Usefulness of galvanically induced nystagmus as a diagnostic test of peripheral vestibular hypofunction.

BACKGROUND: Galvanic Vestibular Stimulation (GVS) has long been used as a vestibular stimulus. A major issue observed in GVS research was the high variability of the responses, which has led some researchers to question its diagnostic utility. OBJECTIVES: Determine the diagnostic accuracy of galvanically induced nystagmus for the diagnosis of subjects with unilateral peripheral vestibular hypofunction. METHODS: A total of 195 dizzy patients were prospectively enrolled, forming a consecutive series as they were received. Individuals with spontaneous nystagmus or using vestibular sedatives were excluded. Nystagmus induced by a 4 mA galvanic stimulus was compared with the caloric test as a reference standard. RESULTS: Of the 195 subjects tested with GVS, 115 were subjects with a unilateral peripheral vestibular hypofunction. The presence of nystagmus showed an AUC of only 0.529 (0.478 to 0.580, p = 0.125), and the maximum slow phase velocity of nystagmus showed an AUC of only 0.523 (0.472 to 0.573, p = 0.439). CONCLUSIONS: Since neither AUC is better than random discrimination, this study concludes that GVS-induced nystagmus is not useful as a diagnostic tool for unilateral peripheral vestibular hypofunction. These findings discourage the use of GVS-induced nystagmus in the clinical setting.

Emotional reaction evaluation provoked by the vestibular caloric test through physiological variables monitoring. / Valoración de la reacción emocional provocada por la prueba vestibular calórica mediante monitorización de variables fisiológicas.

INTRODUCTION AND OBJECTIVES: The emotional evaluation of the causes of vertigo is made using the clinical records and several subjective questionnaires. The aim of the present study is to evaluate the emotional response objectively, in normal subjects, during an induced vertigo crisis. MATERIAL AND METHOD: A caloric vestibular test with cold water was performed on 30 healthy subjects. The following physiological parameters were monitored during the 60seconds prior to and the 60seconds after the stimulation: Skin Conductivity, Peripheral Pulse Volume, Body Temperature, Muscle Contraction, Heart Rate, and Respiratory Rate. The maximum angular speed of the nystagmus slow phase at each stimulation was assessed. RESULTS: Skin conductance presented a statistically significant increase during the vertigo crisis in relation to the prior period while the peripheral pulse volume presented a statistically significant decrease. There was no relationship between the slow phase of the provoked nystagmus angular speed and skin conductance and peripheral pulse volume changes. The decrease in peripheral pulse volume was significantly higher in the second vertigo crisis. CONCLUSIONS: Skin conductance and peripheral pulse volume changed significantly during a vertigo crisis. There was no relation between the provoked vertiginous crisis intensity and the changes produced in those variables. The stress generated by the caloric stimulation is higher in the second crisis, when the subject has experience of the vertigo caused by the stimulation.

Atypical periodic alternating nystagmus responding to high-dose intravenous immunoglobulins: a case report.

BACKGROUND: Acquired periodic alternating nystagmus (PAN) is a rare but well-defined syndrome that consists of a horizontal nystagmus that cyclically reverses its direction. PAN can be caused by degenerative, neoplastic, or toxic diseases of the cerebellum and, in a few cases, by subacute cerebellar ataxia of immune origin. CASE PRESENTATION: A 44-year-old man came to our attention because of rapidly progressive gait instability and blurred vision. Clinical examination showed PAN and a mild pancerebellar syndrome. Eye movement recordings disclosed a short cycle PAN with significant slow-phase velocity only in darkness. Under the effect of a γ-aminobutyric acid type B (GABAB) agonist, PAN was not modified. Right after treatment with intravenous immunoglobulin (IVIg) was started, PAN was essentially eliminated. Three months after last dose of IVIg, this nystagmus reappeared. CONCLUSIONS: IVIg resolved PAN in this patient. This finding may point to an autoimmune mechanism underlying this patient's nystagmus. This case suggests that the usefulness of IVIg at treating PAN might be worth a consideration in similar clinical settings.