USMLE cards Flashcards
Cataract risk factors:
A - age
I - infection
D - diabetes mellitus
C - corticosteroid A - alcohol S - smoking T - trauma S - sunlight
3 - trisomies (13, 18, 21)
M - myotonic dystrophy
Torche - ToRCHeS infections
Milk - galactokinase deficiency /classic galactosemia
M - Marfan syndrome
A - Alport syndrome
N - neurofibromatosis 2
Dry Age-related macular degeneration
% and cause
(nonexudative, > 80%)- Deposition of yellowish extracellular material (“Drusen”) in between Bruch membrane and retinal pigment epithelium with gradual dec. in vision. Prevent progression with a multivitamin and antioxidant supplements.
“Baruch (and pigment) the Druz”
Wet Age-related macular degeneration
% and cause
Wet (exudative, 10- 15%)-rapid loss of vision due to bleeding 2° to choroidal neovascularization. Treat with anti-VEGF (vascular endothelial growth factor) injections (eg, bevacizumab, ranibizumab).
Leukocoria
Loss (whitening) of the red reflex.
causes in children include
C - congenital cataract
a
R - retinoblastoma
T - toxocariasis.
Miosis pathway
Constriction, parasympathetic:
Short ciliary nerves shorten the pupil diameter.
Edinger-Westphal nucleus —(via CN III)—> ciliary ganglion—(short ciliary nerves)—>sphincter pupillae muscles
Pupillary light reflex pathway
Light —(via CN II)—>pretectal nuclei in midbrain—>bilateral Edinger Westphal nuclei;
pupils constrict bilaterally (direct and consensual reflex).
Result: illumination of 1 eye results in bilateral pupillary constriction.
Mydriasis pathway - 1st neuron
hypothalamus —> ciliospinal center of Budge at C8-T2
hypothalamus —> ciliospinal center of Budge at C8-T2 —(T1, along cervical sympathetic chain, lung apex, subclavians)—> superior cervical ganglion—(along internal carotid, cavernous sinus, enters orbit as long ciliary nerve)—> pupillary dilator muscles, smooth muscle of eyelids, sweat glands of forehead and face.
Mydriasis pathway - 2nd neuron
ciliospinal center of Budge at C8-T2 —(T1, along cervical sympathetic chain, lung apex, subclavians)—> superior cervical ganglion
hypothalamus —> ciliospinal center of Budge at C8-T2 —(T1, along cervical sympathetic chain, lung apex, subclavians)—> superior cervical ganglion—(along internal carotid, cavernous sinus, enters orbit as long ciliary nerve)—> pupillary dilator muscles, smooth muscle of eyelids, sweat glands of forehead and face.
Mydriasis pathway - 3rd neuron
superior cervical ganglion—(along internal carotid, cavernous sinus, enters orbit as long ciliary nerve)—> pupillary dilator muscles, smooth muscle of eyelids, sweat glands of forehead and face.
hypothalamus —> ciliospinal center of Budge at C8-T2 —(T1, along cervical sympathetic chain, lung apex, subclavians)—> superior cervical ganglion—(along internal carotid, cavernous sinus, enters orbit as long ciliary nerve)—> pupillary dilator muscles, smooth muscle of eyelids, sweat glands of forehead and face.
Horner syndrome - Associated with lesions along the sympathetic chain:
Associated with lesions along the sympathetic chain:
- 1st neuron: pontine hemorrhage, lateral medullary syndrome, spinal cord lesion above T1 (eg, Brown-Sequard syndrome, late-stage syringomyelia)
- 2nd neuron: stellate ganglion compression by Pancoast tumor.
- 3rd neuron: carotid dissection (painful)
CN Ill damage
CN III has both motor (central) and parasympathetic (peripheral) components.
Common causes include:
PU(peripheral)CIM(central)
P - PCom aneurysm - sudden-onset headache
U - Uncal herniation - coma
C - Cavernous sinus thrombosis - proptosis, involvement of CNs IV, V1/V2, VI
I - Ischemia - pupil sparing (motor fibers affected more than parasympathetic fibers)
M - Midbrain stroke - contralateral hemiplegia
Internuclear ophthalmoplegia
Medial longitudinal fasciculus (MLF): pair of tracts that allows for crosstalk between CN VI and CN III nuclei
Frontal eye field-> PPRF-> nuc VI—(MLF)—>nuc III
Directional term (eg, right INO, left INO) refers to the eye that is unable to adduct.
INO = ipsilateral adduction failure, Nystagmus Opposite.
