Christian Van Nechel

Interference between walking and a cognitive task is increased in patients with bilateral vestibular loss

The aim of this study was to determine whether there is more deterioration in walking under dual-task conditions in patients with bilateral vestibular loss (BVL) than in healthy subjects, as opposed to the findings after unilateral loss. For this purpose, 12 patients with BLV and 12 healthy control subjects performed 3 tasks: walking along a 10-m walkway, counting backwards by two, and both tasks simultaneously. Patients did not differ from controls in their walking speed in the single task condition, or in their cognitive performance in both the single and dual-task conditions. However, walking performance was more affected in patients than in controls under dual-task conditions, as shown by slower gait speed in the dual-task, higher reduction in gait speed from single to dual-task, and lower global dual-score. These findings provide evidence for greater attentional interference between walking and counting in patients with BVL.

Influence of Body Laterality on Recovery from Subjective Visual Vertical Tilt after Vestibular Neuritis

The subjective visual vertical (SVV) is an indicator of vestibular otolithic function and mainly processed by the nondominant parietal cortex. We investigated the hypothesis that recovery from SVV tilt after vestibular neuritis can be influenced by the bodys lateral preference. This prospective cohort follow-up study included 254 consecutive adult patients with vestibular neuritis. The recovery from SVV tilt was faster in patients with a left hand or eye dominance than in those with a right dominance. While in left-handers the side of the neuritis did not affect the speed of recovery, in right-handed subjects, the recovery from a right-sided neuritis was significantly slower than from a left-sided affection. These observations suggest that subjects with a left sensorimotor dominance have developed more significant midline-crossing projections to the parietal cortex, allowing them to cope faster with a unilateral vestibular deficit.

Anchoring the Self to the Body in Bilateral Vestibular Failure

Recent findings suggest that vestibular information plays a significant role in anchoring the self to the body. Out-of-body experiences of neurological origin are frequently associated with vestibular sensations, and galvanic vestibular stimulation in healthy participants anchors the self to the body. Here, we provide the first objective measures of anchoring the self to the body in chronic bilateral vestibular failure (BVF). We compared 23 patients with idiopathic BVF to 23 healthy participants in a series of experiments addressing several aspects of visuo-spatial perspective taking and embodiment. In Experiment 1, participants were involved in a virtual “dot-counting task” from their own perspective or the perspective of a distant avatar, to measure implicit and explicit perspective taking, respectively. In both groups, response times increased similarly when the avatar’s and participant’s viewpoint differed, for both implicit and explicit perspective taking. In Experiment 2, participants named ambiguous letters (such as “b” or “q”) traced on their forehead that could be perceived from an internal or external perspective. The frequency of perceiving ambiguous letters from an internal perspective was similar in both groups. In Experiment 3, participants completed a questionnaire measuring the experienced self/body and self/environment “closeness”. Both groups reported a similar embodied experience. Altogether, our data show that idiopathic BVF does not change implicit and explicit perspective taking nor subjective anchoring of the self to the body. Our negative findings offer insight into the multisensory mechanisms of embodiment. Only acute peripheral vestibular disorders and neurological disorders in vestibular brain areas (characterized by strong multisensory conflicts) may evoke disembodied experiences.

Subjective Visual Vertical Tilt Attraction to the Side of Rod Presentation: Effects of Age, Sex, and Vestibular Disorders

Objective The aim of this study was to evaluate the effect of initial rod position on the subjective visual vertical (SVV) tilt and to investigate the effect of sex and age on the SVV tilt induced by this initial position. Study Design Prospective cross-sectional study. Setting Tertiary referral center. Patients The study included 6598 consecutive patients with a large range of vestibular disorders and 333 control subjects. The mean age was 55 years (range, 3–97), and the sex ratio was 0.6. Intervention SVV was measured by presenting a phosphorescent rod 12 times in total darkness with a 45-degree deviation from the vertical alternatively on the right and left. The patient was asked to replace the bar vertically with a remote control. Results On average, SVV at each iteration was tilted to the side of the rod presentation. It was stronger in female subjects, in younger individuals (<20 years) and seniors (>50). It was also higher in patients with a left vestibular loss in comparison to those with a right involvement. Conclusions These effects suggest that short-term visual memory and multisensory cortical processing interfere with SVV measurements.

