Neuro Flashcards
Orbit dimensions
45 mm wide
35 mm height
Volume 30
Medial wall is 40 mm
Vascular Supply
Common Carotids —> internal and external carotids
External Carotids: facial artery, superficial temporal, occipital, maxillary, middle meningial artery
Internal Carotids: ophthalmic artery —> centra retinal artery , lacrimal artery —> frontal artery (lateral rectus)
Blind spot
17 degrees from fovea
Measures 5 x 7 degrees
Fovea is 4 mm from and 0.8 mm from ONH
Optic Nerve course
Optic Nerve Head (1.5 mm)
Intraorbital Optic Nerve
- Length: 30 mm
- Diameter: 3 mm with myelin, 6 mm with sheath
Optic Canal: 8-10 mm long
Intracranial: 8-12 mm
Optic Chiasm: 8 mm (macular fibers are posterior)
Optic Tract: to LGN (superior 4 are smaller field p cell axons, inferior 2 are large field motion; rotation of 90 degree)
Radiations: to occipital cortex,
Efferent pathway - Cortical Input
Saccades
- from frontal eye fields (Bridgman area 8)
- supplementary eye fields on superior frontal gyrus
- can project to BG, thalamus, brainstem, PPRF, MLF
Smooth pursuit
- originates in area V5 , also with input from medial superior temporal area
Efferent pathway - subcortical
Superficial / dorsal processes sensory signal
Deep / Ventral originates motor signals
Optic Neuropathy Differential
Papilledema Glaucoma Inflammatory - MS, Devic, systemic Vascular Neoplastic Infiltative- thyroid, leukemia, lymphoma, syphilis, granulomatous inflammatory process Hereditary Toxic Traumatic Congenitally anomalous Drusen
Optic Neuritis Treatment Trial
Optic neuritis in fellow eye 35% , 48 % in those that converted to MS
Steroids don’t improve long term outcomes but speed recovery
IV methylprednisone 250 mg q6 for three days followed by oral pred for 11 days
If it’s the first episode, you can use interferon, glatiramer acetate to reduce conversion to MS
If treating with natalizumab and have altered mental status, think PML / JC virus
Fingolimid = macular edema
Chronic Relapsing Inflammatory Optic Neuropathy
Not associated with MS
Steroid dependent
Devic Disease aka NMO
Optic neuritis plus acute myelitis
Aquaporin 4 IgG
Treat with high dose steroids , can do IVIG
AION versus NAION
AION - chalky white hyperemia of ONH, cotton wool spots away from ONH, large CD, delayed chorodial filling
NAION - DM, HTN, HLD, apnea; no treatment, if recurrent think of something else
PION
Coronary bypass grafting
Prolonged spinal fusion surgery
Optic Nerve sheath meningioma
Painless progressive monocular vision loss
Optic atrophy
Optociliary shunt vessels
Hype rosters is on CT, Tram track thickening on MRI, calcification
Treat with fractionated radiation
Optic Nerve Glioma (pilocytic astrocytoma)
Most common primary tumor of ON
No calcification, kinking , no extradural extension, t1 is hypointense
NF1
Observe, chemo, radiotherapy
Malignant optic Nerve glioma of adulthood - rapid vision loss, pain. Death ☹️
Hereditary Optic Neuropathies
Leber: boys, severe vision loss, hyperemia of ONH but no leakage, peripapillary teleangiectasia, tortuousity of medium sized vessels; mutation of mitochondrial 11778 OR 3460 14484
avoid alcohol and smoking
Autosomal dominant optic neuropathy: OPA1 gene on Ch 3 - dynamin GTPase, anchored to mitochondrial membranes ; tritanopia ; vision better than 20/200 due to slowwww progression, there is no treatment
Toxic Optic Neuropathy
Methanol Ethylene glycol Lead Tobacco Ethambutol Linezolid Amiodarone Disulfram Ciprofloxacin Cisplatin Vincristine
Traumatic Optic Neuropathy
International Optic Nerve Trauma Study - no clear benefit with steroids
Corticosteroid Randomization After Significant Head Injury study found increased mortality with those using steroids
Optic Disc Drusen
Impaired ganglion cell Adonai transport - Drusen build up as the product of deteriorating axons
Contrast with ONH hamartomas that are in the inner retina, fleshy and pinkish, do not autoflouresce
Congenital Optic Nerve Head Anomalies
Optic Nerve hypoplasia: small ONH, bilateral, double ring sign
- Syndrome: absent septum pellucidum, dwarfism = deMorsier
- teratogens: quinine, ethanol, anticonvulsants
Congenital tilted disc: bilateral with inferonasal colobomatous excavation
Others: Optic pit (IT) coloboma, dysplastic nerve (PAX2), morning glory ONH (unilateral)
Optic Tract Syndrome
