Abstract
PurposeTo present the extent and site of lesion of auditory dysfunction in a large cohort of individuals with type 2 Stickler Syndrome. Type 2 Stickler Syndrome results from a mutation in the gene coding for α-1 type XI pro-collagen, which has been identified in the human vitreous, cartilage and the cochlea of the mouse. The condition is characterised by classic ocular abnormalities, auditory dysfunction, osteoarthropathy and oro-facial dysplasia.MethodsThis is a population study which used a combination of audiometric, tympanometric, and self-report measures on a series of 65 individuals (mean age 29.2 years, range 3–70, female 63.1%) with genetically confirmed type 2 Stickler Syndrome.ResultsHearing impairment was identified in at least one ear for 69% of individuals. Analysis against age-matched normative data showed that reduced hearing sensitivity was present across all test frequencies. Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively. The proportion of hypermobile tympanic membranes (24%) was less than previously documented in type 1 Stickler Syndrome. When present, this appears to arise as a direct result of collagen abnormalities in the middle ear. Self-report measures of speech and spatial hearing in sound were comparable to a non-syndromic cohort with similar audiometric thresholds.ConclusionsAuditory impairment in type 2 Stickler Syndrome is predominantly associated with cochlear hearing loss of varying severities across affected individuals. The impact on hearing thresholds can be seen across the frequency range, suggesting a contribution of defective collagen throughout the cochlea. Self-report questionnaires showed that difficulties understanding speech, and spatial information in sound (such as that used for localisation), were worse than a young, normal-hearing population but comparable to a non-syndromic cohort with similar audiometric thresholds. Therefore, it is likely that hearing loss in type 2 Stickler Syndrome arises in the auditory periphery, without significant central processing deficits.
Highlights
In 1965, Dr Gunnar Stickler and colleagues described a dominant “hereditary arthro-ophthalmopathy” characterised by premature degenerative osteoarthropathy, and progressive myopia beginning in the first decade of life and frequently resulting in retinal detachment and blindness [1]
Eighty-three patients with genetically confirmed type 2 Stickler Syndrome were recruited for study; 65 subjects were included in the analysis after 18 individuals were excluded due to incomplete audiograms
In the largest global cohort of genetically confirmed type 2 Stickler Syndrome patients, with explicitly stated hearing loss definitions, we find hearing loss to be common
Summary
In 1965, Dr Gunnar Stickler and colleagues described a dominant “hereditary arthro-ophthalmopathy” characterised by premature degenerative osteoarthropathy, and progressive myopia beginning in the first decade of life and frequently resulting in retinal detachment and blindness [1]. Extended author information available on the last page of the article majority result from abnormalities in either Type II, Type IX or Type XI collagen. This cluster of conditions, best referred to as the Stickler Syndromes, is among the most frequently inherited connective tissue disorders, accounting for 1:7500 births [4, 5]. Type 1 Stickler Syndrome, caused by mutations in COL2A1 (the gene encoding the α-1 chain for Type II collagen) accounts for more than 80% of Stickler Syndrome patients [6]. Type 2 Stickler Syndrome results from a mutation in the gene coding for α-1 type XI pro-collagen, which has been identified in the human vitreous, cartilage and the cochlea of the mouse. The condition is characterised by classic ocular abnormalities, auditory dysfunction, osteoarthropathy and oro-facial dysplasia
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