Neuro-ophthalmological emergencies: which ocular signs or symptoms for which diseases?

There are five possible ocular signs or complaints of a life or sight threatening neuro-ophthalmological condition: diplopia, isolated anisocoria, transient visual loss, severe pain in head or neck (with or without photophobia) and oscillopsia/nystagmus. In this review, the ocular signs and symptoms of neuro-ophthalmological emergencies are described together with their practical work-up and the risks associated with missing the diagnosis. Concerning diplopia, the associated signs pointing to a possible threatening condition are emphasized. Six focus points resuming core messages are displayed throughout this review.

Action representation in patients with bilateral vestibular impairments.

During mental actions subjects feel themselves performing a movement without any corresponding motor output. Although broad information is available regarding the influence of central lesions on action representation, little is known about how peripheral damages affect mental events. In the current study, we investigated whether lack of vestibular information influences action representation. Twelve healthy adults and twelve patients with bilateral vestibular damage actually performed and mentally simulated walking and drawing. The locomotor paths implied one (first walking task) and four (second walking task) changes in the walking direction. In the drawing task, participants drew on a sheet of paper a path that was similar to that of the second walking task. We recorded and compared between the two groups the timing of actual and mental movements. We found significant temporal discrepancies between actual and mental walking movements in the group of patients. Conversely, drawing actual and drawing mental durations were similar. For the control group, an isochrony between mental and actual movements was observed for the three tasks. This result denotes an inconsistency between action representation and action execution following vestibular damage, which is specific to walking movements, and emphasizes the role of the vestibular system upon mental states of actions. This observation may have important clinical implications. During action planning vestibular patients may overestimate the capacity of their motor system (imaging faster, executing slower) with harmful consequences for their health.

Subjective Visual Vertical in Idiopathic Bilateral Vestibular Hypofunction: Enhanced Role of Vision, Neck, and Body Proprioception

INTRODUCTION We aimed to study the participation of proprioceptive and visual inputs in subjective visual vertical (SVV) in bilateral vestibular hypofunction and in normal subjects. STUDY DESIGN Prospective case-control study. SETTING Tertiary referral center. MATERIALS AND METHODS SVV (six replicates) was measured on a tiltable rehabilitation seat in 26 adult patients with idiopathic bilateral vestibular hypofunction (IBVH) and 33 adult controls. Subjects were asked to place vertically a 45 degrees-tilted red line on a screen (three replicates to left and three to right alternatively) using a remote control in total darkness and in seven body positions: vertical, head, and body left- and right-tilts to 12 and 24 degrees, and then body left- and right-tilt to 24 degrees with the head upright. RESULTS In the vertical position, SVV did not differ between IBVH and controls. Patients with IBVH were more sensitive to body tilt than controls (SVV: -8.1 ± 4.66 degrees for IBVH versus -0.2 ± 3.23 for control at 24 degrees body and head left-tilt, p < 0.0001, unpaired t test). The visual attraction effect defined by a deviation of the SVV to the side of the initial line presentation appeared to be higher in the IBVH than in controls suggesting higher visual dependence in IBVH. Placing the head upright while the body was still tilted significantly reduced this difference. Similar results were observed for the right-tilts. CONCLUSION Not only otolithic function but also visual plus body and neck proprioceptive entries participate in SVV. The influence of vision and proprioception appears to be enhanced in case of IBVH.

