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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 34  |  Issue : 2  |  Page : 427-432

Video head impulse test in epileptic patients


1 Department of Otolaryngology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Otolaryngology, Menshawy Hospital, Tanta, Egypt
3 Department of Neurology, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Date of Submission04-Oct-2020
Date of Decision11-Jan-2021
Date of Acceptance18-Jan-2021
Date of Web Publication30-Jun-2021

Correspondence Address:
Heba A. M. Eldesoky
MBBCh, Tanta, Gharbia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_360_20

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  Abstract 


Objectives
To assess the vestibulo-ocular function in epileptic patients in the interictal period.
Background
Vertigo or dizziness are common symptoms with epileptic seizures.
Patients and methods
This is a cross-sectional study. The participants included in this study were divided into two groups. The control group consisted of 40 normal participants not complaining of any dizzy symptoms, with an age range of 20–40 years, and the study group (epileptic cases group) consisted of 40 epileptic patients, with age range of 20–40 years. All participants were subjected to vestibular assessment in the form of videonystagmography and video head impulse test (vHIT).
Results
There was no significant statistical difference between both groups regarding age (P = 0.17, Student t test) and sex distribution (P = 0.65, χ2 test). A total of 25 (62.5%) epileptic patients had vestibular symptoms. On videonystagmography, saccadic intrusions in pursuit test were reported in four (10%) epileptic patients, and seven (17.5%) epileptic patients had abnormal velocity in the saccade test; there was a significant statistical difference between both groups regarding the velocity of the saccade test (P = 0.02, Student t test). On vHIT, there was a significant statistical difference between both groups regarding lateral canal gain (P = 0.001, Student t test). A total of 29 (72.5%) patients in the study group had an abnormal gain in at least one canal of the six semicircular canals. Eight (20%) patients in the study group had low gain, and 21/40 (52.5%) patients had high gain. There was a significant statistical relationship between vestibular abnormalities and type of epilepsy, as well as EEG findings.
Conclusion
Vestibular system may be affected with epilepsy; high gain was the most frequently encountered abnormality in the vHIT.

Keywords: epilepsy, vertigo, vestibule-ocular reflex, video head impulse


How to cite this article:
Kabel AE, Eldesoky HA, Salem GM, Moaty AS. Video head impulse test in epileptic patients. Menoufia Med J 2021;34:427-32

How to cite this URL:
Kabel AE, Eldesoky HA, Salem GM, Moaty AS. Video head impulse test in epileptic patients. Menoufia Med J [serial online] 2021 [cited 2024 Mar 28];34:427-32. Available from: http://www.mmj.eg.net/text.asp?2021/34/2/427/319722




  Introduction Top


Epilepsy is characterized by recurrent and unpredictable alteration of normal brain function, which results from excessive and hypersynchronous discharge of the brain neurons. Seizures can affect sensory, motor, and autonomic function. Sensory manifestations may include auditory and vestibular symptoms [1].

Vestibular symptoms, for example, vertigo and dizziness, are common symptoms, reported by epileptic patients. However, vestibular symptoms are rarely encountered as the sole or predominant feature of seizures [2]. In vertiginous epilepsy, vestibular symptoms can range from mild symptoms to frank vertigo [3]. The vestibular cortex consists of a network of multiple distinct cortical areas, for example, temporoparietal areas and parietoinsular areas, which are the core vestibular origin with a bilateral representation of the peripheral and central vestibular systems [4]. Vestibular symptoms may represent a manifestation of the epileptic activity [3]. One of the important vestibular-related functions is gaze stabilization during head rotation or body translation in the space, which is achieved through the vestibulo-ocular reflex (VOR) [5]. Video head impulse test (vHIT) is a test that assesses the VOR gain of the sex semicircular canals (SCCs).

The aim of this work was to assess the vestibulo-ocular function in epileptic patients in the interictal period (the period in between seizures where the patient is clinically seizure free but EEG may be positive) using vHIT and videonystagmography (VNG).


  Patients and methods Top


This cross-sectional study was carried out in the audio-vestibular unit in Menoufia University in the period between September 2018 and February 2020. The ethical approval number of the hospital committee was 984, and its date was 8/4/2018. Written consent was obtained from all the participating participants in this study. Participants included in this study were divided into two groups.

