Brain auditory evoked potentials in children with Down syndrome

Visual assessment in Down Syndrome: The relevance of early visual functions

BACKGROUND

Children with Down Syndrome (DS) have a high prevalence of ocular disorders, and even when ophthalmological deficits (i.e. refractive errors or strabismus) are corrected, visual acuity seems to have a different developmental trend compared to typical children. Unfortunately, there is no consensus about the age at which it is fundamental to perform a first comprehensive visual assessment in this population.

AIMS

We analyzed early visual functions in a sample of 42 Italian children with DS, in order to achieve new insights for early surveillance and intervention.

MATERIAL AND METHODS

DS children were evaluated with the Early Neurovisual Assessment, including Teller Acuity Cards (at 6, 12 and 18 months of age) and the Pediatric Ophthalmological Examination (within the 36th months of age).

RESULTS

Visual acuity in our sample was lower than findings reported in the literature on healthy Italian children, but the values were within the confidence interval reported in previous studies on DS children. Moderate or severe refractive errors (> 3diopters) were present in five children (four had hyperopia and one myopia). Abnormalities in ocular motility were observed in 15 children and pathological findings for fundus oculi or lens were found in another eight. Furthermore, ophthalmological findings correlated with visual acuity at 18 months of age.

CONCLUSION

According to our results, the Early Neurovisual Assessment at 18 months of life is a reliable tool for early detection of visual disorders in children with DS and it is useful for programming early intervention to promote their neurodevelopment.

Prevalence and etiology of sensorineural hearing loss in children with down syndrome: A cross-sectional study

BACKGROUND

The prevalence and causes of sensorineural hearing loss (SNHL) in children with Down syndrome (DS) are poorly delineated.

OBJECTIVE

To describe the prevalence, severity, laterality and underlying etiology of SNHL in a cohort of children with DS.

METHODS

A cross-sectional study was performed among all children with DS followed at the multidisciplinary Downteam of the Antwerp University Hospital. Patients' characteristics, risk factors for hearing loss, audiometric data and results of an etiological work-up were collected.

RESULTS

Among 291 patients in follow-up, 138 patients (47.4%) presented with hearing loss. In the majority this was caused by middle ear effusion and only 13 patients (4.5%) had sensorineural hearing loss, 7 boys and 6 girls with a mean age of 14.4 ± 7.4 years. Hearing loss was bilateral in 8 cases. Hearing loss severity was graded as mild in 38.5%, moderate in 30.8% and profound in 30.8% of the patients. An etiological work-up was completed in 9 children. Four patients presented with single sided deafness due to cochlear nerve deficiency. One patient had a genetic cause and in 2 patients the hearing loss was attributed to excessive noise exposure. The etiology of hearing loss was unknown in 6 patients.

CONCLUSION

Sensorineural hearing loss is uncommon in children with DS with a prevalence of 4.5%. Etiological work-up may allow identifying a specific underlying cause. Cochlear nerve deficiency was found in 4 children with DS and single sided deafness.

Electrophysiological characterization of hearing in individuals with Down syndrome

Introduction

Few studies have performed Brainstem (BAEP) and P300 Auditory Evoked Potentials simultaneously to assess central auditory pathways in normal hearing individuals with Down syndrome (DS), mainly because of the difficulty in applying these procedures to this population. Previous studies have suggested that individuals with DS might present different patterns of response compared with those of individuals with typical development; nevertheless, the identification of these potentials would be crucial for the establishment of an accurate audiological diagnosis.

Purpose

To characterize BAEP and P300 in normal-hearing individuals with DS.

Methods

BAEP and P300 were analyzed in 17 individuals with DS and in 21 individuals with typical development aged 7 to 15 years. The results were quantitatively and qualitatively analyzed using descriptive measures and hypothesis tests.

Results

In the quantitative analysis, latency values were lower in the BAEP for the DS group, with statistically significant difference for wave V and interpeaks III-V and I-V; there were no significant differences in the P300 latency values. In the qualitative analysis, there were a larger number of individuals with early values for BAEP latencies and late latencies for P300 in the DS group; both comparisons showed statistically significant differences.

Conclusion

Children and adolescents with DS can present early responses to the components of BAEP, suggesting that their auditory pathway requires less time for the neural transmission of acoustic stimuli to the brainstem. Concerning P300, individuals with DS may present increased latencies, suggesting impairment in the central auditory pathway for the cortical processing of auditory information.

Prevalence and parental awareness of hearing loss in children with Down syndrome

BACKGROUND

To establish the prevalence of hearing deficit in children with Down syndrome (DS) in Hong Kong as measured by brainstem auditory evoked potentials (BAEP). The secondary objective is to examine the agreement between BAEP and clinical questioning in detecting hearing deficit in DS.

