Video head impulse findings in the ictal period of vestibular migraine

Video head impulse and suppression head impulse test in vestibular migraine

BACKGROUND

Vestibular Migraine (VM) is a frequent cause of recurrent spontaneous vertigo. While some report a normal Video Head Impulse Test (vHIT) in VM, others observed abnormal results on this test. Whether or not methodological discrepancies could be the cause of these differences is not known. There are 2 vHIT methods: subjects fixating an earth-fixed target (HIMP paradigm) or a head-fixed target, the suppression head impulse test (SHIMP paradigm).

OBJECTIVES

The present study aimed to compare VM patients against healthy controls on both HIMP and SHIMP in order to unravel any differences between them.

METHODS

Forty-eight VM patients and 27 healthy controls tested with both the HIMP and SHIMP paradigm. Results: Our 48 VM patients showed mean VOR normal range gains in both the HIMP and SHIMP paradigms, although there were some VOR impairments in individual semicircular SCCs. VM patients with motion sickness had lower horizontal VOR gain than those without motion sickness, with the HIMP, but not the SHIMP paradigm.

CONCLUSION

VM patients have normal VOR gain with either vHIT paradigm.

SIGNIFICANCE

The clinical significance of this observation is that a definitely abnormal vHIT with either method is unlikely to be due to vestibular migraine and an alternative diagnosis should be sought.

Fluctuating Posterior Canal Function in Benign Paroxysmal Positional Vertigo Depending on How and Where Otoconia Are Disposed

OBJECTIVE

Though fluctuations in vestibular function represent a common finding in Menière's disease, we describe how benign paroxysmal positional vertigo (BPPV) may result in fluctuations of vestibulo-ocular reflex for the involved canal depending on the disposition of otoliths.

PATIENT

A 54-year-old woman suffering from refractory posterior canal (PC)-BPPV resulting in fluctuating PC function.

INTERVENTIONS

Diagnostic evaluation and rehabilitative treatment for BPPV involving the affected PC.

MAIN OUTCOME MEASURES

Video-Frenzel and video-head impulse test (vHIT) findings before and after canalith repositioning procedures for PC-BPPV.

RESULTS

BPPV involving the nonampullary arm of right PC was diagnosed based on presenting positional downbeat nystagmus and selective right PC hypofunction at the vHIT. During physical treatment, nystagmus first became positional paroxysmal upbeat likely due to a shift of debris into the ampullary arm of the canal, then turned to spontaneous downbeat nystagmus consistently with a plug effect exerted by particles entrapped within the nonampullary arm of PC and finally receded proving an otoliths fall within the utriculus. Simultaneously, vHIT documented fluctuations for right PC vestibulo-ocular reflex gain as it first increased to normal values, then severely declined and finally normalized, respectively. High-resolution computed tomography scan detected ipsilateral superior canal dehiscence.

CONCLUSIONS

In accordance with recently reported vHIT findings in different types of BPPV, fluctuation of PC function could be likely explained by the effect of particles on cupular dynamic responses depending on the portion of the canal gradually involved. Superior canal dehiscence may have played a role facilitating otoliths mobilization by reducing labyrinthine impedance.