Neurogenetics Flashcards
How does Down syndrome cause intellectual disability?
miR-155 inhibition of SNX27
Mutations in FMR1 cause
fragile X syndrome (CGG trinucleotide repeat)
Repeats in the 5’ UTR of the _ gene affect expression leading to fragile X
FMR1
ALS has a _ inheritance
Autosomal dominant
Nonsyndromic hearing loss has a _ inheritance
Autosomal recessive
Leach-Nyhan Syndrome has a _ inheritance
X linked recessive
_ gene is mutated in Lesch-Nyhan
HPRT1
Rhett syndrome is due to mutations in
MECP2 gene on chromosome X
Rhett syndrome has a _ inheritance
X linked dominant
Leigh syndrome is cause by mutations in _
MT-ATP6
Some gene variants influence susceptibility to brain disease but are not _
100% penetrant
_ gives rise to the neural plate
Dorsal ectoderm
_ give rise to the neurons and glia that form the CNS
Neuroepithelial cells
_ arises from the neural crest
Melanocytes, Schwann cells, neurons, head mesoderm
Neurogenic Placodes contribute to the
PNS and CNS
_ gives rise to neurons
Neurogenic Placode
The olfactory Placode gives rise to_
olfactory epithelium and GnRH neurons
The forebrain (prosencephalon) forms
Lateral ventricles and third ventricle
The midbrain (mesencephalon) forms _
Cerebral aqueduct
The hindbrain (rhombencephalon) forms
Fourth ventricle
The prosencephalon becomes
Telencephalon (lateral ventricle)
Diencephalon (third ventricle)
The mesencephalon becomes the
Cerebral aqueduct
The rhombencephalon becomes
Metencephalon and myelencephalon
The alar plate gives rise to
Primary sensory structures
The basal plate gives rise to
Primary motor structures
Neuroblasts in the CNS undergo _ migration toward the pial surface
Radial
In the cerebellum, granule cells migrate
From an external layer near pial surface to a deeper layer (explains striking motor achievement in first year)
Somatosensory neurons begin as _ cells but change into _
Bipolar, pseudounipolar
The only flexure remaining at birth
Mesencephalic
Caudal neural tube closure defect
Spina bifida
Rostrum neural tube closure failure
Anencephaly
Encephalocele
Partial failure of rostral neural tube closure
Causes of lissencephaly (smooth brain)
Genetic: PAFAH1B1 and DCX
Viral infection during pregnancy
Chiari malformations
Caused by genetics and malnutrition
Dandy-Walker malformation
Vermis of cerebellum does not form due to chromosomal abnormalities
New neurons are produced in
The olfactory epithelium
Neurons migrate from _ to the _ and from _ to the _ of the hippocampus
Subventricular zone
Olfactory bulb
Subgranular zone
Dentate gyrus
Neuronal progenitors replace
Neurons
Glial progenitors replace
astrocytes and oligodendrocytes
Factors blocking neuroregeneration
Glial scar
CSPGs
_ are being tested to create axon regeneration
olfactory ensheathing cells
Telencephalon consists of
Cerebral cortex and basal ganglia
Diencephalon consists of
Epithalmus, thalamus, subthalmus, and hypothalamus
Mesencephalon consists of
Tectum and tegmentum
Metencephalon consists of
Cerebellum and pons
Myelencephalon consists of
Medulla
The Diencephalon forms the walls of the
Third ventricle
What connects the two thalamus?
The intrathalamic adhesion
What seperates the basal ganglia (telencephalon) from the thalamus (diencephalon)?
Internal capsule (collection of axons)
The frontal lobe is seperated from the parietal lobe by
The central sulcus
The frontal lob is separated from the temporal lobe by the
Lateral fissure
The parietal lobe is partially separated from the temporal lobe by
Lateral fissure
The parietal lobe is separated from the occipital lobe by the
Parietal-occipital fissure
The two cerebral hemispheres are separated by the
Longitudinal fissure
Major fiber bundles
Corpus callosum
Cingulum (connects cingulate gyrus with entorhinal cortex)
Fornix (connects the hippocampus with the mammillary bodies of the hypothalamus)
The anterior two thirds of the spinal cord is supplied by
The anterior spinal artery
The posterior 1/3 of the spinal cord is supplied by
The posterior spinal artery
What are watershed areas?
Borders between cerebral arteries vulnerable to stokes because of reduces blood supply
Ischemic stroke is due to
Blockage of the arteries
Hemorrhagic stroke is due to
Rupture of the arteries
What is the blood brain barrier?
Tight junctions between endothelial cells that form a barrier
How do infectious agents get into the brain?
