Eye movements in health and disease Flashcards
what are the extraocular muscles of the eye?
superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique
what are the extraocular muscles of the eye?
superior rectus inferior rectus medial rectus lateral rectus superior oblique inferior oblique
Rectus muscles
originate from common tendinous ring and attach to anterior sclera
superior rectus
elevates eye
adduction
medial rotation
innervated by oculomotor nerve
inferior rectus
depresses eye
adduction
lateral rotation
innervated by oculomotor nerve
medial rectus
adduction
innervated by oculomotor nerve
lateral rectus
abduction
innervated by abducens nerve
oblique muscles
attach to posterior sclera
superior oblique
depresses eye in adduction
medial rotation/ intorsion
innervated by trochlear nerve
inferior oblique
elevates eye when in adduction
lateral rotation/ extorsion
innervated by oculomotor nerve
what happens when the superior tract is damaged?
inferior vision affected
what happens when the inferior tract is damaged?
superior vision affected
lesion at optic chiasm
tunnel vision
non-homonymous bitemporal hemianopia
what happens when there is a lesion in the primary visual cortex?
macular sparing
efferent visual pathway
upper motor neurone from fronto-parietal cortex to brainstem then lower motor neurone - cranial nerve to muscles of the eye
travel through cavernous sinus to orbit
motor pathway to eye
conjugated eye movement requires modification to the basic primary motor pathways to achieve convergence and conjugation
what is convergence?
alignment as objects become closer together
what is conjugation?
simultaneous tracking of objects
how to test superior rectus?
look laterally and upwards
how to test inferior rectus?
look laterally and downwards
how to test medial rectus?
look medially
how to test lateral rectus?
look laterally
how to test inferior oblique?
look medially and upwards
how to test superior oblique?
look medially and downwards
what are the components of MS?
inflammation - autoimmune mediation
demyelination
axonal loss
efferent opthalmic manifestations of MS
extraocular muscle palsy internuclear opthalmoplegia nystagmus saccadic abnormalities uveitis oscillopsia diplopia
afferent opthalmic manifestations of MS
demyelinating optic neuritis
visual field defects
prechiasmal
chiasmal
post-chiasmal
pre-chiasmal defects
optic neuritis
chiasmal defects
junctional scotoma
bitemporal hemianopia defect - rare
post-chiasmal defects
optic tract
geniculocalcarine pathway
what is optic neuritis?
common early presentation of MS - 20%
acute demyelination of optic nerve
clinical features of optic neuritis
more commonly unilateral than bilateral pain on eye movement loss of vision blurred vision partial/ complete typically central reduced visual acuity central scotoma loss of colour vision pale disc relative afferent pupil defect no fundoscopy findings
potential fundoscopy findings
can develop papillitis - blurred margins caused by swollen disc on fundoscopy
what is central scotoma?
blurred spot in centre of vision
what is a relative afferent pupillary defect?
pupils don’t send impulse back to brain to cause dilation or constriction of pupil
clinical features of a relative afferent pupillary defect
affected eye will dilate when light shone in swinging torch test
because of the consensual reflex from when light shone in unaffected eye is removed and there is dilation but the light is not detected by the affected eye so no constriction can occur
prognosis for optic neuritis
often self-resolves in 2-3 weeks
5-10% will not recover fully
can get recurrent attacks
treatment for optic neuritis
oral steroids have no long-term improvement but can speed recovery
IV steroids - methyprednisolone has been shown to reduce progression of MS
Rectus muscles
originate from common tendinous ring and attach to anterior sclera
superior rectus
elevates eye
adduction
medial rotation
innervated by oculomotor nerve
inferior rectus
depresses eye
adduction
lateral rotation
innervated by oculomotor nerve
medial rectus
adduction
innervated by oculomotor nerve
lateral rectus
abduction
innervated by abducens nerve
oblique muscles
attach to posterior sclera
superior oblique
depresses eye in adduction
medial rotation/ intorsion
innervated by trochlear nerve
inferior oblique
elevates eye when in adduction
lateral rotation/ extorsion
innervated by oculomotor nerve
what happens when the superior tract is damaged?
inferior vision affected
what happens when the inferior tract is damaged?
superior vision affected
lesion at optic chiasm
tunnel vision
non-homonymous bitemporal hemianopia
what happens when there is a lesion in the primary visual cortex?
macular sparing
efferent visual pathway
upper motor neurone from fronto-parietal cortex to brainstem then lower motor neurone - cranial nerve to muscles of the eye
travel through cavernous sinus to orbit
motor pathway to eye
conjugated eye movement requires modification to the basic primary motor pathways to achieve convergence and conjugation
what is convergence?
alignment as objects become closer together
what is conjugation?
simultaneous tracking of objects
how to test superior rectus?
look laterally and upwards
how to test inferior rectus?
look laterally and downwards
how to test medial rectus?
look medially
how to test lateral rectus?
look laterally
how to test inferior oblique?
look medially and upwards
how to test superior oblique?
look medially and downwards
what are the components of MS?
inflammation - autoimmune mediation
demyelination
axonal loss
efferent opthalmic manifestations of MS
extraocular muscle palsy internuclear opthalmoplegia nystagmus saccadic abnormalities uveitis oscillopsia diplopia
afferent opthalmic manifestations of MS
demyelinating optic neuritis
visual field defects
prechiasmal
chiasmal
post-chiasmal
pre-chiasmal defects
optic neuritis
chiasmal defects
junctional scotoma
bitemporal hemianopia defect - rare
post-chiasmal defects
optic tract
geniculocalcarine pathway
what is optic neuritis?
