The Middle Ear Flashcards
The tympanic bulla of the temporal bone is a bony shell situated caudal and medial to the (2)
zygomatic and temporomandibular joint (TMJ)
What is the middle ear lined with?
respiratory epithelium
What is the middle ear continuous with?
Nasopharynx
The tympanic bulla in the dog is divided into (2) and what by?
dorsal and ventral compartment
- an incomplete bony shelf.
Tympanic bulla in cats; what is the division and how do they communicate?
Almost completely separated by a bony septum, communicating only by a small slit like medial opening which become a foramen more caudally
The dorsal epitympanic recess contains the auditory ossicles and communicates with the inner ear through (2)
round and oval windows.
What connects the middle ear to the nasopharynx and opens in the middle of the medial wall of the bulla?
Eustachian tube
What nerve passes through the periosteum of the medial bulla?
sympathetic
What separates the external acoustic meatus of the ear canal from the middle ear?
Tympanic membrane
The majority of the tympanic membrane is the ?
pars tensa
pars tensa:
A) What does this look like?
B) What is embedded here?
A) grey-white, translucent, taut membrane
B) malleus
Which “fleshier” part of the TM sits dorsally?
pars flaccida
What allows repair of the TM?
There is a constant centrifugal movement of cells that clear debris from the surface of the membrane
If the TM isn’t present; how can we gauge where it should be?
There are a few hairs that sit at the ventral insertion of the tympanic membrane
The tympanic cavity in cats is almost completely divided into:
A) a large ventral cavity called?
B) and a smaller rostrolateral component (2) )
C) What is it separated by?
A) Hypotympanum
B) Epitympanum and mesotympanum
C) a bony septum.
What are the ossicles of the middle ear role?
concentrate sound waves striking the tympanic membrane, focussing them at the smaller vestibular (oval) window.
What are the ossicles of the middle ear connected by?
A series of ligaments and muscles.
A) Where is the malleus embedded?
B) What does the head articulate with?
A) TM
B) Incus
Incus:
A) What is it within?
B) What does it articulate with?
A) epitympanum
B) Stapes
What is attached to a cartilaginous ring around the vestibular window – the separation between the tympanic cavity and the perilymphatic space of the inner ear.
Stapes
The A) nerve enters the internal auditory meatus alongside the B) nerve.
It travels in the facial canal of the petrous temporal bone before exiting the bulla at the C) foramen. It is exposed within the dorsal D) cavity near the vestibular window.
A) facial
B) vestibulocochlear
C) Stylomastoid
D) Tympanic
The tympanic plexus is formed from the tympanic branches of what nerves (2)
glossopharyngeal nerve
caroticotympanic nerve.
The tympanic plexus spreads along the bony promontory and gives rise to parasympathetic fibres to the A) Which 2 salivary glands, and sensory fibres to B)
A) parotid and zygomatic
B) the middle ear cavity.
What supplies the middle ear, in conjunction with the meningeal and pharyngeal arteries?
The tympanic artery
What is The tympanic artery a branch of?
Maxillary a.
Physiology of hearing sound?
The middle ear conducts sound from the external auditory meatus across the tympanic membrane, through the air-filled tympanic cavity into the fluid-filled inner ear and receptor cells of the cochlear. The ossicles focus sound that strikes the tympanic membrane to the vestibular window.
Which of these arteries is not involved in the vascular supply to middle ear?
Tympanic
Maxillary
Meningeal
Pharyngeal
Maxillary
In dogs, the most common cause of otitis media is?
Infection spreading from the external ear canal across the tympanic membrane.
What are the most common organisms isolated from the canine ear canal (3)
Staphylococcus intermedius (pseudintermedius),
Pseudomonas
Malassezia
In cats, middle ear infections most commonly arise from?
ascending infection through the auditory tube, often associated with episodes of nasopharyngeal viral infection.
Middle ear infections are also implicated in the development of?
Middle ear polyps
Clinical findings with otitis media? (9)
Pain
Otorrhoea
Head shaking
Purulent discharges at the external meatus;
The head being carried lower on the affected side
pain on opening of the mouth (in cases with TMJ involvement);
Facial nerve palsy/paralysis (10% of the cases);
Loss of hearing
vestibular signs, if the otitis media spreads to the inner ear
What does the normal TM look like? (4)
is shiny
translucent
visible malleus and vascular structures.