Hijack transporters
Damage the blood brain barrier
Infection of the meninges
Travel along olfactory and trigeminal nerves
Which cranial nerve is part of the CNS?
CN II
Why can vision be compromised in MS?
The optic nerve is myelinated by oligodendrocytes because it is part of the CNS
Cranial meninges layers
Dura matter- tough, thick external fibrous layer
Arachnoid mater- thin intermediate layer
Pia mater- delicate internal vascular layer
The dura mater is divided into the _ layer and _ layer
Periosteal and meningeal
Pachymeninx
Dura mater
Leptomeninx
Arachnoid and Pia mater
Arachnoid mater
Agains meningeal dura
Arachnoid trabeculae
Arachnoid granulations (transverse the meningeal dura to enter the rural venous sinuses)
Pia mater
Adherent to the brain
Highly vascularized
Potential dural spaces
epidural- between cranium and Periosteal dura
Subdural- between dura and arachnoid
Subpail/intracerebral- deep to Pia, within neural parenchyma
Real spaces
Subarachnoid
Contains CSF, arteries (Circle of Willis) and veins
Within subarachnoid space
_ forms the dural partitions
The meningeal dura
The flax cerebri separates
Right and left cerebral hemispheres
The tentorium cerebelli seperates
Occipital and superior aspect of cerebellum
The flax cerebelli seperates
Right and left hemispheres of cerebellum
The diaphragma sellae has an opening for
The infundibulum
Dural venous sinuses drain
Internal and external veins and CSF into IJVs
Midline sinuses
Superior Sagittal
Inferior sagittal
Straight
Occipital
Confluence
Paired sinuses
Transverse
Sigmoid
Superior petrosal
Inferior petrosal
Cavernous
What courses through the cavernous sinus?
CN III, IV, V1, V2, VI
Internal carotid arteries
Supratentorial Innervation of the dura
V1, V2, V3
Intratentoral innervation of the dura
C2 & C3 carried by CN X and CN XII
Arteries of the dura
Middle meningeal (from maxillary arteries)
Intracranial cerebral arteries (within subarachnoid space)
Small meningeal arteries (from external carotid branches)
Epidural intracranial hemorrhage source
Usually arterial, middle meningeal
Hematoma between cranium and dura mater
Subdural hem orange
Venous, usually cerebral vein/dural sinus
Hematoma between dura and arachnoid mater
Subarachnoid and intracerebral hemmorage
arterial, usually cerebral
Hematoma within subarachnoid space or neural parenchyma
CSF flow
Lateral ventricles
Interventricular foramen
Third ventricle
Cerebral aqueduct
Fourth ventricle
Lateral and medial apertures, central canal of spinal cord
Subarachnoid space
Arachnoid granulationas
Superior sagittal sinus
Bipolar neurons are found in
Vestibular ganglion, olfactory epithelium, retina
Pseudounipolar neurons are found
DRG and trigeminal ganglion
Microglia
Mesodermal origin
Macrophages of CNS
Respond to injury or infection
Ependymal cells
Line the ventricles, help form CSF
Radial glia are found
In the cerebral cortex
Bergmann glia are found
In the cerebellum
Astrocytes
Derived from neural tube
Take up excess potassium or neurotransmitters
Regulate BBB
Respond to injury
Express GFAP
The BBB is comprised of
Endothelial cells forming tight junctions
Foot processes of astrocytes
Pericytes
Oligodendroglia
Derived from neural tube
Mylenation in CNS
Satellite cells
Surround neuronal cell bodies in peripheral ganglia
_ is continuous with the dura mater
The epineurium
Chromatolysis is a hallmark of
Retrograde neuronal degeneration
Neuroregeneration can occur in the
PNS
What acts a a capacitor for cells
The lipid bilayer of the cell membrane (stores charge of opposite sign on two surfaces)
How is the diffusion potential of an ion calculated
The Nernst equation (allows us to estimate changes in the membrane potential based on potassium)
What prevents ions from moving down concentration gradient in cells to establish equilibrium?
Na/K ATPase establishes resting membrane potential
Why is the membrane potential negative?
Cells are more permeable to K (50x more permeable) than Na at rest
Which equation takes into account the permeability of ions?
Goldman-Hodgkin-Katz equation
The membrane potential of the cell becomes more negative as
K leaves
Resting membrane potential is essential for the generation of
Action potentials
Depolarization
The membrane potential becomes less negative
Hyperpolorization
The membrane potential becomes more negative
Reduced ATP levels and the inhibition of Na-K ATPS cause
Depolarization (due to diffusion leading to equilibrium)
An action potential requires
Resting membrane potential (controlled by Na-K ATPase)
Ion channels
Ligand gated ion channels can be opened by
Intracellular ligands
Extracellular neurotransmitters
Voltage gated channels are opened by
Depolarization
In the inactivation state, the channel cannot be opened until
It moves to closed state
The voltage sensor of voltage gated calcium channels is composed of
4 positively charges arganine residues on S4
Na channel inactivation gate
Swing shut
K channel inactivation
Ball and chain
What channels are sufficient to generate an action potential?
