencephalon via olfactory bulbs.
Olfactory system
Olfactory nerve-> olfactory bulb (telencephalon)-> olfactory tract-> olfactory stria-> temporal lobe (lateral stria) the olfactopry area (piriform cortex)
Piriform cortex, over uncus of temporal lobe (inferomedial area)
Concerned with olfaction
How many olfactory nerves are there?
15-20 pairs
What are optic nerves?
Central tracts from the diencephalon
Why should optic nerves be considered central processes rather than cranial nerves?
Lined by oligodendroglia rather than Schwann cells
Not affected by peripheral cranial nerve lesions but are affected by lesions affecting central areas e.g. MS
Segments of the oculomotor nerve
In midbrain
Subarachnoid space
Cavernous sinus
SOF
Extracranial
Passage of oculomotor somatomotor fibres
Originate in the anterolateral region of the periaqueductal grey matter at the level of the superior colliculus.
Fibres pass through the tegmentum of the midbrain, the red nucleus, medial aspect of the CN emerging from the medial surface of the cerebral peduncle at the oculomotor sulcus into the interpeduncular fossa.
Passage of oculmotor visceromotor fibres
Originate from EW nucleus in the periaqueductal grey matter of the midbrain at the level of the superior colliculus. PNS fibres pass with the somatomotor fibres to emerge from the ventral surface of the midbrain.
What happens to the oculomotor nerve as it exits the cavernous sinus ventrally?
Divides into superior and inferior divisions.
With which division of the oculmotor nerve do PNS fibres run as it exits the cavernous sinus
With the inferior divsion
What is the arrangement of cranial nerves in the cavernous sinus as they enter dorsally?
OTOM
What happens to the arrangement of cranial nerves as the cavernous sinus is traversed?
3rd starts moving caudally.
4th and V1 start moving rostrally.
By the ventral surface of the cavernous sinus, the nasociliary branch of V1 is between the upper and lower branches of CN3
Where within the oculomotor nerve do the parasympathetic fibres run
Superficially and superiorly.
Division of the SOF
Divided into three parts by the annulus of Zimm
Outer
Middle
Medial
How does the oculomotor enter the orbit?
Through the SOF, through the annulus of Zimm with superior and inferior parts with the interposed nasociliary branch of V1
Which nerves pass through the annulus of Zimm?
3 (superior and inferior)
Nasociliary
6
What structures pass through the lateral part of the SOF (lateral to the annulus)?
LFT
Lacrimal branch of V1
Frontal branch of V1
4
(From lateral to medial)
What structures are supplied by the superior division of CN3?
SR
LPS
What structures are supplied by the inferior branch of CN3?
MR
IR
IO
With which branch of the lower branch of CN3 do the PNS fibres run?
Run with the branch to IO but deviate to ciliary ganglion which is laterally located between CN2 and lateral rectus
What are the two components of LPS?
Voluntary and involuntary components (can somatically open eyes but kept open involuntarily)
Where does CN3 obtain its sympathetic contribution?
From the carotid sympathetic plexus inside the cavernous sinus
Sympathetic fibres travel with which division of oculomotor?
Upper division
Structures supplied by the lower portion of CN3?
IO, IR, MR
PNS fibres travel with a branch to IO to supply ciliary ganglion
How do post-ganglionic PNS fibres emerge from ciliary ganglion?
As short ciliary nerves and pass between the sclera and the choroid to ciliaris and constrictor pupillae
External ophthalmoplegia=
Failure of somatic extraocular muscles e.g. CN3 palsy
Internal ophthalmoplegia
Failure of PNS component of CN3
Characterised by:
Fixed and dilated pupil
Cycloplegia causing blurred vision and glare of light.
