Otology & Ophthalmology, and specific drugs Flashcards
Each frequency leads to vibration at specific location on basilar membrane (tonotopy):
• Low frequency heard at _____
apex near helicotrema (wide and flexible).
Each frequency leads to vibration at specific location on basilar membrane (tonotopy):
•High frequency heard best at______
the base of cochlea (thin and rigid).
Noise-induced hearing loss and Presbycusis lose hearing in _____frequency
Loss of high-frequency
Cholesteatoma
Overgrowth of desquamated keratin debris within the middle ear space;
may erode ossicles, mastoid air cells - conductive hearing loss.
Often presents with painless otorrhea
Peripheral vertigo Tx:
Treatment:
C - anticholinergics H - antihistamines A - antiemetics S - low-salt diet E - Epley maneuver (BPPV). D - diuretics
Meniere disease triad:
sensorineural hearing loss
vertigo
tinnitus
Hyperopia corrects with:
Correct with convex (converging) lenses.
Myopia corrects with:
Correct with concave (d iverging) lens.
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
Open-angle glaucoma (Primary vs. secondary) causes:
Primary- cause unclear.
Secondary: blocked trabecular meshwork from
WBCs (eg, uveitis)
RBCs (eg, vitreous hemorrhage)
retinal elements (eg, retinal detachment).
Closed or narrow-angle glaucoma causes:
Primary- enlargement or anterior movement of the lens against central iris (pupil margin) - > obstruction of normal aqueous flow through the pupil.
Secondary- hypoxia from retinal disease (eg, diabetes mellitus, vein occlusion) induces vast proliferation in the iris that contracts angle.
Closed or narrow-angle glaucoma: Chronic vs. acute.
Chronic closure- often asymptomatic with damage to the optic nerve and peripheral vision.
Acute closure- true ophthalmic emergency. Very painful, red-eye, sudden vision loss, halos around lights, frontal headache, fixed and mid-dilated pupil, nausea, and vomiting.
Mydriatic agents contraindicated.
Uveitis - Posterior vs. anterior
Anterior uveitis: iritis;
posterior uveitis: choroiclitis and /or retinitis.
May have hypopyon
Age-related macular degeneration
Degeneration of macula (central area of the retina). It causes distortion (metamorphopsia) and eventual loss of central vision (scotomas).
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).
Diabetic retinopathy - Nonproliferative
Damaged capillaries leak blood -> lipids and fluid seep into retina -> hemorrhages and macular edema.
Treatment: blood sugar control.
Diabetic retinopathy - Proliferative
Chronic hypoxia results in new blood vessel formation with resultant traction on the retina. Treatment: anti-VEGF injections, peripheral retinal photocoagulation, surgery
Hypertensive
retinopathy results in
Flame-shaped retinal hemorrhages
arteriovenous nicking
microaneurysms
macular star (exudate)
Retinal vein occlusion cause:
due to compression from nearby arterial atherosclerosis
“blood and thunder appearance”;
Retinal detachment pathology
Separation of the neurosensory layer of the retina (photoreceptor layer with rods and cones) from
outermost pigmented epithelium (normally shields excess light, supports retina)
Central retinal artery
occlusion
Acute, painless monocular vision loss.
The retina is cloudy with attenuated vessels and “cherry-red” spot at the fovea (center of the macula).
Evaluate for embolic source
Retinitis pigmentosa
progressive vision loss beginning with night blindness - rods in peripheral vision affected first
Papilledema
Optic disc swelling (usually bilateral) due to inc. ICP
Leukocoria
Loss (whitening) of the red reflex.
causes in children include
C - congenital cataract
a
R - retinoblastoma
T - toxocariasis.
Retinal detachment risk factors:
May be 2° to retinal breaks, diabetic traction, inflammatory effusions.
more common with high myopia and/or history of head trauma.
Often preceded by posterior vitreous detachment (“flashes” and “floaters”) and eventual monocular loss of vision like a “curtain drawn down.”
Surgical emergency.
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.
Suvorexant
Orexin (hypocretin) receptor antagonist - used for insomnia.
Contraindications:
narcolepsy
combination with strong CYP3A4 inhibitors.
patients with liver disease.
Triptans
5-HT 1B/1D - agonists. Inhibit trigeminal nerve
activation, prevent vasoactive peptide release, induce vasoconstriction - used for Acute migraine, cluster headache attacks.
contraindicated in patients with CAD or vasospastic angina
Memantine
NMDA receptor antagonist; helps prevent excitotoxicity
(mediated by Ca2+). - Used for moderate to advanced
dementia.
Tetrabenazine
Inhibit vesicular monoamine transporter (VMAT)
- dec dopamine vesicle packaging and release.
used for Huntington chorea and tardive dyskinesia.
Local anesthetics - Order of nerve blockade:
small-diameter fibers> large diameter. Myelinated fibers> unmyelinated fibers.
Overall, size factor predominates over myelination such that small myelinated fibers >small unmyelinated fibers> large myelinated fibers> large unmyelinated fibers.
Baclofen
GABA-B receptor agonist in spinal cord.
Use: Muscle spasticity, dystonia, multiple sclerosis.
Cyclobenzaprine
Centrally acting. Structurally related to TCAs. May cause anticholinergic side effects,
sedation.
Use: Muscle spasticity (works in BS).
agonists at opioid receptors
μ = beta-endorphin, delta = enkephalin, K = dynorphin
Pentazocine vs. Butorphanol MECHANISM
K-opioid receptor agonist (both)
Pentazocine - μ-opioid receptor weak antagonist OR partial agonist
Butorphanol - μ -opioid receptor partial agonist.
Pentazocine vs. Butorphanol NOTES
Both can cause opioid withdrawal symptoms if a patient is also taking full opioid agonists.
Butorphanol - Causes less respiratory depression than full opioid agonists, Not easily reversed with naloxone.
Glaucoma drugs - drugs that dec aqueous humor synthesis
B - beta bolckers (Timolol, betaxolol,carteolol)
A - alfa agonists (Epinephrine-a1, apraclonidine, brimonidine -a2)
D - Diuretics (Acetazolamide)
via vasoconstriction (Epinephrine) via inhibition of carbonic anhydrase (Acetazolamide)
Glaucoma drugs - drugs that inc outflow of aqueous humor
Prostaglandins - uveoscleraI pathway (Bimatoprost, latanoprost -PGF2a)
Cholinomimetics, M3 - contraction of the ciliary muscle and opening of the trabecular meshwork
Cholinomimetics-Direct: pilocarpine, carbachol
Cholinomimetics-indirect: physostigmine, echothiophate
