BCSC Neuro-Op Flashcards
What is the pattern deviation plot of a visual field?
It reports the analysis of sensitivity values based on age-expected values for all points tested after shifting (by the 7th highest point). This helps account for media opacities, although optic neuropathy may also cause total deviation depression without pattern deviation abnormalities.
What is the false-positive rate for a visual field?
frequency of patient signalling light when no light is displayed
What is the false-negative rate for a visual field?
Frequency of patient failing to signal when a target brighter than the previously determined threshold for the same spot is displayed
What are fixation losses on a visual field?
the frequency with which the patient signals seeing a light when it is presented in the physiologic blind spot (e.g., 4 signals out of 21 times presented)
What are the two types of contrast sensitivity tests?
Grating tests (give contrast threshold vs. spatial frequency function) and Letter tests
Can contrast sensitivity be diminished in the absence of visual acuity decrease?
Yes
Is contrast sensitivity testing specific for optic nerve dysfunction?
No
How does photostress recovery testing differentiate between optic neuropathy and other etiologies of decreased vision?
Patients with optic neuropathy demonstrate normal recovery times (30 seconds) from photostress (bright light fixation for 10 seconds), while patients with maculopathy or ischemia show slowed recovery from photostress (90-180 seconds)
What is done in PAM (Potential Acuity Meter) testing?
Optotypes are projected onto the retina through a dilated pupil, providing an estimate of best potential visual acuity
How can true edema and pseudoedema of the optic disc be differentiated?
On FA, a truly swollen disc will leak, while pseudoedema (as in LHON) will not leak
What type of light source does OCT use?
near infrared
What is visual evoked potential recording?
Electrical signals produced in response to a visual stimulus are measured via electrodes placed on the scalp overlying the occipital cortex
In which situations is VEP particularly helpful?
1) Patient unable to communicate, 2) confirmation of intact visual pathways in patient with suspected non-organic disease
What does electroretinogram (ERG) measure?
The electrical activity of the retina in response to various light stimuli under different states of light adaptation.
How is electrical activity measured for an ERG?
With electrodes embedded in a corneal contact lens worn for testing
What are the major components of the electrical waveform generated by ERG?
a-wave (photoreceptors), b-wave (inner retina: Muller and ON-bipolar cells), c-wave (RPE, photoreceptors)
What are the 3 forms of ERG?
Full-field ERG, Pattern ERG, and Multi-focal ERG
Is the multifocal ERG signal usually normal or abnormal in optic nerve disease?
Normal
What are common maculopathies and retinopathies that can present similarly to optic neuropathy?
1) Acute Idiopathic Blind-Spot enlargement, 2) MEWDS, 3) Cone Dystrophy, 4) Vitamin A deficiency, 5) Hydroxychloroquine and chloroquine retinopathy, 6) Cancer-associated retinopathy, 7) Melanoma-associated retinopathy
With what findings do patients with optic neuropathies present?
visual acuity loss, visual field loss, dyschromatopsia, RAPD
What are the 3 major groups of ganglion cell nerve fibers entering the optic nerve?
1) Papillomacular fibers, 2) Arcuate fibers, 3) Nasal radiating fibers
What types of scotomata result from damage to the papillomacular fibers?
1) cecocentral scotoma, 2) paracentral scotoma, 3) central scotoma
What types of scotomata result from damage to the arcuate fibers?
1) altitudinal defect, 2) nasal step defect
What types of scotomata result from damage to the nasal radiating fibers?
1) temporal wedge defect
What is a cecocentral scotoma?
A scotoma that extends from central vision temporally to the natural blind spot
How does blind spot enlargement result from optic disc edema?
Displacement of the peripapillary retina
Where does early papilledema begin?
at the superior and inferior poles of the optic disc
What is papilledema?
edema of the optic nerve head that results (specifically) from increased intracranial pressure (ICP)
What are the primary findings of acute papilledema?
1) hyperemia of the optic disc, 2) dilation of disc surface capillary net, 3) telangiectasia of surface and radial peripapillary vessels, 4) grayish, feathered NFL obscuring disc edge and peripapillary retinal vessels
What are features suggestive of true disc edema?
1) hyperemia, 2) microvascular abnormalities of the disc surface, 3) opacification of peripapillary NFL
What is the most common cause of pseudopapilledema?
optic disc drusen
What are conditions that can mimic papilledema?
