**5. Conclusions**

Inner ear and retrocochlear involvement in MPS patients is more frequent than initially suspected. Observation of seromucinous effusion in the middle ear does not exclude the presence of a sensorineural hearing loss. An otological and audiological investigation should be warranted to all defined or suspected MPS patients. Inner ear or central auditory lesions detected by the audiological tests should be further investigated by specific MR imaging processing algorithms.

Early identification of hearing loss not only enables proper acoustic rehabilitation, but also supports the diagnosis of MPS, especially in its milder forms and/or initial stages.
