Prevalence and causes of hearing impairment in Africa.

OBJECTIVE: To systematically assess the data on the prevalence and causes of hearing impairment in Africa. METHODS: Systematic review on the prevalence and causes of hearing loss in Africa. We undertook a literature search of seven electronic databases (EMBASE, PubMed, Medline, Global Health, Web of Knowledge, Academic Search Complete and Africa Wide Information) and manually searched bibliographies of included articles. The search was restricted to population-based studies on hearing impairment in Africa. Data were extracted using a standard protocol. RESULTS: We identified 232 articles and included 28 articles in the final analysis. The most common cut-offs used for hearing impairment were 25 and 30 dB HL, but this ranged between 15 and 40 dB HL. For a cut-off of 25 dB, the median was 7.7% for the children- or school-based studies and 17% for population-based studies. For a cut-off of 30 dB HL, the median was 6.6% for the children or school-based studies and 31% for population-based studies. In schools for the deaf, the most common cause of hearing impairment was cryptogenic deafness (50%) followed by infectious causes (43%). In mainstream schools and general population, the most common cause of hearing impairment was middle ear disease (36%), followed by undetermined causes (35%) and cerumen impaction (24%). CONCLUSION: There are very few population-based studies available to estimate the prevalence of hearing impairment in Africa. Those studies that are available use different cut-offs, making comparison difficult. However, the evidence suggests that the prevalence of hearing impairment is high and that much of it is avoidable or treatable.

A congenital mucocele of the anterior dorsal tongue.

We report on a new-born with a congenital mucocele on the anterior dorsal side of the tongue. The presentation as well as the differential diagnosis of congenital oral swellings is discussed. Because of breastfeeding problems the mucinous swelling was incised and drained two days after birth. Immediately after drainage the swelling disappeared. Congenital oral swellings are rare. Most of them are mucoceles. Post-partum treatment is surgically, but spontaneous remission has been described. High incidence of recurrence should be taken into account when (micro-)marsupialization or incision as sole treatment is performed.

Dysphagia is present but mild in myotonic dystrophy type 2.

The phenotype of myotonic dystrophy type 2 (DM2) shows similarities as well as differences to that of myotonic dystrophy type 1 (DM1). Dysphagia, a predominant feature in DM1, has not yet been examined in DM2. In a recent nationwide questionnaire survey of gastrointestinal symptoms in DM2, 12 out of 29 DM2 patients reported to have difficulty in swallowing for solid food. The aim of the study was to investigate the presence of dysphagia in patients with genetically proven DM2 who reported difficulty in swallowing for solid food at the questionnaire survey. Swallowing function and fiberoptic endoscopic evaluation of swallowing (FEES) were examined by a speech therapist and otorhinolaryngologist, respectively. In DM2 patients who reported difficulty in swallowing the presence of dysphagia could be confirmed (clinically in 100%, by FEES in 88%). A correlation exists between Dysphagia Outcome and Severity Score (DOSS) and age (p=0.05). None of the patients was underweight, and none of the patients had suffered aspiration pneumonia in the past. Dysphagia is present among DM2 patients and is more severe in older patients. However, dysphagia is generally mild, and do not lead to weight loss, or aspiration pneumonia.

[Diagnostic image (367). A man with foetor ex ore]. / Diagnose in beeld (367). Een man met foetor ex ore.

A 54-year-old man presented with foetor ex ore due to a rhinolith in the left nasal cavity.

A novel locus for autosomal dominant non-syndromic hearing loss, DFNA31, maps to chromosome 6p21.3.

BACKGROUND: Non-syndromic hearing loss is the most genetically heterogeneous trait known in humans. To date, 51 loci for autosomal dominant non-syndromic sensorineural hearing loss (NSSHL) have been identified by linkage analysis. OBJECTIVE: To investigate the genes involved in a Dutch family with NSSHL. METHODS: Linkage analysis in a large Dutch pedigree with progressive bilateral loss of the mid and high frequencies, in which a novel dominant locus for postlingual NSSHL (DFNA31) has been identified. RESULTS: DFNA31 was found to be located in a 7.5 cM region of chromosome 6p21.3 between D6S276 (telomeric) and D6S273 (centromeric), with a maximum two point LOD score of 5.99 for D6S1624. DNA sequencing of coding regions and exon/intron boundaries of two candidate genes (POU5F1, GABBR1) in this interval did not reveal disease causing mutations. CONCLUSIONS: Haplotype analysis indicated that the genetic defect in this family does not overlap the DFNA13 and DFNA21 regions that are also located on 6p. Identification of the disease gene will be of major importance in understanding the pathophysiology of hearing impairment.