Weber’s Syndrome
Ventral midbrain pathology
Damage to CN3 and cerebral crus in midbrain
Ipsilateral CN3 palsy
Contralateral hemiparesis
Benedikt’s syndrome
Mdibrain tegmental pathology
Ipsilateral CN3 palsy (CN3 nucleus or fascicle)
Contralateral abnormal motor movements (tremor, athetosis, chorea- due to involvement of red nucleus/rubrospinal tract)
With the addition of:
Contralateral hemianaesthesia (due to involvement of medial lemniscus)
or
Contralateral hemiplegia (if involves corticospinal tract)
Vascular territories of midbrain
Ventromedial surface supplied by paramedian branches of basilar
Ventrolateral perforating branches from the PCA
Aetiology of cranial nerve palsies in meningitis?
Due to fibrin content of CSF causing compressive CN lesions.
Relationship of CN4 to PCA/SCA
Inferior to PCA but superior to SCA
Into what does the CN4 emerge from the back of the midbrain?
Superior medullary velum which has a ridge of white matter centrally known as the frenulum veli
Why might you get a concomitant Horner’s syndrome in patients with cavernous sinus pathology?
Some of the sympathetics run with V1 and V2
What differentiates between SOF pathology and orbital apex?
Orbital apex lesions involve an optic neuropathy (e.g. RAPD) as II is found there
May also be a proptosis, orbital signs
Arrangement of structures in the SOF from superior to inferior
LFTSNIA
Lacrimal
Frontal
Trochlear
Superior branch of III
Nasocilliary
Inferior branch of III
Abducens
What differentiates between SOF pathology and cavernous sinus lesions?
The cranial nerves have started to branch so there may be lesions of the individual nerve branches
Action and location of the nucleus prepositus
Found in the caudal pons and upper medulla
Part of the horizontal gaze holding system
Which three systems are involved in the vascularization of the cranial nerves?
Inferolateral trunk (ICA)
Middle meningeal system (ECA)
Ascending pharyngeal system (ECA)
Which CNs are supplied by the ILS?
III
IV,
VI
V1
Which CN are supplied by the MMS?
V2
V3
VII
Dual arterial supply of VII?
Infrapetrous portion- stylomastoid artery and the MMS
Nerves supplied by the ascending pharyngeal system
IX
X
XI
XII
Syndrome of ILT
EOM involvement and V1
Difficult to demonstrate
Branches of the ILT and their specific CN supplied
Superior/tentorial artery supplies III and IV
Anteromedial branch enters the orbit through the SOF and supplies III, IV, V1,
Anterolateral branch passes through the foramen rotundum and supplies V2
Posterior branch supplies the sensory and motor portions of V3 anastomosing with the cavernous branches of the accessory meningeal artery and middle meningeal artery
Segmental blood suppl to CN3
Posterior perforated sometimes- single artery arising from basilar
Supracavernous region- artery of Bernasconi
Intracavernous region- ILT
Posterior perforated area
CN3 vascular interruption
Isolated CN3 palsy
Supracavernous region
CN3 vascular pathology presentation
III and IV
Intracavernous region
CN3 vascular pathology
Usually will include III, IV, VI and V1
Components of the middle meningeal system
Middle and accessory meningeal arteries
Both arise from the maxillary branch of the ECA
Origin of the stylomastoid artery
Posterior auricular (50%) of cases and occipital (50%)
Blood supply of CN VII in the facial canal
Petrous branch of the MMA after anastomosing with the AMNA
Inferior tympanic artery (ascending pharyngeal)
Stylomastoid artery
Branches of the ascending pharyngeal artery/
Anterior purely pharyngeal branch
Middle tympanic branch
Posterior meningeal branch
Which branch of the ascending pharyngeal supplies CN IX-XII
Posterior meningeal branch
Branches of the neuromeningeal branch of the ascending pharyngeal
Rostrally to caudakl
Jugular
Hypoglossal
Musculospinal arteries
Which CN are supplied by the jugular branch of the neuromeningeal ascending pharyngeal artery?
IX, X, XII in their transcranial portion
Blood supply to hypoglossal
Hypoglossal branch of the neuromeningeal branch of the ascending pharyngeal
Blood supply to CN XI
Dual vascularisation from the jugular and musculospinal branches of the neuromeningeal ascending pharyngeal artery.
