Flashcards in Principles in Neurology_2 Deck (350):
how does hydrocephalus ex vacuo look on imaging?
apparent increase in CSF observed on imaging is actually result of ↓ neural tissue due to neuronal atrophy
what type of hydrocephalus is obstructive?
noncommunicating hydrocephalus is caused by what?
a structural blockage of CSF circulation within the ventricular system (e.g. stenosis of the aqueduct of Sylvius)
how many spinal nerves are there?
31 spinal nerves: • 8 cervical • 12 thoracic • 5 lumbar • 5 sacral • 1 coccygeal
Nerves C1-C7 exit where?
above the corresponding vertebrae
all nerves other than C1-C7 exit where?
below the corresponding vertebrae
what happens in vertebral disc herniation?
nucleus pulposus (soft central disc) herniates through anulus fibrosus (outer ring)
vertebral disc herniation usually occurs where?
posterolaterally at L4-L5 or L5-S1
in adults, spinal cord extends to where?
lower border of L1-L2 vertebrae
in adults, subarachnoid space extends to where?
lower border of S2
lumbar puncture is usually performed at what level?
between L3-L4 or L4-L5 (level of cauda equina)
how do you obtain sample of CSF without damaging spinal cord?
to keep the cord alive, keep the spinal needle between L3 and L5
what info is carried by the dorsal columns?
pressure, vibration, touch, proprioception
the dorsal columns comprise which structures?
Fasciculus cuneatus • Fasciculus gracilis
fasciculus cuneatus conveys what info?
pressure, vibration, touch, proprioception from the upper body, extremities
fasciculus gracilis conveys what info?
pressure, vibration, touch, proprioception from the lower body, extremities
lateral spinothalamic tract conveys what info?
anterior spinothalamic tract conveys what info?
crude touch , pressure
lateral corticospinal tract conveys what info?
intermediate horn sympathetics emerge at what levels?
what is important to remember as a general rule about spinal tract anatomy and functions?
ascending tracts synapse then cross
the dorsal column contributes to which tract?
medial lemniscal pathway
what is the function of the medial lemniscal pathway of the dorsal column?
ascending pressure, vibration, fine touch, and propioception
what is the 1st order neuron in the doral column medial lemniscal pathway?
sensory nerve ending→ cell body in dorsal root ganglion→ enters spinal cord, ascends ipsilaterally in dorsal column
what is synapse I of the dorsal column medial lemniscal pathway?
ipsilateral nucleus cuneatus or gracilis (medulla)
what is the 2nd order neuron in the dorsal column medial lemniscal pathway?
decussates in medulla →ascends contralaterally in medial lemniscus
where is synapse 2 in the dorsal column medial lemniscal pathway?
where is the 3rd order neuron in the dorsal column medial lemniscal pathway?
what is the function of the lateral spinothalamic tract?
what is the function of the anterior spinothalamic tract?
crude touch, pressure
where is the 1st order neuron in the spinothalamic tract?
sensory nerve ending (Aδ and C fibers) (cell body in dorsal root ganglion)→enters spinal cord
where is synapse 1 in the spinothalamic tract?
ipsilateral gray matter (spinal cord)
where is the 2nd order neuron in the spinal thalamic tract?
decussates at anterior white commissure →ascends contralaterally
where is synapse 2 in the spinothalamic tract?
where is the 3rd order neuron in the spinothalamic tract?
what is the function of the lateral corticospinal tract?
descending voluntary movement of contralateral limbs
where is the 1st order neuron in the lateral corticospinal tract?
UMN: cell body in 1° motor cortex→descends ipsilaterally (through internal capsule) until decussating at caudal medulla (pyramidal decussation)→descends contralaterally
where is synapse 1 in the lateral corticospinal tract?
cell body of anterior horn (spinal cord)
what is the 2nd order neuron in lateral corticospinal tract?