Speech recognition scores related to age and degree of hearing impairment in DFNA2/KCNQ4 and DFNA9/COCH.

OBJECTIVE: To analyze the relationship between pure-tone hearing threshold and speech recognition performance in DFNA2/KCNQ4 and DFNA9/COCH, 2 types of high-frequency nonsyndromic hearing impairment. DESIGN: Case series with cross-sectional analysis of phoneme recognition scores related to age and hearing level. SETTING: University hospital. PATIENTS: Forty-five members of 4 separate families, all carrying 1 of 3 different mutations in the KCNQ4 gene at the DFNA2 locus (1p34); 42 members of 7 separate families, all carrying the same Pro51Ser mutation in the COCH gene at the DFNA9 locus (14q12-q13). RESULTS: The deterioration of speech recognition dropped to a 90% score at a higher level of hearing impairment (pure-tone-average at 1, 2, and 4 kHz) in DFNA2-affected patients (65 dB) than in DFNA9-affected patients (46 dB). CONCLUSION: At similar levels of hearing impairment, DFNA2/KCNQ4-affected patients showed better speech recognition performance than DFNA9/COCH-affected patients.

A Dutch family with progressive autosomal dominant non-syndromic sensorineural hearing impairment linked to DFNA13.

We present a Dutch family with autosomal dominantly inherited mid-frequency and high-frequency sensorineural hearing impairment. Genetic linkage analysis in this family indicated linkage to DFNA13 with logarithm of the odds ratio (LOD) scores > +4. The majority of the affected persons presented with hearing impairment from the age of 30 years onwards, although hearing impairment was noted at about 10 years of age in two affected persons. Three individuals represent phenocopies. After correction for presbyacusis, hearing impairment was most marked at 1-2 kHz and showed an annual progression of 0.8 dB per year. By the age of 60 years, the configuration of the audiogram was flat, reflecting the combined effects of the inherited progressive hearing loss and presbyacusis. Vestibular function was intact. Recently, mutations in the COL11A2 gene were found in two other families with non-syndromic hearing impairment linked to DFNA13. Further mutation analysis of the COL11A2 gene will show whether this family also contains a COL11A2 mutation.

Mutations in the KCNQ4 K+ channel gene, responsible for autosomal dominant hearing loss, cluster in the channel pore region.

The DFNA2 locus for autosomal dominant nonsyndromic hearing impairment on chromosome 1p34 contains at least 2 genes responsible for hearing loss, GJB3 and KCNQ4. GJB3 is a member of the connexin gene family and KCNQ4 is a voltage-gated potassium channel. KCNQ4 mutations were first found in a French family, and later also in a Belgian, an American and two Dutch families. Here we present the analysis of the GJB3 and KCNQ4 genes in a third Dutch family linked to DFNA2. No mutation was found in GJB3, but a missense mutation changing a conserved Leu residue into His (L274H) was found in the coding region of the KCNQ4 gene in all patients of this DFNA2 family. Examination of the position of all known KCNQ4 mutations showed a clustering of mutations in the pore region of the KCNQ4 gene, responsible for the ion selectivity of the channel. The clustering of mutations in this domain confirms its importance.

A Dutch family with progressive sensorineural hearing impairment linked to the DFNA2 region.

We studied a Dutch family with DFNA2-linked progressive sensorineural hearing impairment (SNHI). Recent audiograms were obtained from 18 of the affected persons (age 7-81 years) and were used in a gene-linkage analysis. Linear regression analysis of the audiograms, using binaural mean thresholds, disclosed on average a descending slope of approximately 10 dB/octave at any age and an annual threshold increase at any frequency of about 0.7 dB/year. There may have been substantial congenital impairment at higher frequencies, but longitudinal analysis of hearing impairment in the youngest case, who was followed from age 5 years, suggested that the most significant changes in hearing may have occurred in the first two decades of life. Linkage analysis was carried out with special attention to the DFNA2 region because hearing trends were very similar to families previously linked to DFNA2. Linkage to DFNA2 was established with maximum lod scores of 4.7 and 3.2 for the flanking markers of the DFNA2 region (D1S432;MYCL1).

Mutations in the KCNQ4 gene are responsible for autosomal dominant deafness in four DFNA2 families.