Study and control groups

The control group consisted of 40 normal participants not complaining of any dizzy symptoms, with an age range of 20–40 years. The study group (epileptic cases group) consisted of 40 participants recruited from neurology clinic, with an age range from 20 to 40 years, and diagnosed as epileptic patients, according to the criteria of international league against epilepsy classification [6], with exclusion of patients having other neurological disorders, systemic diseases, congenital nystagmus, poor vision, neck problems in addition to a history of past or concurrent oto-vestibular disease, for example, Meniere's disease and benign paroxysmal positional vertigo. Participants were assessed in the interictal period.

All participants in the study group were subjected to the following: full history taking [cause, type and duration of epilepsy, frequency of epileptic attack, antiepileptic drugs (AEDs), EEG records, and audiovestibular symptoms], neurological examination, vestibular office tests (observation of spontaneous nystagmus and gaze-evoked nystagmus, posture and gait tests, Romberg's test, and positioning and positional tests), otoscopic examination, basic audiological assessment (pure tone audiometry and immittancemetry), and vestibular assessment in the form of VNG (NysStar VNG, Difra System, Eupen, Belgium) and vHIT (HeadStar vHIT; Difra System).

EEG

It was done at the Neurology Department, Menoufia University Hospitals, and was performed under normal standard conditions. Electrodes were placed according to the international 10–20 system of surface electrode placement using monopolar and bipolar montages. The EEG tracing was analyzed according to frequency, amplitude, symmetry of the background activity, and the presence of any abnormality. The EEG findings were classified as normal or abnormal. The abnormal epileptogenic activity was classified into generalized, temporal, and frontal, temporal with secondary generalization, and frontal with secondary generalization.

Videonystagmography

It is a recording technique for eye movement using a video camera mounted on goggles. Before VNG testing, the patients were instructed to stop all medications except AEDs 48 h before the evaluation. The following tests were done: spontaneous nystagmus, gaze evoked, oculomotor tests (saccade, smooth pursuit, and optokinetic tests), and head shake and positional tests. The technique of the tests and interpretation of the results were done according to British Society of Audiology [7].

Video head impulse test

It was used for individual assessment of the six SCC function. The goggles of the vHIT were tightened over the head of the patient to avoid slippage, which may interfere with the results. Standard calibration was done to calibrate the patient's eye in relation to the targets. Participant's head was abruptly and unpredictably turned in the plane of each SCC in about 100 ms while the patient was fixating on a stationary target, located 1 m at the eye level of the patient. The gains of the VOR and saccades (overt and covert) were recorded; 20 head impulses were applied to each canal in each side [8]. Noisy records were removed manually. In horizontal SCCs testing, the examiner placed his hands on the top of the patient's head, and the patient's head was suddenly turned to the right and the left in the plane of the horizontal canal. In vertical SCC testing, the examiner placed his dominant hand on top of the patient's head, and the fingers were directed in the plane of vertical SCC; nondominant hand was placed on the chin of the patient. For the left anterior right posterior position, the head is turned to right 45° with the aid of head detection guide provided by the device. For the right anterior left posterior position, the head was turned to the left with the help of the head detection guide. In both positions, the head of the patient was moved forward to stimulate anterior canal and backward to stimulate posterior canals [8]. Gain results, beyond the range of the normal values in our laboratory for the same age group, were considered abnormal, which are 0.8–1.4 in lateral canal and 0.7–1.4 in the vertical canals (which were the same default cutoff values for the Difra device) in addition to saccadic intrusions.

Statistical analysis

Results were analyzed using SPSS (version 22, SPSS Inc., Chicago, Illinois, USA), in which qualitative data were expressed as number and percentages and quantitative data were expressed as mean and SD. Student t test was used for comparison between groups having quantitative variables. χ2 test was used to study the association between two qualitative variables. P value of less than or equal to 0.05 was considered statistically significant.


  Results Top


There was no significant statistical difference between both groups regarding age and sex distribution [Table 1]. History and patient symptoms are demonstrated in [Table 2]. All participants in the control and study group had no concurrent illness. They had normal otoscopic, neurological, and vestibular office test results.
Table 1: Demographic characteristics of the studied groups

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Table 2: History among the studied group of epileptic cases (n=40)

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Basic audiological assessment

Hearing assessment was normal except one case in the study group, which had bilateral mild sensorineural hearing loss. All participants had within normal tympanogram results, with preserved, ipsilateral, acoustic reflexes.