Na channels
The depolarization of Na channels ultimately leads to
The opening of virtually all Na channels
Channels move from
Open to inactivation to closed
Slow sodium channel inaction contributes to
Epilepsy
Threshold
The membrane potential above which an action potential is gen
K channels open slower than Na channels leading to
Hyperpolorization
Axon potential is _ down the axon
Propagated
Myelin reduces _ to increase conduction velocity
Capacitance
What increases conduction velocity?
Myelin (decreases capacitance)
Diameter (increased=decreased resistance)
How are neurotransmitters loaded?
Proton pump
Vesicular neurotransmitter transporter
Anionic transmitters
SNARE proteins
Mediate fusion of vesicle
Munc18-1
Assembles SNARE complex
Synaptotagmin
Senses Ca++ and prevents spontaneous fusion
When Ca++ binds promotes fusion
Excitatory neurotransmitters
Acetylcholamin and glutamate
Inhibitory neurotransmitters
GABA
Glycine
Organophosphate poisoning
S
L
U
D
G
E
M
Fast _ transmission uses ligand-gated ion channels
Ionotropic
Slow _ transmission uses receptors coupled to G proteins
Metabotropic
Two classes of neurotransmitter receptors
Ionotropic and metabotropic
Group I metabotrobic glutamate receptors
Potentiate NMDAR-induced Ca++ influx (worsen conditions like ALS)
Group II and Group III
Reduce NMDAR induced Ca++ influx
Termination of neurotransmitter effects
reuptake, glial cell transporters
Diffusion, enzymatic degradation
excitatory post-synaptic potential
Na+ influx causes membrane depolarization
Inhibitory post synaptic potential
Cl- influx leads to Hyperpolorization
The periorbita is continuous with the
Periosteal layer of the dura
The periorbita forms the
Orbital septa
The lateral walls of the orbit are
Perpendicular
The medial walls of the orbit are
Parallel
Fovea centralis
Area of most acute vision
Densely populated with cones
Can we see at the optic disk?
No
The visual axis is offset _ from the orbital axis
27.5 degrees
Relationship of sinuses to eye
Medial wall-ethmoid sinuses
Inferior wall- maxillary sinuses
THe medial wall of the orbit is known as
Lamina papyracea “paper thin wall
Most susceptible to fracture
Blow out fracture
Fractures of the walls of orbit due to translation of the globe posterior leading to an increase in pressure causing fracture
3 layers of the globe
Fibrous layer
Vascular layer
Neural layer
The fibrous layer is divided into
Sclera post 5/6
Cornea ant. 1/6
The vascular layer of the globe is composed of
Choroid post 5/6
Ciliary body
Iris
The neural layer is composed of
Retina (has both visual and non-visual parts)
Sclera
Maintains shape
Provides attachment for extra-ocular muscles
Covered by conjunctiva (palpebral, bulbar)
Between the palpebral and bulbar is the the conjunctival sac
Cornea
Most significant refractive media of eye
Avascular (fed by aqueous humor and lacrimal fluid)
Highly sensitive (greatest density of nerve endings CN V1)
Choroid (vascular layer)
Pigmented layer between sclera and retina
Fed by ciliary branches of opthalmic artery
Vascular supply to outermost layer of retina (rods and cones)
Ciliary body
Ciliary muscle (sphincter surrounding lens) contraction releases tension (close vision) and relaxation increases tension (far vision)
ciliary processes (produces aqueous humor-carries nutrients and oxygen)
Aqueous humor
Maintains shape of the eye globe
Maintains proper distance between refractive surface (cornea-lens-retina)
Nutrition source for avascular tissues of the eye (lens and cornea)
Controls IOP
Accommodation
Lens thickens
Pupil constricts
Eyes converge
The ciliary body allows for
Lens accommodation
Iris
Sphincter pupillae
Dilator pupillae
Sphincter pupillae
Parasympathetic fibers from CN III narrows aperture of pupil
Dilator pupillae
Sympathic innervation from internal carotid plexus
Widens aperture of pupil
Retina
Optic part- outer layer is pigmented epithelium, inner layer contains light-receptive neurons
Ciliary part, radial part (non visual)
Transition zone between visual zone and non visual zone is the ora serrata
Transition zone between visual zone and non visual zone of the retina is the
ora serrata
The anterior segment is divided into
Anterior and posterior chambers (divided by iris)
The lens and the ciliary body separates the
Anterior segment from the posterior segment
The anterior chamber is full of
Aqueous humor
The posterior segment is filled with
vitreous humor
Central retinal artery
Supplies all retinal neurons except rods and cones
Subject to increases in CSF pressure
Located deep to dura mater
No collateral anastomoses (blindness a concern)
Ciliary branches
Supply choroid vascular layer
Blood supplies rods and cones
Venous drainage of the eye
Superior and inferior ophthalmic vein
Infection of the superficial face can drain into the Supra-orbital vein and infra-orbital vein drain into the cavernous sinus and may lead to serous infection
The frontal nerve gives rise to
Supratrochlear (medial)
Supraorbital (lateral
The nasociliary nerve branches into
Anterior and posterior ethmoid
The ciliary ganglion
Nasocilliary branch (sensory)
Inferior division of occulomotor (parasympathetic)
Sympathetic root from internal carotid plexus
Long and short ciliary branches
Where is the ganglion cell of the retinal located
the diencephalon (thalamus)
What is the pathway of visual information?
