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Radiation-induced otitis media--study of a new test, vestibular-evoked myogenic potential
1Department of Otolaryngology, National Taiwan University College of Medicine, University Hospital, 1 Chang-te Street, Taipei, Taiwan.
Purpose:
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 And Materials:
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.
Conclusion:
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.
Insights
The vestibular-evoked myogenic potential (VEMP) test, particularly with tapping, can differentiate radiation-induced otitis media (ROM) from chronic otitis media (COM). This aids in understanding treatment limitations for post-irradiated ears.
Area of Science:
- Otolaryngology
- Neuroscience
- Medical Imaging
Background:
- Differentiating radiation-induced otitis media (ROM) from chronic otitis media (COM) is challenging using current physical examination and audiovestibular tests.
- Radiation history is crucial but not always available for accurate diagnosis.
Purpose of the Study:
- To evaluate the efficacy of the vestibular-evoked myogenic potential (VEMP) test in distinguishing ROM from COM.
- To explore the diagnostic value of VEMP in patients with a history of radiation exposure.
Main Methods:
- Compared VEMP responses in 18 ears of ROM patients and 18 ears of COM patients.
- Utilized both tone-burst and tapping stimulation methods for VEMP testing.
- Included additional control groups to assess the impact of neck soft tissue fibrosis/edema on VEMP.
Main Results:
- Tone-burst VEMP did not significantly differentiate ROM from COM.
- Tapping-evoked VEMP showed normal responses in 89% of COM ears but delayed responses in 61% of ROM ears.
- Neck fibrosis/edema alone did not significantly affect VEMP responses, suggesting ROM's distinct pathology.
Conclusions:
- Tapping-evoked VEMP effectively differentiates ROM from COM, with delayed responses indicating broader involvement in ROM.
- The findings suggest ROM involves larger affected areas (retrolabyrinthine, brainstem) compared to COM.
- This distinction may explain the limited benefit of surgical interventions like grommet insertion or tympanoplasty in post-irradiated ears.