LMN: leaves spinal cord
where is synapse 2 in the lateral corticospinal tract?
when do you see weakness in motor neuron lesion?
UMN + • LMN+
when do you see atrophy in motor neuron lesion?
UMN - • LMN +
when do you see fasciculations in motor neuron lesion?
UMN - • LMN +
how do reflexes present in motor neuron lesion?
UMN ↑ • LMN ↓
how does tone present in motor neuron lesion?
UMN ↑ • LMN ↓
when do you see Babinski sign in motor neuron lesion?
UMN + • LMN -
when do you see spastic paralysis in motor neuron lesion?
UMN + • LMN -
when do you see flaccid paralysis in motor neuron lesion?
UMN - • LMN +
when do you see clasp knife spasticity in motor neuron lesion?
UMN + • LMN -
what do you see in lower motor neuron lesion?
everything lowered (less muscle mass, ↓ muscle tone, ↓ reflexes, down going toes)
what do you see in upper motor neuron lesion?
everything up (tone, DTR, toes)
What is the area of the spinal cord affected in poliomyelitis and Werdnig-Hoffman disease?
IMAGE pg 429
what are the characteristics of spinal cord lesions in poliomyelitis and Werdnig-Hoffman disease?
LMN lesions only, due to destruction of anterior horns; flaccid paralysis
what area of the spinal cord is affected by Multiple Sclerosis?
IMAGE pg 429
what are the characteristics of the spinal cord lesions in multiple sclerosis?
mostly white matter of cervical region; random and asymmetric lesions, due to demyelination; scanning speech, intention tremor, nystagmus
what areas of the spinal cord are affected in ALS?
IMAGE pg 429
what are the characteristics of spinal cord lesions in ALS?
combined UMN and LMN deficits with no sensory, cognitive, or oculomotor deficits; both UMN and LMN signs
ALS can be caused by what?
defect in superoxide dismutase I
ALS commonly presents as what?
fasciculations with eventual atrophy; progressive and fatal
what is the treatment for ALS?
Riluzole treatment modestly ↑ survival by ↓ presynaptic glutamate release
what area of the spinal cord is affected by complete occlusion of the anterior spinal artery?
IMAGE pg 429
what are the characteristics of spinal cord lesions caused by complete occlusion of the ASA?
spares dorsal columns and Lissauer's tract
which territory of ASA is a watershed area?
upper thoracic territory is a watershed area, as artery of Adamkiewicz supplies ASA below T8
what area of the spinal cord is affected by tabes dorsalis?
IMAGE pg 429
tabes dorsalis is caused by what?
tabes dorsalis results from what?
degeneration (demyelination) of dorsal columns and roots
tabes dorsalis causes what?
impaired sensation and propioception and progressive sensory ataxia (inability to sense or feel the legs)
tabes dorsalis is associated with what?
Charcot's joints • shooting pain • Argyll robertson pupil
what is Argyll robertson pupil?
small bilateral pupils that further constrict to accommodation but not to light
in tabes dorsalis, exam will demonstrate what?
absence of DTRs and positive Romberg
what area of the spinal cord is affected in syringomyelia?
IMAGE pg 429
what are the characteristics of the spinal cord lesion in syringomyelia?
syrinx expands and damages anterior white commissure of spinothalamic tract (2nd-order neurons) → bilateral loss of pain and temperature temperature sensation (usually C8-T1)
syringomyelia is seen with what?
Chiari I malformation
what area of the spine is affected by Vitamin B12 or Vitamin E deficiency?
