Neuro-ophthalmology Flashcards
To review high yield N-O topics and concepts.
(start 72) When an imaging study fails to demonstrate the expected pathology in relation to the clinical presentation, the clinician’s first step is to..
reexamine the study parameters, ideally with a neuroradiologist.
Best quantifies torsional strabismus
double Maddox rod - when vertical diplopia is present
Diagnostic of neurosyphilis
positive CSF VDRL
Patient presents with intraocular inflammation and positive RPR. Next step?
lumbar puncture with CSF examination, followed by antibiotic therapy (series of IV or IM dosing)
Consists of paired subnuclei for the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles as well as paired subnuclei for the pupillary constrictor muscles and single subnucleus for the levator palpebrae
CN III nuclear complex
Subnuclei for the superior rectus supply..
the contralateral superior rectus muscle
Actions of the superior oblique muscle
intorts, depresses, abducts the eye
Presentation of bilateral CN IV palsy
crossed hypertropia (right hyper on left gaze and left hyper on right gaze) extorsion of at least 10 degrees, large V-pattern esotropia greater than 25 PD (esotropia greatest on downgaze), and chin-down positioning (as hypertropia decreases in upgaze)
Cerebral achromatopsia is a feature of this type of lesion
occipital lobe
Pursuit and reflexive saccade movements are initiated in this region
parietal lobe, abnormal OKN responses can be seen related to a parietal lobe lesion
Abnormal OKN response. Where is the lesion?
Parietal lobe
VF defects commonly present with disc drusen
enlarged blind spot and ARCUATE SCOTOMAs
2 ways B-scan can differeniate calcified drusen from papilledema
1) highly reflective, calcified drusen maintain high echogenicity with lowering of U/S gain
2) with papilledema, intraorbital portion of ON is widened and will decrease in width with prolonged lateral gaze (30 degree test”); ODD do not produce widening of the intraorbital nerve.
Anatomic location of most ODD
anterior to lamina cribosa and posterior to Bruch membrane (lamina choroidalis portion of the intraocular optic nerve)
When does aberrant regeneration occur?
after trauma or compression by an aneurysm or tumor but does not occur with microvascular ischemia
What is primary aberrant regeneration?
aberrant regeneration without a h/o CN III palsy - evidence of a slowly expanding parasellar lesion - m/c meningioma or carotid aneurysm within the cavernous sinus.
Eyelid retraction in downgaze, eyelid elevation or pupil constriction on attempted adduction, and globe retraction on attempted upgaze
aberrant regeneration
Branch of the posterior cerebral artery that supplies the primary visual cortex
calcarine branch
Supply most of the blood supply to the skull and its contents. Be specific
Common carotid arteries arising from the innominate artery on the right and directly from the aorta on the left
Systemic evaluation for patient with suspected oculopharyngeal muscular dystrophy
genetic testing - PABPN1 - encodes for polyadenylate binding protein nuclear 1, only associated gene.
Diagnosis of OPMD (oculopharyngeal muscular dystrophy) relies on this molecular diagnosis
expansion of a GCN trinucleotide in the first exon of PABPN1 (commercially available test)
postpartum or recent SSRI + recurrent HA + hemianopic field loss with MRA showing “string of beads” appearance of cerebral arteries.
Reversible cerebral vasoconstriction syndrome (RCVS)
Prognosis of RCVS (reversible cerebral vasoconstriction syndrome)
resolves within 3 months
T1 MRI with contrast of brain with enhancing lesion of tectum of midbrain would confirm the diagnosis
Dorsal midbrain syndrome (Parinaud) syndrome
Signs of dorsal midbrain syndrome
1) convergence-retraction nystagmus (co-contraction of EOMs wtih attempted upgaze)
2) Conjugate limitation of vertical gaze (upgaze deficit)
3) skew deviation
4) eyelid retraction in primary position (Collier sign)
5) convergence abnormalities (convergence spasm or convergence palsy)
6) mid-dilated pupils, poorly reactive pupils with light-near dissociation
Most likely cause of diplopia in parinaud/pretectal syndrome
Skew deviation
Cause for optic disc edema with exudate in macula start pattern
M/c Bartonella henselae, less common syphilis, toxoplasmosis, lyme disease, tuberculosis, viruses. May also be postviral autoimmune process
Most common cause of divergence insufficiency (DI) in an otherwise healthy adult patient?`
Connective tissue involution between the superior and lateral rectus muscles causing inferior displacement of the lateral rectus muscles (sagging eye syndrome)
What is divergence insufficiency?`
acquired ocular misalignment defined by an esodeviation that is greater at distance than near fixation without lateral incomitance, and without abduction deficits.
Website for BCSC Self-assessment
https://bcscap.aao.org/Dashboard
Characteristic optic nerve appearance in dominant optic atrophy
Temporal pallor with an area of triangular excavation (wedge-shaped pallor)
Characteristic optic nerve appearance in Leber hereditary optic neuropathy (LHON)
Peripapillary telangiectasia
Characteristic optic nerve appearance in glaucoma
Superotemporal or inferotemporal notching
Characteristic optic nerve appearance in optic nerve hypoplasia
Yellow peripapillary halo with ring of pigmentation
What test would best distinguish a retinopathy from an optic neuropathy?