The retina is part of the
Eye and the brain (diencephalon)
Light enters the eye via the pupil and is focused on the _ by the _
Retina
Lens
The initial processing of visual information occurs in
The retina
_ contains the highest concentration of cones where the finest visual discrimination occurs
Fovea (within the macula)
Where do the axons of the ganglion cell exit the retina?
The optic disk
What artery supplies the retina?
The central retinal artery (travels with optic nerve)
What are the layers of the retina the photons travel though?
Ganglion cell axons
Ganglion cell layer
Inner plexiform layer
Inner nuclear layer
Outer plexiform layer
Out nuclear layer
photoreceptor layer
Retinal pigmented epithelium
Light travels from
Ganglion cell axons to photoreceptor layer
Information travels from
The photoreceptor layer to the ganglion cell axons
Photoreceptors synapse with bipolar cells and horizontal cells in the _ layer
Outer plexiform layer
Bipolar cells synapse with amacrine cells and ganglion cells in the _ layer
Inner plexiform
Ganglion cell axons form
Optic nerve, chasm, tract and the brachium of the superior colliculus (synapse of Retino-recipient nuclei)
Rods
Specialized for low light environment
Outside of fovea
Responsible for peripheral vision
Cones
Color detection and fine visual discrimination
Require lots of light
In the fovea
Rods have _
Rhodopsin
the nucleus of the photoreceptors are in the
Outer nuclear layer
The outer segments of the photoreceptor cells are in the
Photoreceptor layer
The synaptic body of the photoreceptor cells is in
The outer plexiform layer
How many types of cones and rods are there?
3 cone
1 rod
Red cones
Long
Green cones
Medium
Blue cones
Short
Why is color blindness more common in men?
Opsins are on X chromosome
Protanopia
Loss of L cones (no red vision)
Deuteranopia
Loss of M cones (loss of green vision)
Tritanopia
Loss of S cones (loss of blue vision)
How do we sharpen edges
Specific response to input from a portion of photoreceptor:
Light on center only
Light on surround only
What cells perform lateral inhibition
Horizontal and amacrine cells
Whether the lesion in the the optic tract, chiasm, or nerve is important because
Each location results in different visual defects
The hypothalamus and the third ventricle are _ to the optic chiasm
Dorsal
The infundibulum is _ to the optic chiasm
Ventral
Retinal ganglion cells project to
Suprachiasmatic nucleus- circadian pacemaker (photosensitive ganglion)
Pretectal nuclei- pupillary response to light
Superior colliculus- reflexive eye and head movements in response to visual stimuli (mostly rods)
Lateral geniculate nucleus of the thalamus-fine visual discrimination (mostly cones)
The superchiasmatic nucleus receives input from
Photosensitive ganglion cells which have their own pigment (melanopsin)
Where is melanopsin?