IMAGE pg 429
what are the characteristics of the spinal lesion in Vitamin B12/E deficiencies?
subacute combined degeneration- demyelination of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts
what are the symptoms caused by spinal cord lesions in VitB12/VitE deficiency?
ataxic gait • paresthesia • impaired position and vibration sense
poliomyelitis is caused by what?
what is the transmission of poliovirus?
poliovirus replicates where?
in the oropharynx and small intestine
how does poliovirus spread after replication in the oropharynx and small intestine?
by blood to CNS
poliovirus infection causes what?
destruction of cells in anterior horn of spinal cord (LMN death)
what are the LMN lesion signs of poliomyelitis?
weakness, hypotonia, flaccid paralysis, atrophy, fasciculations, hyporeflexia, and muscle atrophy
what are the signs of infection of poliomyelitis?
malaise, HA, fever, nausea
what are the findings in poliomyelitis?
CSF with ↑WBC with slight elevation of protein, no Δ in CSF glucose. virus recovered from stool or throat
what is Werdnig-Hoffman disease?
Congenital degeneration of anterior horns of spinal cord → LMN lesion
what is the typical presentation of Werdnig-Hoffman syndrome?
'floppy baby' with marked hypotonia and tongue fasciculations
what is the prognosis for Werdnig-Hoffman syndrome?
infantile type has median age of death of 7 months
what is the inheritance of Werdnig-Hoffman syndrome?
autosomal recessive inheritance
what is Friedreich's ataxia?
Autosomal-recessive trinucleotide repeat disorder (GAA) in gene that encodes frataxin
Friedreich's ataxia leads to impairment in what?
what are the symptoms of Friedreich's ataxia?
staggering gait • frequent falling • nystagmus • dysarthria • pes cavus • hammer toes • hypertrophic cardiomyopathy (cause of death)
Friedreich's ataxia presents how?
in childhood with kyphoscoliosis
what is Brown-Sequard syndrome?
Hemisection of the spinal cord
what are the findings in Brown-Sequard syndrome?
1. Ipsilateral UMN signs below the level of the lesion • 2. Ipsilateral loss of tactile, vibration and propioception sense below the lesion • 3. contralateral pain and temperature loss below the level of the lesion • 4. Ipsilateral LMN signs at the level of the lesion
why are there ipsilateral UMN signs below the level of the lesion in Brown-Sequard?
due to corticospinal tract damage
why is there ipsilateral loss of tactile, vibration, propioception sense below the level of the lesion in Brown-Sequard syndrome?
dorsal column damage
why is there contralateral pain and temperature loss below the level of the lesion in Brown-Sequard syndrome?
spinothalamic tract damage
what happens in Brown-Sequard syndrome if the lesion occurs above T1?
patient may present with Horner's syndrome due to damage of sympathetic ganglion
What causes Horner's syndrome?
sympathectomy of face
what are the symptoms of Horner's syndrome?
Ptosis • Anhydrosis • Miosis
Horner's syndrome is associated with which conditions?
spinal cord lesion above T1: • Pancoast tumor • Brown-Sequard syndrome • late-stage syringomyelia
The 3-neuron oculosympathetic pathway pojects from where?
hypothalamus to the intermediolateral column of the spinal cord, then to the superior cervical (sympathetic) ganlgion, and finally to the pupil, the smooth muscle of the eyelids, and the sweat glands of the forehead and face
interruption of which pathway causes horner's syndrome?
3-neuron oculosympathetic pathway
what is the sensory distribution of the C2 dermatome?
posterior half of a skull cap
what is the sensory distribution of the C3 dermatome?
high turtleneck shirt
what is the sensory distribution of the C4 dermatome?
what is the sensory distribution of the T4 dermatome?
at the nipple
what is the sensory distribution of the T7 dermatome?
at the xiphoid process
what is the sensory distribution of the T10 dermatome?
at the umbilicus
why is the T10 dermatome important?
early appendicitis pain referral
what is the sensory distribution of the L1 dermatome?
at the inguinal ligament
what is the sensory distribution of the L4 dermatome?
includes the Kneecaps
what is the sensory distribution of the S2,S3,S4 dermatomes?
erection and sensation of penile and anal zones
diaphragm and gallbladder pain referred to the right shoulder via what?
biceps reflex = which nerve root?
