CRANIAL NERVES Flashcards
causes of anosmia
• Head injury (cribriform plate) → ipsilateral anosmia
• Tumours in the frontal, temporal lobes
• Parkinsons disease
• Rare congenital:
o Congenital anosmia secondary to cleft palate in males
o Familial dysautonomia
o Turner syndrome
o Kallmann syndrome: hypogonadothropic hypogonadism
eye examination sequence
EYE EXAMINATION (II,III, IV, VI)
- Inspection:
- Visual acuity each eye separately: ●Snellen ●Close distance
- Colour vision
- Visual fields: ● with both eyes open: sensory lesions above thalamus (cortical) produce CONTRALATERAL inattention ●individual eye’s fields ●blind spot
a. Visual field are described from patient’s point of view - Eye movements: ●H-test
- Pupils
a. Accommodation
b. Light reflex
c. Fundoscopy
pupillary reflex arc
- Aff: light perception: CNII
- Eff: pupillary constriction – PNS ofCNIII
- bypasses lateral geniculate body & the cortex
does pupillary light reflex pass through lateral geniculate body and the cortex?
no, bypasses it
corneal reflex ars
- Aff: corneal sensation – Vi
* Eff: blinking – CNVII
gag reflex
- Aff: laryngeal sensation – CNIX
* Eff: gag – CNX
qccommodation reaction pathw
Aff: frontal lobes, ●Eff: PNS of CNIII
on general inspection of eyes
● Ptosis: complete/partial
!!Ptosis is NOT a feature of CNVII palsy – in facial nerve palsy the eye doesn’t close
● Ocular deviation
● Pupils: shape, regularity, size, asymmetry
● Proptosis
how to measure visual acuity and troubleshooting
Always inspect with glasses or through pinhole – any uncorrected visual loss can then be assumed to be neurological rather than refractive If cannot read any letters: ● CF (count fingers 1m), ● HM (hand movements 30cm), ● PL (perception of light)
abnormal eye position in CNIII palsy
eye is down and out position on primary gaze. Limited movement in all directions except abduction, associated may be ptosis and pupil dilatation
eye position in CNIV pal
affected eye cannot look down and in
what movement affected by CNVI palsy
limited abduction
Voluntary eye movements (saccadic) initiated in …
frontal eye fields
pursuit is controlled by
occipital lobe
vestibulo-ocular reflex is controlled
in the cerebellum
converge is controlled in
????
which reaction is stronger: pupillary to light or to accommodation?
to accommodation
Weakness of the extraocular muscles results in double vision in which direction
in the direction od movement of that muscle
in double vision, which image arises from the affected eye
the outer image is from the affected eye
DDx ptosis
- congenital
- \horner’s (always PARTIAL ptosis)
- CNIII palsy (usually complete)
- Myasthenia Gravis (usually complete)
- Myopathy
eye movements in the internuclear ophthalmoplegia
possible ddx in uni or bi-lateral ION
caused by a lesion in the medial longitudinal fasciculus. May be damaged by demyelination (MS)
(usually bilateral) or vascular disease (uniloateral). Produces horizontal diplopia and reduces adduction on the side of the lesion and nystagmus on the contralateral abducting eye.
in internuclear ophthalmoplegia, can the eyes move medially (adduction) when converging?
YES, convergence is preserved
jerky VERTICAL NYSTAGMUS is due to…
brinstem leasion.
if upbeat : lesion in the midbrain or floor of 4th ventricle
downbeat nystagmus : foramne magnugm lesion, phenytoin or alscohol also
what do you need to do when examining the pupils?
● Symmetry of pupils, regularity of shape
● Direct reflex + Consensual reflex when the patient is looking into the distance
If no response from shining a light into the eye, but there is normal response on accommodation – this is AFFERENT papillary defect, indicates significant optic nerve disease.