What on otoscope suggests middle ear dx? (3)
loss of translucency,
a change in colour
rupture/perforation
If the tympanic membrane is intact but abnormal, what diagnostics should be performed? (4)
myringotomy is performed and samples for:
- cytology,
- histopathology
- bacteriology should be taken.
What is the most sensitive for detecting middle and inner ear disease?
MRI
Medical management is only effective with otitis media if?
Disease of the external ear canal is adequately controlled.
How to medically manage otitis media?
The middle ear is lavaged using warm saline to remove debris and topical and systemic antibiotics (based on culture and sensitivity results) are administered for 4-6 weeks.
With otitis media, when i TECA +/- LBO recommended? (3)
If infection is established
osseous changes to the tympanic bone
stenosis of the external ear canal,
Polyps of the middle ear are inflammatory in nature, arising from the epithelium of (2)
the tympanic chamber
auditory tube
Middle ear polyps is the most common middle ear disease in cats and is often identified in young cats following an episode of?
upper respiratory viral infection
How can polyps lead to horners?
pressure on the tympanic plexus.
Why may polyps cause vestibular signs?
sustained pressure on the inner ear,
Polyps extending into the nasopharynx may cause what signs? (4)
difficulty with swallowing,
nasal discharge
dysphagia
respiratory distress
What breathing in cats is often suggestive of the presence of a nasopharyngeal polyp?
Stertorous
How to diagnose polyps? (3)
Otoscope
Nasopharyngeal exam under GA
CT
Treatment options of polyps?
Traction removal followed by oral prednisolone
A ventral bulla osteotomy
When is surgical management of polyps advised? (2)
neurological signs
external ear polyps.
Which of these clinical signs is suggestive of the presence of a nasopharyngeal polyp in cats?
Stertorous breathing
Purulent discharge
Otorrhoea
Head tilt
Stertorous breathing
What type of mass is a Cholesteatomas?
Cystic
What do Cholesteatomas arise from?
the squamous epithelium of the middle ear that expand over time
What do Cholesteatoma have the potential to cause? (2)
local destruction of the bone of the bulla
secondary inflammation
What do most Cholesteatoma arise 2ry to?
Otitis media
What signalment increases the chance of a Cholesteatoma? (2)
Male
Brachycephalic
Clinical signs of Cholesteatoma?
Similar to otitis media/externa
Why might Cholesteatoma not be visible on otoscope when chronic? (3)
stenosis
exudate,
chronic changes
Cholesteatoma;
What is the mass seen as and where does it protrude from?
mass is frequently pearly white in colour and protrudes from the middle ear to the external ear canal
Cholesteatoma; how is the TM seen?
Not intact
Cholesteatoma; what is used to assess middle ear changes (3)
CT
MRI
Radiographs if above not available
What is seen in the bulla with Cholesteatoma? (4)
Lysis
Sclerosis
Proliferation
May expand and be filled with soft tissue
With a suspected Cholesteatoma what samples should be submitted? (3)
Cytology
Histology
Culture
What is the aim with surgery for a Cholesteatoma?
remove the entire epidermoid cystic structure and to strip the epithelium from the margins including the bulla wall.
What surgical approach for a Cholesteatoma? (2)
Ventral osteotomy
TECA - LBO
Cholesteatoma;
A) Recurrence rate?
B) Surgical is curative how often?
A) High
B) 50%
What symptoms prior to removal have a higher chance of recurrence with a Cholesteatoma?
Neurological sign
What medical management may be needed for ongoing tx of Cholesteatoma? (2)
Secondary infections
Corticosteroids
What neoplasia of the ear have been reported? (3)
Ceruminous gland adenocarcinoma,
squamous cell carcinoma
lymphoma
Patients that have reduced drainage through the auditory tube have reduced hearing and may also develop ?
otorrhoea
What is Secretory otitis media?
an accumulation of mucinous material in the tympanic cavity
Which breed is Secretory otitis media common in?