We have previously found linkage to chromosome 1p34 in five large families with autosomal dominant non-syndromic hearing impairment (DFNA2). In all five families, the connexin31 gene ( GJB3 ), located at 1p34 and responsible for non-syndromic autosomal dominant hearing loss in two small Chinese families, has been excluded as the responsible gene. Recently, a fourth member of the KCNQ branch of the K+channel family, KCNQ4, has been cloned. KCNQ4 was mapped to chromosome 1p34 and a single mutation was found in three patients from a small French family with non-syndromic autosomal dominant hearing loss. In this study, we have analysed the KCNQ4 gene for mutations in our five DFNA2 families. Missense mutations altering conserved amino acids were found in three families and an inactivating deletion was present in a fourth family. No KCNQ4 mutation could be found in a single DFNA2 family of Indonesian origin. These results indicate that at least two and possibly three genes responsible for hearing impairment are located close together on chromosome 1p34 and suggest that KCNQ4 mutations may be a relatively frequent cause of autosomal dominant hearing loss.

Proximal symphalangism and congenital conductive hearing loss: otologic aspects.

OBJECTIVE: Results of stapedectomy are reported in a Belgian 26-year-old woman and two Dutch brothers having the proximal symphalangism syndrome (McKusick 18580). STUDY DESIGN: Case reports are presented. A review of the results of ear surgery for congenital conductive hearing loss in this syndrome is given. SETTING: The Belgian patient was treated in a general hospital. The Dutch patients were treated in a university hospital, which was a tertiary referral center. PATIENTS: Patients were referred to have an evaluation of their hearing impairment. INTERVENTION: Based on the syndromal diagnosis and based on routine audiometric tests, a congenital ossicular fixation was considered to be the cause of the hearing loss. By exploratory tympanotomies, this was confirmed. Reconstructive procedures including stapedotomy were performed. MAIN OUTCOME MEASURES/RESULTS: Long-term audiometric data are presented to evaluate the outcome of the surgical interventions. CONCLUSIONS: Congenital stapes ankylosis eventually combined with a congenital fixation of the short process of the incus in the fossa incudis, causing the congenital conductive hearing loss. Surgical intervention is very successful in most reported cases, but negative side effects are incidentally found as well.

Hearing impairment and neurological dysfunction associated with a mutation in the mitochondrial tRNASer(UCN) gene.

We studied a large Dutch family with maternally inherited, progressive, sensorineural hearing loss in 27 patients. Only in a single family member was the hearing loss accompanied by neurological symptoms including ataxia and dysarthria. DNA analysis of the mitochondrial genome revealed the insertion of a C at nucleotide position 7472 in the tRNASer(UCN) gene (7472insC mutation). We determined the percentage of mutant DNA (heteroplasmy) in blood from all family members, and found no correlation between hearing loss and leucocyte heteroplasmy. The 7472insC mutation was previously identified in a smaller family from Sicily with sensorineural hearing loss in 9 family members, six of them also presenting neurologically with ataxia and myoclonus. The presence of the 7472insC mutation in two different pedigrees strongly supports its pathogenicity. However, the interfamilial difference in penetrance of the neurologic abnormalities is most likely to be strongly influenced by secondary factors different from the 7472insC mutation, as heteroplasmy or age of the patients were similar in both families. This mutation should therefore be analysed in families with maternally inherited hearing loss, irrespective of whether the hearing loss is non-syndromic or accompanied by neurologic abnormalities.

Early-onset sensorineural hearing loss and late-onset neurologic complaints caused by a mitochondrial mutation at position 7472.

OBJECTIVES: To detect a mitochondrial mutation responsible for maternally transmitted hearing loss with late-onset neurologic features in a 3-generation Dutch family, and to describe the hearing loss, associated symptoms, and vestibular dysfunction. PATIENTS AND METHODS: All maternally related family members (n = 69) were investigated using standard audiometry. In a selected group, vestibulo-ocular examinations and additional neurologic and ophthalmologic examinations were performed. Twenty milliliters of venous blood was taken from all participants for genetic studies. SETTING: University medical center. RESULTS: All maternally related individuals carried an extra C at position 7472 of the mitochondrial genome. Hearing loss was the only symptom or presenting symptom in most family members and most pronounced at higher frequencies. Hearing loss at lower frequencies was demonstrated in individuals 10 years and older. Most patients had vestibular hyperreactivity and were susceptible to motion sickness, suggesting vestibulocerebellar dysfunction. Neurologic complaints were infrequent and presented by older individuals; however, numerous enlarged mitochondria were found in a muscle biopsy specimen of an individual with hearing impairment but without neurologic symptoms. CONCLUSIONS: Respiratory chain dysfunction should be considered as a possible cause of progressive sensorineural hearing loss. More research into the causes of high-frequency impairment should be considered, especially when sensorineural hearing loss, syndromal or nonsyndromal, is exclusively maternally transmitted. Maternal transmission of hearing impairment can also be valuable in the diagnosis of unclear neurologic syndromes.