● Accommodative reflex
● Exclude RAPD (swinging light) – partial CNII damage → intensity and speed of reflex are ↓
what is the likely cause of intact accommodation with absent light
Argyll Robertson pupils (pupils small and irregular) in diabetes and neurosyphilis.
a larger, regular, reacting sluggishly to accommodation but NO direct or consesual response to lpupil is…
holmes-aldie pupil
ophthalmoscope: what lens to use if the pt is shortsighted
(-) anticlockwise (red)
ophthalmoscope: what lens to use if the pt is farsighted
clockwise Green (+)
where is the optic disc in relation to the macula\?
optic disc is 15degrees medial to hte macula
background diabetic retinopathy appearane
dot blood haemorrhages
miscroaneurysms
soft exudates
pre-proliferative diabetic retinopathy appearance
hard exudates
intraretinal microvascular abnormalities
cotton wool spots
proliferative diabetic retinopathy appearnce
neovascularisation on the disc or in the retine
hypertensive retinopathy features
AV nipping silver wiring flame shaped haemorrhages exudates cotton wool spots blurred disc margin
central renal artery occlusion appearance
retinal pallor,
affects all four quadrants
cherry-red spots
central retinal vein occluson appearance
central retinal vein occluson appearance
dialted tortuous veins, widespread haemorrhage
cotton wool spots
causes of CNIII palsy
SURGICAL • Generally affect the pupil • Posterior communicating artery aneurysm • SOL in midbrain/sphenoid wing near cavernous sinus • Haemorrhage MEDICAL • Often pupil is unaffected • Causes of mononeuritis multiplex (MM) • Demyelination • Infarction
causes of VI palsy
- Causes of MM
- Vascular lesion
- Malignancy
- Demyeliantion
- Infection – lyme disease, syphilis
- Raised ICP
- Wernickes encephalopathy can cause palsy bilaterally
causes of internuclear ophthalmoplegia
MS
vascular disease/event
afferent pupillary defect meaning and DDx
- Pupil unreactive to light (direct reflex is absent)
- Consensual reflex is absent
- Indicates a complete optic nerve lesion - causes dilated pupil
RAPD meaning (pathology) and D
- Incomplete damage to one optic nerve
- Direct and indirect reflexes are intact in each eye but differ in relative strength
- When light is swung from one eye to the other, the affected eye dilates slightly when illuminated and constricts when unaffected eye is illuminated (consensual stronger than direct reflex in affected)
sparing of the pupil in CNIII palsy: ddx and pathology
PNS fibres undamaged (run in a discrete bundle on the surface of the nerve). Diabetic CNIII infarction is usually painless and pupil sparing, unlike compression by a PCA aneurysm
complete external ophthalmoplegia ddx
COMPLETE EXTERNAL OPHTHALMOPLEGIA: immobile eye when III, IV, VI nerves are paralysed at the orbital apex or within the cavernous sinus (thrombosis or meningioma).
CNV lesion findings
o Complete lesion causes unilateral sensory loss on the face, anterior 2/3 of tongue and buccal mucosa. Jaw deviated to the side of lesion when opened.
note that the angle of jaw is supplied by C1
and teh V1 goes up on the top of the head all the way to the vertex
CNVII lesions findings
o weakness/palsy of facial expression mu
o Loss of taste from anterior 2/3 of tongue (via chorda tympani)
o Hyperacusis (supplies stapedius muscle)
o The upper face receives bilateral supranuclear innervation
o UMN lesions in facial palsy: findings
o UMN lesions cause weakness of the lower part of the face contralaterally. Frontalis is spared, brow furrowing is spared
LMN lesions in facial palsy: findi
o LMN lesions cause ipsilateral weakness of all facial muscles: angle of mouth falls, unilateral dribbling develops. Cornea may be damaged if the lid does not close.
combination of • Unilateral III, IV, V and VI involvement possible ddx
lesion in cavernous sinus
combination of unilateral V, VII, VIII involvement ddx
cerebellopontine angle lesion (usually a tumour)
unilateral IX, X, XI involvement ddx
jugular foramen lesion
combined bilateral X, XI, XII ddx
bulbar palsy if LMN Sx are present, pseudobulbar if UMN signs are present
weakness of the eye and facial muscles that worsens with repeated contractions possible ddx
myasthenia
what is acoustic neuroma
Schwann cell-derived tumours that commonly arise from the vestibular portion of CNVIII. >90% are unilateral. Bilateral in NF2
aetiology and risk factors for acoustic neuroma
- NF2
- Exposure to loud noise
- Childhood exposure to low-dose radiation
features of acoustic neuroma (findingS)
Symptoms of CN compression by tumour
CNVIII: hearing loss, tinnitus, unsteadiness while walking
CNV: facial numbness, parasthesia, pain (17%)
CNVII: facial weakness (6%)
With tumour progression → compression of CPA → ipsilateral ataxia + nystagmus
Compression of the lower CNs (IX, X, XI) → dysphagia, dysarthria
Look for Sx of neurofibromatosis
management of acousti
Mx: surgery to prevent further disability, does not restore hearing. Three approaches: retromastoid suboccipital, translabyrinthine and middle fossa
Radiation: for small <3cm neuromas and if unfit for surgery
bells palsy aetiology and features
Lyme disease and HIV seroconversion may cause that. Bell’s phenomenon: upward conjugate eye movement when eyes are closed.
