Key points• The semicircular canals of the labyrinths are a source of information for self-motion perception and reflex eye movements.• Prolonged vestibular asymmetric stimulation of standing humans about the earth-vertical axis, made of fast body rotation to one side and slow rotation to the other side, induced different adaptive mechanisms in the perception of body motion and in the vestibulo-ocular reflex (VOR).• Motion perception became progressively more asymmetric, increasing gradually in response to the fast body rotation and decreasing in response to the slow rotation. VOR became gradually more symmetric, decreasing for fast body movement and increasing for slow movement.• These oppositely directed adaptive effects in motion perception and VOR persisted for at least 30 min.• Long-lasting asymmetric stimulation discloses independent brain mechanisms for perception of body motion and eye movement control.• These adaptive mechanisms may enhance awareness toward the side where the body is moving faster, while improving eye stabilizing properties of the VOR.Abstract Self-motion perception and the vestibulo-ocular reflex (VOR) were investigated in healthy subjects during asymmetric whole body yaw plane oscillations while standing on a platform in the dark. Platform oscillation consisted of two half-sinusoidal cycles of the same amplitude (40 • ) but different duration, featuring a fast (FHC) and a slow half-cycle (SHC). Rotation consisted of four or 20 consecutive cycles to probe adaptation further with the longer duration protocol. Self-motion perception was estimated by subjects tracking with a pointer the remembered position of an earth-fixed visual target. VOR was measured by electro-oculography. The asymmetric stimulation pattern consistently induced a progressive increase of asymmetry in motion perception, whereby the gain of the tracking response gradually increased during FHCs and decreased during SHCs. The effect was observed already during the first few cycles and further increased during 20 cycles, leading to a totally distorted location of the initial straight-ahead. In contrast, after some initial interindividual variability, the gain of the slow phase VOR became symmetric, decreasing for FHCs and increasing for SHCs. These oppositely directed adaptive effects in motion perception and VOR persisted for nearly an hour. Control conditions using prolonged but symmetrical stimuli produced no adaptive effects on either motion perception or VOR. These findings show that prolonged asymmetric activation of the vestibular system leads to opposite patterns of adaptation of self-motion perception and VOR. The results provide strong evidence that semicircular canal inputs are processed centrally by independent mechanisms for perception of body motion and eye movement control. These divergent adaptation mechanisms enhance awareness of movement toward the faster body rotation, while improving the eye stabilizing properties of the VOR.

To the best of our knowledge, this is the first class I study on the efficacy of the GLM in the treatment of LC-BPPV in both geotropic and apogeotropic forms. GLM proved highly effective compared to the sham maneuver (P < 0.0001). The present class I study of the efficacy of the GLM changes the level of recommendation of the method for treating LC-BPPV from level U to level B for the geotropic variant and from level B to level A for the apogeotropic variant of LC-BPPV.

Residual dizziness (RD) following the resolution of a benign paroxysmal positional vertigo (BBPV) episode is frequently reported by patients. Possible causes are still under debate in the literature. This study discusses the possible role of otolithic function and of elapsed time from onset of symptoms to diagnosis in the genesis of RD. In total, 116 patients younger than 65 years with their first episode of BPPV and without any other comorbidities were enrolled in the study. Before a bedside examination, subjective visual vertical (SVV) was determined in the case of a history suggestive of BPPV. SVV was tested 1 week later in those patients with BPPV of the posterior semicircular canal, and in whom positioning maneuvers showed resolution of BPPV. At 1 week control, reported RD and Dizziness Handicap Inventory (DHI) were recorded. Diagnosis and treatment of BPPV occurred within 4 days in 43 patients (group A), between 5 and 8 days in 38 patients (group B) and in more than 9 days in 35 patients (group C). Higher values of reported RD and DHI were recorded in group C, while higher values of SVV deviation were recorded in group A with an inverse relationship between SVV and DHI. Initial peripheral vestibular function asymmetry due to BPPV can induce a new central adaptation. This adaptation becomes better established the longer otoconia remain floating in the endolymph. Because of these changes, the brain is unable to quickly readapt to the old pattern after resolution resulting in more persistent RD.

In TTH patients (ETTH, CTTH, ETTH + MwoA), the stabilometric findings show a proprioceptive alteration induced by cervicofacial muscle contraction, which was peripheral in origin. In MwoA patients the alterations appear under OKN and support a control impairment in involuntary oculomotility of central origin.

The aim of the study was to assess the effects of optokinetic stimulation (OKS) on vestibular postural control in migraine patients with recurrent vertigo. 15 patients with vestibular migraine (VM) were enrolled in a posturographic study in eyes open (OE) and eyes closed (CE) condition. The tests were performed between attacks of headache and vertigo at three different time: before, during, and 60 min after OKS. Data of patients with VM were compared with those obtained from two control groups matched for sex and age (15 for each group): (a) normal subjects not suffering from migraine without history of recurrent vertigo (N group); (b) subjects suffering from migraine with no history of recurrent vertigo (M group). Mean sway path velocity and sway area were analyzed. OKS increased the instability in all groups during the stimulus, and both the velocity and area values were higher in M and VM group. However, there was not significant difference between these two groups when stability was examined in OE condition before, during and after OKS stimulation. Conversely, in CE condition a significant greater instability was induced after OKS stimulation only in VM. In particular, post-stimulus values were significantly higher than the pre-stimulus one only in this group, while no significant difference was observed in other groups. A spatial analysis of the sway area evidenced that the instability induced by the OKS in VM group occurred along the direction of OKS. We suggest that this enhanced instability observed after OKS during the intercritical period may be considered an useful marker to support the diagnostic definition of VM in the absence of other vestibular signs.