Triceps reflex = which nerve root?
Patella reflex = which nerve root?
Achilles reflex = which nerve root?
what is the Babinski sign?
dorsiflexion of the big toe and fanning of other toes
Babinski reflex is a sign of what?
UMN lesion, but normal in 1st year of life
what defines primitive reflexes?
CNS reflexes that are present in a healthy infant, but are absent in a neurologically intact adult
when do primitive reflexes normally disappear?
within 1st year of life
primitive reflexes are inhibited by what?
a mature/developing frontal lobe
when can primitive reflexes reemerge in adults?
following frontal lobe lesions →loss f inhibition
what is the Moro reflex?
hang on for life reflex- abduct extend limbs when startled, and then draw together
what is the rooting reflex?
movement of head toward one side if cheek or mouth is stroked (nipple seeking)
what is the sucking reflex?
sucking response when roof of mouth is touched
what is the palmar reflex?
curling of fingers if pam is stroked
what is the plantar reflex?
dorsiflexion of large toe and fanning of other toes with plantar stimulation
what is the Galant reflex?
stroking along one side of the spine while newborn is in ventral suspension causes lateral flexion of lower body toward the stimulated side
which cranial nerves lie medially at the brainstem?
III, VI, XII • Motor=Medial
what is the function of the pineal gland?
melatonin secretion, circadian rhythms
what is the function of the superior colliculi?
conjugate vertical gaze center
what is the function of the inferior colliculi?
what is Parinaud syndrome?
paralysis of conjugate vertical gaze due to lesion in superior colliculi (e.g. pinealoma)
what is CNI?
what is the function of the olfactory nerve?
CNI is the onlt CN without what?
thalamic relay to cortex
what is CNII?
what is the function of CNII?
what is CNIII?
what is the function of CNIII?
eye movement (SR, IR, MR, IO), pupillary constriction, accommodation, eyelid opening (levator palpebrae)
what is the pathway used by CNIII to affect pupillary constriction?
sphincter pupillae: Edinger-Westphal nucleus, muscarinic receptors
what is CNIV?
what is the function of CNIV?
eye movement (SO)
what is CNV?
what is the function of CNV?
mastication, facial sensation, somatosensation from the anterior 2/3 of the tongue
what are the divisions of facial sensation by branches of CNV?
ophthalmic • maxillary, • mandibular
what is CNVI?
what is the function of abducens nerve?
eye movement (LR)
what is CNVII?
what is the function of CNVII?
facial movement • taste from anterior 2/3 of tongue • lacrimation • salivation (submandibular and sublingual glands) • eyelid closing (orbicularis oculi) • stapedius muscle in ear
which nerve crosses through the parotid gland but does not innervate it
what is CNVIII?
what is the function of CNVIII?
what is CNIX?
what is the function of CNIX?
taste and somatosensation from posterior 1/3 of tongue • swallowing • salivation (parotid gland) • monitoring carotid body and sinus chemo and baroreceptors • stylopharyngeous (elevates pharynx and larynx)
what is CNX?
what is the function of CNX?
Taste from epiglottic region • swallowing • palate elevation • midline uvula • talking • coughing • thoracoabdiminal viscera • monitoring aortic arch chemo and baroreceptors
what is CNXI?
spinal accessory nerve
what is the function of the spinal accessory nerve?
head turning, shoulder shrugging (SCM, trapezius)
what is CNXII?
what is the function of CNXII?
CNI is what type?
CNII is what type?
CNIII is what type?
CNIV is what type?
CNV is what type?
CNVI is what type?
CNVII is what type?
CNVIII is what type?
CNIX is what type?
CNX is what type?
CNXI is what type?
CNXII is what type?
where are cranial nerve nuclei located?
tegmentum portion of brain stem between dorsal and ventral portions
Midbrain contains the nuclei of which cranial nerves?