• Profound unilateral facial weakness.
• Develops over 24-48h
• Pain behind the ear on onset
• Difficulty closing the eye
• Slurred speech, losing food from the corner of the mouth
• Reduced taste
• Hyperacusis
• Tx: steroids (prednisolone 10d) and antivirals (acyclovir)
• 75% improve spontaneously in 6mo
• 25% develop synkinesis, crocodile tears
CN IX anatomy
exits the skull through jugular foramen with CN X and CN XI
lesions of CN IX cau
- Loss of gag reflex (interrupted afferent limb)
- Hypersensitive carotid sinus reflex (syncope)
- Loss of general sensation in the pharynx, back of the tongue
- Loss of taste from posterior 1/3 tongue
- Glossopharyngeal neuralgia: stabbing pain in the root of the tongue
CN X lesions cause
- Ipsilateral paralysis of the soft palate, pharynx, larynx → dysphonia, dyspnoea, dysarthria, dysphagia
- Anaesthesia of pharynx+larynx → unilateral loss of cough reflex
- Aortic aneurysm and tumours of neck/thorax frequently compress the nerve
- Complete laryngeal paralysis if bilateral can cause asphyxia and death
- Oculocardiac reflex: pressure on the eyes slows the heart rate (aff CN V1, eff CN X)
how to inspect cranials controling the mouth
Soft palate movement (IX, X)
o “say ahh”
Mention gag reflex
Mention swallow test
Tongue movement (XII)
o Wiggle the tongue from side to side
o Stick your tongue straight out (will deviate towards the site of lesion)
o Power (push against cheek)
features of Horners syndrome
Features:
b. Miosis
c. Partial ptodid
d. Enophthalmos
e. Hemifacial loss of sweating
ddx for weakness of 1 or two muscles unilaterallly
a. Look for parotid enlargement or surgical scar over parotid
b. Usually due to aberrant reinnervation
ddx for bilateral
a. Myotonic dystrophy: frontal balding, furrowed brow, haggard face, thin neck and myotonia
b. Myasthenia gravis
c. Ocular myopathy - ophthalmoplegia, facial weakness, furrowed brow
d. Bilateral Horner‘s – with intrinsic cord lesions eg syringomyelia
e. Syphillis
characteristics of normal pressure hyd
- Dementia.
- Urinary incontinence.
- Gait abnormalities.
- Dementia may improve with ventricular shunting.
- How is NPH diagnosed?
By brain imaging (CT or MRI). The radiologic hallmark: ventriculomegaly out of proportion to cerebral atrophy. Ventriculomegaly that results from cerebral atrophy. In a patient with a gait apraxia and ventricles that are too big for her or his brain, the response to treatment with gait
improvement is the ultimate diagnostic test.
via CN XI, Ipsilateral cerebral hemisphere supplies what?
Ipsilateral cerebral hemisphere supplies the contralateral trapezius and ipsilateral SCM.thus a single UMN lesion gives bilateral signs.
if you find Unilateral weakness of SCM + trapezius:
peripheral accessory palsy. Look for ipsilateral IX and X lesions: ? jugular foramen lesion (glomus tumour or neurofibroma)
If you find weakness of ipsilateral SCM and contralateral trapezius:
UMN weakness on SCM side
Bilateral wasting and weakness of SCM: ddx
myopathy or MND(look for bulbar abnormalities)
Small tongue with fasciculations: ddx
BILATERAL LMN lesions, MND (progressive bulbar palsy type_, syringobulbia
Small tongue with recude speed of movements ddx
bilateral UMN (look for jaw jerk, labile emotions): pseudobulbar palsy
Tongue deviates to one With unilateral wasting + fasciculations =
towards lesion unilateral LMN (rare|)
tongue deviates to one side with normal bulk
unilateral UMN (common): stroke towards lesion
