Progressive supranuclear palsy syndrome presenting as progressive nonfluent aphasia: a neuropsychological and neuroimaging analysis

There is currently considerable interest in the clinical spectrum of progressive nonfluent aphasia (PNFA) and progressive supranuclear palsy (PSP) and the intersection of these two entities. Here, we undertook a detailed prospective clinical, neuropsychological, and neuroimaging analysis of 14 consecutive patients presenting with PNFA to identify cases meeting clinical criteria for PSP. These patients had further detailed assessment of extrapyramidal and oculomotor functions. All patients had high-resolution MR brain volumetry and a cortical thickness analysis was undertaken on the brain images. Four patients presenting with PNFA subsequently developed features of a PSP syndrome, including a typical oculomotor palsy. The neuropsychological profile in these cases was similar to other patients with PNFA, however, with more marked reduction in propositional speech, fewer speech errors, less marked impairment of literacy skills but more severe associated deficits of episodic memory and praxis. These PSP-PNFA cases had less prominent midbrain atrophy but more marked prefrontal atrophy than a comparison group of five patients with pathologically confirmed PSP without PNFA and more prominent midbrain atrophy but less marked perisylvian atrophy than other PNFA cases. In summary, although the PSP-PNFA syndrome overlaps with PNFA without PSP, certain neuropsychological and neuroanatomical differences may help predict the development of a PSP syndrome.

Management of the patient with chronic dizziness

In this review we present a pragmatic approach to the patient with chronic vestibular symptoms. Even in the chronic patient a retrospective diagnosis should be attempted, in order to establish how the patient reached the current situation. Simple questions are likely to establish if the chronic dizzy symptoms started as benign paroxysmal positional vertigo (BPPV), vestibular neuritis, vestibular migraine, Meniere's disease or as a brainstem stroke. Then it is important to establish if the original symptoms are still present, in which case they need to be treated (e.g. repositioning maenouvres for BPPV, migraine prophylaxis) or if you are only dealing with chronic dizzy symptoms. In addition the doctor or physiotherapist needs to establish if the process of central vestibular compensation has been impeded due to additional clinical problems, e.g. visual problems (squints, cataract operation), proprioceptive deficit (neuropathy due to diabetes or alcohol), additional neurological or orthopaedic problems, lack of mobility or confidence, such as fear of falling or psychological disorders. A general neurological examination should also be conducted, amongst other reasons to make sure your patient's ;chronic dizziness' is not due to a neurological gait disorder. Treatment of the syndrome of chronic dizziness is multidisciplinary but rehabilitation and simple counselling should be available to all patients. In contrast, vestibular suppressants or tranquilisers should be reduced or, if possible, stopped.

Vertigo as a migraine trigger

BACKGROUND

It is reported in some individual patients that vestibular stimuli can trigger migraine attacks. This study used a case-control design to examine systematically the hypothesis that vertigo induced by vestibular stimulation (rotation/caloric testing) can act as a specific migraine trigger.

METHODS

A total of 123 new patients attending neuro-otology or neurology clinics were studied with questionnaires and physician interview to ascertain migraine history according to International Headache Society criteria. A total of 79 who underwent rotation/caloric vestibular testing (test group) were compared with 44 control patients in whom no such testing was carried out (control group). The principal outcome measure was the occurrence of a migraine attack within 24 hours of exposure to vestibular stimulation.

RESULTS

Of those participants with a past history of migraines, 19/39 (49%) of the test group experienced a migraine in the study time window, compared with 1/21 (5%) of the control group. Binary logistic regression analysis confirmed that vestibular testing was associated (p < 0.05) with migraine attacks.

CONCLUSIONS

The results indicate that induced vertigo can act as a migraine trigger, a finding with implications for the diagnosis of patients with episodic vertigo and migraine headache. While such patients may well have basilar migraine or migrainous vertigo, alternatively, another disorder causing episodic vertigo (e.g., benign paroxysmal positional vertigo or Ménière disease) may be triggering migraine headaches.

Locomotor adaptation and aftereffects in patients with reduced somatosensory input due to peripheral neuropathy

We studied 12 peripheral neuropathy patients (PNP) and 13 age-matched controls with the "broken escalator" paradigm to see how somatosensory loss affects gait adaptation and the release and recovery ("braking") of the forward trunk overshoot observed during this locomotor aftereffect. Trunk displacement, foot contact signals, and leg electromyograms (EMGs) were recorded while subjects walked onto a stationary sled (BEFORE trials), onto the moving sled (MOVING or adaptation trials), and again onto the stationary sled (AFTER trials). PNP were unsteady during the MOVING trials, but this progressively improved, indicating some adaptation. During the after trials, 77% of control subjects displayed a trunk overshoot aftereffect but over half of the PNP (58%) did not. The PNP without a trunk aftereffect adapted to the MOVING trials by increasing distance traveled; subsequently this was expressed as increased distance traveled during the aftereffect rather than as a trunk overshoot. This clear separation in consequent aftereffects was not seen in the normal controls suggesting that, as a result of somatosensory loss, some PNP use distinctive strategies to negotiate the moving sled, in turn resulting in a distinct aftereffects. In addition, PNP displayed earlier than normal anticipatory leg EMG activity during the first after trial. Although proprioceptive inputs are not critical for the emergence or termination of the aftereffect, somatosensory loss induces profound changes in motor adaptation and anticipation. Our study has found individual differences in adaptive motor performance, indicative that PNP adopt different feed-forward gait compensatory strategies in response to peripheral sensory loss.

