Week 3: ENT 1 (anatomy of the ear, history and examination) Flashcards
1
Q
The ear is subdivided into 3 main parts:
A
1) the external ear 2) the middle ear 3) the inner ear
2
Q
referred ear pain explanation
A
-
Branches of
- Cervical spinal nerves
- Vagus
- Trigeminal (auriculotemporal n.)
- Glossopharyngeal (tympanic n.)
- Small contribution from CNV II – vestibulocochlear)
e.g. someone with pathology affecting parts of the pharynx/larynx may manifest itself as pain from the ear
3
Q
Otalgia with a normal ear examination should leave you to suspect an alternative site of pathology
A
- Otalgia can be non-otological or otlogical in origin
- There are many non-ontological causes for otalgia
- TMJ (temporal mandibular joint )dysfunction (CN Vc)
- Disease of oropharynx (CN IX)
- Disease of larynx and pharynx including cancers (CN IX and X)
4
Q
the external ear includes
A
- Pinna- outer curve of the ear
- External auditory meatus lined with skin air filled canal leading to the middle ear
- Supplied by the greater auricular nerve, lesser occipital and facial nerve
5
Q
the pinna
A
- Pinna consist of elastic cartilage thrown into folds and fibrofatty lobules
- Supplied by the greater auricular nerve, lesser occipital and facial nerve
6
Q
External auditory canal
A
- Oblique tube 3cm in length
- Outer 1/3 is cartilage, inner 2/3 is bony
- Ceruminous glands only exist in the outer 1/3 →wax
- Tympanic membrane from the medial boundary of the canal
- Nerve supply- auriculotemporal nerve and auricular branch of the vagus nerve
- Blood supply: Auriculotemporal branch of superficial temporal artery Posterior auricular branch of the external carotid artery
7
Q
external acoustic meatus
A
Skin lined cul-de-sac 2.5cm in length
- Sigmoid shaped
- Lined with keratinising, stratified squamous epithelium continuous onto lateral surface of tympanic membrane
- Embryology- EAM from cleft of the 1st and second pharyngeal arches lined with ectoderm
- Cartilaginous outer 1/3
- Hair
- Sebaceous
- Ceruminous (wax0 glands lined cartilage part
- Barrier for foreign objects
- And bony inner 2/3 (petrous bone)
8
Q
self cleaning function of EAM
A
- Epithelial migration
- Surface of the skin moves laterally from the tympanic membrane towards the ear canal
9
Q
Middle ear
A
- Air filled cavity
- Pharyngotympanic tube (PT) intermittently opens→ allows air filled cavity of the PT equilibrate with air pressure in the Nasopharynx (NP)
- Ossicles
- Middle ear lined with pseudostratified columnar ciliated epithelium with goblet cells (resp epithelium)
10
Q
ossicles
A
- Malleus- largest and lateral process is attached to tympanic membrane
- Incus- head of malleus articulates with incus
- Stapes – two limbs (anterior crus and posterior crus) attached to oval window footplate
11
Q
The tympanic membrane
A
- forms the lateral boundary of the middle ear cavity. It is a circular shape and roughly 1cm in greatest diameter.
- Nerve supply- outer surface by the auriculotemporal nerve and the auricular branch of the vagus.
- The membrane is normally greyish/ pinkish in colour.
- When the membrane is examined with an otoscope, the concavity of the structure produces a cone reflex in the anteroinferior quadrant.
- The tip of the handle of malleus forms the deepest concavity of the membrane called the umbo, which is where the cone of light radiates from.
- The pars flaccida is the weakest and most flaccid area of the tympanic membrane.
- It plays a vital role in the pathophysiology of cholesteatoma.
- The pars tensa forms the remainder of the tympanic membrane.
