The pathophysiology of acute vestibular dysfunction has been debated for decades. By seeking to clarify the underlying aetiology, this study muddies the waters further by advocating systemic and intratympanic steroids as first line treatment if the aetiology is uncertain. The study was conducted to determine whether the patterns of lesion and innervation were the same, thereby supporting the neuritis hypothesis (NH). After applying certain exclusion criteria and diagnostic tests, 25 adults presenting with acute vertigo and nystagmus without hearing loss, for which no aetiological diagnosis but peripheral vestibulopathy was made, were included. All had diagnostic tests performed within 10 days of onset or did not commence steroids in the first three days. After diagnostic tests (vHIT and caloric for hSSC, vHIT for a- and pSCC, cVEMP for saccule and oVEMP and SVV for untricle) the dysfunction level (DL) of each receptor was apportioned as follows: 0, no dysfunction; 1, slight dysfunction or possible false positive; 2, deﬁnite dysfunction; and 3, strong dysfunction or total loss of function. After combining test abnormalities, the authors determined four different patterns: definite and probable intralabyrithine (ILP) and definite and probable neuritis (NP). For example, definite NP – all receptors of the same innervation are equally affected or unaffected (dysfunction of the receptors differs no more than by 1 DL) and definite ILP – isolated DL ≥2 in only one receptor or 3-point difference between two receptors with same innervation or 2-point difference between two receptors with same innervation on both innervations (2-point difference on the superior AND inferior nerve branch). Only six patients (24%) were consistent with NP of which four (16%) were definite. In 19 (76%), there was a discordance between lesion and innervation (ILP).
Concluding that the NH was not supported in 76% of cases, the authors argue that other loci, other than or in addition to the vestibular nerves, may be involved in acute peripheral vestibulopathy. If intralabyrithine pathology is suspected, they made a case for systemic but preferably intratympanic steroids.
This is a huge leap in my view but to be fair to the authors, the limitations were fully addressed including the classifications, availability of tests and the fact that not all neurons may be affected to the same degree. Apparently, a large multicentre European study combining oral and IT steroids in ILP is underway.