Videonystagmography results

All the participants in the control group had normal VNG test results. In the study group, there were no abnormalities in spontaneous nystagmus, gaze evoked nystagmus, head shake testing, and positional test. VNG abnormalities were reported in 7/40 (17.5%) patients in the epileptic group. The abnormalities were reported in the saccade and pursuit test. In the saccade test, there was no statistically significant difference between control and study group regarding the accuracy (P = 0.09 and 0.18 in right and left sides, respectively; Student t test) and latency (P = 0.06 and 0.07 in right and left sides, respectively; Student t test) of saccade test, and there was a significant statistical difference between both groups regarding the velocity of saccade in both ears [Table 3]. Overall, seven (17.5%) epileptic patients had abnormal velocity (slow) in the saccade test. In pursuit test, four (10%) patients had saccadic intrusions. There was no statistically significant difference in the gain of pursuit tests (P value of gain = 0.55, Student t test) between both groups, and no asymmetry was noted. Four (10%) epileptic patients had abnormal slow velocity in association with saccadic intrusions. In the optokinetic test, no significant difference was noted regarding the gain of optokinetic nystagmus between the two groups (P = 0.21 and 0.31 for right and left sides, respectively; Student t test), and no asymmetry was noted. There was a significant statistical relationship between VNG abnormalities and type of epilepsy (P = 0.02, χ2 test), and VNG abnormalities were more reported in simple partial type.
Table 3: Results of velocity of saccade test among the studied groups

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Video head impulse test results

All participants in the control group had normal gain in all the SCCs. There was a significant statistical difference between both groups regarding lateral canal gain, and no significant statistical difference was noted in other canals [Table 4]. vHIT abnormalities and number of affected canals are demonstrated in [Figure 1]. Abnormal gain in vHIT was reported as follows: 16/80 (20%) ears in lateral SCC, 16/80 (20%) ears in posterior SCC, and 13/80 (16.3%) ears in anterior canal. No overt or covert saccades were reported in the study group. All the epileptic patients with abnormal vHIT had vestibular symptoms as well. All patients with abnormal VNG results (seven patients) had abnormal vHIT results as well. There was no significant statistical relationship between abnormal vHIT gain and patient characteristics, such as age (P = 0.07, Student t test), sex (P = 0.21, χ2 test), frequency of epileptic attacks (P = 0.37, χ2 test), type of therapy (P = 0.10, χ2 test), and type of epilepsy (P = 0.28, χ2 test). There was a significant statistical difference between patients with abnormal gain and patient with normal gain regarding the duration of the epileptic disease (P value = 0.006, Student t test). Regarding EEG findings, there was a statistically significant relationship between EEG findings and VNG and vHIT abnormalities, and abnormalities were more reported in temporal epileptic activity [Table 5].
Table 4: Comparison between the studied groups regarding the gain of video head impulse test in the three semicircular canals in 80 ears in both groups

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Figure 1: vHIT abnormalities and the number of canals affected. This figure shows vHIT abnormalities and number of canals affected in the epileptic patients. vHIT, video head impulse test.

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Table 5: Relationship between EEG findings and vestibular abnormalities among the studied epileptic cases

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  Discussion Top


The VOR stabilizes images on the retina during head movement. The anatomical component of the VOR is SCC, vestibular, and ocular motor nuclei (in the brainstem), as well as the extraocular muscles [9]. VOR processing is completed through the basic brain stem circuits and also the cortical vestibular circuits, especially parietal-vestibular nuclei projections. Cortical control of the VOR has been reported in behavioral and electrical stimulation studies. Additionally, cortical lesions cause modulation in the vestibule ocular function [10]. Vestibular dysfunction in epilepsy may occur owing to central or peripheral vestibular affection [11]. vHIT may be more appropriate in vestibular assessment of epileptic patients, especially when other vestibular tests are contraindicated like caloric test in decompensated epilepsy. To our knowledge, no studies assessed vHIT in epileptic patients, so this study assessed VOR function in the epileptic patients using vHIT.

Vestibular symptoms in epilepsy may accompany the seizure itself or may occur as adverse effects of AEDs [12]. Vestibular symptoms, that pace or accompany the seizure attack, are known as vertiginous aura [13]. In the current study, two-thirds of the epileptic patients had vestibular symptoms (vertigo that lasted for seconds to minutes and sense of imbalance that occurred as an aura-symptoms or on starting administration of AEDs).

All participants in the epilepsy group were under AED therapy. Monotherapy in epilepsy is preferred because it decreases the likelihood of adverse effects and drug interactions [14]. In the current study, 85% of epileptic patients received only one drug as an antiepileptic therapy.