Infarction in anterior chorodial artery
Homonymous hemianopia, bow tie optic atrophy, mild RAPD in other eye
Macula sparing homonymous hemianopia
Stroke in part of primary cortex supplied by PCA
Transient Monocular Vision Loss
Ocular Stuff: tear film, EBMD, pigment dispersion, hyphema, angle closure, vitreous debris, orbit mass if gaze evoked
Optic Nerve : compressive , Drusen, papilledema, demyelination (Uthoff)
Vascular: emboli, vasculitis, vasospasm, hypoperfusion, hyperviscosity
Transient Binocular Vision Loss
Migraine Tumor AV malformation TIA of basilar or PCA Occipital seizures
Higher Cortical Disorders of recognition
Object agnosia: interruption of signal flow from occipital lobe to temporal lobe
Prosopagnosia: bilateral inferior occipitotemporal lobe damage - can’t recognize faces
Akinetopsia: V5 loss of perception of motion
Alexia without agraphia: interruption of visual information between occipital love and dominant angular gyrus (Gertsmann = acalculia, right left confusion, finger agnosia)
Cerebral achromatopsia: bilateral inferior occipitotemporal lobe lesions
Higher Cortical Disorders of Visual Spatial Relationships
Simultanagnosia
Balint: bilateral occipitoparietalesions = simultanagnosia, Optic ataxia, acquires motor apraxia
Visual allesthesia: world is flipped !
Higher Cortical Disorders of Visual Deficit
Anton: Cortical blindness but deny it
Riddoch Phenomenon: preservation of perception of motion
Supranuclear Causes of Diplopia
Convergence insufficiency Divergence insufficiency Ocular tilt Skew deviation Thalamic esodeviation
Cranial Nerve III
Nucleus: affect or spare both upper lids and may affect CL Superior Rectus
Brainstem (ipsilateral CN III palsy)
1. Weber: ventral midbrain and cerebral peduncle = contralateral hemiparesis
2. Benedikt: red nucleus and substantia nigra = contralateral ataxia or tremor
3. Claude: dorsal midbrain and superior cerebellar peduncle = contralateral ataxia
4 Nothnagel: dorsal lesion with CNIII nuclear lesion = supranuclear dysfunction
Nerve:
- complete = Down and out, ptosis +- pupil
Pupil Involving: aneurysm of posterior communicating artery (if other stuff is normal, likely okay) or microvascular
Pupil Sparing: microvascular disease if complete, if partial still think aneurysm
Aberrant regeneration without hx of palsy - think cavernous sinus lesion
Cranial Nerve IV
Nucleus: rare
Brainstem: pineal tumor = dorsal midbrain
Nerve: Diplopia worse in contralateral gaze, ipsilateral head tilt, down gaze
If bilateral - crossed hypertropia, extorsion of 10 degrees, large V pattern eso. New is usually microvascular , image if no improvement 3 months
Cranial Nerve VI
Nucleus: horizontal gaze palsy due to MLF
Brainstem:
- Foville: ipsilateral abduction palsy, facial weakness, loss of taste, facial hypothesia
- Millard-Gubler: Ventral pons = contralateral hemiplegia, ipsilateral facial weakness, abduction deficit
Nerve
Gradenigo: chronic inflammation of petrous bone causes an ipsilateral abducens palsy and facial pain
If older than 50 likely vascular only image if no improvement at 3 months
If young - neuroimaging, Duane type 1, spasm of the near reflex, MG, TED, medial orbital was fracture with entrapment
Internuclear Diplopia
Disrupts MLF - connect VI nucleus on one side of pons to contralateral medial Rectus subnucleus
INO = unilateral slowed Adduction saccadic velocity with abducting nystagmus of other eye
Bilateral causes vertical gaze evoked nystagmus because of vestibular nuclei that go through MLF
One and a half = horizontal gaze palsy and ipsilateral INO (large pontine abnormality)
Ocular Neuromyotonia
Rare but episodic Diplopia after skull based radiation therapy, responds to carbamazepine
Supranuclear Ocular Motor Systems
- Ocular Fixation: fast; keeps stationary object on fovea, countered by square waves
- Vestibulo- Ocular: slow; holds image on fovea during brief head movements
- Optokinetic: slow; holds image on fovea during sustained head movement
- Saccadic: fast; brings object to fovea
- Smooth pursuit: slow; holds moving object on fovea
- Vergence: slow; moves eyes opposite so object remains on each fovea
Wallenberg Syndrome
Results from occlusion of proximal vertebral artery
Ipsilateral loss of pain and temperature on face, cerebellar ataxia,first order Horner, ocular head tilt reaction.