Contents of Dorello’s canal
CN VI and the interior petrosal sinus
Light reflex impact:
Lesion of ipsilateral CN3
Loss of direct but not consensual response
Light reflex impact:
Contralateral CN3 palsy
Preserved direct but loss of consensual response
Light reflex impact:
Ipsilateral CNII lesion
Loss of direct and consensual resonse
Light reflex impact:
Contralateral CN II lesion
Does not affect ipsilateral pupillary responses
Possible levels for lesions of conjugate horizontal gaze
Supranuclear
Nuclear
Internuclear
Which trigeminal fibres bypass the trigeminal ganglion
Proprioceptive fibres carried in V3 bypass the trigeminal ganglion and continue into the brainstem to synapse directly on the mesencephalic nucelus.
This nucleus may thus be considered a sensory ganglion hat has been displaced into the brainstem.
Muscles innervated by V3
Muscles of mastication- masseter, temporal, medial and lateral pterygoid
Anterior belly of digastric
Tensor tympani
Tensor veli palatini
Describe the corneal reflex arc
Afferent fibres from the ophthalmic branch of V that synapse on the trigeminal sensory nucleus
Efferent limb consists of somatic motor fibres that begin in the trigeminal sensory nucleus on the stimulated side, projecting bilaterally to CNVII nuclei and terminating on orbicularis oculi
Loss of direct and consensual corneal response
Ipsilateral CN V lesion
Loss of direct but not contralaetral conreal reflex
Ipsilateral CN VII lesion
Passage of internal genu of the facial nerve
Fascicles project dorsomedially, looping around CNVI to form facial colliculus in the floor of the fourth then passing ventrolaterally to exit the brainstem at the pontomedullary junction.
How do fibres from the intermediate nerve distribute
In two branches- the superficial petrosal nerve-> lacrimal gland via pterygopalatine
Chorda tympani-> submandibular ganglion
Isolated unilateral facial paralysis involving forehead
CNVII lesion distal to stylomastoid foramen
Unilateral facial paralysis with loss of taste in anterior two thirds of tongue, forehead involved
Lesions within facial cnala proximal to takeoff of chorda tympani
Unilateral facial paralysis, loss of taste sensation and tinnitus/deafness with loss of tearing (forehead involved)
Lesions within IAM
Why do supranuclear facial palsies result in forehead sparing?
COritcobulbar fibres to supply the face provide contralateral innervation of the lower face but bilateral innervation of the upper face.
What are the functional components of the glossopharyngeal nerve
Somatic motor to stylopharyngeus
Visceral motor to parotid gland via otic ganglion
Somatic sensory, cell bodies in inferior glossopharyngeal ganglion supply skin of external ear
Visceral sensoy, cell bodes in inferior glossopharyngeal ganglion and carry sensation from the posterior third of tongue, pharynx and eustachian tube as well s chemo and baro-receptive impulses from the carotid sinus and body terminating in the solitary tract nuclei
Special sensory, taste from posterior third of tongue
What is the location of the cell bodies of the vagus nerve?
Superior and infeior ganglia which lie within the jugular fossa of the petrous temoral bone.
Ipsilateral anosmia
Ipsilateral optic atrophy
Contralateral papliioedema
Foster Kennedy Syndrome
Olfactory groove or sphenoid wing meningioma
UMN lesion of the hypoglossal
Tongue deviation to the contralateral side
Pain in distribution of V1 and V2
Oculosympathetic paresis (ptiosis and miosis) with preservation of sweating.
+/- loss of sensation in V1/2
Raeder Paratrigeminal Syndrome
Usually due to middle cranial fossa lesions between the trigeminal ganglion and the ICA.