VNG is a diagnostic system for recording and analysis of eye movement. In the study group, the abnormalities were reported in the oculomotor tests. VNG abnormalities were reported in 17.5% patients in the epileptic group. Catch-up saccade in the pursuit test is a central sign suggesting a brain disorder rather than ear disease [15]. Hamed [11], stated that long-term treatment with AED may cause abnormalities in pursuit eye movements, and AEDs act as a norepinephrine antagonist that affect eye movement.

In the current study, there was a significant statistical difference between both groups regarding the velocity of the saccade test in both ears, as the saccade in the epileptic cases was slower than the saccade in the control group. Drug ingestion should be the first consideration in cases of saccadic slowing. Anticonvulsants are one of the most common drugs that cause saccadic slowing as the patient becomes drowsy [16]. If drowsiness and drug effect are excluded, saccadic slowing indicates central nervous system affection [17]. Vestibular symptoms such as dizziness, unsteadiness, imbalance, ataxia, and rotational vertigo are frequently reported as common ictal manifestations of many focal epileptic seizures such as temporal and tempro-parieto-occipital [3]. These ictal symptoms are usually related to discharges arising from or involving temporal or parietal areas which are supposed to be a crucial component of the vestibular cortex [18]. In the current study, vestibular abnormalities were more reported in temporal epileptic activity (according to EEG findings) and also more reported in simple partial type of epilepsy. Caloric test was done to few patients, but unfortunately, seizure attack was precipitated by caloric testing in one patient, although the patient had been under control so the caloric test was excluded from the study.

Video head impulse test results

In the current study, there was a statistical difference between epileptic cases and control group regarding lateral canal vHIT gain in both ears, and there was no statistical difference in other canals. Fujiwara et al.[19] stated that vertical canals produced fewer abnormalities than did horizontal canal in vHIIT.

In the current study, 73% of the epileptic cases group had abnormal vHIT gain (either high or low) in one (37.5%) canal, two (30%) canals, and three (5%) canals.

Brain stem lesions can significantly reduce VOR gain unilaterally or bilaterally owing to the involvement of the vestibular nucleus and nucleus prepositus hypoglossi [20]. Seizures may cause disruption in brain stem connections [21]. Additionally, brain stem lesions may cause secondary generalization of seizures [22]. In the current study, low gain of the VOR was reported in 20% of the epileptic cases, which may be interpreted by brain stem involvement in epilepsy.

High gain in vHIT has been the most frequently encountered abnormality in our study as more than half of the epileptic patients with abnormal vHIT had high gain. The increased VOR gain may occur owing to hypersensitivity of the vestibular end organs and overexcitation of the vestibular nerve [23]. The AEDs have adverse effects on the vestibular system. The long treatment with AEDs may cause vestibular symptoms owing to central or peripheral vestibular affection [11]. The vestibular dysfunction, secondary to AED, may occur owing to the interference of firing within the CNS neurons in addition to the delayed conduction in the brain stem pathways from the inhibitory effect of GABA neurotransmitter [24]. Vestibular symptoms may occur in the early stages of treatment, and they can be relieved by decreasing the dose of drug [25]. Coadministration of two or more of an AED increases the risk of adverse effects such as dizziness [26].

Vestibular abnormalities in the current study may be explained by the effect of epilepsy on cortical vestibular areas, for example, temporal and frontal cortex [3], in addition to brain stem involvement [21]. Gandelman-Marton et al.[27] reported poorer postural function in epileptic patients than controls. El-Gohary et al.[28] reported occurrence of central and peripheral vestibular dysfunctions in epileptic children.

In the current study, no significant differences were obtained in the demographic and clinical characteristics between patients with and without vHIT abnormalities. However, there was a significant statistical relationship between vHIT abnormalities and duration of epilepsy. Prolonged epilepsy duration (>10 years) is a risk factor for poor control of seizures [29]. Therefore, vestibular abnormalities may be related to the control of the disease.

Limitations

This study assessed the VOR and SCCs function only. Further studies on vestibulospinal and otolith function are recommended to evaluate the remaining parts of the vestibular system in epileptic patients and to correlate between vestibular abnormalities and different types and doses of AEDs.


  Conclusion Top


Vestibular system may be affected with epilepsy. The vHIT abnormalities, especially high gain, were frequently encountered in epileptic patients in the current study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest:



 
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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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