CKCS
Why might Secretory otitis media develop congenitally?
congenital dysfunction of auditory tube drainage
Which breeds commonly have evidence of middle ear secretions identified on advanced imaging?
Brachycephalic
Dogs that have what (2) of the soft palate are also reported to be at risk of middle ear disease, hypoplastic bullae and impaired hearing.
congenital hypoplasia
malformations
What is Primary ciliary dyskinesia?
rare congenital condition where there is a failure of middle ear drainage, leading to a build-up of mucous and cellular debris and the development of a secondary sterile otitis media.
In patients with reduced drainage, what may provide temporary relief?
myringotomy
In patients with reduced drainage, what may provide longer-term relief of sign (2)
Tympanostomy tubes
grommets placed in the pars tensa of the tympanic membrane
Alternative surgical tx in patients with reduced drainage?
TECA
The aims of the surgical procedures of the middle ear (3)
eliminate the primary cause
to remove debris
Remove diseased tissue
Indications for surgery for middle ear? (2)
Septic otitis media/interna where medical management has failed;
Treatment of patients where neurologic signs are identified that may be relieved by tympanic decompression.
The surgical approach to the middle ear is determined by the
of the problem. For example, in chronic otitis externa with associated otitis media, a lateral approach with
A) is ideal. In patients with otitis media and no external ear canal disease,
B) is adequate e.g. cats with inflammatory polyps.
A) TECA - LBO
B) VBO
How is a cat positioned for a VBO?
dorsal recumbency. (Placement of a cervical support helps extend the neck to allow easier access to the bulla.)
How to palpate the right area for VBO?
The ventral aspect of the bulla is palpated – this will lie in the triangle formed by the caudal aspect of the mandible, the mandibular symphysis and the caudal border of the larynx.
VBO: Where is the incision?
The incision is centred over the bulla and a dissection down through the muscles is performed.
VBO:
Which structures need to be retracted from the site? (5)
mandibular salivary gland
bifurcation of the linguofacial and maxillary veins
hyoglossus and styloglossus muscles
Which structure is avoided in a VBO?
Linguofacial vein
VBO:
The ventral aspect of the bulla is identified via palpation and a periosteal elevator is used to ?
strip the periosteum away from it.
VBO:
How to perform the osteotomy? (2)
drill
increasing gauges of Steinmann pins.
VBO:
CARE! If the bony wall of the bulla has been affected by the disease process
Why?
bone is likely to be soft and there is potential to damage the underlying bony promontory.
VBO:
What is used to remove any mucous secretions from within the hypotympanic chamber.
Suction
VBO:
The septum between the laterally situated hypotympanic cavity and the true middle ear is opened carefully, sticking as ?as possible to avoid damage to the promontory and the overlying nerves.
lateral
VBO:
8
If present, polypoid material is removed from the A) chamber, and occasionally the B)
A) mesotympanic
B) external acoustic meatus.
VBO:
Following removal of material. What is then performed? How is it closed?
Lavage and suction of the bulla is performed.
Closure of the muscles over the bulla, the subcutaneous tissues and the skin is then performed.
Complications of VBO in cats (2)
Horner’s syndrome
Vestibular signs
Horners syndrome in cats; usually transient, if it lasts how long it is permanent?
6 weeks
Why might vestibular signs occur post VBO? (2)
iatrogenic during bulla curettage
present pre-operatively if the polypoid material has been causing pressure on the labyrinth.
The prognosis for recovery from inflammatory polyps following VBO is?
excellent.
When is VBO indicated in dogs? (2)
Failed LBO (lateral bulla osteotomy)
neoplastic conditions of the middle ear.
How to position a patient for a VBO?
Dorsal recumbency with the neck extended and a cervical support placed
What is the difference to the ventral aspect of the bulla in dogs compared to cats? (2)
- Much less obvious
- situated a lot deeper within the soft tissues
In dogs:
Whatsits midway between the wing of the atlas and the angle of the mandible?
Bulla
VBA in dogs:
The jugular process of the skull can often be palpated, and the bulla usually lies approximately?rostral and medial to this bony prominence
5-10 mm
VBO in dogs; what must be retracted medially or laterally to gain access to the bulla?
The digastricus muscle
