Path 1 - Ear

drraythe's version from 2016-04-30 21:24

Ear General

Question Answer
The structure of the ear can be broken into what main parts?External
What makes up the external ear?Skin-covered cartilaginous pinna & external ear canal
What makes up the middle ear?An air-filled cavity & the tympanic membrane
What connects the air-filled cavity of the middle ear to the nasopharynx?Eustachian tube
What is the purpose of the tympanic membrane?Transfers sound waves to the ear ossicles
What makes up the inner ear?Cochlea & Semicircular Canals
What is the Cochlea responsible for?Sound
What are the Semicircular Canals responsible for?Position & balance
What is the general fxn of the ear?Hearing & equilibrium
What are the 2 main czs of deafness?Nervous damage or interference w/ the mechanism for conducting sound waves
What are typical clinical expressions of dz in the ear?Pain
Irritation & scratching
Exudate in the ear canal or middle ear
Head tilt
Disturbance of balance
What is Macrotia?Abnormally large pinna
What is Microtia?Abnormally small pinna
What is Anotia?Absence of the pinna
What is Polyotia?Extra pinnae
What is Atresia?Absence of the external auditory meatus (deafness)
What is Persistent Meatul Plug?Failure of the meatul plug to be shed

Dzs of the Ear

Question Answer
Which is the most common ear neoplasm of cats?Ceruminous Gland Adenomas/Carcinomas
What can an infarction in blood vessels to the ear cz?Ear-Tip Necrosis
What can cz ear blood vessel infarction (Auricular necrosis / Ear-Tip Necrosis)?Frostbite (Cattle, Pigs)
Ergot poisoning (Cattle)
Thrombosis during septicemia (Pigs)
Trauma (Scratching, Rubbing, Head shaking)
What are neoplasms of the external ear?SCC
Ceruminous Gland Adenoma/Adenocarcinoma

Acoustic Neurinoma
What is the most common neoplasm of the ear?Ceruminous Gland Adenoma/Adenocarcinoma
What is the most common etiology of SCC in the ear?Solar Dermatitis
**What is most prevalent reason for deafness in animals?Absence/degeneration of Organ of Corti
Associated w/ white coat color
Which 2 genes are associated w/ absence/degeneration of the Organ of Corti & therefore deafness?Merle
**What are lesions associated w/ congenital/hereditary deafness?Atrophy of support macula cells → Cochleosaccular Degeneration
Then Collapse of walls of Cochlea & saccular membranous labyrinth
Then 2° degeneration of neurons w/in the spiral ganglia
What are the 2 types of acquired deafness?Conductive
What can cz Acquired Peripheral Neurologic Deafness?Toxicity
Acoustic (loud noise)
Storage dz
What toxicities can cz Peripheral Neurologic Deafness? How do they cz it?Aminoglycosides (-mycins)
Loop diuretics (Furosamide, Bumetanide Ethacrynic acid)
Salicylates (Aspirin)
Some Analgesics
Loss of inner/outer hair cells
How do loud noises cz deafness?Degeneration/necrosis of hair cells
Which storage dz czs deafness in goats & what is the pathogenesis?B-mannosidosis
Accumulation of oligosaccharides w/in lysosomes of tissue of the middle/inner ear → vacuolation of hair cells
What things can be ototoxic?Chemical agents
Loop Diuretics
Aspirin (Salicylates)
Hygromycin B
Salvon (antiseptic)
How do Aminoglycosides cz ototoxicity?Degenerate apical portion of Cochlear hair cells
What does Hygromycin B cz in dogs? Swine?Dogs - permanent deafness
Swine - cataracts
What are sequelae to ototoxicities?Deafness
Vestibular Dz
What are the CS of Vestibular Dz?Head tilt
Falling toward affected side
Ataxia w/o weakness
Czs of Central Vestibular Dz?Listeria
Organophosphate Poisoning
Czs of Peripheral Vestibular Dz?Labrynthitis form of Otitis Media
Senility: Deterioration & atrophy of the Organ of Corti leads to loss in the ability to hear high tones & speech sounds. Whats that called?Presbyacusis
Auricular Hematomas are common in which species?Dogs
What czs Auricular Hematomas?Trauma such as excessive scratching or head-shaking or intrachondral fracture of the pinnal cartilage
What animals are predisposed to Auricular Hematomas?Animals w/ pendulous ears
What lesions are assoc w/ Auricular Hematomas?Firm, warm, fluid-swelling on the pinna due to accumulation of blood w/ thickening or deformity due to fibrosis
What can delay healing of Auricular Hematomas?2⁰ infxns or repeated trauma