Photostress recovery
Characterized by short severe attacks of pain with cranial autonomic features (ptosis, miosis)
Paroxysmal hemicrania
Bouts of unilateral excruciating headaches with autonomic features lasting 15-180 minutes
Cluster headaches
Continuous unilateral headache
Hemicrania continua
Episodic very brief sharp stabbing stabbing pains/HA with no autonomic features
Idiopathic stabbing headache
Specific steps of cocaine test
Instill 2 drops of cocaine 4% or 10% in each eye 5 minutes apart
Measure anisocoria 45 minutes to 1 hour
Postcocaine anisocoria >1mm is diagnostic of Horner syndrome on the side of the smaller pupil
Mechanism of cocaine
Blocks reuptake of norepinephrine released at sympathetic nerve terminals in the eye causing pupillary dilation, eyelid retraction, conjunctival blanching
Portion of a CN that travels within brainstem
Fasicle
What structures lie adjacent to the fascicles of CN III?
Substantia nigra + red nucleus -(Benedikt syndrome)
superior cerebellar peduncle - (Nothnagel) (superior cerebellar peduncle + red nucleus = Claude syndrome)
cerebral peduncle - (Weber syndrome)
corticospinal tracts
Nothnagel syndrome
CN III + superior cerebellar peduncle
Benedikt syndrome lesion
CNIII + red nucleus + substantia nigra
Weber syndrome
CNIII + cerebral peduncle
Claude syndrome
CNIII + superior cerebellar peduncle + red nucleus
CN IV courses below the
Pineal gland
Where does the CN VI nucleus lie?
Below the 4th ventricle and it’s fasicles pass medial to the superior olivary nucleus
Passes medial to the superior olivary nucleus
Fasicles of CN VI
M/c hereditary optic neuropathy
Dominant optic atrophy
M/c mutation in DOA
OPA1 gene on chromosome 3
Optic neuropathy with cardiac conduction defects
Leber hereditary optic neuropathy pre-excitation syndrome
Eye movement dysfunction in congenital ocular motor apraxia
Horizontal saccades
Increased latency and intermittent failure of initiation
Nerve that courses along surface of clivus
Abducens nerve
Underneath the petroclinoid (gruber) ligament to enter the dorello canal
Structure in brainstem responsible for excitatory burst in horizontal movement
Paramedian Pontine Reticular Formation
Located adjacent to the CN VII nucleus
Neural integrator for horizontal movement
Nucleus prepositus hypoglossi (NPH)
Excitatory burst cells and neural integrator for vertical/torsional movement
Rostral interstitial nucleus of the medial longitudinal fasiculus
(riMFL)
Interstitial nucleus of Cajal (INC)
CN IV palsy with lesion at predescussation fasicular or nuclear level
Ipsilateral RAPD without vision or color loss (decussation of nasal pupillary fibers)
Contralateral Horner’s 2/2 proximity of sympathetic fibers
Assessment that may best distinguish between a retinopathy and optic neuropathy.
Electrophysiology
Electroretinogram (ERG) and visual evoked potentials (VEP) can be very specific in localizing etiology to retina or optic nerve
Electrophysiology consistent with a retinopathy compared to an optic neuropathy
Abnormal ERG and VEP would be seen in a retinopathy whereas a normal ERG and abnormal VEP is highly suggestive of an optic neuropathy.
Within the cavernous sinus, what cranial nerve do the sympathetic fibers run with?
CN VI
Sympathetic fibers destined for the dilator muscles leave the carotid in conjunction with CN VI for a few millimeters. Further anteriorly in the cavernous sinus, the sympathetic fibers join the nasociliary branch of CN V1. The sympathetic fibers do not join any of the other cranial nerves within the cavernous sinus.
When does optic neuropathy occur after radiation therapy?
on average 18 months and produces subacute optic neuropathy
Where are saccadic eye movements generated?
Frontal eye fields located in the frontal lobe, one on each side. Each frontal eye field initiates saccades to the contralateral side.
Where are smooth pursuit eye movements generated?
Medial temporal (MT) visual area (V5) in the parietal lobe. Each generates smooth pursuit eye movements to the ipsilateral side.
Name for inability to initiate saccades
ocular motor apraxia - results from injury to the frontal lobe or may occur in childhood conditions
Condition visual evoked potential (VEP) testing is most helpful in confirming
Demyelinating optic neuropathy. Measures electrical signals over the occipital cortex produced in response to verbal stimulus. Shows increased latency in demyelination
Formed hallucinations + insomnia + excessive daytime somnolence. Where is the lesion?
MIDBRAIN - constant hallucinations frequently associated with inverted sleep-wake cycle (peduncular hallucinosis)
Pallinopsia
illusion of persistent afterimages that can be a/w visual hallucinations
Region of brain that produces olfactory and gustatory hallucinations, with complex formed hallucinations in the ipsilateral or contralateral field
temporal lobe
Lesion to this region of brain commonly cause unformed hallucinations, geometric colors or patterns
Occipital lobe
Slowly progressing facial palsies strongly suggest this. Preferred imaging test?
MRI brain. Brainstem mass.