What the "broken escalator" phenomenon teaches us about balance

Gait adaptation is crucial for coping with varying terrain and biological needs. It is also important that any acquired adaptation is expressed only in the appropriate context. Here we review a recent series of experiments that demonstrate inappropriate expression of gait adaptation. We show that a brief period of walking onto a platform previously experienced as moving results in a large forward sway aftereffect, despite full awareness of the changing context. The adaptation mechanisms involved in this paradigm are extremely fast, just 1-2 discrete exposures to the moving platform result in the motor aftereffect. This aftereffect occurs even if subjects deliberately attempt to suppress it. However, it disappears when the location or method of gait is altered, indicating that aftereffect expression is context dependent. Conversely, making gait self-initiated increases sway during the aftereffect. This aftereffect demonstrates a profound dissociation between knowledge and action. The absence of generalization suggests a relatively simple form of motor learning, albeit involving high-level processing by cortical and cerebellar structures.

The Influence of Adaptation on Visual Motion Detection in Chronic Sixth Nerve Palsy After Treatment with Botulinum Toxin

PURPOSE

To investigate changes in visual motion perception after treatment with botulinum toxin in patients with unilateral chronic lateral rectus muscle palsy.

METHODS

Five patients and control subjects were asked to report the perceived drift direction of a sinusoidal grating that was initially stationary and then began to accelerate at 0.09 degrees /sec2 in a horizontal direction. The grating had a field size of 18.5 degrees and was presented monocularly with a contrast just above threshold for visibility for central vision. Both the paretic and non-affected eyes were tested. Psychophysical testing was performed under the following conditions: 1) before treatment and testing, patients occluded their paretic eye for at least three days to avoid diplopia. 2) After treatment with botulinum toxin, alignment was corrected and patients stopped occluding their paretic eye for at least three days before testing. The control subjects occluded their non-dominant eye for three days before testing.

RESULTS

In condition 1, no differences in motion detection values between patients and control subjects were found. In condition 2, motion detection thresholds were raised approximately 0.15 degrees /sec as compared to pre-treatment values and compared to the control group.

CONCLUSIONS

After treatment, a raised threshold for motion detection is one mechanism used to avoid oscillopsia and visuo-vestibular disorientation during head movements in patients with chronic paralytic squint. This study lends evidence that perceptual-adaptive, compensatory mechanisms develop to reduce oscillopsia and disorientation rather than being caused by abnormal cortical motion processing or defective eye muscle action.

Nauseogenicity of off-vertical axis rotation vs. equivalent visual motion

INTRODUCTION

Off-vertical axis rotation (OVAR) provokes motion sickness. The visual motion equivalent to OVAR in simulators is also nauseogenic. Our experiment compared the nauseogenicity of OVAR vs. visual motion.

METHODS

There were 12 subjects who undertook the following conditions: A) OVAR in darkness at 0.2 Hz, 18 degrees tilt; B) same OVAR with eyes open in the light; and C) stationary, seated upright, watching a video of the visual motion experienced in B. The conditions were counterbalanced and performed at the same time of day with a minimum 5-d separation between conditions. Stimulation was stopped at moderate nausea with a 20-min maximum cut-off. Motion sickness susceptibility was rated on a standardized questionnaire (MSSQ).

RESULTS

Time (mean +/- SD minutes) to moderate nausea was significantly shorter for real OVAR conditions (A: 7.1 +/- 5.5; B: 7.7 +/- 6.7) vs. video (C: 15.7 +/- 6.4). Subjects with relatively low susceptibilities to motion sickness developed nausea more slowly with vision (B-A time difference correlated with MSSQ scores r = -0.7, P < 0.05). Headache was more prominent with visual field motion (C).

CONCLUSIONS

OVAR was twice as nauseogenic as visual motion. Headache during visual motion suggests mechanisms in common with migraine. We hypothesize that subjects who fared better in the light used visual cues to resolve sensory conflict, whereas subjects who were equally susceptible in light and dark made poor use of visual cues; perhaps a form of 'field dependency'. This may explain why some people prefer 'a view of the road ahead' to help against motion sickness whereas others shut their eyes.