CN III • CN IV
pons contains the nuclei of which cranial nerves?
CN V, VI, VII, VIII
medulla contains the nuclei of which cranial nerves?
CN IX, X, XII
spinal cord contains the nuclei of which cranial nerves?
Sensory (aLar plate)
motor (basal plate)
what separates the medial and lateral cranial nerve nuclei
what is the afferent branch of the Corneal reflex?
V1 ophthalmic (nasociliary branch)
what is the efferent branch of the corneal reflex?
VII (temporal branch; orbicularis oculi)
what is the afferent branch of the lacrimation reflex?
V1 (loss of reflex does not preclude emotional tears)
what is the efferent branch of the lacrimation reflex?
what is the afferent branch of the jaw jerk reflex?
V3 (sensory- muscle spindle from masseter)
what is the efferent branch of the jaw jerk reflex?
V3 (motor- masseter)
what is the afferent branch of the pupillary reflex?
what is the efferent branch of the pupillary reflex?
what is the afferent branch of the gag reflex?
what is the efferent branch of the gag reflex?
what are the 3 vagal nuclei?
Nucleus Solitarius • Nucleus aMbiguus • Dorsal motor nucleus
function of nucleus solitarius?
Visceral Sensory information (taste, baroreceptors, gut distention)
which CN synapse on neurons in the nucleus solitarius?
VII • IX • X
function of nucleus ambiguus?
Motor innervation of pharynx, larynx, and upper esophagus (swallowing, palate, elevation)
which CN synapse on neurons in the Nucleus Ambiguus?
IX • X
function of the motor nucleus?
sends autonomic (parasympathetic) fibers to heart, lungs, and upper GI
which CN synapse on dorsal motor nucleus?
CN I traverses what pathway?
which cranial nerves traverse the middle cranial fossa through the sphenoid bone?
which structures traverse the optic canal?
CNII • ophthalmic artery • central retinal vein
which structures traverse the superior orbital fissure?
CN III, IV, V1, VI, ophthalmic vein, sympathetic fibers
which structures traverse the foramen rotundum?
which structures traverse the foramen ovale?
which structures traverse the foramen spinosum?
middle meningeal artery
Which cranial nerves traverse the posterior cranial fossa through the temporal or occipital bone?
CN VII- XII
which cranial nerves traverse the internal auditory meatus?
which structures traverse the jugular foramen?
CNIX, X, XI jugular vein
which structures traverse the hypoglossal canal?
which structures traverse the foramen magnum?
spinal roots of CN XI, brain stem, vertebral arteries
what is the cavernous sinus?
a collection of venous sinuses on either side of the pituitary
which drainage pathway goes through the cavernous sinus?
blood from the eye and superficial cortex → cavernous sinus → internal jugular vein
which structures pass through the cavernous sinus?
CNIII, IV, V1, V2 and VI and postganglionic sympathetic fibers en route to the orbit • + cavernous portion of internal carotid artery
what can cause cavernous sinus syndrome?
mass effect, fistula, thrombosis
what are the clinical features of cavernous sinus syndrome?
ophthalmoplegia and ↓ corneal and maxillary sensation with normal vision
what is the clinical presentation of a CN V motor lesion?
Jaw deviates toward side of lesion due to unopposed force from opposite pterygoid muscle
what is the common clinical presentation of a CN X lesion?
Uvula deviates away from side of lesion. Weak side collapses and uvula points away
what is the clinical presentation of a CN XI lesion?
weakness turning head to contralateral side of lesion. shoulder droop on side of lesion • left SCM contracts to help turn head to the right
what is the clinical presentation of a CN XII (LMN) lesion?
tongue deviates toward side of lesion (lick your wounds) due to weakened tongue muscles on the affected side
what are the diagnostic features of conductive hearing loss?
Rinne test= abnormal (bone > air) • Weber= localizes to affected ear
what are the diagnostic features of sensorineural hearing loss?
