I rarely, as the proverb has it, ‘look a gift horse in the mouth’ and this ring-bound paperback did carry a title that definitely sparked my interest. Audiogram interpretation can be a great group exercise, especially if one knows the pitfalls, such as the masking dilemma of the double conductive loss, the perils of a vibrotactile response or the peculiarities of bone conduction. There is one huge drawback for any UK reader, however, in that the UK and USA are quite unable to agree on common audiometric symbols. To those of us who, for decades, have simply ‘known’ that an isosceles triangle is an unmasked bone conduction threshold, it is almost impossible to ‘see’ into an audiogram where it is instead a masked right air conduction threshold. By the end of six months in Michigan, I was just beginning to interpret local audiograms. So my interpretation was far from rapid here.
But we will have US readers and, especially for trainees, this manual does achieve its stated aim. (My colleagues in audiology looked blank when I asked about European practice). The eight-step guide to interpretation is particularly good, taking the reader from the recognition of any hearing loss up to the use of acoustic reflexes. Masking strategies (never an easy topic) are particularly well covered, but the greatest attraction must be the pattern recognition in audiometry, often at a glance with increasing maturity (i.e. age!). We are presented with 12 classical appearances, ranging from noise-induced hearing loss and congenital sensorineural deafness to Ménière's disease. Immittance testing is particularly well explained and I was glad to see the cautions suggested regarding interpretation.
The bulk of the book is the Audiogram Workbook, with 65 typical pure tone audiograms, a brief history and immittance test results, all of which are subjected to their eight-stage interpretation. Finally comes the assessment, which I did often find disappointingly brief and scanty, representing a missed opportunity maybe.
The exercises start with the basic simple stuff: 15 audiograms of normal findings, early presbyacusis and Eustachian tube dysfunction. Even here some things did surprise me; for example, a 13 year old with a suggested 80 dB air–bone gap, attributed to a conductive loss. That is quite some air–bone gap! I did not know the middle-ear transformer mechanism was that good, I confess.
The intermediate exercises (audiograms 16–40) and advanced exercises (audiograms 41–65) proved really interesting and, whilst I disagreed with some conclusions, I found I was really enjoying working through these. I was glad to see ossicular disruption with an intact drum following trauma, but would like to have seen more thought given to ossicular integrity in some of the often incredible air–bone gaps associated with perforations. I thought 40–50 dB thresholds for otitis externa surprising, but did really question audiogram 39. A 92-year-old man has unmasked bone conduction thresholds of 0 dB at 4 kHz (we all wish). He also has an air–bone gap at high frequencies, not low. The following audiogram showed the classical masking dilemma of the double conductive loss (again with an 80 dB air–bone gap!), but failed to deliver the real message: the peril that one ear may have a sensorineural loss. We all know the worry of the stapedectomy on what might be a ‘dead ear’ (bad result) or the ‘only hearing ear’ (potentially awful result). Audiogram 26, conducted three months after a stroke, is from a man with tinnitus, vertigo and sudden deafness, but he also has a facial paralysis. The sole recommendation is ‘ENT referral’. The fear must be a suggestion that the stroke is implicated, rather than the need to hunt for those vesicles and start anti-viral drugs urgently.
The advanced audiograms did show the bone conduction perils of the Carhart's notch or the reverse, with superior semi-circular canal dehiscence. Again, I would love to have seen just a few more sentences to explain why surgery of the former gives a better result than expected, or that the latter is not a conductive loss at all. I also wanted the ‘hidden bone conduction’ of far advanced otosclerosis. I will freely admit I missed the diagnosis in the large vestibular aqueduct case and cursed out loud as I read the conclusion.
This book represents a very clever idea. The guide to interpretation is of great value to any novice. The audiograms inevitably do repeat Eustachian tube dysfunction, chronic otitis media and asymmetric sensorineural losses, but contain many a gem. The authors aimed for a simple concise manual, but I would have welcomed just a little bit more explanation at the close of each case. It does represent very good value and is recommended to readers west of Long Island, New York.
