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 (+)