Superior Vestibular Dysfunction in Severe Decompression Sickness Suggests an Embolic Mechanism
ABSTRACT Both nitrogen bubble embolism and the difficulty of inner ear tissues to wash out nitrogen have been discussed as possible reasons for the selective vulnerability of the inner ear to decompression illness. This case report suggests that nitrogen bubble embolism plays a crucial role in the pathogenesis of inner ear lesions in decompression accidents.
The current patient, a 48-yr-old male dive master, suffered a severe decompression illness with vertigo as the only residual symptom. At the 1-mo follow-up, neuro-otological evaluation revealed a selective lesion of the superior vestibular division of the left labyrinth with normal functioning inferior vestibular division. At vestibular testing, there was no caloric response from the affected left ear, and the head impulse tests for the lateral and anterior semicircular canal were also impaired. Tests of vestibular evoked myogenic potentials (VEMP) showed divergent results. Ocular VEMP in response to left ear stimulation were absent, whereas the cervical VEMP were completely symmetrical and normal. Thus, the lesion profile implies a partial vestibular loss selectively affecting the superior vestibular division of the inner ear.
The most likely explanation for such a selective injury seems to be bubble microembolism coupled with both the specific anatomy of this terminally supplied subunit, and with the slow nitrogen wash-out of the vestibular organ.
SourceAvailable from: Tatjana Tomanovic[Show abstract] [Hide abstract]
ABSTRACT: Abstract Conclusions: Persistent geotropic nystagmus indicates a condition of a light cupula, which is accompanied by vestibular disability and a high incidence of pathological findings in the vestibular tests. The prevalence of migraine is high. Objectives: To examine subjective symptoms and characteristics of nystagmus in patients with persistent geotropic nystagmus using vestibular tests, as well as possible correlations to migraine in this group. Methods: We enrolled 20 patients with a mean age of 53 years. The slow phase velocity (SPV) of the geotropic nystagmus and the nystagmus with the patient's head in the supine (S) and prone (P) positions was recorded. All patients completed caloric tests, subjective visual horizontal (SVH), and vestibular evoked myogenic potential (VEMP). All tests were repeated at follow-up (FU). Results: SPV of the geotropic nystagmus directed to the left was 5.5°/s and that to the right was 3.5°/s. In 72% of patients, nystagmus in the P position was opposite to that in the S position. The vestibular tests were pathologic in about 60% of patients. At FU geotropic nystagmus was found in 40% of patients, but was significantly less intense. The vestibular test results remained at the same level at FU. Recurrent vertigo was reported in 78% of the patients. In all, 40% of the patients suffered from migraine.Acta Oto-Laryngologica 07/2014; 134(9):1-11. DOI:10.3109/00016489.2014.928421 · 0.99 Impact Factor