1) optic disc drusen, 2) hyaloid remnants on disc surface, 3) glial tissue on disc surface, 4) congenital appearance, 5) vitreopapillary traction, 6) NFL myelination
What are causes of papilledema (i.e. increased ICP -> disc edema)?
intracranial mass, hydrocephalus, CNS infection, infiltration by inflammatory or neoplastic process, cerebral venous thrombosis, pseudotumor cerebri
Should neuroimaging be obtained urgently in suspected papilledema?
Yes
What portion of the disc is last to become blurred/edematous in acute papilledema?
the temporal portion
Is the absence of spontaneous venous pulsations useful in assessing for papilledema?
Only if they were known to be visible previously, as this is a physiologic variant in 20% of individuals
What findings are seen in chronic papilledema?
1) pale optic disc, 2) gliosis of peripapillary NFL, 3) optociliary shunt vessels due to chronic CRV obstruction, 4) refractile bodies of the disc
Do most patients with IIH have papilledema?
Yes
What are symptoms associated with IIH?
Headache, nuasea, transient visual obscurations, diplopia (2/2 abducens paresis), visual field loss, pulse synchronous bruit
What are associations/possible etiologies of IIH?
vitamin A (>100,000 U/day), tetracycline, minocycline, doxycycline, retinoic acid, lithium, sleep apnea
What medical therapies can be used for IIH aside from analgesics?
acetazolamide and topiramate (furosemide or IV steroids second-line)
What are surgical therapies for IIH?
optic nerve sheath fenestration (ONSF) or CSF diversion procedure (VP or LP shunt)
Does headache improve after optic nerve sheath fenestration?
No, ONSF does not change ICP
What is the presentation of Anterior Ischemic Optic Neuropathy (AION)?
Painless monocular vision loss developing over hours to days, visual field loss (often altiduinal or arcuate), RAPD, optic disc edema in patients usually > 50 yo
What are the two classifications of AION?
Arteritic AION (AAION) and Non-arteritic AION (NAION)
What are indications that a patient has AAION rather than NAION?
1) chalky white disc edema (vs. hyperemic), 2) cotton wool spots away from optic disc (vs. adjacent to disc), 3) delayed choroidal filling (vs. normal), 4) normal or large cup in fellow eye (vs. small)
What is the cause of AAION?
AAION is caused by inflamatory and thrombotic occlusion of the short posterior ciliary arteries
What is the most common cause of AAION?
GCA, which results in headache, scalp tenderness, anorexia, weight loss, fever, jaw claudication
What is occult GCA?
GCA with elevated ESR but no systemic symptoms or with normal ESR and systemic symptoms. It occurs in 20% of AAION patients.
What percent of AION is AAION?
only 5%-10% of AION is AAION
Are patients with AAION usually older or younger than NAION patients?
AAION patients are older
What is the immediate management of suspected AAION?
IV steroids (methylprednisolone 1g/day for first 3-5 days, followed by prednisone 1mg/kg/day tapered over 3-12 monhts) + daily aspirin. Temporal artery biopsy may be delayed up to 10 days without compromise of results
What is the primary goal of AAION therapy?
To prevent contralateral vision loss (which occurs in 95% of cases within days to weeks if untreated)
What is the presumed etiology of NAION?
compromised optic disc microcirculation with structural “crowding” of the disc
To what does the term “disc at risk” refer?
Refers to the optic disc in the contralateral eye in NAION, which typically has a small diameter and small or absent physicologic cup
What are the characteristic findings in Foster Kennedy and pseudo-Foster Kennedy syndrome?
One optic disc is atrophic, while the other is edematous. Atrophic disc indicates chronic injury while edematous disc indicates recent or ongoing injury.
What is the difference between Foster Kennedy and pseudo-Foster Kennedy syndrome?
Only the etiology of the findings. NAION (prior occurrence in one eye, new recurrence in contralateral) –> pseudo-FK; intracranial mass (chronic compression of one nerve, increased ICP causing edema of other) –> FK.
What percent of AION is NAION?
90%-95%
What are risk factors for NAION?
Structural crowding of optic cup, systemic hypertension, DM, hyperlipidemia
What condition is important to rule out when suspecting NAION?
optic neuritis, which is indicated by optic nerve enhancement with gadolinium on MRI
Does vision improve after NAION?
It can, by 3 lines in 31% of patients after 2 years
Do therapies exist for NAION?
No proven therapy exists. ONSF does not work per Ischemic Optic Neuropathy Decompression Trial (IONDT).
What is the appearance of the optic disc in optic neuritis?
Normal in 2/3 of cases, edematous in 1/3
What are the 3 common types of optic neuritis?
