Abstract

Background and Objective: When vestibular neuritis (VN) is suspected, we are generally not interested in the amplitude change of nystagmus according to the positional change. It is because positional nystagmus is not essential in diagnosing VN. But there might be a typical pattern of amplitude change of positional nystagmus also in these patients. If we understand this pattern of nystagmus change, it might be helpful in diagnosing subacute VN when spontaneous nystagmus is not present. Also it may be helpful in distinguishing VN from other diseases that can accompany non-specific positional nystagmus such as migraine associated dizziness. Accordingly, we aimed to find a typical pattern of amplitude change in positional nystagmus in VN patients. We especially aimed to affirm this typical pattern of positional nystagmus in subacute VN as well as in acute VN. Materials and Methods: From 2002 through 2008, the videonystagmography of 182 patients who were diagnosed as VN were retrospectively reviewed. Only the patients who presented with an acute spinning vertigo lasting for more than several hours and who were confirmed of unilateral vestibular hypofunction though either caloric test or rotation chair test were included. The patients were divided into acute or subacute VN by the presence or absence of spontaneous nystagmus (SN). The amplitude of nystagmus was compared between the ipsilesional head roll test (iHRT) and contralesional HRT (cHRT). In order to exclude the effect of neck proprioception, that of the ipsilesional body roll test (iBRT) and cBRT was also compared. Results: Among the 182 patients, 135 were classified as acute VN, and 47 as subacute VN. In the acute VN group, a stronger nystagmus was elicited when the head (p<0.01) and body (p<0.01) was turned to the ipsilesional side. The mean amplitude of nystagmus during iHRT (6.3°/sec) and iBRT (6.6°/sec) was significantly greater than that during cHRT (4.7°/sec) and, cBRT (4.5°/sec) respectively (p<0.01, p<0.01). In the subacute VN group, a stronger nystagmus was elicited when the body (p<0.02) was turned to the ipsilesional side but it was not true during HRT (p=0.35). Also, the positional nystagmus during iHRT (1.8°/sec) and iBRT (2.3°/sec) had no significant difference with that during cHRT (1.8°/sec) and, cBRT (1.3°/sec) respectively. Conclusions: In acute VN, the positional nystagmus becomes stronger when the head or body is turned to the ipsilesional side compared to the contralesional side. But this typical pattern of positional nystagmus is not evident in subacute VN. The typical pattern of positional nystagmus, which can be found in acute VN, may not be helpful in diagnosing subacute VN.