The integration of multisensory motion stimuli is impaired in vestibular migraine patients

DOI: https://doi.org/10.1007/s00415- 020- 09905- 1

Abstract-Summary In the hypothesis that the integration of different vestibular stimuli is functionally impaired in VM, we tested whether the combination of abrupt vestibular stimuli and

2.2 Biology

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full-field, moving visual stimuli would challenge vestibular migraine patients more than controls and other non-vestibular migraineurs.

In three clinical centers, we compared the performance in the functional head impulse test (fHIT) without and with an optokinetic stimulus rotating in the frontal plane in a group of 44 controls (Ctrl), a group of 42 patients with migraine (not vestibular migraine, MnoV), a group of 39 patients with vestibular migraine (VM) and a group of 15 patients with vestibular neuritis (VN).

The comparison of the fHIT results without and with optokinetic stimulation unveils a functional vestibular impairment in VM that is not as large as the one detectable in VN, and that, in contrast with all the other patient groups, mainly impairs the capability to integrate different vestibular stimuli.

Extended: The comparison of the number of subjects with an abnormal %CA value in each group was based on the Chi-square test; for these analyses, we consid- ered not only the CW and CCW data separately but also the CW OR CCW condi- tion, where a subject was considered as abnormal if he/she showed an abnormal value in either the CW or CCW rotation.

Introduction Vestibular migraine (VM) is likely to be the most common cause of spontaneous episodic vertigo in adults and accounts for about 10% of all patients presenting at a dizziness unit [313], with a prevalence in the general population of about 1% [314]. Vestibular abnormalities have been found in up to 70% of VM patients (see von Brevern and Lempert 2016 [315] for a review); they include ictal [316] and interic- tal signs [317] and these latter are not specific to VM but can be also observed in migraineurs without a history of vestibular symptoms [318–323], so that the fea- tures of vestibular impairment in VM are still elusive.

Compared the performance between the regular fHIT and the fHIToks in terms of the percentage of correctly read optotypes (percentage of correct answers, %CA), i.e., the measure used in the fHIT, to assess whether it could differentiate VM patients from healthy subjects and from patients with non-vestibular migraine, and to compare the behavior of VM patients with that of patients with a unilateral ves- tibular deficit.

Materials and Methods The VN was included in the study as a group of subjects with a well-defined ves- tibular condition, to be specifically compared with the VM patients.

We tested the subject’s horizontal gaze stabilization abilities with the described regular fHIT paradigm: We imposed at least 20 head impulses in each direction dur- ing which the pre-sized (6 LogMAR lines larger than SVA threshold) Landolt C optotype appeared on screen for 80 ms with randomized orientation.

As an additional analysis, the mean VOR gain values from the subjects recorded in Siena were compared using a repeated measure analysis of variance considering both a within-subject factor (the task factor: fHIT without or with oks) and a between-subject factor (the group factor: Ctrl, MnoV and VM) and their interaction; the CW and the CCW data were analyzed separately.

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2 Mechanisms

Results Both for CW and CCW, the mean values of the three groups proved to be statisti- cally different for fHIT, for fHIToks and for fHIT–fHIToks difference.

The Scheffé test showed that the Ctrl and the MnoV groups showed the same behavior; whereas, the VM group was always different from the other two: more specifically the VM fHIT and fHIToks mean values were lower and the fHIT–fHI- Toks ones were larger than those of the other two groups.

The VN group showed significantly lower mean values than the VM group in the fHIT task for both CW and CCW directions, especially for the CW rotation, namely for the rotations toward the affected side of the VN group.

Both for the CW and the CCW directions, there was no statistically significant difference between the three groups, whereas the VOR gain values proved to be significantly lower in the fHIToks than in the fHIT task.

Discussion Even if the following considerations derive from analyses performed on subgroups of subjects, this impairment is attributable to a reduced capability in the integration of visual and vestibular signals, and not to a reduced visual acuity or a VOR gain reduction induced by the presence of the optokinetic stimulation.

When we considered the integration of different sensory inputs (fHIToks and fHIT–fHIToks difference), the percentage of abnormal subjects was always larger in the VM than in the VN group, and reached a borderline significant level for the fHIT–fHIToks difference in the CW OR CCW condition.

VM subjects showed a vestibular abnormality that mainly consisted in the

reduced capability to integrate different sensory signals reporting motion.

It is noteworthy that, compared to VN, VM patients showed a lesser impairment in the fHIT, but at least the same and frequently an even larger impairment when the integration of vestibular and visual information is required.

Acknowledgement A machine generated summary based on the work of Versino, Maurizio; Mandalà, Marco; Colnaghi, Silvia; Ricci, Giampietro; Faralli, Mario; Ramat, Stefano. 2020 in Journal of Neurology.

Duration and frequency of migraines affect cognitive function: evidence from neuropsychological tests and event-related potentials