Rinne= normal (air>bone) • Weber= localizes to unaffected ear
sudden extreme loud noises can produce hearing loss due to what?
tympanic membrane rupture
what causes noise induced hearing loss that begins with high frequency hearing loss?
damage to stereociliated cells in organ of corti
what is the cause of an UMN facial lesion?
lesion of motor cortex or connection between cortex and facial nucleus
what are the symptoms of UMN facial lesions?
contralateral paralysis of lower face; forehead spared due to bilateral UMN innervation
what are the symptoms of LMN facial lesions?
Ipsilateral paralysis of upper and lower face
what causes facial nerve palsy?
complete destruction of the facial nucleus itself or its branchial efferent fibers (facial nerve proper)
what are the symptoms of facial nerve palsy?
peripheral ipsilateral facial paralysis with inability to close eye on involved side
what is the prognosis for idiopathic facial nerve palsy?
gradual recovery in most cases
facial nerve palsy is seen as a complication in what?
AIDS • lyme disease • herpes simplex • [less common] herpes zoster • sarcoidosis • tumors • diabetes
what is idiopathic facial nerve palsy called?
what 3 muscles close the jaw?
Masseter • teMporalis • Medial pterygoid • M's Munch
what is the muscle that opens the jaw?
Lateral pterygoid • Lateral Lowers
the muscles of mastication are innervated by what?
the ciliary body comprises which structures?
ciliary muscle • ciliary process
what are the fluid filled spaces in the anterior segment of the eye?
anterior chamber • posterior chamber
what is the fluid filled space in the posterior segment of the eye?
refractive errors are characterized by what?
impaired vision that improves with glasses
what happens in hyperopia?
eye too short for refractive power of cornea and lens → light focused behind retina
what happens in myopia?
eye to long for refractive power of cornea and lens → light focused in front of the retina
what happens in astigmatism?
abnormal curvature of cornea resulting in different refractive power at different axes
what happens in accommodation?
focusing on near objects → ciliary muscles tighten → zonular fibers relax → lens becomes more convex
accommodation occurs with what?
convergence and miosis
what happens in presbyopia?
↓ change in focusing ability during accommodation due to sclerosis and decreased elasticity
what is uveitis?
inflammation of the uveal coat
uveal coat consists of what?
iris, ciliary body, choroid
uveitis is often associated with what?
systemic inflammatory disorder: • sarcoid • RA • juvenile idiopathic arthritis • TB • HLA-B27
what is retinitis?
retinal edema and necrosis leading to scar
cause of retinitis is often what?
viral: • CMV • HSV • HZV
retinitis is associated with what?
clinical features of central retinal artery occlusion?
acute, painless monocular vision loss • retina whitening with cherry red spot
function of the canal of Schlemm?
collects aqueous humor from trabecular meshwork
function of trabecular meshwork?
collects aqueous humor that flows through anterior chamber
function of ciliary epithelium?
produces aqueous humor
receptor type on ciliary muscle?
receptor type on Ciliary epithelium?
receptor type on eye sphincter?
receptor type on eye dilator muscle?
glaucoma is characterized by what?
optic neuropathy, usually with ↑ intraocular pressure • painless
open/wide angle glaucoma is characterized by what?
peripheral then central vision loss usually with ↑ IOP; • optic disc atrophy with cupping
open/wide angle glaucoma is associated with what?
↑age • African American • family Hx • ↑IOP
open angle glaucoma is more common where?
what causes open angle glaucoma?
1° cause unclear • 2° causes: • uveitis • trauma • corticosteroids • vasoproliferative retinopathy that can block or ↓ outflow at the trabecular meshwork
what happens in closed/narrow angle glaucoma?
enlargement or forward movement of lens against central iris leads to obstruction of normal aqueous flow through pupil → fluid builds up behind iris, pushing peripheral iris against cornea and impeding flow through the trabecular meshwork
features of closed angle glaucoma with chronic closure?
often asymptomatic with damage to optic nerve and peripheral vision
which type of glaucoma is an ophthalmic emergency?
closed angle with acute closure
what happens in closed angle glaucoma with acute closure?