Pain and sensory disturbance in V1 (due to impairment of ophthalmic nerve)
Ipsilateral lateral rectus palsy (due to abducens impairment)
Gradenigo’s syndrome
Usually due to inflammatory lesion at the apex of the petrous bone
May also include oculosympathetic paresis with preservation of facial sweating
Pain and sensory disturbance in V1
Ipsilateral ophthalmoplegia
Proptosis
Conjunctival injection
Cavernous sinus syndrome
Oculosympathetic paresis with preservation of facial sweating may occur
Pain and sensory disturbance in V1
Ipsilateral ophthalmoplegia
Not cavernous sinus syndrome
SOF syndrome
Retro-orbital pain and sensory loss in V1
Ipsilateral ophthalmoplegia
Granulomatous lesion
Tolosa-Hunt Syndrome
Granulomatous lesion in the cavernous sinus
Ipsilateral facial paralysis
Ipsilateral lateral rectus palsy
Contralateral hemiplegia
Millard-Gubler Syndrome
Due to ventral pontine lesion
Ipsilateral facial paralysis
Paralysis of conjugate gaze to the side of the lesion (abducens and PPRF)
Contralateral hemiplegia
Foville’s Syndrome
Progressive sensorineural hearing loss
Tinnitus
Vertigo
Unsteadiness
CN VII palsy
Facial pain and sensory loss with depressed corneal reflexes
CPA syndrome
Symptomology of CPA syndrome
Vestibular schwannomas- early prominent hearing loss, late CNVII and trigeminal involvement, infrequent lower CN palsies
Meningiomas- early CN VII and trigeminal involvement, late haring loss and more common lower CN involvement
Loss of taste in the posterior third of the tongue
Paralysis of VC, palate and anaesthesia of larynx/pharynx
Ipsilateral trapezius and SCM weakness
Vernet’s syndrome
Due to a lesion in the jugular foramen, most commonly a glomus jugulare tumour
Vagal ganglionic anatomy if not done
Laterality of smooth pursuit
Ipsilateral (saccadic eye movements are contralateral)
Retinal disparity
Disparirty between the location of images on the two retinas
Retinal blur
Defocused images
Stimuli to retinal vergence
Retinal blur which leads to accommodation linked vergence
Sense of nearness (proximal vergence)
Cues such as perspective and size (tonic verngence)
What are the three levels of the accommodation reflex
Convergence
Accommodation of the lens
Pupillary constriction
Accommodation of the lens
Involves contraction of the ciliary muscle
Reduces tension on the suspensory ligament of lens
Causes lens to become more spherical
What differentiates between a posterioorly and centrally located INO
In a posteriorly located INO, vergence system is intact
In centrally located it is impaired
Anatomy of vertical gaze movements
Originate bilaterally and pass to the pretectal area (vertical gaze centre)
Thence to CN3 and 6
What are the two major vertical gaze palsies?
Parinaud’s
Steele-Richardson-Olszewski
Steel-Ricahrdson-Olsweiski syndrome
Primary supranuclear palsy
Downward gaze palsy with nuchal rigidity and progressive dementia
(Parkinson plus syndrome)
Which of the oculomotor subnuclei are crossed?
Superior rectus subnucleus supplies contralateral size
Possible patterns of CN3 nuclear palsies
Complete CN3 ipsilateral plus bilateral ptosis and SR palsy
Bilateral ptosis with normal EOM (CCNN involved)
Bilateral CN3 palsy with lid sparing
https://youtu.be/3je8-2dz-GQ
What is the significance of ptosis w.r.t nuclear CN 3?
There is a central caudate nucleus which provides bilateral innervation to the LPS.