Foot rotation contribution to trunk and gaze stability during whole-body mediated gaze shifts: a principal component analysis study

Large gaze displacements are mediated by combined motion of the eye, head, trunk, and foot. We applied principal component analysis (PCA) to examine the degree of variability and linearity in the angular velocity pattern of the various segments involved that participate in this task. Ten normal subjects stood up and had to visually fixate and realign their bodies with LED targets separated 45 degrees apart, ranging from +/-45 to 360 degrees. The outbound movement in this paradigm is unpredictable whereas the return (inbound) movement occurs under spatially predictable conditions. Under such predictable conditions, subjects generate in approximately 15% of the trials gaze shifts, with periods of fairly constant high gaze velocity (single-step gaze shifts). PCA showed that gaze velocity variability did not change if the feet were rotating or not. Foot velocity was variable and showed additional PCs suggestive of non-linear motion components. Trunk and head-in-space velocity showed intermediate levels of variability but its variability decreased during the foot stepping movements. The results suggest that the feet, trunk, and head are less tightly controlled by the central nervous system than gaze velocity. Movements of the feet seem to aid trunk stability and motion rather than gaze control.

Mechanisms underlying visually induced body sway

We investigate the relationship between visually induced perceptual illusions of body motion (vection) and visually induced postural responses (VEPRs). Ten standing healthy subjects were tested in two visual conditions known to induce directionally opposite VEPRs: subjects fixated either a static head-mounted or an earth-fixed visual display in front of a horizontally translating visual background. The VEPR was in the direction of background motion when fixating the head-mounted display but transiently reversed in the earth-fixed condition. In contrast, vection occurred in only one direction (opposite to background motion) and developed later than VEPRs. The different time course and in-congruency between direction of VEPRs and direction of vection suggests that perceptual and postural responses are not causally related. However, since vection did increase VEPR magnitude in the direction of background motion, we postulate that VEPRs might be mediated by two different mechanisms: (1) a short latency system, driven by transient visual stimuli and sensitive to visual geometry (parallax-no parallax), responsible for automatic postural sway adjustments and (2) a longer latency, vection-enhanced postural mechanism, related to the conscious perception of self-motion during longer duration (locomotor, vehicular) body displacements.

Head accelerations during particle repositioning manoeuvres

Benign paroxysmal positional vertigo (BPPV) due to canalithiasis can be treated with particle repositioning manoeuvres, which aim to evacuate trapped particles from the semicircular canals (SCC). The movement of particles within the SCC is affected by gravity as well as by the accelerations of the head during the manoeuvres. Moreover, as experienced by the particles, gravity is indistinguishable from an upward acceleration of the SCC in free space. We used a set of three orthogonal linear accelerometers to measure the net three-dimensional linear acceleration vector acting on the head during the Hallpike manoeuvre and Epley and Semont particle repositioning manoeuvres (which are used to treat posterior canal BPPV). The projection of the net acceleration vector onto the SCC planes showed that both the Epley and Semont manoeuvres approximated to stepwise, 360 degrees , backward rotations in the plane of the targeted posterior canal. Angular velocity measurements however showed that the rotational component during the central stages of these two manoeuvres is opposite in direction. A simple model of head rotations during particle repositioning manoeuvres was created which showed good agreement to the linear acceleration measurements. Analysis of modelled and measured data identified that speed of movement during the Semont manoeuvre should be critical to its clinical success.

Posterior parietal rTMS disrupts human Path Integration during a vestibular navigation task

In contrast to vision, the neuro-anatomical substrates of vestibular perception are obscure. The vestibular apparati provide a head angular velocity signal allowing perception of self-motion velocity. Perceived change of angular position-in-space can also be obtained from the vestibular head velocity signal via a process called Path Integration (so-called since displacement is obtained by a mathematical temporal integration of the vestibular velocity signal). It is unknown however, if distinct cortical loci sub-serve vestibular perceptions of velocity versus displacement (i.e. Path Integration). Previous studies of human brain activity have not used head motion stimuli hence precluding localisation of vestibular cortical areas specialised for Path Integration distinct from velocity perception. We inferred vestibular cortical function by measuring the disrupting effect of repetitive transcranial magnetic stimulation on the performance of a displacement-dependent vestibular navigation task. Our data suggest that posterior parietal cortex is involved in encoding contralaterally directed vestibular-derived signals of perceived angular displacement and a similar effect was found for both hemispheres. We separately tested whether right posterior parietal cortex was involved in vestibular-sensed velocity perception but found no association. Overall, our data demonstrate that posterior parietal cortex is involved in human Path Integration but not velocity perception. We suggest that there are separate brain areas that process vestibular signals of head velocity versus those involved in Path Integration.

Visuo-vestibular Influences on the Moving Platform Locomotor Aftereffect

After walking onto a moving platform subjects experience a locomotor aftereffect (LAE), including a self-generated stumble, when walking again onto a stationary platform. Thus this LAE affords examination of the role of vestibular input during an internally generated postural challenge. The experiments involved walking onto the stationary sled (BEFORE trials), walking onto the moving sled (MOVING), and a second set of stationary trials (AFTER). We investigated 9 bilateral labyrinthine defective subjects (LDS) and 13 age-matched normal controls (NC) with eyes open. We repeated the experiment in 5 NC and 5 LDS but this time the AFTER trials were performed twice, first eyes closed and then on eye reopening. During MOVING trials, LDS were considerably unstable, thus confirming the established role of the vestibular system during externally imposed postural perturbations. During AFTER trials, both groups experienced an aftereffect with eyes open and closed, shown as higher approach gait velocity, a forward trunk overshoot, and increased leg EMG. However, there were no significant group differences due to the fact that stopping the forward trunk overshoot was accomplished by anticipatory EMG bursts. On eye reopening the aftereffect reemerged, significantly larger in LDS than that in NC. The lack of group differences in AFTER trials suggests that when facing internally generated postural perturbations, as in this adaptation process, the CNS relies less on vestibular feedback and more on anticipatory mechanisms. Reemergence of the aftereffect on eye reopening indicates the existence of a feedforward visuo-contextual mechanism for locomotor learning, which is adaptively enhanced in the absence of vestibular function.

