Current RMA Instruments
| Reasonable Hypothesis SOP | 98 of 2019 as amended |
| Balance of Probabilities SOP | 99 of 2019 as amended |
Changes from previous instruments
ICD Coding
ICD-10-AM Codes: H90.3 H90.4 H90.5
Brief description
Sensorineural hearing loss is loss of hearing due to damage to the hearing mechanism of the inner ear (the cochlear) or the nerve between the cochlear and the brain (the auditory nerve).
Sensorineural hearing loss is a functional impairment of hearing rather than a discrete disease. It is most commonly related to excessive noise exposure, but may also be a manifestation of several diseases or injury mechanisms.
Confirming the diagnosis
The diagnosis requires an audiogram, showing a permanent hearing loss, measured by valid bone conduction, of at least 25 decibels at 500, 1000, 1500, 2000, 3000, 4000 or 6000 hertz (Hz). Loss of 25 decibels means a hearing threshold level of 25dB or below (i.e. 30, 35 etc). A decrease from a previous reading by 25 dB (e.g. from 10 to 35 dB) is not required.
The audiogram should be performed by an Audiologist. The relevant medical specialist is an Ear, Nose and Throat surgeon.
Additional diagnoses covered by these SOPs
- Bilateral sensorineural hearing loss
- Neural hearing loss (cochlear [8th cranial] nerve injury or disease)
- Noise-induced sensorineural hearing loss
- Perceptive deafness/hearing loss
- Presbyacusis
- Recruitment syndrome (a symptom of SNHL, not a separate disease/injury)
- Sensorineural deafness
- Sensory hearing loss (cochlear organ injury or disease)
- Unilateral sensorineural hearing loss
Diagnoses which may be covered by SOP (further information required)
- Mixed hearing loss - code and determine the conductive and sensorineural components separately
- Non-conductive hearing loss
- Sudden hearing loss
Conditions not covered by these SOPs
- Central hearing loss - determine as part of the underlying brain injury or disease
- Conductive hearing loss*
- Congenital deafness#
- Diplacusis#
- Hyperacusis*
- Meniere’s disease* - the sensorineural hearing loss component is excluded from the SNHL SOP
- Psychogenic / hysterical deafness#
- Temporary or transient hearing loss - not a disease or injury.
*another SOP applies - the SOP has the same name unless otherwise specified
# non-SOP condition
Clinical onset
This is a threshold diagnosis. Clinical onset will date from the first reliable audiogram to show a permanent hearing loss of the required level. Hearing loss may be temporary. A reliable audiogram showing normal hearing (< 25 decibel (dB) loss at the relevant frequencies) rules out a clinical onset before that audiogram, even if there is a preceding abnormal audiogram.
Clinical worsening
The natural history for hearing is for it to deteriorate slowly with age (presbyacusis). Demonstration of clinical worsening would require an audiogram showing a decline in hearing from previously recorded levels, that is not attributable to the passage of time.
Further comments on diagnosis
Audiometry
Procedure
Audiometry is a procedure which measures hearing thresholds at different frequencies in an individual, compared to a reference hearing standard which is based on the hearing thresholds of young persons (18-25 years) with normal hearing. This standard is calibrated into the audiometer as a reference zero.
As a result of the calibration an average normal young person’s audiometry would read zero dB on all frequencies from 250 Hz to 8000 Hz. Normal variation in the population means that people with normal hearing can have thresholds above or below zero. However, testing is not usually done for thresholds above zero.
The 25 dB threshold used in the SOP definition is an internationally recognised standard. An audiogram showing hearing loss of less than 25 dB at all frequencies up to 6000 Hz can be regarded as showing hearing within the normal range. If bone conduction values are all less than 25 dB, but some or all air conduction values are 25 dB or more, a conductive hearing loss may be present.
Any other available audiograms should be examined to establish that an observed hearing threshold shift is permanent.
Reliability
Audiometry requires a co-operative subject who accurately and reliably signals the hearing of the provided tone. Reliability is the ability to reproduce the same measurement on repeating the audiometric testing. A significant variance in measurements taken at the same sitting by the same operator would indicate a poor reliability.
A large difference between ears indicates poor reliability or a significant pathology which needs investigation. It could indicate the presence of a brain or acoustic nerve tumour.
A large difference between air and bone measurements (air-bone gap) may indicate a reliability problem or it indicates conductive hearing loss or mixed hearing loss.
If the audiogram is not reliable, a repeat audiogram should be sought with 3 measurements at each frequency, with the frequencies measured in random sequence on the same day, and including both air and masked bone conduction at 500, 1000, 1500, 2000, 3000, 4000 and 6000 Hz. If a reliable audiogram cannot be achieved by this process, an estimate of the hearing should be sought from an ENT surgeon.
Air conduction
Air conduction is recorded on an audiogram using the symbols “O” and “X” for air conduction in the right and left ears, respectively. Air conduction measures the total hearing loss, that is, the conductive and sensorineural components combined.
Bone conduction
Bone conduction is recorded on an audiogram using the symbols “[” and “]” for masked bone conduction, or the symbols “<” and “>” for unmasked bone conduction, in the right and left ears, respectively. The symbol “˄” denotes unmasked bone conduction in the better ear. For diagnostic purposes masked bone conduction is preferable, but bilateral unmasked bone conduction is acceptable. With unmasked bone conduction testing the sound may be heard in the other ear. Masking prevents confusion as to which ear is sensing the sound.
Air conduction values may only be used for the diagnosis of sensorineural hearing loss when bone conduction is unobtainable or invalid (see below).
Bone conduction measures that part of a hearing loss that is due to sensorineural loss. Air conduction measures the total hearing loss. As part of a hearing loss cannot exceed the total hearing loss, it follows that bone conduction cannot legitimately exceed air conduction (at any given frequency in the one ear). Hence, a bone conduction value that shows more decibel loss than the corresponding air conduction value is not valid and must not be used. In this event, the air conduction value at that frequency in that ear may be considered for diagnostic purposes. Note that it is common to obtain one or two erroneous bone conduction measurements as part of the random error of normal measuring, but a higher number of erroneous measurements indicates a non-reliable audiogram.
Presbyacusis
Presbyacusis denotes degenerative hearing loss due to age. However, presbyacusis is a form of sensorineural hearing loss and falls within the scope of the words in the SNHL SOP definition. Hence, in the event of a diagnosis of presbyacusis (with at least 25 dB loss), the SOP should be applied, with the diagnosis changed to sensorineural hearing loss. In the event of a successful claim a discount for the effects of presbyacusis will be applied, if appropriate, in the assessment process.