Suzanne de Bruijn

26 Chapter 1.1 Table 1. Clinical characteristics and classification of hearing loss Characteristic Class Definition Type Thresholds averaged over 0.5, 1 and 2 kHz Conductive HL resulting from abnormalities in outer or middle ear structures, normal bone-conduction thresholds (<20 dB HL), air-bone gap >15 dB HL Sensorineural HL resulting from abnormalities in inner ear structures, air-bone gap <15 dB HL Mixed HL with combinatory involvement of conductive and sensorineural HL, >20 dB HL bone-conduction threshold, >15 dB HL air-bone gap Severity Criteria should be applied to the better hearing ear, thresholds averaged over 0.5, 1, 2 and 4 kHz Mild 20-40 dB HL Moderate 41-70 dB HL Severe 71-95 dB HL Profound >95 dB HL Audiometric configuration Low frequency, ascending >15 dB HL difference between the poorer low frequency thresholds and those for the higher frequencies Mid frequency, U-shaped >15 dB HL difference between the poorest thresholds in the mid-frequencies, and those at higher and lower frequencies High frequency, gently sloping 15-29 dB HL difference between the mean of 0.5 and 1 kHz and the mean of 4 and 8 kHz. High frequency, steeply sloping >30 dB HL difference between the above frequencies Flat <15 dB HL difference between the mean of 0.25 and 0.5 kHz thresholds, the mean of 1 and 2 kHz and the mean of 4 and 8 kHz Frequency ranges Low ≤ 0.5 kHz Mid >0.5 kHz, ≤2 kHz High >2 kHz, ≤8 kHz Extended high >8 kHz Symmetry of HI Symmetrical Bilateral HL, <10 dB HL difference between the ears Asymmetrical Unilateral or bilateral HL, asymmetrical HL if >10 dB HL difference between the ears in at least two frequencies exists Age of onset Congenital/prelingual Onset of HL before speech develops Postlingual Onset of HL after speech developed Progression Averaged over 0.5, 1 and 2 kHz Progressive Deterioration of >15 dB HL Non-progressive Deterioration of ≤15 dB HL Additional symptoms Tinnitus Presence of e.g. low or high tone pitch noise Vestibular symptoms Presence of vestibular problems and/ or abnormal vestibular function Classifications and definitions of audiological phenotypes as recommended and described by the GENDEAF study group. 40 kHz, kilohertz; HL, hearing loss; dB, decibel.