Grey matter activation by caloric stimulation in patients with unilateral peripheral vestibular hypofunction

A combination of the caloric test with functional magnetic resonance imaging (fMRI) is a promising method for a comprehensive diagnostics of pathologies of the vestibular system. The aim of this study was to investigate the potential pattern of grey matter local activation in fMRI using cold and hot caloric stimulation in patients presenting unilateral peripheral vestibular injury.

Forty right-handed participants aged 27 to 56 with the diagnosis of right-sided peripheral vestibular hypofunction were included. Stimulation was performed separately for the right and the left ear with cold (C, 14-15 °C) stimulus and hot (H, 48-49 °C) stimulus. Grey matter activation was assessed in BOLD technique using a 3T scanner.

We observed activity within the parieto-insular vestibular cortex (PIVC), thalamus, insula and retroinsular area, hippocampus, and cerebellum, as well as oculomotor centers located in the precentral gyrus, superior temporal gyrus, and intraparietal sulcus. Cold stimulus resulted in more areas of activation in response to the right ear activation rather than to the left ear. The ipsilateral activity was noted for insular cortex and intraparietal sulcus. The differences between hot and cold stimuli were noted for the right ear.

In this preliminary study, the combination of the caloric test and fMRI allowed to present specific pattern of grey matter activation in patients with unilateral peripheral vestibular injury. Further studies are necessary to develop patterns or cortical maps differentiating various balance disorders and to analyze the dynamics of cortical plasticity after the injury.