12
Q
Inner ear
A
- Fluid filled structures
- Located in the petrous part of the temporal bone
- Cochlear canal
- Where action potentials are generated for sending signals to the brain to be perceived as sound
- Fluid filled
- Semi-circular canals
- 3
- Orientated at 90 degrees to one another
- Fluid filled
- APs carried to the brain to be perceived as position and balancer
13
Q
two importnant structures of the inner ear
A
- Vestibular apparatus
- Cochlea
- Both fluid filled tubes
- Involved in hearing (cochlea) and balance (vestibular)
14
Q
cochlea
A
Fluid filled tube with specialised hair cells that generate AP when moved. Arranged in a spiral housed within the petrous part of the temporous bone. Cochlear duct sit inside the cochlear (allowed out petrous bone) that has specialised hair cells etc…
- Movement at the oval window (by the movement of the ossicles causing movement on the footplate onto the oval window) causes movement of fluid in the cochlear duct
- Waves of fluid cause movement of special sensory cells (stereocilia)→ generates AP via CN VIII (vestibulocochlear) → temporal region of brain
15
Q
Vestibular apparatus
A
- Fluid movement (generated by position and rotation of head)
- Converted into APs (CNVIII) → perceived as position sense and balance
16
Q
Inner ear pathology presents with a combination of
A
- Hearing loss
- Tinnitus
- Disturbances in balance and vertigo (specific to inner ear)
17
Q
Mechanism of hearing
A
- Auricle and external auditory canal focuses and funnels sound waves towards the tympanic membrane which vibrates
- Vibration of TM causes vibration across chain of ossicles (amplifies) and ends in vibration of the foot of the stapes on the oval window
- Fluid filled cochlea duct
- Within the duct is the organ of corti – where we found the stereocilia
- Vibration created by ossicles leads to waves in the channels of fluid which lead to movement of stereocilia (nerve cells) AND TRIGGERS AP IN COCHLEAR PART OF CN VIII
- Generate sound
- PRIMARY AUTITORY CORTEX= TEMPORAL LOBE
20
Q
Before starting ear exam
A
- Wash hand
- Introduce self and make sure patient comfortable
- Ask about any pain or tenderness
- Patient should be position on chair and place yourself to the side of patient
- Children should be sat across the parent/nurse lap, with the side of the ehad held to the chest by the carers hand
- Flailing arms can be secured with the cares other hand
- Examine opportunistically and incorporate play as part of the examination
22
Q
otoscopy method
A
- Ensure the otoscope has good magnification and illumination. Use the largest speculum that will fit comfortable in the external auditory canal (EAC)
- Start with the “normal” ear
- Gently pull the pinna upwards and backwards to straighten the ear canal to best visualise the tympanic membrane. In children, pulling the pinna downwards and backwards may provide better visualisation
- Hold the otoscope like a pencil and use your little finger as a fulcrum against the cheek to avoid injury should the patient move suddenly
- Inspect systematically
Looking at: external auditory canal, tympanic membrane, ossicles
28
Q
Free field speech testing
A
- Free field testing is a good screening tool for hearing loss
- Use of masking improves the accuracy of testing:
- Rub the tragus of the contralateral ear whilst performing this to prevent sound being heard in the contralateral non-test ear
- Use polysyllabic phrase (number or letter) e.g. ‘C5’, ‘37’ or motivational phrases in children e.g. ball, sweets, crisps
- Test normal ear first.
- Perform, in order of intensity at 60cm (arms length) and 15cm: whisper, conversational speech, loud voice.
- Patient should be able to repeat >50% of the letters/numbers correctly.
30
Q
Webers
A
- Vibrating 512Hz tuning fork applied firmly to the midline of the forehead, apex of head (see Figure 4)
Ask the patient if he/she can hear a tone in the right ear, left ear or centre of the head - The “louder” ear may be due to conductive hearing loss in that ear (sound travels through the bone), or sensorineural hearing loss in the other ear
- You can work out which this is by performing Rinne’s test.
32
Q
summary of webers and rinnes
A
35
Q
interpreting audiometry
A
Hearing Disability is defined as:
- Normal hearing is defined to be 20dB or better.
- Mild hearing loss is between 21-40dB.
- Moderate hearing loss is between 41-70dB.
- Severe hearing loss is considered to be 71-90dB.
- Profound hearing loss is worse than 90dB.
36
Q
audiogram example
A
40
Q
If the pressure in the middle ear decreases
A
retraction of the TM- otitis media with effusion (not getting pressure equilibrating- air in middle ear space gets reabsorbed → leaving mucosal fluid- negative middle ear pressure)
41
Q
If pressure in the middle ear increases
A
- bulging – acute otitis media (inflammatory exudate produced by mucosa increased air pressure)
