Deafness and Hearing Tests Flashcards
What is Weber’s test?
Hold tuning fork (256Hz or 512Hz) in middle of forehead. If localisation (heard louder) to the unaffected ear then sensorineural problem with affected ear and if localisation to the affected ear then there is coductive problem with the affected ear.
What is Rinne’s test?
Put tuning fork (256Hz or 512Hz) on mastoid process then adjacent to ear canal and see which is louder. Normally air conduction should be better than bone conduction (Rinne +ve). In conductive hearing loss bone will be better than air and in sensineural air will still be better than conductive.
What is pure tone audiometry?
Quantified hearing loss and assesses its nature. Tones are played via sound conduction at differing frequencies. The dB of the tone is increasing until it is heard at a 50% response rate. This information is then shown on a graph. Any Db less than 20 is assumed to be normal.
What is acoustic impedance audiometry?
This is effectively a measure of middle ear pressure by measuring the compliance of the tympanic membrane.
What are the 3 graph types that tympanometry makes?
Normally it is most compliant when canal pressure = middle ear pressure this is a Type A graph. If the middle ear is full of fluid, then all the energy will be reflected back to the tube this is flatline type B graph. Type C graph suggests eustachian tube dysfunction and there is a negative pressure. If the ossicles aren’t working, then the drum will have a higher peak than normal as it is free to move.
What are otoacoustic emissions?
Assesses cochlea function by recording sound vibrations produced by the outer hair cells in the cochlea. All neonates are tested using this in neonatal screening. This tests the peripheral audiometry system I.e. the sensory part.
What are audiological brainstem responses?
Audiological Brainstem responses (ABR)
Records electrical activity along the auditory pathway in response to a sound. If a child’s OAE is abnormal then they undergo this test. Headphones are put on a child which produce clicks. Electrodes on child’s head then detects electrical stimulation from these clicks. This tests the neural pathway of CNVIII.
What are the normal hearing frequencies for a human?
0-140dB
20-20’000Hz
25-8000Hz is most important for speech
Vowels lower frequency and easier to hear
How does hearing loss in children usually present?
Most commonly presents with learning difficulties and problems with speech. Can also present with behavioural issues in school.
What can cause genetic conductive hearing loss?
Congenital abnormalities of the pinna, external ear canal. Drum or ossicles.
What are some common causes of genetic sensorineural hearing loss?
Autosomal dominant – Waardenburg syndrome, Klippel Feil syndrome, and Branchio-oto-renal syndrome
Autosomal recessive – Pendred syndrome, Usher’s syndrome, Jervell and Lange-Nielson Syndrome
Polygenic – accounts for 70% of congenital hearing loss. Most genes involved are recessive but they vary in presentation and age.
X-linked – Alport’s Syndrome and Turner’s Syndrome
What can cause non genetic deafness?
Intrauterine infection such as CMV, Rubella, toxoplasmosis, HSV and syphilis
Perinatal causes – prematurity, hypoxia, IVH, kernicterus and infection
Infections – meningitis, encephalitis, labyrinthitis, measles and mumps
Other – ototoxic drugs, acoustic or cranial trauma
Give some examples of ototooxic drugs?
Examples of ototoxic drugs: streptomycin, vancomycin, gentamicin, chloroquine, hydroxychloroquine and vinka alkaloids)
How is hearing loss managed in children?
Give lots of support and help to the parents and child
Maximise the child’s hearing i.e. sitting at front of class, hearing aids, cochlear implants (if hearing aids aren’t helpful) support to develop spoken or signed communication.
If an adult presents with sensorineural hearing loss what must you exclude?
If unilateral SNHL then must exclude acoustic neuroma, cholesteatoma and effusion from nasopharyngeal cancer.
