Description, interpretation, analysis and importance of hyperventilation -induced nystagmus in the study of the peripheral and central vestibular disorders

Abstract

Recent clinical studies have revealed the usefulness of the hyperventilation-induced nystagmus in retrolabyrinthine and central vestibular diseases with the appearance either excitatory (ipsilateral) or paretic (contralateral) nystagmus. The objectives of this study have been: 1) to get to know the sensitivity of the exam, according to the best literature available; 2) to get to know the physiopathology of this hyperventilation-induced nystagmus, and 3) to carry out an analysis and interpretation ofthis exam in order to reach solid conclusions of the highest level in evidence based medicine. An exhaustive research of literature published on this topic in the last 25 years was carried out. The main source of information being the most important medical data- based publications and also a thorough revision of these texts. The scarce number of publications on this topic (not more than 40) is what strikes the attention most, as well as the very few studies of the physiopathology of the hyperventilation- induced nystagmus. The method of the test is a simple one; this fact makes its application an attractive one, with a low number of false positive. Most of the studies published are focused on its application in the vestibular schwannoma and in the vestibular neuritis. As to what the Vestibular schwannoma is concerned, ofa group of 107 patients studied, the test was positive in 80% of the cases, with the appearance of ipsilesional or contralesional nystagmus. In vestibular neuritis the test was positive in 68 % of a number of 272 patients; this amount was in direct correlation with the time of evolution of the disease. In multiple sclerosis, in patients with vestibular symptoms, the test gave positive in 75%, whereas in those patients without vestibular symptoms itwas positive only in 7%. In patients with cerebellar diseases, particularly degenerative ones this test was positive in 78% of the cases. The search of hyperventilation- induced nystagmus was a statistically non significant one in some peripheral diseases such as Méniére’ disease or BPPV, as well as in other central vestibular disease, except those of vascular origin due to vertebra-basilar dysfunction. The study and the analysis ofliterature on the hyperventilation-induced nystagmus allow the conclusion that this a test of easy application. When a vestibular schwannoma is suspected, the test guides in the study of those patients that require an MRI. It also helps in the differential diagnosis ofa Vestibular neuritis. Finally, in degenerative and vascular central vestibular disorders, it allows a thorough and more suitable study of the patients.