Otorhinolaryngological Findings in Patients from Southwestern Colombia with Clinical, Enzymatic and Molecular Diagnosis of Mucopolysaccharidosis II, IV-A and VI

Study of the peripheral and central auditory pathways in patients with mucopolysaccharidosis

OBJECTIVE

To investigate the peripheral and central auditory pathways in mucopolysaccharidosis (MPS) individuals.

METHOD

The research sample comprised 15 individuals (one female and 14 males), aged 8 to 46 years. The following procedures were used: medical history survey, otoscopy, speech and pure-tone threshold audiometry, acoustic immittance measures, and central auditory pathway assessment with brainstem auditory evoked potentials (BAEP) and long-latency auditory evoked potentials (LLAEP).

RESULTS

The pure-tone audiometry identified hearing loss in 13 individuals, and more than 90 % of the hearing loss was sensorineural. The degree of hearing loss was between mild to moderately severe with descendent configuration. Type A tympanogram predominated, and acoustic reflexes were present according to the types and degrees of hearing loss. Among the individuals with abnormal BAEP, longer wave III and V absolute latencies were the main findings. In addition, the unilateral absence of wave I was observed in two cases. In the LLAEP, longer latencies were observed in 14 individuals, and the most impaired components were the P1 and P3 in children and adolescents and the P2, N2 and P3 in adult individuals.

CONCLUSION

The peripheral auditory pathway assessment revealed a predominantly sensorineural hearing loss, affecting mainly high frequencies, and in the central pathway was observed abnormal brainstem and cortical auditory processing in individuals with MPS.

Hearing Loss in Mucopolysaccharidoses: Current Knowledge and Future Directions

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by a deficiency of one of the enzymes involved in the degradation of glycosaminoglycans. Hearing loss is a common clinical presentation in MPS. This paper reviews the literature on hearing loss for each of the seven recognized subtypes of MPS. Hearing loss was found to be common in MPS I, II, III, IVA, VI, and VII, and absent from MPS IVB and MPS IX. MPS VI presents primarily with conductive hearing loss, while the other subtypes (MPS I, MPS II, MPS III, MPS IVA, and MPS VII) can present with any type of hearing loss (conductive, sensorineural, or mixed hearing loss). The sensorineural component develops as the disease progresses, but there is no consensus on the etiology of the sensorineural component. Enzyme replacement therapy (ERT) is the most common therapy utilized for MPS, but the effects of ERT on hearing function have been inconclusive. This review highlights a need for more comprehensive and multidisciplinary research on hearing function that includes behavioral testing, objective testing, and temporal bone imaging. This information would allow for better understanding of the progression and etiology of hearing loss. Owing to the prevalence of hearing loss in MPS, early diagnosis of hearing loss and annual comprehensive audiological evaluations are recommended.