Depersonalisation/derealisation symptoms and updating orientation in patients with vestibular disease

BACKGROUND

Patients with vestibular disease have an increased rate of reporting symptoms of depersonalisation/derealisation (DD) and similar symptoms can be provoked in healthy subjects during caloric vestibular stimulation.

OBJECTIVE

To assess the relationship between DD symptoms in patients with peripheral vestibular disease and their ability to update orientation in the environment.

METHODS

Sixty healthy subjects and 50 patients with peripheral vestibular disease completed a DD questionnaire (Cox and Swinson, 2002) and a General Health Questionnaire (GHQ)-12 (Goldberg and Williams, 1988). This was followed by a test of updating spatial orientation in which subjects were exposed to 10 manually driven whole body rotations of 45 degrees, 90 degrees or 135 degrees in a square room, which contained distinctive features on the walls, in such a way that the features and corners subtended 45 degrees with respect to the subject. After each rotation subjects reported which wall or corner they were facing. Estimation error was calculated by subtracting the reported rotation from the actual rotation.

RESULTS

DD scores were significantly higher in vestibular patients than in healthy subjects (p<0.05, t test). In patients, the lowest symptom scores and the lowest estimation errors were found in those with a unilateral canal paresis without balance symptoms whereas the highest scores and largest estimation errors were found in those with bilateral vestibular loss (p<0.05, ANOVA). Across all patients, DD scores were related to estimation errors (adjusted r2 = 0.25, p<0.05, ANCOVA).

CONCLUSIONS

Patients with peripheral vestibular disease have a deficit in the ability to update orientation on the environment and a high prevalence of DD symptoms, which may imply a high order effect of the vestibular impairment. Derealisation symptoms in vestibular disease may be a consequence of a sensory mismatch between disordered vestibular input and other sensory signals of orientation.

The peripheral nervous system and the perception of verticality

Orientation of the body with respect to gravity is based on integration of visual, vestibular and somatosensory signals. Here, we investigated the subjective postural vertical (SPV) and visual vertical (SVV) in three patients with bilateral somatosensory deafferentation and a group of age-matched normal subjects. Our hypothesis was that the patients with bilateral somatosensory deafferentation may show tilt induced bias in the construction of their SPV, with a normal SVV. Patient 1 had a severe Guillain Barré syndrome and almost complete absence of peripheral sensation, the two other patients had a thoracic spinal injury with a sensory loss from T6-7 down. On initial testing, compared with normal subjects and the patients with spinal injury, Patient 1 had a significant bias in SPV towards the side of a preceding tilt in both directions. Several months later, after significant improvement of sensation, this tilt-induced bias in SPV had resolved completely. In addition, Patient 1 had a significantly enlarged "cone of verticality", which did not change following improvement in peripheral sensation, reflecting persisting disturbance in the perception of body verticality. In the two patients with spinal injury, bias towards the side of a preceding tilt was not significant. These findings confirm the importance of somatosensory input from the trunk to the perception of SPV in the seated position.

Guidance of visual direction by topographical vibrotactile cues on the torso

Vibration on localised areas of skin can be used to signal spatial orientation, multi-directional motion and also to guide arm and hand movements. This study investigated the possibility that vibration at loci on the skin might also be used to cue gaze direction. Eight subjects made eye or (head + eye) gaze saccades in the dark cued by vibration stimulation at discrete loci spaced on a horizontal contour across the chest. Saccade and gaze amplitudes, latencies, and directions were analysed. In the first experiment, performed without training, subjects could only use vibration cues to direct their gaze in cardinal directions and gross quadrature. There was a high variability in the relationship between locus on the trunk and gaze direction in space, both within and between subjects. Saccade latencies ranged from 377 to 433 ms and were related to the loci of vibration; the further from the body midline the quicker the response. Since the association of skin loci with gaze direction did not appear intuitive a sub-group of four subjects were retested after intensive training with feedback until they attained criterion on midline identical with 0 degrees and 15 cm (to right/left of midline) identical with 45 degrees gaze shifts right and left. Training gave a moderate improvement in directional specificity of gaze to a particular locus on the skin. Gaze direction was linearly rescaled with respect to skin loci but variability and saccade latencies remained high. The uncertainty in the relationship between vibration locus and gaze direction and the prolonged latencies of responses indicate circuitous neuronal processing. There appears to be no pre-existing stimulus-response compatibility mapping between loci on the skin and gaze direction. Vibrotactile cues on the skin of the trunk only serve a gross indication of visual direction in space.