If there is a nuclear CN3 lesion there is either bilateral ptosis (involvement of CCN) or no ptosis
L down and out eye with bilateral ptosis and impaired upgaze in R eye
L nuclear CN3 palsy
Involvement of central caudal nucleus which provides bilateral innervation to LPS
R impaired upgaze is due to involvement of L SR subnucleus which is crossed
L CN3 palsy with unilateral ptosis
By definition cannot be nuclear
Isolated CN3 MR subnucleus lesion
Rare as medial rectus subnucleus is so large difficulty to knock it out in an isolated fashion
More likely to be an INO
Pupil in nuclear CN3 palsy
Usually bilateral as EW in close proximity if nuclear lesion
Cause of light-near dissociation in Parinaud’s
Involvement of pre-tectal nucleus impacting on light reflex
The near pathway has cortical projections
Argyll-Robertson pupil basis
Neurosyphilis affecting pre-tectal pathway
How to differentiate between CN3 palsy and EW lesion
Look for preservation of accommodation pathway
https://youtu.be/4FhYD0TndqU
Bilateral ganglionic (ciliary) light near dissocisation
Can be post optic nerve sheath fenestration
HSV
HZV
DM autonomic ganglionopathy
Autoimmune
B/L Adie’s Tonic pupil
N3 palsy
Optic atrophy
Proptosis
Isolated involvement of superior or inferior divisoin
Orbital lesion
Most common CNIV lesion
Contusion of nerve in subarachnoid course against the edge of the tentorium, may be bilateral
Parkinson’s Syndrome
CN6
Cavernous sinus lesion
6th nerve palsy with Horners
Sympathetic fibres join the 6th for a short period within the cavernous sinus
Direction of nystagmus in peripheral destructive lesion
In a peripheral vestibular lesion, the fast phase of the nystagmus is usually directed away from the side of a destructive lesion
Left destructive lesion.
Unopposed right firing-> crossed to LPPRF, abduction so conjugate gaze towards left with corrective fast saccade to right
Most common form of nystagmus seen in clinical practice
Drug indued
Relaionship between barbiturates and eye movements
Intoxication will cause degeneration of smooth pursuit movements followed by saccadic eye movements
Sever barbiturate intoxication eliminates even caloric responses
Patient with intact pupillary light reflex but absent caloric may be in barbiturate coma
Distinguishing physiologic end point nystagmus from pathological
Symmetrical
Absence of other associated neurological signs
Pattern of gaze evoked nystagmus
Central cause
Bilateral horizontal gaze evoked nystagmus usually associated with nystagmus on upgaze
Rarely with down gaze nystagmus
Gaze paretic nystagmus
Patient unable to sustain eccentric gaze
Eyes have tendency to wander towards the primary position with corrective saccadic movements to eccentric position
Most commonly caused by durg intoxication
Spasmus nutans
Syndrome of infancy which typically spontaneously resolves
Triad of head nodding, nystagmus and head-turning.
Nystagmus is commonly monocular and variable
Ocular bobbing is associated with
Massive pontine lesion
Opsoclonus in younger children may represent
Remote effect of neuroblastoma
Square wave jerks
Pairs of saccades that are directed away from and back to fixation
May be associated with cerebellar lesions
Why is strictly upbeat nystagmus more likely to be central
Peripheral vestibular lesions tend to generate mixed waveforms, combinations of rotatory/horizontal/upbeat
Upbeat nystagmus with normal MRI
Think Wernicke’s, paraneoplastic/autoimmune
Difference between opsoclonus and ocular myoclonus
Opsoclonus is continued disorganised chaotic repetitive saccadic movements occuring in all direction
Ocular myoclonus is continuous rhythmic oscillation of the eyes
Describe the passage of sympathetic innervation to pupil
Originates in posterolateral hypothalamus
First ordered descending sympathetic fibres passes through lateral tegmentum of brainstem to reach intermediolateral gray matter of C8-T2 (ciliospinal centre of budge)
Intermediolateral gray projects second-order neurone up the sympathetic chain to the superior cervical ganglion
Superior cervical ganglion sends third-order neurone via the ICA to CN6 then V1 via the long ciliary nerve to dilator pupillae
What are the other sympathetic fibres that travel with the pupillodilator pathway
Sudomotor and vasomotor to the face via ECA
Second via the ICA then ophthalmic artery to orbit to the superior tarsal muscle which elevates the eyelid
Location of ciliary ganglion
Temporal side of the ophthalmic artery between the optic nerve and lateral rectus
How to test for pharmacological mydriasis
Instil 1% pilocarpine into the eye
In the normal person or with interruption of parasympathetic innervation, the pupil will constrict as the drug acts directly at the NMJ
If there is pharmacological blockade it will not constrict
Traumatic mydriasis
Ocular trauma can result in transient loss of parasympathetic tone or via direct injury to the pupillary sphincter
Weak miotic will cause constriction in patient with loss of parasympathetic tone but not in pupillary sphincter injury
Diagnostic test for Adie’s tonic pupil
Instillation of very weak miotic (0.125% pilocarpine)
This solution would not work in a normal person but in patients with a tonic pupil with ciliary dysfunction, there is parasympathetic supersensitivity which leads to pupillary constriction after instillation of weak mioitc agent.
