Radiation-induced otitis media--study of a new test, vestibular-evoked myogenic potential.
OBJECTIVE
Excluding the radiation history, current physical examination and audiovestibular function tests fail to differentiate radiation-induced otitis media (ROM) from chronic otitis media (COM). This study applied the newly developed vestibular-evoked myogenic potential (VEMP) test to investigate whether the VEMP test can be of help in differentiating between them.


METHODS
Fourteen irradiated nasopharyngeal carcinoma (NPC) patients with ROM (18 ears) and 14 age-matched, and gender-matched patients with COM (18 ears) were enrolled. Each patient underwent stimulation with a short tone burst initially, and then by tapping the forehead using a tendon hammer. To define the effect of the neck soft tissue on the VEMP response further, an additional two groups (10 non-NPC patients with ROM but no neck fibrosis/edema and 10 non-NPC patients without ROM but with neck fibrosis/edema) were included for comparison.


RESULTS
The occurrence of normal VEMPs in the ROM ears (33%) did not differ significantly from that in the COM ears (56%) by tone-burst stimulation. However, using tapping evocation, most (89%) COM ears revealed normal VEMPs, and most (61%) ROM ears demonstrated delayed VEMPs. Furthermore, most (90%) non-NPC patients with ROM but no neck fibrosis/edema revealed delayed or absent VEMPs. In contrast, all non-NPC patients with neck fibrosis/edema but no ROM demonstrated normal VEMPs bilaterally, implying that the effect of neck soft tissue on the VEMP response is less.


CONCLUSIONS
Through tapping evocation, most COM ears revealed normal VEMPs, and most ROM ears demonstrated delayed VEMPs, indicating that ROM is different from COM because of the larger affected areas such as retrolabyrinthine or brainstem involvement. This result can explain why grommet insertion or tympanoplasty is not beneficial to postirradiated ears, possibly because both operations spare the inflammation outside the middle ear cavity.
Yang
Tsung-Lin
TL
Department of Otolaryngology, National Taiwan University College of Medicine, University Hospital, 1 Chang-te Street, Taipei, Taiwan.
Young
Yi-Ho
YH
D000293:Adolescent; D000328:Adult; D000368:Aged; D002908:Chronic Disease; D003937:Diagnosis, Differential; D004432:Ear, Middle / Q000503:physiopathology / Q000528:radiation effects*; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D010033:Otitis Media / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D011832:Radiation Injuries / Q000175:diagnosis* / Q000503:physiopathology