Using vibrotactile feedback of instability to trigger a forward compensatory stepping response

We evaluated the effectiveness of vibrotactile feedback to enhance protective stepping with a view to developing a prosthesis for patients with balance disorders. Subjects standing on a moving walkway were exposed to an unpredictable, abrupt backwards translation of the support surface that required a step response to remain standing. The subjects were 15 normal young, 15 normal elderly and 9 patients with either bilateral vestibular loss or peripheral neuropathy. The initial passive displacement of the body was recorded by a gyroscope placed on the leg which triggered a vibration pulse to the trigeminal distribution on the forehead to cue a forwards step. Stepping responses and postural sway, with and without vibration feedback, were compared. Vibration produced significantly shorter stepping reaction times only in the elderly normals with naturally slower stepping. Patients did not benefit in any way. We conclude that the effectiveness of vibration biofeedback appears limited. Any enhancement of compensatory stepping might be triggered by speeding the decision to step rather than by creating a specific stimulus-response loop.

Vestibular Perception and Navigation in the Congenitally Blind

Vestibular input is required for accurate locomotion in the dark, yet blind subjects’ vestibular function is unexplored. Such investigation may also identify visually dependent aspects of vestibular function. We assessed vestibular function perceptually in six congenitally blind (and 12 sighted) subjects. Cupula deflection by a transient angular, horizontal acceleration generates a related vestibular nerve signal that declines exponentially with time constant ≈4–7 s, which is prolonged to 15 s in the evoked vestibular-ocular reflex by the brain stem “velocity storage.” We measured perceptual velocity storage in blind subjects following velocity steps (overall perceptual vestibular time constant, experiment 1) and found it to be significantly shorter (5.34 s; range: 2.39–8.58 s) than in control, sighted subjects (15.8 s; P < 0.001). Vestibular navigation was assessed by subjects steering a motorized Bárány-chair in response to imposed angular displacements in a path-reversal task, “go-back-to-start” (GBS: experiment 2); and a path-completion task, “complete-the-circle” (CTC: experiment 3). GBS performances (comparing response vs. stimulus displacement regression slopes and r2) were equal between groups ( P > 0.05), but the blind showed worse CTC performance ( P < 0.05). Two blind individuals showed ultrashort perceptual time constants, high lifetime physical activity scores and superior CTC performances; we speculate that these factors may be inter-related. In summary, the vestibular velocity storage as measured perceptually is visually dependent. Early blindness does not affect path reversal performance but is associated with worse path completion, a task requiring an absolute spatial strategy. Although congenitally blind subjects are overall less able to utilize spatial mechanisms during vestibular navigation, prior extensive physical spatial activity may enhance vestibular navigation.

The assessment of increased sensitivity to visual stimuli in patients with chronic dizziness

Patients with chronic vestibular dysfunction often experience visually-induced aggravation of dizzy symptoms (visual vertigo; VV). The Situational Characteristics Questionnaire (SCQ), Computerized Dynamic Posturography or Rod and Frame Test (RFT) are used to assess VV symptoms. This study evaluates whether correlations exist between these three tests, their ability to identify patients with VV and whether emotional state correlates with VV symptoms. Tests were completed by 20 normal controls (Group NC), 20 patients with vestibular dysfunction plus VV (Group VV) and 13 without VV (Group NVV). Additionally, the Vertigo Symptom Scale (VSS-V) was applied to quantify general, non-visually induced vertigo (dizziness, lightheadedness and/or spinning) and imbalance. Autonomic (VSS-A) and psychological symptoms (Hospital Anxiety and Depression questionnaire; HAD) were also assessed. With the SCQ 100% of Group VV scored outside normal ranges and scores differed significantly between Group VV and both Groups NC and NVV. RFT values were not significantly different between groups; only 15% of patients scored outside normal ranges. Posturography scores were abnormal for 50% of patients; significant differences were noted between Groups NC and VV for composite scores and ratios 3/1, 4/1, 5/1 and 6/1 (indicative of abnormal sensory re-weighting). There were no correlations between the three data sets in patients. Anxiety and depression scores significantly differed between Groups NC and VV but not between patient groups; this indicates that psychological symptoms may be present in either patient group. The SCQ can be used to corroborate an initial clinical diagnosis of VV and quantify its severity in patients with vestibular dysfunction. Posturography data suggested patients with VV have a sensory re-weighting abnormality. The rod and frame test results and posturography findings agree less with the clinical diagnosis of VV. Psychological symptoms may need to be addressed.

Self-initiated gait increases susceptibility to the moving platform after-effect

Walking onto a stationary platform previously experienced as moving results in a large forward sway, despite awareness of the changing context. This after-effect demonstrates aberrant motor prediction. Here, we compared after-effect magnitude when gait initiation was either externally triggered or self-initiated. Both participant groups adapted their walking speed similarly when walking onto the moving platform. When it was kept stationary however, after-effect magnitude was more than doubled in the self-initiated group. We attribute this to a stronger association made between the action (gait initiation) and its consequence (platform movement) when the action is initiated by oneself. This increased sense of agency reduces the ability to switch off the acquired motor response when it is no longer appropriate.

