Ear anatomy and embryology Flashcards
Inner ear is located in
Ear is in
Roof of ext, middle and inner ear
Internal acoustic meatus connects inner ear to which cranial fossa
Which cn passes through int acoustic meatus
Petrous part of temporal bone Temporal bone , Anterior plate of petrous bone posterior plate separates it from posterior cranial fossa
Posterior cranial fossa
7 nd 8
Acoustic neuroma
Tumour Arises from the internal acoustic meatus then it goes intracranially, so there can be diplopia due to 6 cn involvement( upper pole of tumour, cn 5 , 6 involved)
Lower pole involve 9,10 ,11
Cn 6 arises at the junction of pons and medulla ( quite posteriorly) nd has the
Longest intracranial course may be involved in many conditions
Pathology of petrous apex cn involved
Sigmoid sinus
5 and 6
Posterior boundry of mastoid exit through juglar foramen and continues in neck as internal juglar vein
Base of skull foramen 1 optic canal 2 superior orbital fissure 3 foramen rotundum 4 foramen ovale 5 foramen spinosum 4 foramen lacerum 5 internal acoustic meatus 6 juglar foramen 7 hypoglossal canal
Optic nerve, opthalmic artery Cn 3,4,6,5(opthalmic branch) Cn 5( maxillary branch) Cn 5( mandibular branch) Middle meningeal artery and vein Greater petrosal nv( passes over the foramen) cn 7,8 Cn 9, 10, 11 Cn 12
Meiners disese
Apex of organ of corti ( responsible forr low frequency sensation) is affected early in meiners disease
Base of organ of corti senses sound at high frequency
Arcuate eminence
Posterior semicircular canal
Lateral semicircular canal
Projection of superior semicircular cannal into roof of inner ear( base of skull)
If arcuate eminence ( roof) is absent - superior semicircular canal dehiscence syndrome aka third window syndrome
Bulges posteriorly towards the mastoid
Bulges laterally towards the middle ear
Bonny labyrinth develops from
Membranous labrynth develops. From
Mesoderm from enchonderal ossification ( first develops into cartilage then into bone)
Sub ectoderm
Oval window
’ Connects middle ear to vestibule of inner ear
Otosclerosis- fixation of oval window →no vibration transmission
Utricle and saccule overstimulation by oval window hypermobility or utricle and saccule dilationlation leads to proximity of u nd s towards the oval window leading to to vertigo ( utricle and saccule dilation— meiners , syphlis— hypermobility)
Secondary tympanic membrane
Round window -connecting middle ear to scala tympani
Significance of round window- sound transmission shering action on organ of corti
Electrodes transmission to inner ear via round window in cochleaer implant (round window is the path of choice for middle to inner transmission eg steroids , gentamicin )
Connection of Brain to inner ear
Internal acoustic meatus
Cochlear aqueduct ( CSF → perilymph)
Meningitis can lead to labrynthitis
Congenital abnormality of inner ear
Michael Aplasia → absent
Mondini → cochlea /sm has 1 1/2 turns only
Alexander →deformity of basal turn high frequency sound affected
Schiebie → deformity of saccule and cochlea (sc)
Endolymphatic sac
Orientation of semicircular canals
Lies between 2 layers of dura ( menengeal and endosteal)
Lateral lies inside posterior and superior and posterior have a common opening called crus commune
Internal and middle ear development
From brachial arches
Ectodermal lining _ external auditory canal develops from first cleft( only cartilagenous part present at birth , pinna develops from the same cartilage-defect in formation of pinna is called meatal atresia—hearing loss— Tt BAHA invasive surgery-reconstruction done after 6years of age in children by costal rib cartilage )
Mesodermal arch _ first arch: malleus, incus _ second arch: supra structure of stapes
Endodermal pouch: tubotympanic recess - proximal part: Eustachian tube
- distal part: middle ear, mastoid antrum
Calluaral fistula
All the cleft during the formation of external auditory canal develops in the neck
The lateral part fuses and the medial part leads to formation of EAC
If lateral part remains unfused it leads to formation of an opening in neck called a callural fistula
Mc site of preauricularsinus
Junction of tragus and helix
1-Crowbecks sign 2-Griesinger sign 3-tragal sign 4- Hennebert sign 5- lighthouse sign( pulsatile otorrhoea) 6- pulsation/ browns sign ( pulsation and blanching ) 7- pulsatile tinnitus 8- Phlep s sign ( absence of crest of bone b/w ICA and JV) 9 Reservoir sign/ tea pot sign ( pus in mastoid refilling while drainage) 10- Gradenigo’s triad 11-Delta sign/ Empty triangle sign 12-tobey ayer/ Queckenstedt’s test 13-Schwatz sign / flamingo pink sign 14- schwatz surgery 15- red reflex/ rising sun app 16 red TM/ cartwheel app 17 vanderhoeve syndrome 18- kernigs sign 19- Brudzinski singn 20- hitzelberger sign 21 -double ring/ halo/ target sign 22 -double density sign 23- Holman miller sign 24- Dodd’s/ crescent sign 25- irwin moore sign 26- Moure sign 27- Boyce sign 28 -Boyce position 29- roses position 30 bryce sign
1-Papilledema in eye on compresssing and releasing the IJV
2-Swelling of mastoid due to mastoid emissary vein obstruction in lateral sinus thrombosis
3- furuncle of EAC
4-congenital syphlis, some cases of meiners ,SSCD
5- ASOM; acute mastoiditis
6,7,8- Glomus
9- mastoiditis
10- triad of petrositis- inv of cn V, palsy of VI nv and ear discharge
11- lateral sinus thrombosis osis due to obstruction walls apper like empty triangle
12- lateral sinus thrombosis inc in csf when press and release the IJV
13- active otosclerosis ( n appearance in otosclerosis is pearly white )
14- acute mastoiditis( opening of mastoid air cells nd pus removal)
15 glomus
16 ASOM
17 osteogenesis imperfecta association with otosclerosis and blue sclera
18 meningitis complication of CSOM
19- meningitis
20-acoustic neuroma/ vestibular schwannoma- hypoesthesia in EAC inv sensory part of facial nv
21. Csf rhinorrhea
22. Allergic fungal sinusitis
23- angiofibroma ( post wall of mazxillary antrum pushed anteriorly)
24- antrichoaanal polyp ( column/ crescent of air seen when bulge doesnot arise from post pharyngel wall whersas in angiofibroma where bulge arise from post pharyngeal wall it is not seen)
25-chronic tonsillitisOn pressing anterior pillar there is expulsion of cheesy material
26- post cricoid CA , laryngeal crepitus is heard on holding and moving the larynx
27 zenkers diverticulum pharyngeal pouch gurgling sound of swelling
28. Direct laryngoscopy bronchoscopy oesophagoscopy
29- tonsillitis, adenoidectomy, tracheostomy
30. Laryngocele on pressingswelling hissing sound
Meiners
Reverse meiners
Dipalcusis
Triad of vertigo followed by deafness and tinnitus
Deafness and tinnitus preceed vertigo
Ears perceive sound at different frequencies see in meiners
