Assessment of skin microvascular endothelial function in patients with acute unilateral vestibular syndrome

Abnormalities in labyrinth vasculature, resulting in labyrinth ischemia may be responsible for acute unilateral vestibular syndrome (AVS). However, since no tools for the study of the labyrinth microvasculature are available in clinical settings, labyrinth microvascular abnormalities in AVS patients (AVS-pts) can only be hypothesized on the basis of the their cardiovascular risk profile. Considering that skin microcirculation may mirror vascular function in other body districts, we examined skin endothelial function in 20AVS-pts and in 20 healthy control subjects (CS), with the aim of predicting labyrinth microvascular abnormalities in the same AVS-pts, potentially involved in the pathogenesis of their AVS. AVS-pts and CS underwent laser-Doppler flowmetry measurement of the skin forearm vasodilator response (SVR) to iontophoresis of the endothelial-dependent vasodilator acetylcholine (ACh) and to the endothelial-independent vasodilator sodium nitroprusside (SNP). SVR to ACh was significantly lower than to SNP in AVS patients (p < 0.005, ANOVA for repeated measures), consistent with skin endothelial dysfunction, while no significant differences in SVR between ACh and SNP were observed in CS. Accordingly with an arbitrary cut-off of 30% or greater reduction in SVR to ACh compared to SNP, endothelial dysfunction was found in 4 (20%) of CS, and in 14 (70%) of AVS-pts (6 with associated co-morbidities potentially responsible for endothelial dysfunction, and 8 without these co-morbodities). This study shows that the investigation of skin endothelial function in AVS-pts may be helpful in identifying AVS-pts in whom an ischemic origin of AVS might be more probable, in spite of their low cardiovascular risk profile.