common early presentation of MS - 20%
acute demyelination of optic nerve
clinical features of optic neuritis
more commonly unilateral than bilateral pain on eye movement loss of vision blurred vision partial/ complete typically central reduced visual acuity central scotoma loss of colour vision pale disc relative afferent pupil defect no fundoscopy findings
potential fundoscopy findings
can develop papillitis - blurred margins caused by swollen disc on fundoscopy
what is central scotoma?
blurred spot in centre of vision
what is a relative afferent pupillary defect?
pupils don’t send impulse back to brain to cause dilation or constriction of pupil
clinical features of a relative afferent pupillary defect
affected eye will dilate when light shone in swinging torch test
because of the consensual reflex from when light shone in unaffected eye is removed and there is dilation but the light is not detected by the affected eye so no constriction can occur
prognosis for optic neuritis
often self-resolves in 2-3 weeks
5-10% will not recover fully
can get recurrent attacks
treatment for optic neuritis
oral steroids have no long-term improvement but can speed recovery
IV steroids - methyprednisolone has been shown to reduce progression of MS
what are the types of nystagmus?
unilateral bilateral purely downward purely torsional pendular is most common
oculomotor nerve palsy
eye moves down and out
ptosis
pupil involvement
diplopia
why does an oculomotor palsy cause diplopia?
no conjugation of eyes
why does an oculomotor palsy cause pupil involvement?
carries parasympathetic fibres to sphincter and ciliary muscles
causes of oculomotor nerve palsies
posterior circulation aneurysm brainstem lesions microvascular ischaemia cavernous sinus disease strokes
abducens nerve palsy
limited abduction
most common nerve palsy of eye
esotropia
head turn for compensation
what is esotropia?
eye turned inwards
causes of abducens nerve palsy
trauma space occupying lesion raised ICp ischaemia inflammation cavernous sinus disease
why is abducens nerve palsy the most common?
most superficial/ on the outside
trochlear nerve palsy
head tilt to compensate
torsional diplopia
worse on downward gaze
cannot look down
causes of trochlear nerve palsy
trauma
aneurysm
cavernous sinus disease
space occupying lesion
internuclear opthalmoplegia
most common abnormality in MS
often bilateral
causes of internuclear opthalmoplegia
cerebrovascular disease
lesion in medial longitudinal fasciculus
clinical features of internuclear opthalmoplegia
disorder of conjugate lateral gaze
adduction deficit in ipsilateral affected eye
pendular nystagmus in abducting contralateral eye
patients present with horizontal nystagmus
what is cavernous sinus thrombosis?
blood clot in cavernous sinus
can be life-threatening
causes of cavernous sinus thrombosis
- oral contraceptives
- pregnancy
- blood clotting disorders
- haematological diseases
- malignancies
- head trauma
- neurosurgical procedures
- IBS
- collagen vascular diseases
- blood vessel disorders
- hyperhomocysteineamia
- haematological conditions
- nephrotic syndrome
- dehydration
- infections
what infections can cause cavernous sinus thrombosis?
In paranasal region
- rhinogenic infections
- mid-facial infections
- dental infections
- otogenic infections
- meningitis
- pharyngitis
- tonsillitis
- orbital and periorbital cellulitis
what is the pathophysiology of cavernous sinus thrombosis?
thrombogenesis occurs in vertebral venous system
decreases cerebral drainage, increasing ICP
oxygenated blood in brain decreases
causes cerebral oedema and infarcts/ strokes
clinical features of cavernous sinus thrombosis
- symptoms depend on the size and location of thrombosis
- non-specific symptoms
- raised ICP
- cerebral ischaemia
- headache – acute, subacute or chronic and may progress in severity over days/ weeks
- bilateral papilloedema
- vision impairment – diplopia/ vision loss
- nausea and vomiting
- impaired consciousness
- seizures – focal or generalised
- cranial nerve dysfunction – diplopia, tinnitus, unilateral deafness, facial palsy
- paralysis
- aphasia
- behavioural changes
- delirium
- amnesia
- progressive and slow development of symptoms
diagnosis of cavernous sinus thrombosis
neuroimaging
lab tests
neuroimaging for cavernous sinus thrombosis
MRI with venography, if not CT with venography
neuroimaging findings in cavernous sinus thrombosis
absence of flow intraluminal venous thrombus focal oedema secondary to ischaemia intraparenchymal haemorrhage empty delta sign
lab tests for cavernous sinus thrombosis
D-dimer - elevated in acute disease FBC coagulation studies baseline renal function tests prior to starting treatment CRP blood cultures lumbar puncture ESR antibody studies LFTs thrombophilia screening EEG
treatment for cavernous sinus thrombosis
general stabilisation
treat raised ICP
treat underlying cause
anticoagulation
antimicrobial therapy if infection present
surgical intervention if no improvement with medical therapy or if anticoagulation is contraindicated
medical management of cavernous sinus thrombosis - anticoagulation
1st line = LMW heparin
2nd line = unfractionated heparin
long-term = vitamin K antagonists (warfarin) for 3-12 months
antimicrobial therapy for cavernous sinus thrombosis
vancomycin
3rd/4th generation cephalosporin
metronidazole for 3-4 weeks
rarely caused by fungal infection but if the case = immunosuppression, amphotericin B
other medical managements of cavernous sinus thrombosis
fluids neuroprotective measures ICP management anticonvulsants if seizures present corticosteroids in certain conditions
invasive procedures for cavernous sinus thrombosis
endovascular thrombolysis
catheter thrombectomy
surgery for cavernous sinus thrombosis
decompressive hemicraniectomy
haematoma evacuation
shunt placement
abscess drainage