Contralateral loss of pain and temperature on body
Saccadic System
Volitional : pre motor areas that project to frontal eye fields —> pulse and step
- horizontal integration: CNVIII and CNXII
- vertical integration: interstitial nucleus of Cajal
Gaze evoked nystagmus if problem with integrators, if asymmetric it is an ipsilateral lesion of brainstem or cerebellum
Reflexive : superior colliculi to PPRF —> burst cells and omnipause cells
Dolls head will determine if supranuclear or nuclear
Specific Conditions:
- Slowed saccades with Parkinson’s like Syndrome with imbalance and impaired cognition = PSP
- Hyper metric saccades = cerebellum
- Unidirectional hypermetric saccades = Wallenberg
- Congenital ocular motor apraxia affects horizontal, not vertical ; if acquired need bilateral strokes
Smooth Pursuit Dysfunction
Abnormal gain
Delayed initiation
Normal OKn drum smooth pursuits when the drum is rotated away from the lesion
Vergence System
Fusional vergence is tested by placing a base out prism in front of one eye while the patient fixates , divergence is with base in prism
- normal is 25 for distance, 35 for near
Normal AC/A = 3-5
= pupillary distance + (deviation near - distance)/ 3
Dorsal Midbrain Syndrome
Convergence retraction nystagmus
Conjugate limitation of vertical gaze
Mid dilated pupils with light near dissociation
Collier sign - retraction of eyelids in primary position
Types of Nystagmus
Jerk: slow phase from target, fast phase back
Pendular: back and forth slow without fast - acquires think MS, if congenital only horizontal
Palatal nystagmus: lesion in Giullian mollaret triangle producing inferior olivary hypertrophy
See saw: one eye elevates, other depresses and extorts. Chiasm Or midbrain.
Infantile Nystagmus
- Reversal of normal OKN nystagmus - slow phase is opposite to rotation of drum
- Slow phase increases exponentially with distance from fixation
Sensory: Often due to pregeniculate vision loss
Latent nystagmus - conjugate horizontal jerk nystagmus accentuated by monocular fixation
Spasmus Nutans: asymmetric small amplitude high frequency shimmering movements , resolve spontaneousku
Vestibular nystagmus
Peripheral: 1. Viral vestibular neuronitis 2. Meniere disease 3. BPPV 4 aminoglycosides 5. Large cerebellarpontine angle tumor - Bruns nystagmus
Central:
- Downbeat : Arnold chiari I, antibodies to GAD And vestibulocerebellum
- Upbeat
- Torsional
- Periodic alternating nystagmus
Pupil shape irregularity
Tadpole: focal spasm of dilator that produces peaking
Midbrain corectopia: rostral midbrain disease
Causes of light near dissociation
Severe loss of afferent light to both eyes
Prp
Peripheral neuropathy causing loss of axons to iris sphincter
Adie
Aberrant regeneration
Loss of pretectal light input to EW , infection or compression
Causes of Ptosis!
Aponeurotic: attenuation, disinsertion
Mechanical : mass or cicatricial
Myogenic: CPEO, steroid eye drops, myotonic dystrophy
Neurogenic: apraxia, CNIII palsy, Horner, Miller Fisher, migraine
Neuromuscular : botox, MG
Traumatic : laceration, FB, post surgical
Causes of Eyelid Retraction !
- Mechanical : buphthalmos, axial myopia, orbital fractures with entrapment, proptosis from mass
- Myogenic: carcinomatous infiltration, postsurgical, TED
- Neurogenic : aberrant regeneration CNIII, dorsal midbrain, Marcus Gunn jaw winking, progressive supranuclear palsy
Seventh Nerve Palsy Location and effects
1 supranuclear : contralateral weakness of lower 2/3 of face
2. Nuclear: ipsilateral gaze palsy and monoplegia
Peripheral is ipsilateral - monoplegia
Overactivity of 7
- Benign essential blepharospasm: bilateral, basal ganglia, Botox ; Meige: facial grimace
- Hemifacial spasm: unilateral, CP angle, Botox
- Eyelid myokymia: unilateral
- Facial myokymia: unilateral, nucleus, glioma or MS
Pupillary response pathway
Retina Midbrain pretectal EW Ciliary ganglion Short ciliary Nerve Iris sphincter
Random Eponyms
Miller Fisher: areflexia, ataxia, ophthalmoplegia
Melkersson-Rosenthal: recurrent unilateral or bilateral facial paralysis with chronic facial swelling