Photosensitive ganglion cells traveling to the superchiasmatic nucleus
The pretectal area receives direct retinal input and projects to
The accessory oculomotor nucleus
The projection from the retinal ganglion cells to the pretectal area is the _ limb
Afferent
The projection from the accessory motor nucleus to the ciliary ganglion via CN III is part of the _ limb
Efferent
The superior colliculus of the midbrain receives direct retinal input via
The brachium of the superior colliculus
The superior colliculus receives input from
Visual cerebral cortex
Pretectal nuclei
The superior colliculus is involved in
Visual reflexes
The superior colliculus projects to
The spinal cord via the tectospinal tract
Pulvinar of the thalamus
The brachium of the superior colliculus carries information from
The retinal ganglion cells to the superior colliculus
The lateral gesticulate nucleus receives input from the retina via
The optic tract
The optic radiations are a collection of myelinated axons that originate _ and terminate _
In the lateral geniculate nucleus
Primary visual cortex
Optic radiations are _ organized
Retinotopically
The primary visual cortex is found
Along banks of calcarine fissure
The primary visual cortex is supplied by
Calcarine artery and branches of middle cerebral artery
Which axons cross the optic chiasm to the contralateral side
Ganglion cell axons originating from the nasal retina
Which ganglion cell axons remain ipsilateral
Ganglion cell axons from the temporal retina
Axons from the retinal ganglion cells continue after the optic chiasm to form
The optic nerve
Dorsal visual stream
Parietal lobe
Where is it
Ventral visual stream
Temporal lobe
What is it
Object recognition requires
Parahippocampal gyrus
Face recognition requires
Occipitotemporal gyrus
The occulomotor nucleus complex is located in the
Rostral midbrain
The trochlear nucleus is located
In the caudal midbrain
The abducens nucleus is located in the
Caudal pons
Lesion of CN III
Ipsilateral loss whether the nucleus or nerve is affected
Loss of control of eye movement muscles
Loss of control of pupil response to light
The trochlear nerve crosses so damage to the left trochlear nucleus causes deficits on the
Opposite side (damage to the nerve causes ipsilateral loss)
A lesion at the decussation of the trochlear nerve will affect both eyes
Loss of the control of the superior oblique will result in an eye which is positioned
Upwards and outwards when looking forward
A lesion of the abducens nerve will result in a _ loss
Ipsilateral
Brain stem gaze centers project to oculomotor, trochlear, and abducens nuclei and
Coordinate eye movement
Brain gaze centers
Midbrain- riMLF, INC
Pons- PPRF, RIP
Medulla- MVN, NPH
Conditions associated with damage to gaze centers
PSP, NPC, SCA2, MSA, OMAS
Vertical gaze is controlled by
RiMLF an INC of the dorsal midbrain (important for upward eye movements)
Lateral gaze is controlled by
PPFR (located in dorsal pons)
Projects to abducens nucleus which has a projection to oculomotor nucleus allowing PPRF to control lateral gaze
Vestibular nuclei regulate eye movement in response to
Head movement allowing eyes to stay fixated on the object even when the head is turning
The vestibular nuclei project to the abducens nucleus with
MLF
Eye fields within cerebral cortex control eye movements via
Projections to the brain stem gaze centers
How is the afferent system assessed?
Phychophysical tests-Visual acuity, color vision, contrast sensitivity, stereo-acuity, visual field
Imaging- OCT, MRI/CT
Electrophysiology
Assessment of visual association
Screening tools- Montreal cognitive assessment, Boston cookie theft picture
Detailed neuro-psychological profile
Before starting the eye exam you need to
Take a thorough history
Ocular exam
Visual acuity
confrontation visual fields
Extraocular motility and alignment
Pupils
Adnexa
Anterior segment
IOP
Posterior segment
OD
Right eye
OS
Left eye
Sc
Without correction
Cc
With correction
Ph
Pinhole
CF
Counting fingers
HM
Hand motion
LP
Light perception
NLP
No light perception
If someone can typically see something at 40 feet but you must stand 20 feet away to see
20/40
How to check acuity in children
CSM (corneal reflex)
Allen pictures/lea symbols
Tumbling E’s
HOTV chart
Refractive error
Shape of eye keeps image from focusing clearly on the retina
Most common type of vision problem
Treated with glasses
Myopia
Nearsightedness
Distance objects look too blurry
Eye too long, image focused in front of retina
Hyperopia
Farsightedness
Near objects blurry
Eye to short, image focused behind retina
Astigmatism
Distant and mid-range objects poured or distorted
Irregular shape to the cornea
Presbyopia
Middle/older adults unable to focus on near field objects
Loss of ability of lens to change focus with age
Checking visual fields
Confrontation
Tangent screen
Goldmann- test far out into field
Automated- normal database for comparison but less personalizable
Extraocular motility and alignment is used to asses for
Tropic and Phoria
Ductions are _ movements
Monocular
Versions are _ movements
Binocular, simultaneous, conjugate movements in same direction
Vergences are _ movements
Binocular, simultaneous, disconjugate or disjunctive movements
How do you test for the relative afferent pupillary defect? (Pupils dilate when light is shined)
Swinging flashlight test
Anisocoria
Abnormal pupil size
Mydriatic pupil indicates
Loss of parasympathetic input to the iris sphincter
A mitotic pupil could be due to
Loss of sympathetic input to the iris dilator muscle
Normal position of the eye lids
Lower- at the limbus
Upper-2mm below limbus
Should you see fluorescein staining on the cornea?
