Neurophthalmology Flashcards
causes of monocular diplopia?
often due to refractive problem in anterior aspect of eye
most commonly result of astigmatism-abnormal corneal curvature, new onset of which could occur with corneal deformation due to overlying lid lesion or after surgery with tight corneal stitches through cornea.
also occurs with lens displacement, cataract irregularities and keratoconus-primary problem of corneal curvature.
a patient presents with a ‘down and out eye’, ptosis and a DILATED PUPIL. Should we be worried, and if so how would we investigate?
YES!
clinical presentation of oculomotor nerve palsy with involvement of PNS fibres which travel on the outside of the nerve, to cause pupil dilation which occurs with nerve compression e.g. aneurysm of posterior communicating artery-our big concern here, or a tumour.
investigate with magnetic resonance angiogram (MRA) and angiography
down and out-SO and LR functioning, ptosis-loss of oculomotor nerve innervation to LPS
if pupil was not dilated, quick investigations to ascertain cause include BP and blood glucose to investigate for HTN and DM as causes of a vaso-occlusive abnormality producing the nerve palsy.
cranial nerve with longest intracranial course?
trochlear nerve (CN IV)
what type of diplopia is seen with abducens nerve palsy?
horizontal diplopia-2nd image is displaced to the side of 1st image, rather than above seen with vertical diplopia
patient may turn their head towards affected side in order to look through normal eye to avoid diplopia
presentation of a trochlear nerve palsy?
upward deviation of affected eye, and twisting so patient may tilt their head away from the lesion-try and cope with vertical diplopia
usual cause of trochlear nerve palsy?
trauma
but can also be caused by ischaemia e.g. in a diabetic, may be congenital with later decompensation, and can be due to a tumour.
what investigation should always be carried out in presentation of trochlear nerve palsy?
MRI scan of head in order to exclude closed head trauma
if no trauma, check patient’s BP and glucose, and then r/v in 6 weeks.
where is likely lesion location if nerve palsy is of all 3 nerves: oculomotor, trochlear and abducens?
cavernous sinus
considerations in cause of abducens nerve palsy?
consider raised intracranial pressure
-especially if bilateral presentation
commonly vasculitic event e.g. diabetes, or HTN, so if patient was for example an elderly diabetic, no need to image.
usually just check BP and glucose, but if young patient, bilateral palsy, or not recovering at 6wks then scan the patient.
what ocular complaints are seen with patients with myasthenia gravis?
this is an AI disease in which autoantibodies are produced against the nicotinic ACh receptors post-synaptically at the NMJ of striated muscle
patients get a ptosis and diplopia-both are worse on prolonged upgaze
a Tensilon test can be used in diagnosis confirmation-acetylcholinesterase inhibtor given and look for improvement in their symptoms, but can cause sweating, bradycardia, bronchospasm and salivation.
can instead hold ice pack over closed eye and look for improvement on removal
features of optic neuritis?
reduced vision, especially colour vision, often sudden onset central scotoma, and reduced contrast sensitivity
pain on eye movements
afferent pupillary defect
optic nerve head oedema-cause of optic disc swelling producing enlarged blind spot
enhancement of optic nerve on MRI
assoc. with MS
occurs in younger patients
with MS-MRI scan shows demyelinating lesions, can give patients IV steroids and r/f to neurology for interferon treatment.
why do diabetic patients with oculomotor nerve palsy tend to have pupil sparing?
oculomotor nerve palsy result of ischaemic insult to oculomotor nerve fibres which usually is of the deeper fibres rather than the PNS fibres that run along the surface and supply the sphincter pupillae muscle, which are therefore affected by compression due to aneurysm or tumour.
what nerve palsy might be expected with idiopathic intracranial HTN, and what other features might be found on patient presentation?
abducens nerve palsy, likely bilateral-when pt asked to look to the R the R eye will be unable to look outwards due to lateral rectus paralysis and pt will experience horizontal diplopia, same for L in that when asked to look to left L eye will be unable to move out to the L.
patient may have hx of headaches, nausea, and may be obese, transient visual loss when pt bends over-increasing pressure on optic nerve
ophthalmoscopy: optic disc swelling-examination may reveal enlarged blind spot
confirmed high pressure on lumbar puncture
when might a patient present with a vertical diplopia?
thyroid eye disease
diseases more common in patients with myasthenia gravis?
thymoma
Grave’s disease
causes of optic neuritis?
MS
viral infections
TB
sarcoidosis
how does internuclear ophthalmoplegia present?
there is weak adduction of the affected eye, and horizontal jerk nystagmus of normal other eye during abduction
result of medial longitudinal fasciculus lesion, which connects the oculomotor nerve of 1 eye to the abducens nerve of the other eye so that when a pt wants to look in 1 particular direction, both eyes move to that direction-e.g. to look R-R eye abducts and L eye adducts
most common cause=MS
despite the most common cause of a 6th nerve palsy being trauma, what other differential cause should be considered which means that the palsy is a false localising sign?
raised IC pressure
what type of squint do nerve palsies cause?
a paralytic/incomitant squint
causes of isolated nerve palsies?
vascular disease: DM, HTN, aneurysm, cavernous sinus thrombosis
inflammation: sarcoidosis, vasculitic e.g. GCA, GB syndrome
infection: herpes zoster
trauma: most common cause of 4th and 6th nerve palsies
neoplasia: meningioma, acoustic neuroma, glioma
rasied IC pressure
orbital disease e.g. neoplasia
how is internuclear ophthalmoplegia treated? what may it be caused by?
if microvascular cause, spontaneous resolution usually occurs
recovery more variable in patients with MS
gaze difficulty in myasthenia gravis patients?
inability to maintain upward gaze
ptosis also accompanied by weak eye closure
What investigation is required in presentation of bilateral abducens nerve palsy?
MRI-looking to exclude a cause of raised ICP
If this is normal may need LP to exclude benign intracranial HTN
Why should we do a blood test in patients over 55 yrs presenting with abducens nerve palsy?
To rule out GCA as cause-do ESR
What condition is associated with bilateral optic nerve gliomas?
Neurofibromatosis
What condition do we query if hypo density around optic nerve?
Meningioma
