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ENT clinic - otosclerosis

ENT GPSI Dr Raj Singh on a common cause of progressive hearing loss in young adults

 

A 19-year-old student presented to his GP shortly after starting his first term at the local university.

He described a five-year history of gradually progressive hearing loss, originally in his right ear but bilateral for around two years. He had never presented with the problem before as he found he could compensate at school – for example, by sitting near the front in class.

But he was finding it more difficult to cope at university – with loud social situations particularly stressful – and he felt the problem had recently got much worse. He also described the recent development of mild, intermittent tinnitus. There was no family history of hearing problems and he was otherwise healthy.

Auroscopy was normal, but Weber and Rinne testing revealed conductive hearing loss in his right ear and was inconclusive in his left. He was referred to ENT, where pure-tone audiometry confirmed purely conductive, predominantly low-tone hearing loss in both ears and he was diagnosed with otosclerosis.

Three months later he had a stapedectomy in his right ear, which almost totally restored his hearing in that ear. He is currently being monitored for possible surgery on his left ear.

The problem

  • Otosclerosis is a failure in sound conduction caused by a pathological increase in bone turnover, leading to sclerosis and ankylosis of the stapes footplate in the fenestra ovalis.
  • The process sometimes extends to the cochlea itself.
  • There is an autosomal dominant inheritance pattern, but variable penetrance – so often there is no family history – and environmental factors have also been implicated, including oestrogens and measles infection.1
  • European prevalence estimates range from around 1.4% to 2.1% – seen in one UK study2 – but there are suggestions the incidence has declined with fewer measles infections.3
  • It typically presents between the ages of 15 and 35, is more common in women than men and most common in Asian and Caucasian populations.
  • If untreated, otosclerosis leads to significant hearing loss of about 50-60dB – though total deafness is uncommon. 

 

Features

  • The main symptoms are progressive hearing loss – bilateral in around 70% of cases – and tinnitus.

     

  • The hearing loss is usually in the lower range and particular difficulty hearing deep, male voices is a characteristic sign.

     

  • There are usually no vestibular symptoms, but some patients might also experience
  • mild dizziness and in rare cases there is severe rotatory nystagmus as in Ménière's disease.

 

 

Diagnosis

  • Auroscopy is usually normal, although increased vascularity of the promontory will cause a reddish-blue discolouration behind the tympanic membrane in about 10% of cases – Schwartz's sign.

     

  • Weber and Rinne testing usually shows a conductive pattern deafness.

     

  • If the cochlea has become involved, there may be a mixed conductive/sensory pattern of hearing loss.

     

  • Paget's disease – which shares some pathophysiological similarities – can present with exactly the same pattern of hearing loss, but usually also with other features of the disease such as bone pain. This usually affects older age groups.

     

  • Audiometry is the primary investigation of choice and will usually reveal a purely conductive, mostly low-tone loss.

     

  • Characteristic audiogram patterns can seal the diagnosis if there is the mixed conductive/sensorineural loss seen with cochlea involvement.

     

  • In a few cases, CT scanning will be used to look for abnormal bone deposition in the temporal bone.

 

Management

  • Hearing aids can be very effective, but advances in surgical treatment over the past 20 years make this the most popular management option.

     

  • There are two surgical options, both with the aim of enhancing the vibration of fluid within the cochlear canal.Stapedectomy involves the extraction of the stapes footplate, while stapedotomy involves small holes being made in the footplate. Both are done as day cases.3

     

  • Restoration of normal hearing loss is seen in up to 95% of cases for both procedures, but total hearing loss occurs after about 1% of procedures for unknown reasons and does not seem to be linked to surgical skill.

 

 

Dr Raj Singh is an ENT GPSI in Manchester

 

 

References

1 Schrauwen I and Van Camp G. The etiology of otosclerosis: a combination of genes and environment. Laryngoscope 2010 ;120:1195-202

2 Vartiainen E and Vartiainen T. Effect of drinking water fluoridation on the prevalence of otosclerosis. J Laryngol Otol 1997;111:20-2

3 Niedermeyer HP and Arnold W. Otosclerosis and measles virus – association or causation? J Otolaryngol Head Neck Surg 2008;70:63-70

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