Influence of pitch tilts on the perception of gravity-referenced eye level in labyrinthine defective subjects

We investigate the role of vestibular information in judging the gravity-referenced eye level (i.e., earth-referenced horizon or GREL) during sagittal body tilt whilst seated. Ten bilateral labyrinthine-defective subjects (LDS) and 10 age-matched controls set a luminous dot to their perception of GREL in darkness, with and without arm pointing. Although judgements were linearly influenced by the magnitude of whole-body tilt, results showed no significant difference between LDS and age-matched controls in the subjective GREL accuracy or in the intra-subject variability of judgement. However, LDS performance without arm pointing was related to the degree of vestibular compensation inferred from another postural study performed with the same patients. LDS did not utilize upper limb input during arm pointing movements as a source of graviceptive information to compensate for the vestibular loss. The data suggest that vestibular cues are not of prime importance in GREL estimates in static conditions. The absence of difference between controls and LDS GREL performance, and the correlation between the postural task and GREL accuracy, indicate that somatosensory input may convey as much graviceptive information required for GREL judgements as the vestibular system.

Depersonalisation/derealisation symptoms in vestibular disease

BACKGROUND

Depersonalisation is a subjective experience of unreality and detachment from the self often accompanied by derealisation; the experience of the external world appearing to be strange or unreal. Feelings of unreality can be evoked by disorienting vestibular stimulation.

OBJECTIVE

To identify the prevalence of depersonalisation/derealisation symptoms in patients with peripheral vestibular disease and experimentally to induce these symptoms by vestibular stimulation.

METHODS

121 healthy subjects and 50 patients with peripheral vestibular disease participated in the study. For comparison with the patients a subgroup of 50 age matched healthy subjects was delineated. All completed (1) an in-house health screening questionnaire; (2) the General Health Questionnaire (GHQ-12); (3) the 28-item depersonalisation/derealisation inventory of Cox and Swinson (2002). Experimental verification of "vestibular induced" depersonalisation/derealisation was assessed in 20 patients and 20 controls during caloric irrigation of the labyrinths.

RESULTS

The frequency and severity of symptoms in vestibular patients was significantly higher than in controls. In controls the most common experiences were of "déjà vu" and "difficulty in concentrating/attending". In contrast, apart from dizziness, patients most frequently reported derealisation symptoms of "feel as if walking on shifting ground", "body feels strange/not being in control of self", and "feel 'spacey' or 'spaced out'". Items permitted discrimination between healthy subjects and vestibular patients in 92% of the cases. Apart from dizziness, caloric stimulation induced depersonalisation/derealisation symptoms which healthy subjects denied ever experiencing before, while patients reported that the symptoms were similar to those encountered during their disease.

CONCLUSIONS

Depersonalisation/derealisation symptoms are both different in quality and more frequent under conditions of non-physiological vestibular stimulation. In vestibular disease, frequent experiences of derealisation may occur because distorted vestibular signals mismatch with the other sensory input to create an incoherent frame of spatial reference which makes the patient feel he or she is detached or separated from the world.

The effect of trial number on the emergence of the 'broken escalator' locomotor aftereffect

Walking onto a stationary platform, which had been previously experienced as moving generates a locomotor aftereffect (LAE), which resembles the 'broken escalator' phenomenon. Experimentally, this is achieved by having subjects walk initially onto a stationary sled (BEFORE condition), then onto a moving sled (MOVING condition, or adaptation trials) and then again onto the stationary sled (AFTER condition). Subjects are always appropriately warned of the change in conditions. In this paper, we ask how many adaptation trials are needed to produce such a LAE. Thus, in two experiments, the number of MOVING trials was varied between 20 and 5 (Experiment 1) and between 8 and 1 (Experiment 2). Gait velocity, trunk position, foot contact timing and EMG of the ankle flexor-extensors muscles were measured. In comparison with BEFORE trials all groups in the AFTER trials walked inappropriately fast, experienced a large overshoot of the trunk and showed increased leg EMG, indicating that all groups showed a LAE. In each experiment, and for all variables, no significant difference between the groups (i.e. 20 down to one MOVING trials) was found. The study shows that this LAE, in contrast to other motor aftereffects reported in the literature, can be generated with only one or two adaptation trials and without requiring unexpected 'catch' trials. The fast aftereffect generation observed is likely to depend on two types of mechanisms: (1) the nature of the sensorimotor adaptation process, involving multiple sensory feedbacks (visual, vestibular and proprioceptive), anticipatory control and large initial task errors and (2) the involvement of two phylogenetically old neural mechanisms, namely locomotion and fear. Fear-relevant mechanisms, which are notably resistant to cognitive control, may be recruited during the adaptation trials and contribute to the release of this LAE.

Cardio-respiratory responses evoked by transient linear acceleration

INTRODUCTION

Predictive control of the responses to re-orientating stimuli and its interaction with vestibular signals may be an important factor in protecting against spatial disorientation. Here we evaluated the influence of stimulus predictability on the cardio-respiratory responses to transient fore-aft linear accelerations.

