Neurological Conditions Flashcards
diagnosis of squint
- corneal reflection - should fall centrally and symmetrically on corneas
- cover test
cover test and eccentric fixation
the cover test relies on the ability to fixate, so if there is eccentric fixation, the deviating eye will not move to take up fixation
corneal reflection will show malalignment
causes of eccentric fixation
foveal vision can be so poor that it is not used for fixation
convergent squint
esotropia
- eye is too far in so moves outward
who is esotropia seen in
children commonly, can be due to hypermetropia
divergent squint
exotropia
occurs in older children and are often intermittent
paralytic squint
diplopia is worst on looking in th direction of the pull of the paralysed muscle
often sudden onset
monocular diploplia
rare, occurs with cataracts or corneal scars
hypertropia
the eye is too high so moves downwards on cover test - vertical diplopia
converse for hypotropia
oculomotor palsy
eye looking down and out
ptosis, proptosis (due to reduced recti tone)
fixed pupillary dilation
causes of CNIII palsy
microvascular
tumour
ANEURYSM
MS - demyelination
congenital cavernous sinus lesions
superior orbital fissure syndrome
what is the classical location of an aneurysm causing oculomotor palsy
posterior communicating artery
what are the actions of the superior oblique muscle
intorsion, depression in adduction and weak abduction
trochlear nerve palsy
diplopia and the patient may hold their head tilted (ocular torticollis)
the eye looks upwards on adduction, and cannot look in and down
bilateral trochlear nerve palsy
- presentation and cause
results in torsion and chin depression (as eyes are looking too far up)
can be cause by blunt head trauma
cause of trochlear nerve palsy
microvascular (diabetes - 30%)
CONGENITAL - presents in adulthood due to decompensated ability to overcome vertical deviation
tumour
TRAUMA - 30%
abducens nerve palsy
horizontal plane diplopia, worse when looking in the distance (this uses lateral rectus to abduct the eye)
eye is medially deviated and cannot move laterally from the midline
causes of CNVI palsy
microvascular
SOL/tumour causing raised ICP (papilledema may be present)
trauma to base of skull
congenital
multiple sclerosis
what is the most common cause of CNVI palsy
The nerve leaves the brainstem at the level of the pons and then runs upwards and over the petrous temporal bone. Raised ICP can stretch the nerve and hinder its function causing a CNVI palsy. This is called a false localising sign
treatment of CNVI palsy
botulinum toxin can eliminate the need for surgery in selected VI palsies
Inter-Nuclear Ophthalmoplegia
- The MLF facilitates conjugate eye movements on lateral gaze.
- Abduction is normal in either eye, whereas adduction is impaired, resulting in dissociation of eye movements
- When each eye is tested independently by covering the other eye, medial rectus function is shown to still be present.
- E.g. when an attempt is made to gaze contralaterally, the affected eye adducts minimally, whilst the unaffected eye abducts with nystagmus (repetitive, uncontrolled movements).
what is the main cause of INO
injury/dysfunction in the medial longitduinal fasciciulus
how does the patient with INO usually present
dont usually complain of diplopia
MLF
found in the brainstem and is a set of crossed fibres formed of both ascending and descending fibres that links CNIII, IV and VI (and CNVIII) to integrate the movements of the eyes, and head
what is the likely cause in young patients with bilateral INO
multiple sclerosis - demyelination of nerves in brain and spinal cord
what is a possible cause of INO in older patients with one sided lesions
stroke