METHODS

Consecutive DS patients attending the Down's Clinic in a regional pediatric referral center were recruited into this cross-sectional study. BAEP data performed within 12 months were retrieved. The care-taker was interviewed with a structured questionnaire to detect any symptom of hearing impairment. BAEP findings and clinical questionings were compared in an agreement analysis using quadratic weighted kappa statistics.

RESULTS

Fifty DS patients (35 male, 15 female, mean age 11.70 years ± 5.74 standard deviation) were recruited. Eighteen patients (36.0%) were identified having hearing deficit by BAEP. Among patients with hearing impairment, 13 patients (72.2%) had a conductive deficit, and most have mild to moderate hearing loss. Five patients (27.8%) had sensorineural deficit and most have moderate to severe degree. Eight (44.4%) had bilateral hearing deficit. Care-takers of 13 patients (26.0%) reported symptoms of hearing impairment, with 9 (69.2%) having mild symptoms, 3 (23.1%) had moderate symptoms and 1 (7.7%) had severe symptoms. The weighted kappa was 0.045 (95.0% confidence interval - 0.138-0.229), indicating very poor strength of agreement between BAEP and clinical questioning. For patients with conductive hearing impairment, only 1 patients (7.7%) recalled history of otitis media.

CONCLUSIONS

The estimated point prevalence of hearing impairment in Chinese DS children in Hong Kong is 36%. Our finding of poor strength of agreement between objective testing and symptom questioning reflects significant underestimation of hearing impairment by history taking alone. In view of the high prevalence and low parental awareness, continuous surveillance of hearing is mandatory for DS patients throughout childhood and adolescence.

High Prevalence of Hearing Loss in Down Syndrome at First Year of Life

Introduction: Infants with Down syndrome (DS) are at higher risk of hearing loss (HL). Normal hearing at one year of age plays an important part in language development. An audit was conducted to determine the impact of the newborn hearing screening program on the incidence, type and timing of diagnosis of HL during first year of life. Materials and Methods: Infants with DS were scheduled for Universal Newborn Hearing Screening (UNHS) within 4 weeks of life. If they passed, they had a high-risk screen at 3 to 6 months. They were referred to the otolaryngology department if they did not pass the UNHS or the high-risk screen. Information was obtained from the computerised data tracking system and case notes. Infants born from April 2002 to January 2005 and referred to the DS clinic of our hospital were analysed. Results: Thirty-seven (82.2%) of 45 infants underwent UNHS, of which 12 (32.4%) infants did not pass. Of remaining 33 infants, 27 had high-risk screen done of which 14 (51.8%) did not pass. Twenty-eight infants were referred to the ear, nose, throat (ENT) clinic: 12 from UNHS, 14 from high-risk screens and 2 from the DS clinic. Eleven (39.2%) defaulted follow-up. Fourteen (82.3%) of 17 infants who attended the ENT Clinic had HL. Twelve (85.7%) were conductive, and 2 (14.2%) mixed. Nine (64.2%) had mild-moderate HL and 3 (21%) had severe HL. The mean age of diagnosis was 6.6±3.3 months. All were treated medically, plus surgically if indicated. By 12 months of age, the hearing had normalised in 4 (28.6%) infants and remained the same in 3 (21.4%). Five (35.7%) defaulted follow-up. Thirty-five out of 45 (77.8%) underwent complete hearing screen in the first year of life (UNHS & High-risk screen). Six out of 45 (13.3%) had incomplete screening. Fourteen out of 41 (34.1%) had HL of varying degrees. Four out of 45 (8.8%) did not have any audiological assessment in first year of life. Conclusion: The incidence of HL in the first year of life was high (34.1%). Eighty-five percent were conductive with 64.2% in mild-moderate range. One third of infants hearing normalized after treatment, one third remained unaltered and one third of infants did not attend follow-up. An aggressive approach involving early screening after birth and continued surveillance and early referral to appropriate agencies are essential for establishing timely diagnosis and treatment. Measures to reduce the high default rate during long-term follow-up are needed. Parent education and integrated multidisciplinary follow-up clinic may be useful. Key words: Deafness, Trisomy, UNHS

Auditory brainstem evoked responses in newborns with Down syndrome

Auditory brainstem evoked responses (ABRs) were compared in 15 newborns with Down syndrome and 15 sex-, age-, and weight-matched control newborns. Participants had normal ABRs based upon values specific to 32- to 42-weeks postconceptional age. Although Wave III and Wave V component latencies and the Wave I-III interpeak latency (IPL) were shorter in ABRs of infants with Down syndrome, the Wave III-V IPL was not, pointing to anomalies in the lower rather than upper brainstem auditory pathways. Shorter Down syndrome ABR latencies have been reported at many ages. Extending these findings to newborns suggests that the underlying basis for this develops prenatally. ABR patterns in infants with Down syndrome were similar to reports for intrauterine growth restricted newborns.