A double sided handout with pictures on was supplied at the lecture.

Revision of structure:

See handout for some of the notes on the embryology of the ear.
Otic pit ==> otic vesicle ==> membranous labyrinth

The pinna can develop to form an accessory auricle. Developmentally, each auricle is comprised of 6 parts. Abnormalities on the external ear can often indicate the presence of abnormalities inside the ear.

Note: the Eustachian tube, ear and mandible are all 1st branchial arch derivatives, and can therefore all be abnormal at the same time.

To test for sensory or mechanical (conductive) hearing loss you use a tuning fork to put vibration through the bone at the front (Waber), use a tuning fork to put vibration onto the bone behind the ear (Rinne). The sound is often louder in the damaged ear because the normal ear can’t hear it properly through the bone, it is still looking for external sounds.

You can also put pressure on the ear drum by pushing air down the external auditory canal. If there is a hole in the ear drum, or there is a lot of fluid in the middle ear, the ear drum won’t move.

A noise box can be used to put louder noise into the good ear in order to isolate the ear you are testing.

In sensori-neural loss (recruitment) there comes a time in old age where the threshold limit for pain from sounds is a lot narrower.

CONGENITAL:

• hereditary/familial
• spontaneous

• infection
• trauma
• neoplasia (tumour formation)
• drugs (ototoxic - to neural epithelium of the inner ear)
• metabolic disorders (diabetes)
• autoimmune disorders

• Otosclerosis - where the stapes gets excess bone formation in females (sex-linked genetic disorder)
• Tinnitus - like the noise you get in your ears after coming out of a pop concert. It could actually be caused by a beetle or a fly in the ear.
• Exostoses - when someone does too much scuba diving, etc. the cold water causes the body to grow extra bone into the external auditory canal which restricts the amount of sound entering it a lot.
• Wax can be a cause of hearing loss.
• Abuse - middle ear can be filled with blood as a result of a fractured skull.
• Cauliflower ear - also affects the out third of the external auditory canal which is also cartilaginous.
• Viral infection - Herpes osta - shingles, affects the nerve supply.
• Infection of the back of the nose - glue ear - can get infected and rupture the ear drum. (Orangey fluid).
• Congenital disorders tend to be multiple/composite problems.
• Infections in the middle ear cleft, eg: mastoiditis.
• Acoustic neuroma - a not uncommon tumour of the vestibulocochlear nerve (of the family of neurofibromatosis) where the tissue changes type within the tumour.

• Gromits - allows the air to get the fluid out of the ear.
• Damaged ossicles - you can hook an artificial one onto the remaining ossicles, made of teflon.
• You can repair the ear drum surgically.
• Hearing aids - in the ear aids - have an amplification block to stop the sound from getting too loud. Post-aural aid doesn’t have as much problem with feedback.
• Profound hearing loss - have a transmitter coil and on the other side of the skin, a receiver coil with wires going into the cochlea - cochlear implant. Therefore you can stimulate neurones electrically in the cochlea.
• A bone-anchored hearing aid can be used to get to the nerve for hearing. This is done by putting some metal studs into the bone and transmitting the sound through the bone.