METHODS

There were 13 normal subjects and 6 patients with bilateral loss of vestibular function who were exposed to linear acceleration of +0.26 Gx peak while seated upright and restrained on a motorized bogie. Accelerations were: (1) 'unpredictable', triggered by the experimenter either at the end of expiration or at the end of inspiration; or (2) 'predictable', triggered by the subjects pressing a button. The two conditions included false trials when nothing would happen. Respiratory frequency, electrocardiogram, and trunk acceleration were recorded.

RESULTS

For unpredictable accelerations, in all subjects, the RR interval decreased within the first to second beat after acceleration onset. In normal subjects this decrease was maintained or more evident during the third, fourth, or fifth heart beat after onset. Cardiac responses were not significantly different when acceleration was triggered at the end of inspiration or at the end of expiration. Self-triggered acceleration also provoked prolonged, but attenuated, heart rate responses in healthy subjects, while responses were absent in the patients. All subjects responded with a consistent rapid inspiration to the onset of acceleration, whether predictable or not.

DISCUSSION

A vestibulo-cardiac response is evoked by transient linear acceleration, independently from the phase of the breathing cycle and from the predictability of the stimulus. A vestibular signal of motion appears to be required to produce a prolonged increase in heart rate.

The assessment of increased sensitivity to visual stimuli in patients with chronic dizziness

Patients with chronic vestibular dysfunction often experience visually-induced aggravation of dizzy symptoms (visual vertigo; VV). The Situational Characteristics Questionnaire (SCQ), Computerized Dynamic Posturography or Rod and Frame Test (RFT) are used to assess VV symptoms. This study evaluates whether correlations exist between these three tests, their ability to identify patients with VV and whether emotional state correlates with VV symptoms. Tests were completed by 20 normal controls (Group NC), 20 patients with vestibular dysfunction plus VV (Group VV) and 13 without VV (Group NVV). Additionally, the Vertigo Symptom Scale (VSS-V) was applied to quantify general, non-visually induced vertigo (dizziness, lightheadedness and/or spinning) and imbalance. Autonomic (VSS-A) and psychological symptoms (Hospital Anxiety and Depression questionnaire; HAD) were also assessed. With the SCQ 100% of Group VV scored outside normal ranges and scores differed significantly between Group VV and both Groups NC and NVV. RFT values were not significantly different between groups; only 15% of patients scored outside normal ranges. Posturography scores were abnormal for 50% of patients; significant differences were noted between Groups NC and VV for composite scores and ratios 3/1, 4/1, 5/1 and 6/1 (indicative of abnormal sensory re-weighting). There were no correlations between the three data sets in patients. Anxiety and depression scores significantly differed between Groups NC and VV but not between patient groups; this indicates that psychological symptoms may be present in either patient group. The SCQ can be used to corroborate an initial clinical diagnosis of VV and quantify its severity in patients with vestibular dysfunction. Posturography data suggested patients with VV have a sensory re-weighting abnormality. The rod and frame test results and posturography findings agree less with the clinical diagnosis of VV. Psychological symptoms may need to be addressed.

The effects of vestibular system lesions on autonomic regulation: Observations, mechanisms, and clinical implications

The loss of labyrinthine inputs in patients or animal models has been demonstrated to affect autonomic regulation. Considerable evidence suggests that vestibular-autonomic responses serve to adjust blood pressure and respiratory activity during movement and postural alterations. However, following peripheral vestibular lesions, compensation rapidly occurs, such that autonomic disturbances are not readily evident in patients with chronic labyrinthine dysfunction. This manuscript summarizes the evidence suggesting that vestibular inputs influence autonomic regulation, but that cardiovascular and respiratory responses linked to movement recover quickly subsequent to the loss of labyrinthine signals. In addition, the clinical implications of dysfunction of vestibulo-autonomic reflexes are described. Furthermore, the mechanisms potentially responsible for the return of the ability to produce posturally-related adjustments in blood pressure and respiration following vestibular lesions are discussed. In particular, evidence that somatosensory signals can replace labyrinthine inputs to vestibular nucleus neurons that participate in autonomic regulation is provided.

Vision and vertigo: some visual aspects of vestibular disorders

This review deals with two syndromes, oscillopsia and visual vertigo. Oscillopsia is the illusion of oscillation of the visual surroundings. For diagnosis purposes one should ask, when does the oscillopsia occur? If oscillopsia is only present during head (or whole body) movements, the likely underlying cause is a bilateral defect in the vestibulo-ocular reflex (VOR). The more common causes are post meningitic vestibular damage, gentamicin ototoxicity or bilateral idiopathic vestibular failure. When oscillopsia develops after specific head positions, it is usually due to a positional nystagmus, usually the result of brainstem-cerebellar disease. When the oscillopsia is largely unrelated to head movements, one should ask, is it fairly constant or is it in attacks (paroxysmal)? If the oscillopsia is constant it is usually due to the presence of a clinically observable nystagmus; the most common is downbeat nystagmus but the most visually disabling is pendular nystagmus. If the oscillopsia comes in brief attacks it is usually due to a paroxysmal nystagmus as observed in irritative VIII nerve and brainstem lesions. However, the most common cause of paroxysmal oscillopsia is a non organic condition called voluntary nystagmus. Treatment of oscillopsia is often pharmacological but disappointing; the best chance of success is carbamazepine for paroxysmal disorders secondary to structural vestibular nerve/nuclear lesions.Visual vertigo should not be confused with oscillopsia. It can be defined as dizziness provoked by visual environments with large size (full field) repetitive or moving visual patterns. Patients with visual vertigo report discomfort in supermarkets and when viewing movement of large visual objects, eg crowds, traffic, clouds or foliage. Visual vertigo is present in many patients with a history of a peripheral vestibular disorder, particularly those who are visually dependent (ie subjects who use vision preferentially for postural and space orientation control). Patients with visual vertigo benefit from the addition to their standard vestibular rehabilitation of optic flow (optokinetic) stimuli and exercises involving visuo-vestibular conflict.

