遅発性内リンパ水腫について 特にメニエール病との関連

Abstract

Delayed endolymphatic hydrops (DEH), a disease entity that can be differentiated from Meniere's disease, typically develops in patients who have experienced a profound, long-term hearing loss in one ear. This condition was first reported by Kamei et al. ('71), who indicated that it occurred in about 20% of patients who had had unilateral profound deafness since early childhood (UPDC), and it appeared at various stages of adulthood, during or after puberty. Wolfson and Leiberman ('75) and Nadol et al. ('75) reported other types of unilateral profound deafness causing this condition that were due to viral and bacterial labyrinthitis, head trauma, or sudden deafness. Schuknecht ('78) defined DEH and classified it into two types: the ipsilateral type, in which vestibular symptoms identical to the vestibular symptoms of Meniere's disease develop in a previously deafened ear, and the contralateral type, in which a fluctuating hearing loss and/or vestibular symptoms develop in the hearing ear. The underlying pathophysiologic mechanism for the development of DEH has been explained as progressive endolymphatic hydrops in the inner ear due to delayed atrophy or fibrous obliteration of the endolymphatic resorption system, resulting from a previous inner-ear injury. In the ipsilateral type, episodic vertigo is not usually accompanied by fluctuating hearing levels and tinnitus because the hearing loss is profound. The period between the onset of pre-existent deafness in one ear and the onset of DEH ranges from several months to 74 years. The cause of the pre-existent deafness is UPDC in more than half of the cases of both types of DEH. Almost all kinds of other degenerative disorders of the inner ear are mostly due to inflammation (viral and bacterial) and trauma (physical and acoustic). The ipsilateral type of DEH is more frequently seen than the contralateral type. The onset age of the contralateral type is higher, in general, than that of the ipsilateral type. Medical treatment may be effective for both types of DEH. Complete relief from episodic recurrent vertigo may be expected in 65% of cases within 5 years after the onset of vertigo and in 90% of cases within 10 years. Labyrinthectomy or vestibular nerve section in the deaf ear is curative in the ipsilateral type, but no satisfactory surgical therapy is available for the contralateral type of the disease. The audiological definition of DEH by Schuknecht seems, however, to be somewhat arbitrary, as the patients' symptoms form a continuous spectrum with other Meniere's syndrome cases, occurring in association with less-marked degrees of sensorineural hearing loss. The existence of the contralateral type of DEH due to UPDC, which often shows typical symptoms of Meniere's disease, seems to suggest that Meniere's disease may occur as a delayed sequela of subclinical damage of the inner ear, especially damage sustained in childhood.