No
Angle of the eye
Sit of aqueous drainage- evaluate using gonioscopy
Opacity of the lens is
A cataract (must use slit lamp exam to determine location)
Gold standard to check IOP
Goldmann applanation
Do no check eye pressure if
You suspect a ruptured globe
Direct opthalmoscope
Upright image field up to equator in dilated pupil
indirect opthalmoscope
Real, inverted image, binocular, up to ora serrata
Normal cup to disc ration
0.3
If larger or asymmetric suspect glaucoma
Ocular exam is gold standard for all physical exams including looking at
Disc and macula
Fluorescein staining is the easiest way to look for
Corneal abrasions
Dilation is safe if you
Check AC depth (often only way yo look at posterior segment)
Steps of pupil exam
Observe in room light, bright light, and dark light
Test light reflex by having patient in dark room look at the distance at a large target to avoid accommodation
Swinging flashlight test to asses for asymmetry in the afferent pathways
If sluggish pupil response, test near response by having patient focus on close-up target
RAPD
Swinging flashlight
One pupil is slow to constrict compared to the other
A relative afferent pupillary defect usually means the patient has
Ipsilateral optic nerve
Large retinal lesion
NOT cataract, refractive error, cornea
Optic neurophathy causes
Loss of vision
Relative afferent pupillary defect
Optic disc edema, atrophy, cupping
Optic disc may also appear normal
Two most common acute optic neuropathies
Optic neuritis
Ischemic optic neuropathy
Typical case of optic neuritis
You patient
Acute unilateral loss of vision
Ipsilateral relative afferent pupillary defect
Central field defect or color vision loss
Pain/discomfort with eye movement
Disc edema
Patients improve to normal in 3-12 months
Treatment of optic neuritis
IV steroids (NOT oral steroids unless given in super high doses)
Strong association with MS (need MRI)
Features of typical ischemic optic neuropathy
Older patients
Arthritic and non-arteretic forms
Actule, unilateral loss of vision
Ipsilateral relative afferent pupil defect
Swollen optic nerve
Little visual recovery
Usually painless
NO association with MS
Treatment of ischemic optic neuropathy
No treatment but help control risk factors
Giant cell arthritis
Elderly patients
Headache
Scalp tenderness
Jaw claudication
Fever, malaise
Associated with poly Alia rheumatic a
Visual loss
*EMERGENCY
-Stat ESR, CRP, CBC
-Immediately start high dose steroids
-perform temporal artery biopsy
Disc pallor causes
Old optic neuritis
Chronic papilledema
Compressive optic nerve lesion
Advanced glaucoma
Disc elevation or swelling
Papilledema
Pseudopapilledema
Papilitis due to optic neuritis, inflammatory optic neuropathy, or infectious optic neuropathy
Ischemic optic neuropathy
Papilledema symptoms
Headache
Minimal vision problems early
Profound vision loss over time
Papilledema characteristics
Blurred swollen margin
Disc hypermedia
Peripapillary hemmorages
Loss of spontaneous venous pulsations
Usually bilateral, can be asymmetric
Enlarged blind spots
Causes of papilledema
Serve HTN
Brain tumor
Venous sinus thrombosis
Intracranial hemorrhage
Meningitis
Idiopathic intracranial hypertension
Idiopathic intracranial HTN
Diagnosis of exclusion
Common in young obese females
Normal neuroimaging
Elevated opening pressure on lumbar puncture with normal CSF analysis
Idiopathic intracranial HTN treatment
Acetazolamide (if this fails surgical treatment)
Pseudopapilledema
Elevated nerves, but no edema
Vessels sharp and distict
Spontaneous venous pulsations
Crowded disc
Optic nerve drusen
Anisocoria
Unequal pupils efferent pathway
In Anisocoria which pupil is abnormal
In bright light, the larger pupil is abnormal due to damage to the parasympathetic fibers or circular sphincter muscle
Anisocoria withdriasis (adie tonic pupil)
Damage of the parasympathetic ciliary ganglion
Benign and idiopathic
Dilute pilocarpine super sensitivity
Light-near dissociation
Irregular pupil
Vermiform movement
Other causes of Anisocoria with mydriasis
Cranial nerve III palsy (not likely if isolated)
pharmacologic
Iris sphincter trauma/damage
In dim light a smaller/Miotic pupil is abnormal due to
Sympathetic fibers or dilator muscle
Anisocoria with mitosis is commonly caused by
Horner syndrome
sympathetic pathway in Horner syndrome
Central neuron
