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.
What constitutes sudden sensorineural hearing loss?
Sudden onset SNHL definition – loss of >30dB in 3 contiguous tones over 3 days. Can include abrupt or rapidly progressive. This is an otological emergency.
What causes sudden onset sensorineural hearing loss?
Noise exposure, gentamicin toxicity, mumps, acoustic neuroma, MS, TB or vasculopathy.
How should sudden onset SNHL be investigated?
Important to classify sensorineural vs conductive hearing loss.
Assess drug history and examine EAC and TM
Bloods (FBC, CRP, U+A, LFT and TSH), autoimmune profiling, clotting studies, fasting glucose and cholesterol.
Pure tone audiometry
MRI scan – to exclude lesions
How should sudden onset SNHL be managed?
Immediate referral to specialist
Presume inflammatory cause until proven otherwise
High dose Prednisolone for 4 days tapered over 8 days antivirals can be added
Once cause is discovered treat this
What is otosclerosis?
Replacement of normal bone with vascular spongy bone around the stapes footplate which leads to its fixation and consequence conductive hearing loss.
What are the causes and risk factors for otoscelrosis
Autosomal dominant with incomplete penetrance
More common in females
Usually occurs in early adult life
Accelerated by pregnancy
How does otosclerosis present?
Unilateral progressive conductive hearing loss (hears better with background noise)
Tinnitus and mild transient vertigo
Schwartz sign – pink tinge to the eardrum
Family History
How is otosclerosis managed?
Hearing aids including Bone anchored hearing aid (BAHA), Cochlear implant if severe
Surgical options – stapedectomy (contraindicated with SNHL in the other ear)
What is presbyacusis?
Age related hearing loss affecting high frequencies mostly. Starts from age 30 and thought to affect high frequency over low because these hairs are first in the labyrinth so receive the highest energy of sound waves. Deafness due to loss of hear cells is progressive and not usually noticed until hearing speech is impaired.
How does presbyacusis present?
Gradual progression of difficulty understanding speech, increased volume or TV, radio and phone and hyperacusis in certain tones. Hearing is worst when background noise is present
How is presbyacusis investigated?
Otoscopy: Normal, to rule out otosclerosis, cholesteatoma and conductive hearing loss (Foreign body, impacted wax etc.)
Tympanometry: Normal middle ear function with hearing loss (Type A)
Audiometry: Bilateral sensorineural pattern hearing loss
How is presbyacusis managed?
Hearing aids
What causes noise induced hearing loss?
Can be a single event causing acoustic trauma or persistent loud noise that causes damage over time. There is a relationship between volume and duration for example 5 hours at 85dB usually causes damage. Sounds greater than 180dB cause acoustic trauma.
How does noise induced hearing loss present?
Bilateral symmetrical sensori-neural hearing loss and tinnitus
Can be noise induced temporary threshold drift (improves as you move away from source)
Audiometry shows a notch at 3,4 or 6kHz which improves at 8kHz
What is the management of noise induced hearing loss?
Avoid exposure and abide by health and safety laws – use earmuffs
If hearing loss established, then hearing aids
What is acoustic neuroma?
Indolent histologically benign subarachnoid tumours of the Schwann cells surrounding nerves VIII or V. They produce a space occupying lesion. May be bilateral if neurofibromatosis type 2.
How does acoustic neuroma present?
Unilateral sensori-neural hearing loss an tinnitus
Ipsilateral cerebellar or raised ICP signs if large
Giddiness is common
Vertigo rarely
Numb face if VII involved and V palsy also
How is acoustic neuroma managed?
Audiogram and Gadolinium enhanced MRI for everyone with unilateral deafness/tinnitus
Surgery – difficult and often not needed if elderly