Hutchinson’s pupil
AKA surgical CN3 palsy
Midrbain pupillary abnormaltiy
Light naer dissociation
Impairment in upgaze
Classic structural lesion associated with pinpoint pupils
Pontine
Pharmacological test for Horner’s syndrome
INstillation of 10% cocaine to block noradrenaline reuptake
In normal person, this causes pupillary dilatation
In Horner’s there is no dilatation as there is no accumulation of Norad
How to distinguish Horner’s syndrome from simple anisocoria
Check pupillary light reflex, if both react then patient may have simple anisocoria
Turn the lights off- if the smaller pupil is abnormal then the anisocroia will become more pronounced, a dilatation lag of the smaller pupil implies poor sympathetic tone and suggests diagnosis of Horner’s
Muscles involved in eye opening
LPS (CN3)
Superior tarsal muscle/Muller’s muscle that is embedded in the levator muscle and inserts on tarsal plate (sympathetic fibres)
Frontalis helps to retract eyelid in extreme upgaze (CN7)
Explain Bell’s phenomenon
LPS and SR innervated by superior division of oculomotor
To coordinate simultaneous eyelid opening and upgaze the tone should remain equal.
During forced lid closure which is caused by contraction of orbicularis oculi muscle (CN7) rather than normal lid closure which is associated with loss of tone in LPS, the SR tone remains high causing elevation of the eye- Bell’s phenomenon
Def: lid retraction
When there is sclear showing between eyelid and iris
How to differentiate between lid retraciton in thyroid eye disease and midbrain syndrome
Dorsal midbrain syndrome is typically bilateral retraction
Light-near dissociation seen
No suggestion of led retraction on downrad gaze
What is the most common cause of lower eyelid retraction
CN7 palsy
Coria
Pupil
Anisocoria in which bigger pupil is not reacting properly to light
Problem with bigger pupil- PNS
Ansiocoria in which smaller pupil doesn’t dilate in dark
Issues with smaller pupil-> sympathetics
How to test anisocoria is due to ciliary ganglion problem
Near reflex is preserved so there is light near dissociation
Low dose pilocarpine will cause constriction
Right unilaterally dilated pupil
Which is worse in light
No features of CN3 palsy
Light near dissociation
Dilates with low dose pilocarpine
No structural abnormality
Adie’s tonic pupil
Degree of ptosis in Horner’s
1-2mm
Apraclonidine eye drop
Direct SNS
Alpha agonist with differential activity for alpha 1 and 2
Under normal conditions, alpha 2 predominates, so if put into normal pupil it will either stay the same size or get smaller
In denervated eye, alpha 1 predominates and it will cause dilatation
Facial nerve
Stylomastoid artery highlighted- branch of posterior auricular artery and should be presreved as it supplies the facial nerve
Anastomoses with superficial petrosal branch of middle meningeal artery
Greater superficial petrosal nerve
Hypoglossal nerve coming through above occipital condyle
Vidian nerve
Consequence of sacrificing vidian nerve
Dry eye
Dry eye post trans-sphenoidal
Vidian nerve sacrific
What is this structure?
What is its innervation?
Tensor tympani
V3
What is this structure?
What is it a branch of?
Greater petrosal nerve
VII
What is this structure?
What is it passing underneath
VI
Passing under Grubner’s ligament
What is this structure visualised via temporal craniotomy?
Greater petrosal nerve
Why is there bilateral SR weakness in nuclear third nerve palsy?
SR is crossed but the crossing fibres pass in close proximity to the other subnuclei which means with nuclear 3rd nerve palsy the SR subnucleus and the crossing fibres are often both involved
Pharyngeal araches
