Conclusion: Similarly to almost all delayed endolymphatic hydrops (DEH) cases with both precedent sudden deafness and mumps deafness, two-thirds of DEH cases with precedent deafness of unknown cause with onset in early childhood developed DEH symptoms within 40 years after the precedent deafness. In spite of the diagnosis of precedent deafness, viral labyrinthitis may build up the late endolymphatic hydrops in most DEH cases up to four decades.
Objective: To clarify the characteristics of DEH in Japan.
Methods: Clinical information on 198 DEH cases was collected by nationwide, multicenter surveys conducted by the Peripheral Vestibular Disorders Research Committee of Japan.
Results: The incidence of the ipsilateral type of DEH was 47.5%, which was almost equal to that of the contralateral type. In both types of DEH, the most common diagnosis of precedent deafness was deafness of unknown cause with onset in early childhood: 43.9% in both types of DEH. Sudden deafness and mumps deafness were the subsequent diagnoses of precedent deafness. The distribution of time delay of the onset between precedent deafness of unknown cause with onset in early childhood and DEH was different from that between precedent sudden and mumps deafness and DEH.