Preganglionic
Postganglionic
Testing for Horner syndrome
Topical cocaine test confirms
Topical apraclonide test confirms
Hydroxyamphetamine localizes
Horners syndrome acquired causes
Carotid dissection
Carotid aneurysm
Apical lung tumor
Neuroblastoma
Lesions of the retina and optic nerve produce VF defects
Only on ipsilateral eye
Pre-chiasmatic lesion
Affects vision in one eye only
Visual field patterns of optic neuropathy
Optic nerve VF defects
Papillomacular bundle
enlarged blind spot nerve fiber layer defects (disc edema)
Nerve fiber layer defects
Junctional visual field loss
Only complains of vision loss OD
Bitemporal hemiopsia
Look for chiasmal lesion
Bitemportal visual field loss
Lesions of chiasm (pituitary adenoma)
Requires neuroimaging studies
Binasal heteronymous hemianopia
Lateral chiasm or bilateral optic nerve
Bilateral internal carotid artery aneurysms, hardened atherosclerotic ICAs, hydrocephalus/enlarged 3rd ventricle
More commonly caused by glaucoma, optic disk drusen, chronic raised intracranial pressure
Post chiasmal lesions cause
Homonymous hemianopsia
The LGN has _ blood supply and _
Dual blood supply
Ocular dominance columns
LGN
Congruity means
Same shape and size
The more anterior the lesion the more _ and the more posterior lesion the more _
Incongruous
Congruous
Triad of optic tract lesions
Homonymous hemiaopia
Optic atrophy
contralateral RAPD
A unilateral Homonymous hemianopsia does NOT decrease
Acuity (if bilateral, acuity will decrease)
Temporal lobe lesions
Inferior radiations
Superior Homonymous hemianopsia “pie in the sky”
Incongruous
Parietal lesions
Inferior defects “pie on the floor”
Occipital lobe lesions
Very congruous
Macular sparing
May spare or involve temporal crescent
Neurologically isolated
Damage to the where pathway
Dorsal dream
Vision for action
Visio-special disorders
Neglect is seen in
Parietal lobe lesions
Bilateral parietal damage (balint syndrome)
Simultanagnosia
Optic ataxia
Oculomotor apraxia
Damage to what pathway
Ventral (temporal stream)
Discrimination of shapes/objects
Visio-perceptual disorders
Akinetopsia
Can’t see moving objects due to bilateral lesion in temporal lobe
Prosopagnosia
Inability to recognize familiar faces (temporal)
Topographagnosia
Inability to navigate familiar landmarks (temporal)
Alexia without a graphic
Inability to read
Ability to write preserves (temporal lesion)
Anosognosia
Deficient of self awareness
Denial of blindness
Alexia with a graphic
Parietal lobe lesion
Inability to read and write
Why do the eyes move?
Best visual acuity
Prevent retinal adaptation
Eye movement categories
Visual fixation
Smooth pursuit
Saccades
Vestibular
Optokinetic
Vergence
The pursuit system
Maintains stability of object on fovea while it moves
Initiation from ipsilateral parietal lobe
Saccadic system
Bring stationary objects in line with fovea
Contralateral frontal lobe/frontal eye fields
Horizontal gaze center
PPRF
Vertical gaze center
RiMLF and INC
The vestibulo ocular system is necessary to
Maintain image/object on fovea while head moves
VOR cancelation
Follow moving object as head moves
Conjugate gaze abnormalities
Gaze palsie that restricts movement of both eyes
Vertical gaze
Midbrain (3rd nerve)
INC
RiMLF
Horizontal gaze
Pons (6th nerve)
PPRF
Internuclear opthalmoplegia
Lesion of MLF
ipsilateral adduction defect
Supranuclear disorder
Dorsal midbrain syndrome
Vertical gaze policy
Light/near disassociation
Convergence-retraction nystagmus
Lid retraction
Pineal tumor
Double vision
If still present when one eye is closed it is NOT ocular misalignment
Lesion of CN III
Ptosis
Eye down and out
Parasympathetic pupillomotor-Susceptible to compression
Central somatomotor fibers- susceptible to ischemia
A pupil involved third nerve palsy is _ until proven otherwise
Posterior communicating artery aneurysm
Third nerve palsy is caused by
DM, HTN
PCommA aneurysm (pupil involving)
Trauma
Brain neoplasm
Locations for CN III palsy’s
Fascicle
Nerve nucleus
Edge of tentorium cerebelli
Cavernous sinus
Subarachnoid space
Orbital apex
Trochlear nerve palsy
Vertical diploplia
May develop contralateral head tilt
Causes of abducens nerve palsy
Trauma
Commonly congenital in children
Location of 4th nerve palsy
Nuclear fascicular, subarachnoid space, cavernous sinus, orbit
Abducens nerve palsy