Otitis Externa

Question Answer
List 8 possible czs of Otitis Externa(1) ↑ cerumen
(2) Bacteria (Proteus, Pseudomonas, Staph, Dermatophilus)
(3) Yeast (Malassezia)
(4) Foreign Body
(5) Parasites (MITES, ticks, sandlfies)
(6) Auto Immune Dz (Pemphigus Foliaceous)
(7) Chronic inflammation
(8) Metabolic Disorders (Hypotheyroidism, Male-Feminizing Syndrome, Sertoli Cell Tumor, Ovarian Disorders like Hyperestrogenism)
List 6 things that predispose an animal to Otitis Externa(1) Excessive moisture
(2) Nature of the ear canal
(3) Impeded drainage
(4) Hx of Foreign Bodies
(5) A lipid-rich environment (Malassezia)
(6) Inappropriate Tx
What is the most common ear dz?Otitis Externa
How does the nature of the ear canal predispose an animal to Otits Externa?Ear canals are encased in a bony/cartilaginous shell & are often narrow & L-shaped in many animals. If something is impeding drainage &/or czing swelling the external bony or cartilaginous shell of the ear means that swelling can ONLY occur INTO the lumen which further impedes drainage & contributes to ↑ swelling
What kind of parasites can cz Otitis Externa?Ticks
Which mites cz Otitis Externa in dogs & cats?Dogs - Sarcoptes
Cats - Otodectes
What kind of bacteria can cz Otitis Externa?Proteus
What metabolic disorders can cz Otitis Externa?Hypothyroid (↓ immune response)
Hyperestrogenism (Sertoli or Ovarian Neoplasm)
What does metabolic Otitis Externa manifest as?Chronic Ceruminous Otitis Externa
What does chronic inflammation Otitis Externa eventually cz?Distortion of pinna
What autoimmune dz can cz Otitis Externa?Pemphigus foliaceus - crusts & pustules
What can impede the drainage of the ear canal?Inflammation
Excessive hair growth
Pendulous external ears
What are gross lesions associated w/ Otitis Externa?Hyperplastic epithelium
Chronic → narrowed lumen
Severe narrowing → partial deafness, spread to middle ear
What are parasites that can cz Otitis Externa?Ticks
Mites (Dogs - Sarcoptes, Cats - Otodectes)
What are the common mites in dogs w/ Otitis Externa?Sarcoptes
What are the common mites in cats w/ Otitis Externa?Otodectes
What are common lesions of parasitic Otitis Externa?Hair Loss
Thickening &/or Fissuring of the pinna

Otitis Media

Question Answer
What are etiologies of Otitis Media?Extension of infxn thru tympanic membrane from external ear or nasopharynx
Hematogenous Bacterial Infxn (Arcanobacterium pyogenes, Pasturella, Pseudomonas)
Where can infxns extend from?From external ear through tympanic membrane
From nasopharynx in association w/ upper respiratory infxns (Cat flu)
What are bacteria commonly implicated in Otitis Media? (3)Arcanobacterium pyogenes
What are lesions associated w/ Otitis Media?Inflammation of tympanic lining, congestion & exudate into tympanic cavity (serious implication in the horse)
Empyema of the guttural pouch (accumulation of pus)
Rupture of the Tympanic membrane
Deafness due to fibrosis
Spread of infxn to bone
Explain lesions in a horse w/ Otitis Media & what can happen?Exudate accumulates in the guttural pouch diverticula of the ventral portion of the Eustachian tube
Extension of inflammation into the wall of adjacent internal carotid artery → arteritis → hemorrhage into the guttural pouch
What are potential sequelae of Otitis Media? (6)Salpingitis/Eustachitis
Nasopharyngeal inflammatory polyps
Fibrosis of ossicles → deafness
to inner ear → Vestibular Dz
Guttural pouch mycosis
Spread to adjacent bone → osteomyelitis & osteolysis
What are neoplasms of middle ear?SCC
What is the main cz of Otitis Media?A respiratory infxn that spreads through the Eustachian tube/nasopharynx
List 5 sequelae of Otitis Media(1) Eustachitis/Salpyngitis
(2) Nasopharyngeal polyps
(3) Fibrosis of ear ossicles
(4) Guttural Pouch Mycosis
(5) Inner ear dz = Vestibular Dz

Otitis Interna (Labrinthitis)

Question Answer
What is etiology of Otitis Interna?Suppurative infxn from Otitis Media or URT infxn
Hematogenous (bacteria, virus, fungi, algae)
What are potential sequelae of Otitis Interna? (4)Impaired hearing → deafness due to destruction of the Organ of Corti
Loss of balance → Vestibular Dz/Nystagmus
Meningoencephalitis (CN8 / CN7)
Spread to adjacent bone → Temporal Osteomyelitis
How can Otitis Interna cz Meningoencephalitis?Spread along CN8 into cranial cavity
Neuritis of portions of CN7

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