↑ IOP pushes iris forward → angle closes abruptly
clinical features of closed angle glaucoma with acute closure?
very painful • sudden vision loss • halos around lights • rock hard eye • frontal headache
what is contraindicated in the treatment of closed angle glaucoma with acute closure?
epinephrine because of its mydriatic effect
what are cataracts?
painless, often bilateral, opacification of lens → ↓ in vision
what are the risk factors for cataracts?
age • smoking • EtOH • excessive sunlight • prolonged corticosteroid use • classic galactosemia • galactokinase deficiency • diabetes (sorbitol) • trauma • infection
what is papilledema?
optic disc swelling (usually bilateral) due to ↑ ICP (2° to mass effect)
fundoscopic findings in papilledema?
enlarged blind spot and elevated optic disc with blurred margins
which cranial nerves innervate extraocular muscles?
CN VI → Lateral Rectus • CN IV → Superior Oblique • CN III → the rest • LR6SO4R3
action of superior oblique muscle?
abducts, intorts, and depresses while adducted
what happens in CNIII damage?
eye looks down and out; ptosis, pupillary dilation, loss of accommodation
what happens in CN IV damage?
eye moves upward, particularly with contralateral gaze and ipsilateral head tilt • (problems going down stairs)
what happens in CN VI damage?
medially directed eye that cannot abduct
how do you test Superior rectus?
look up and out (temporal)
how do you test lateral rectus?
look straight out to the side (temporal)
how do you test inferior rectus?
look down and out
how do you test superior oblique?
look down and in
how do you test medial rectus?
look straight in (nasal)
how do you test inferior oblique?
look up and in
what is pupillary miosis?
what are the neurons in the control of miosis?
1st: Edinger-Westphal nucleus to ciliary ganglion via CN III • 2nd: short ciliary nerves to pupillary sphincter muscles
what is mydriasis?
what are the neurons in the control of mydriasis?
1st: hypothalamus to ciliospinal center of Budge (C8-T2) • 2nd: exit at T1 to superior cervical ganglion (travels along cervical sympathetic chain near lung apex, subclavian vessels) • 3rd: plexus along internal carotid, through cavernous sinus; enters as long ciliary nerve to pupillary dilator muscle
what is the circuit activated in the pupillary light reflex?
light in either retina sends a signal via CN II to pretectal nuclei in midbrain that activate bilateral Edinger-Westphal nuclei; pupils contract bilaterally
what is the result of the pupillary light reflex?
illumination of 1 eye results in bilateral pupillary constriction
what is Marcus Gunn pupil?
afferent pupillary defect ( due to optic nerve damage or retinal detachment)
findings in Marcus Gunn pupil?
↓ bilateral pupillary constriction when light is shone in affected eye relative to unaffected eye
what are the 2 components of CN III?
motor = central • parasympathetic = peripheral
center of CNIII does what?
motor output to ocular muscles
center of CNIII is affected primarily by what?
vascular disease: • ↓diffusion of oxygen and nutrients to the interior fibers from compromised vasculature that resides on outside of nerve
signs of center of CNIII compromise?
ptosis + down and out gaze
peripheral fibers of CNIII are first affected by what?
compression: • posterior communicating artery aneurysm • uncal herniation
what are the signs of compression of peripheral fibers of CN III?
diminished or absent pupillary light reflex • "blown pupil"
what happens in retinal detachment?
separation of neurosensory layer of retina (photoreceptor layer with rods and cones) from outermost pigmented epithelium (normally shields excess light, supports retina)→degeneration of photoreceptors → vision loss
retinal detachment may be due to what?
retinal breaks • diabetic traction • inflammatory effusion
retinal breaks are more common in whom?