Horizontal diplopia and esotropia
Causes of 6th cranial nerve palsy
Idiopathic
Trauma
Ischemic
Locations of 6th nerve palsy
Nucleus
Fascicles
Subarachnoid space
Orbit
Isolated
5th cranial nerve lesion
Decreased corneal sensation
Hermetic infections
Neurotrophic corneal ulcers
7th cranial nerve palsy
Eyelid closure
Exposure keraopathy
Thyroid eye disease
Commonly affects IR and MR
Eyelid retraction, proptosis, chemosis
Treat with steroids, decompression surgery
Myasthenia gravis
Ptosis and diplopia
Nystagmus
Spontaneous back and forth movement
Trabeculotomy
Cloudy cornea
POAG
Goniotomy
Clear cornea
What is the primary site of resistance in POAG
Trabecular meshwork
PACG presentation
Fixed, mid-dilated pupil
Ciliary flush
Corneal edema
Narrow or closed anterior chamber angle
PACG management
Laser iridotomy
Suspect glaucoma if
CDR >0.5
CDR asymmetry >0.3
ISNT
Glaucoma pattern field loss obeys
Horizontal meridian
Most common cause of irreversible blindness
Glaucoma
Most common cause of reversible blindness and visual impairment
Cataract
The lens of the eye is suspended by
Zonules
Common cause of medication induced cataracts
Corticosteroids
Posterior sub-capsular cataract causes
Diabetes mellitus
Corticosteroids
Amblyopia
Loss of visual acuity not correctable by glasses in otherwise heathy eye
Treatable before 10 but ideally begin before 5
Brain problem
Types of amblyopia
Refractive
Strabistic
Form-deprivation
Occlusion
Refractive amblyopia
Difference in refractive state between 2 eyes
Commonly asymmetric hyperopia
Treatment with glasses and patch
Strabismic amblyopia
Eye is misaligned
Diplopia in adults or suppression in children
Treatment- glasses, patch
Form-deprivation amblyopia
Light not able to reach retina for transduction to cortex
Medial opacity (cataract, corneal scar, hyphema, vitreous hemmorage), ptosis, capillary hemangioma
Occlusion amblyopia
Iatrogenic from over-patching normal eye
The cover test can be used to detect
Strabismus
Comitant strabismus
Misalignment equal in all gaze positions
Incomitant strabismus
Degree of misalignment varies with eye position
3rd, 4th, 6th CN palsy
Also may be due to trauma
Heterophobia
Latent tendency for the eyes to deviate
Manifests only when binocular vision is interrupted
Esodeviation
Most common ocular misalignment
Pseudoesotopia
No misalignment on cover test
Re-examine in 3 months
Infantile esotropia
Within first 6 months
Large angle
Cross fixation
Treat surgically, sometimes glasses needed
Exodeviations
Latent or manifest divergence
Intermittent exotropia is induced by
Daydreaming, fatigue, illness, visual distraction
Vertical strabismus
Vertical misalignment
Commonly caused by superior oblique palsy
Can be acquired due to trauma
Torticollis
Leuocoria
White pupil
Caused by: cataract, retinal detachment, rentipathy of prematurity, retinal vascular abnormality, intraocular tumor
Retinoblastoma
Associated with chromosome 13
Retinopathy of prematurity
Abnormal retinal blood vessels
Treatment: laser ablation, anti-VEGF injection
The choroid is fed by
Ciliary branches of ophthalmic which supply photoreceptors
When the ciliary muscle contracts
Tension on the zonules decreases and the lens becomes more spherical allowing for close vision
When the ciliary muscle relaxes
Tension on zonule increases and the lens becomes thinner allowing for far away vision
Sphincter pupillae is innervated by
Parasympathetics from CN III
Dilator pupillae is innervated by
Sympathetics from internal carotid plexus
Optic neurons receive blood supply from
Central retinal
What seperates the anterior and posterior segments
Lens
What seperates the anterior and posterior segments
Iris
What secretes aqueous humor
Ciliary processes
Parasympathetic innervation of the eye
Edinger westphal nucleus in midbrain synapse in ciliary ganglion and travel in short ciliary nerves to reach the pupillary sphincter and ciliary muscles
Sympathetic innervation of the eye
Superior cervical ganaglion and postganglion fibers travel along interval carotid plexus to reach ciliary ganglion
Pass through ganglion to dilator pupillae and superior tarsal muscles
Afferent fibers travel along sympathetic pathway from iris and cornea
Horners syndrome is a loss of _ innervation
Sympathetic
Lacrimal pathway
Lacrimal gland, lacrimal duct, Canalicular, lacrimal sac, nasolacrimal duct