Postviral, infectious, and demyelinating (MS)
What are the clinical characteristics of neuroretinitis?
Acute loss of vision with disc edema and a star pattern of exudates in the macula
Do patients with neuroretinitis have an increased risk of MS?
No
What is the most common cause of neuroretinitis?
Cat-scratch disease (caused by Bartonella henselae or Bartonella quintana)
What are characteristic findings in diabetic papillopathy?
Hyperemic edema of disc, dilatino of disc surface microvasculare difficult to distinguish from NVD
What is papillophlebitis?
A subset of CRVO in the young, with unusually prominent disc edema, normal acuity pupils, and color vision, and blind spot enlargement
What is the natural history of papillophlebitis?
It will usually resolve spontaneously over 6-12 months, with minimal visual loss
What is the predominant theory regarding the etiology of optic disc drusen?
impaired ganglion cell axonal transport, possibly related to a small scleral canal and mechanical obstruction
Do most patients with optic disc drusen experience symptoms?
No, most patients with optic disc drusen do not experience symptoms (>90%). 8.6% may experience transient visual obscurations.
What methods can be used to identify optic disc drusen (and differentiate it from papilledema)?
1) B-scan ultrasound (highly reflective), 2) FA (autofluorescence, no leakage), 3) CT, 4) OCT
From which conditions must optic disc drusen be differentiated?
1) Papilledema, 2) Astrocytic hamartoma of the retina (2/2 tuberous sclerosis or neurofibromatosis)
What are two ways in which to differentiate astrocytic hamartomas from optic disc drusen?
1) Astrocytic hamartomas do not autofluoresce (unlike ODD), and 2) Astrocytic hamartomas typically obscure the retinal vessels (unlike the deeper ODD)
What demographic is most often affected by Leber hereditary optic neuropathy?
Males 10-30 years old
What is the clinical presentation of LHON?
acute, severe, painless, vision loss (<20/200), central or cecocentral visual field impairment
What are the fundus findings in LHON?
1) hyperemia and elevation of the optic disc with pseudoedema (no leakage on FA), 2) peripapillary telangienctasia, 3) tortuosity of medium-sized retinal arterioles
What is the etiology of LHON?
Mutation in mitochondrial DNA (three known mutations can lead to the disease)
Does visual recovery occur after LHON?
rarely; more common with the 14484 mutation
Does a proven therapy exist for LHON?
Not presently, although in vitro studies suggest estrogen may have a protective effect
What is the gene thought to cause autosomal dominant optic atrophy (ADOA)?
OPA1 gene on chromosome 3
Where does focal notching of the optic disc usually occurin chronic open-angle glaucoma?
inferior or superior pole
What is the usual size of the optic disc in optic nerve hypoplasia?
Small, disc diameter is 1/2 to 1/3 the diameter of a normal disc
What syndrome involving optic nerve hypoplasia is most common?
Septo-optic dysplasia (ONH, absent septum pellucidum, pituitary dwarfism)
What are common associations of ONH?
midline or hemispheric brain defects, endorcrinologic abnormalities, congenital suprasellar tumors
What percent of patients with congenital tilted disc syndrome have bilateral involvement?
80%
Where is the colobomatous excavation of the optic nerve tissue in Congenital Tilted Disc Syndrome?
inferonasal optic disc
What conditions are included in the spectrum of Excavated Optic Disc anomalies?
1) Optic pit, 2) Coloboma, 3) Dysplastic nerve, 4) Morning glory disc
What is an optic pit?
a depression of the optic disc surface located inferotemporally, associated with mild visual field defect (paracentral or arcuate), and possible serous detachment of macula
From what do optic nerve colobomas result?
incomplete closure of the embryonic fissure, usually inferiorly
What is the morning glory disc anomaly?
a funnel-shaped staphylomatous excavation of the optic nerve and peripapillary retina. Retinal vessels characteristically emanate from the periphery of the disc.
Is neuroimaging warranted in a patient with morning glory disc anomaly?
Yes, the patient may have a basal encephalocele or CNS vascular anomalies.
What are the characteristics of retrobulbar optic neuritis?
Subacute, monocular vision loss developing over several days, accompanied by periorbital pain, RAPD, red dyschromatopsia in a young (32yo) female (77%) patient.
When does vision recovery usually occur in retrobulbar optic neuritis?
Within 1 month
Did the Optic Neuritis Treatment Trial (ONTT) demonstrate any long-term vision benefit of corticosteroids for optic neuritis?
No. They did not improve visual outcome, but IV steroids did speed time to recovery by 1-2 weeks.