pts w/ high myopia
retinal breaks are often preceded by what?
posterior vitreous detachment (flashes and floaters) and eventual monocular vision loss "curtain drawn down"
which cause of retinal detachment presents as a surgical emergency?
what is age-related macular degeneration?
degeneration of central area of retina
age related macular degeneration causes what?
distortion (metamorphopsia) and eventual loss of central vision (scotomas)
what is the more common subtype of age related macular degeneration?
dry, nonexudative >80%
dry ARMD is characterized by what?
deposition of yellowish extracellular material beneath retinal pigment epithelium ("drusen") with gradual ↓ in vision
prevent progression of dry ARMD with what?
multivitamin and antioxidant supplements
what is the less common subtype of ARMD?
wet, exudative 10-15%
wet ARMD is characterized by what?
rapid loss of vision due to bleeding secondary to choroidal neovascularization
what is the treatment for wet ARMD?
anti-VEGF injections or laser
what causes unilateral anopia?
cut optic nerve
what cause bitemporal hemianopia?
lesion of optic chiasm
what causes homonymous hemianopia?
lesion of optic tract
what causes left upper quadrantic anopia?
right temporal lesion (meyers loop) • MCA
what causes left lower quadrantic anopia?
right parietal lesion (dorsal optic radiation) • MCA
what causes homonymous hemianopia with macular sparing?
what causes central scotoma?
path of meyers loop?
inferior retina; loops around inferior horn of lateral ventricle
path of dorsal optic radiation?
superior retina; takes shortest path via internal capsule
what is the medial longitudinal fasciculus?
pair of tracts that allows for crosstalk between CN VI and CNIII nuclei
MLF coordinates what?
both eyes to move in same horizontal direction
how much myelin in MLF?
MLF lesions seen in which patients?
lesion in MLF causes what?
INO= internuclear ophthalmoplegia
what happens in INO?
lack of communication such that when CNVI nucleus activates ipsilateral lateral rectus, contralateral CN III nucleus does not stimulate medial rectus to fire
what happens to abducting eye in INO?
nystagmus (CN VI overfires to stimulate CN III)
how is convergence in INO?
what is dementia?
↓ in cognitive ability, memory, or function with intact consciousness
What are the causes of dementia?
AD • Pick's disease • Lewy body dementia • CJD • Multi-infarct • Syphilis • HIV • Vit B1/B3/B12 deficiency • NPH
what is the most common cause of dementia in the elderly?
what is the second most common cause of dementia in the elderly?
who has an ↑ risk of developing Alzheimer's?
Down syndrome patients
what is the frequency of familial form Alzheimer's?
Early onset Alzheimer's is associated with which proteins on which chromosomes?
APP (21) • presenilin-1 (14) • presenilin-2 (1)
late onset familial Alzheimers is associated with which protein on which chromosome?
which protein on which chromosome is protective against Alzheimer's?
what are the histologic/gross findings in AD?
1. Widespread cortical atrophy • 2. ↓ ACh • 3. Senile plaques • 4. Neurofibrillary tangles
What are the features of senile plaques in AD?
extracellular β-amyloid core • may cause amyloid angiopathy → intracranial hemorrhage
how is Aβ synthesized?
cleaving amyloid precursor protein
features of neurofibrillary tangles in AD?
intracellular, abnormally phosphorylated tau protein= insoluble cytoskeletal elements
tangles in AD correlate with what?
degree of dementia
clinical presentation of Pick's disease?
dementia, aphasia, parkinsonian aspects; • change in personality
what structures are spared in Pick's disease?
parietal lobe and posterior 2/3 of superior temporal gyrus
other name for Pick's disease?
histologic/gross findings in Pick's disease?
Pick Bodies: spherical tau protein aggregates • Frontotemporal atrophy
clinical features of Lewy body dementia?
Parkinsonism with dementia and hallucinations