Maturation of subjective visual vertical in children

Objective: The attraction of the subjective visual vertical (SVV) to the side of initial rod presentation has already been described in adults. The aim of this study was to evaluate this phenomenon in children and to analyze the effect of sex and maturation in this population. Study Design: Retrospective cross-sectional study. Setting: Tertiary referral center. Patients: Six hundred and one individuals aged between 4 and 19 years. Intervention: All subjects underwent a complete balance workup. SVV was measured by presenting a laser line 12 times in total darkness with a 45 degrees deviation from the vertical alternatively on the left and the right. The patient was seated and asked to replace the bar vertically with a remote control. Results: On average, SVV was tilted to the side of the rod presentation at each iteration. The cumulative tilt to the side of presentation after 12 measures was higher in the 4 to 7 years age group and decreased progressively with age (25 ± 2.2 degrees in 4–7 years, n = 109 versus 5 ± 1.4 in 15–19 years, n = 204, p < 0.001, analysis of variance [ANOVA]). The cumulative tilt was higher in girls than in boys in the 15 to 19 years group (8 ± 2.5 degrees, n = 104 versus 2 ± 1.2, n = 100, respectively, p < 0.001, ANOVA). This phenomenon appeared independent from the type of vestibular disorder. Conclusion: Young children are highly attracted to the side of rod presentation during SVV measurements. This phenomenon gradually disappears with maturation, faster in boys than in girls.

Bilateral Duane's syndrome associated with hypogonadotropic hypogonadism and anosmia (Kallmann's syndrome)

A case of bilateral Duanes retraction syndrome (DRS) type III associated with Kallmanns syndrome (hypogonadotropic hypogonadism and anosmia) is reported. Both anomalies may result from a disturbance of embryogenesis during the second month of gestation. The authors associate bilateral type III DRS with congenital horizontal gaze paralysis.

Sixth cranial nerve neuromyotonia mimicking intermittent Duane syndrome type II: case report

A 14-year-old girl was referred to our department in March 2015 for intermittent diplopia. Three years earlier she had been treated with chemotherapy and radiotherapy for a posterior fossa medulloblastoma. Visual acuity was 20/20 in each eye. Slit-lamp and funduscopic examinations were normal. No patent ocular deviation was found in primary position (Fig. 1a). Cover test and ocular motility examination showed 6 diopters of esophoria in primary position, 2 diopters of esophoria on left gaze and 12 diopters of esotropia on right gaze, together with a slight right abduction deficit. The Lancaster test revealed abduction deficit on the right eye as well as secondary hyperdeviation on the left eye, compatible with a right sixth nerve palsy. When turning her gaze to the left no change in the right palpebral fissure was detected (Fig. 1b) at the initial examination. However, after sustained right lateral gaze and slow return to primary position, a major right exotropia occurred (Fig. 1c). Thereafter, when turning her gaze to the left, a decrease of palpebral fissure and a limitation of adduction were found on the right eye, mimicking Duane syndrome type II (Fig. 1d). The right exotropia resolved itself after a few minutes. Right globe retraction was not evaluated. This intermittent motility picture associated with brainstem radiotherapy history allowed us to diagnose sixth right nerve neuromyotonia. The effort of adducting the right eye while the right lateral rectus was still excited (due to myotonia) caused co-contraction of both horizontal muscles. This co-contraction explains an adduction deficit and a globe retraction, hence a decrease in the right palpebral fissure. Oral treatment with carbamazepine (100 mg per day) partially improved the symptoms. Ocular neuromyotonia is a very rare acquired disorder of ocular motility, characterized by intermittent diplopia and strabismus [1–4]. Dozens of patients with this pathology have been reported in the literature and four cases have been described after radiotherapy for brainstem medulloblastoma [2–5]. In most cases, ocular neuromyotonia results from irradiation of the skull base, usually sellar and/or parasellar areas [1, 4], with symptoms appearing several months or years after treatment [1, 4]. Radiotherapy causes damage to cranial nerve axons (segmental axonal demyelination) leading to spontaneous and repetitive discharges from ocular motor nerves [2, 4]. This axonal hyperexcitability induces an unintentional contraction and a delayed relaxation of their respective extraocular muscles [1–3]. These phenomena may occur several times during the day, lasting from seconds to minutes and resolving spontaneously [1, 4]. Apart from these episodes, ocular motility is normal. The most commonly affected cranial nerve is the oculomotor (third) nerve, but the trochlear and abducens nerves can also be involved. In our case, neuromyotonia involved the right sixth nerve. It occurred after sustained right gaze, leading to active abduction and restriction of adduction with palpebral fissure narrowing in the right eye, mimicking intermittent Duane syndrome type II. No & Aurélie Taylor Aurelie.Taylor@erasme.ulb.ac.be