Nonsyndromic autosomal dominant progressive sensorineural hearing loss: audiologic analysis of a pedigree linked to DFNA2.

An analysis was performed of the regression of the individual hearing threshold on age in the affected persons in a six-generation Dutch family with nonsyndromic autosomal dominant sensorineural hearing loss, which showed linkage to the DFNA2(1p34) region, similar to at least four previously reported nonrelated families. The offset threshold was significantly higher at the high frequencies (around 30 dB at 2 to 8 kHz) than at the lower ones (approximately 0 dB at 0.25 to 1 kHz). Hearing impairment at the higher frequencies may therefore have been present already at birth or in early childhood. The regression coefficient, or the 'annual threshold increase,' expressed in dB/y, was about 1 dB/y on average, but the higher frequencies (1 to 8 kHz) showed significantly more rapid progression than the lower frequencies (0.25 to 0.5 kHz).

Congenital conductive hearing loss in the lacrimoauriculodentodigital syndrome.

An inherited middle ear anomaly that was causing hearing impairment in a 12-year-old girl was treated successfully by a stapedotomy combined with a malleovestibulopexy. Cup-shaped ears, abnormal or absent thumbs, and skeletal deformities of the forearms were present in several members of 3 generations of a family. An autosomal dominant pattern of inheritance was recognized. These features are present in a number of previously described syndromes, but they correspond best with the lacrimoauriculodentodigital syndrome.

A new type of maxillofacial dysostosis, inherited as an X-linked or autosomal recessive trait.

Two brothers with congenital conductive hearing loss and phenotypic characteristics of maxillofacial dysostosis are described. In the oldest boy a malformed ossicular chain was present and the conductive hearing loss was improved by a malleo-vestibulo-pexy, with post-operative hearing gain of approximately 30 dB. Although superficially similar to Treacher Collins syndrome, the facial characteristics are more typical of maxillofacial than of mandibulofacial dysostosis. These cases most likely represent a new type of maxillofacial dysostosis inherited as an X-linked or autosomal recessive trait.

Non-syndromic dominant sensorineural hearing loss: from a few phenotypes to many genotypes.

Sensorineural hearing loss affects approximately 1 in 2 persons at about 80 years of age and 1 in 750 in childhood. The best known forms of hearing loss with an autosomal dominant pattern of inheritance are the syndromic-mediated ones. At present, the non-syndromic autosomal dominant inherited forms can only be distinguished by the shape of the tone-audiogram. Based on gene linkage studies twelve different genotypes for autosomal dominant hereditary non-syndromic forms of sensorineural hearing loss have been recognized in a period of almost 2 years. In view of the great diversity of types that have been recognized in such a short period, it can be expected that over the next 10 years, several dozens genetically-mediated forms of autosomal dominant inherited sensorineural hearing loss will be detected. Similar developments are taking place in the non-syndromic autosomal recessive hereditary forms of sensorineural hearing loss and deafness. The above indicates clearly that before too long, new genetic investigation techniques will enable us to distinguish between forms of sensorineural hearing loss that could not be distinguished in the past.

Hearing loss in the Saethre-Chotzen syndrome.

A three-generation family with Saethre-Chotzen syndrome and an isolated case are presented. The proband presented with conductive hearing loss. His mother and grandmother showed minor features of the syndrome including conductive hearing loss. Symptoms of the craniosynostosis syndromes can include stapes ankylosis, a fixed ossicular chain in a too small epitympanum, and small or even absent mastoids. The proband was treated with a bone-anchored hearing aid (BAHA) instead of reconstructive middle ear surgery. Current literature on the results of ear surgery is reviewed. In general, reconstructive middle ear surgery should be considered if congenital anomalies of the middle ear are the only presenting symptom. In cases with additional anomalies such as atresia of the ear canal or damage due to chronic ear infections, the outcome of reconstructive surgery to correct the anomalous ossicular chain is unsatisfactory. In such cases of the BAHA is probably the best solution.