Is treatment of retrobulbar optic neuritis with IV steroids appropriate?
If pateint requires rapid return of vision (e.g. is monocular), then yes. Otherwise, no, given the potential for complications and lack of long-term benefit.
What are the diagnostic criteria for neuromyelitis optica?
1) optic neuritis, 2) myelitis, 3) 2 of a) spinal cord lesion involving 3+ vertebral segments, b) MRI nondiagnostic for MS, c) positive NMO-IgG serology
When should testing for NMO-IgG be considered?
1) progressive vision loss for >2 weeks, 2) lack of vision improvement by 1 month, 3) recurrent optic neuritis
What is optic perineuritis?
Inflammation of the optic nerve sheath
Does optic perineuritis respond to steroids?
Yes, immediately and dramatically
What are the two means by which optic nerve dysfunction can occur in thyroid eye disease (TED)?
1) EOM enlargement leading to compression of the optic nerve, 2) stretching of the optic nerve 2/2 proptosis
With what do intraorbital and intracanalicular compressive optic neuropathy present?
slow progressive vision loss, RAPD, monocular field loss
What are the two most common types of primary optic nerve tumors?
1) optic nerve glioma, 2) optic nerve sheath meningioma
What is the diagnostic triad of the optic nerve sheath meningioma (ONSM)?
1) painless, slowly progressive monocular vision loss, 2) optic atrophy, 3) optociliary shunt vessels
What are optociliary shunt vessels?
Preexisting optic disc channels that dilate in response to chronic obstruction of outflow through the central retinal vein. Optociliary shunt vessels shunt retinal venous outflow to the choroidal circulation and would be more accurately called “retinochoroidal collaterals”
What is the treatment of choice for optic nerve sheath meningioma?
Fractionated radiation therapy (produces stability or vision improvement in up to 94.3% of patients)
Where are optic pathway gliomas (OPGs) found?
Involving the optic nerve, the optic chiasm, or both
What percent of OPGs are detected by the first and second decades of life?
70% and 90%, respectively
Is biopsy of OPGs usually recommended?
No, may cause additional vision loss and high-resolution neuroimaging provides sufficient diagnostic accuracy
What are the two classifications of malignant optic nerve gliomas?
Anaplastic astrocytomas or glioblastoma multiforme
What is the usual clinical presentation of toxic or nutritional optic neuropathy?
gradual, progressive, painless vision loss that is bilateral and symmetric
What are two exceptions to the typically gradual vision loss seen in toxic optic neuropathies?
Methanol toxicity and Ethylene glycol toxicity both produce rapid vision loss
What are the most commonly implicated medications in toxic optic neuropathy?
1) ethambutol, 2) linezolid, 3) isoniazid, 4) chloramphenicol, 5) hydroxyquinolines, 6) penicillamine, 7) cisplatin, 8) vincristine, 9) lead ingestion
What is the time to development of optic atrophy after optic nerve trauma?
4-8 weeks
What is the clinical characterization of Posterior Ischemic Optic Neuropathy (PION)?
Ischemic damage to the retrobulbar portion of the optic nerve results in abrupt, severe vision loss, RAPD, with initially normal-appearing discs.
What are the 3 clinical scenarios in which PION occurs?
1) perioperative, 2) arteritic (esp. GCA), 3) non-arteritic
What is the prognosis for vision recovery in PION?
Poor
What is the most common clinical scenario in which PION occurs?
Perioperative scenario, particularly those involving substantial blood loss, hypotension, or prolonged anesthesia duration.
What are the most common causes of infiltrative optic neuropathy?
1) leukemia, 2) lymphoma, 3) granulomatous inflammation (sarcoid, syphilis, TB, fungal infection
How should cases of suspected infiltrative optic neuropathy be evaluated initially?
1) MRI brain and orbits with fat suppression and gadolinium contrast, 2) screening tests for myeloproliferative, inflammatory, and infectious disorders that are common causes (see other questions), 3) LP with CSF analysis (may need to be repeated, as sensitivity of single test is low)
What is the median survival time for meningeal carcinomatosis?
4-9 weeks, even with aggressive therapy
What percent of isolated optic atrophy without clear cause is due to a compressive lesion?
Approximately 20%
Where are nasal and temporal retinal fibers segregated?
At the optic chiasm
What is a junctional scotoma?
A field loss due to injury of an optic nerve at its junction with the optic chiasm. It is characterized by 1) Diminished visual acuity and central visual field loss in the ipsilateral eye and 2) temporal hemianopia in the contralateral eye