Clinical grand round: A rapidly progressive pyramidal and extrapyramidal syndrome with a supranuclear gaze palsy

The case history of a patient with a rapidly progressive spastic tetraparesis, pseudobulbar palsy, supranuclear gaze palsy, and extrapyramidal signs is presented. The patient died 17 months after symptom onset, and the differential diagnosis and pathological findings are reviewed.

The effects of vestibular system lesions on autonomic regulation: observations, mechanisms, and clinical implications

The loss of labyrinthine inputs in patients or animal models has been demonstrated to affect autonomic regulation. Considerable evidence suggests that vestibular-autonomic responses serve to adjust blood pressure and respiratory activity during movement and postural alterations. However, following peripheral vestibular lesions, compensation rapidly occurs, such that autonomic disturbances are not readily evident in patients with chronic labyrinthine dysfunction. This manuscript summarizes the evidence suggesting that vestibular inputs influence autonomic regulation, but that cardiovascular and respiratory responses linked to movement recover quickly subsequent to the loss of labyrinthine signals. In addition, the clinical implications of dysfunction of vestibulo-autonomic reflexes are described. Furthermore, the mechanisms potentially responsible for the return of the ability to produce posturally-related adjustments in blood pressure and respiration following vestibular lesions are discussed. In particular, evidence that somatosensory signals can replace labyrinthine inputs to vestibular nucleus neurons that participate in autonomic regulation is provided.

Simulator based rehabilitation in refractory dizziness

Patients with chronic vestibular symptoms are common in neurological practice but the most effective treatment remains an open question. The purpose of our study was to conduct a controlled, between-group comparison of patients' responses to a customised exercise regime (Group C, for customised) versus treatment additionally incorporating simulator based desensitisation exposure (Group S, for simulator) integrating whole-body or visual environment rotators. Forty chronic peripheral vestibular patients who had previously undergone conventional vestibular rehabilitation without notable improvement were randomly assigned into Group C or S. Individuals attended therapy sessions twice weekly for eight weeks and were provided with a customised home programme. Response to treatment was assessed at four-week intervals with dynamic posturography, vestibular time constants, and questionnaires concerning symptoms, symptom-triggers and emotional status. At final assessment posturography and subjective scores had significantly improved for both groups, although Group S showed greater improvement. A statistically significant improvement for visual vertigo symptom scores was noted only for Group S (p < 0.01; total improvement 53.5 %). Anxiety and depression levels significantly decreased for both groups; improvements were significantly correlated particularly to improvements in visual vertigo (SCQ) (p < 0.01; r = 0.53 and r = 0.57, respectively). Significant differences were noted between groups (p = 0.02) for posturography scores. Vestibular time constants showed no notable change in either group.

CONCLUSIONS

Both groups improved but exposure to simulator motion gave overall better results. These effects were also observed in psychological symptoms and partly relate to simulator effects on visual vertigo symptoms. Visual motion and visuo-vestibular conflict situations should be incorporated in the rehabilitation of patients with refractory dizziness.

Effectiveness of primary care-based vestibular rehabilitation for chronic dizziness

BACKGROUND

Dizziness is a very common symptom and is usually managed in primary care. Vestibular rehabilitation for dizziness is a simple treatment that may be suitable for primary care delivery, but its effectiveness has not yet been determined.

OBJECTIVE

To evaluate the effectiveness of nurse-delivered vestibular rehabilitation in primary care for patients with chronic dizziness.

DESIGN

Single-blind randomized, controlled trial.

SETTING

20 general practices in southern England.

PATIENTS

170 adult patients with chronic dizziness who were randomly assigned to vestibular rehabilitation (n = 83) or usual medical care (n = 87).

INTERVENTION

Each patient received one 30- to 40-minute appointment with a primary care nurse. The nurse taught the patient exercises to be carried out daily at home, with the support of a treatment booklet.

MEASUREMENTS

Primary outcome measures were baseline, 3-month, and 6-month assessment of self-reported spontaneous and provoked symptoms of dizziness, dizziness-related quality of life, and objective measurement of postural stability with eyes open and eyes closed.

RESULTS

At 3 months, improvement on all primary outcome measures in the vestibular rehabilitation group was significantly greater than in the usual medical care group; this improvement was maintained at 6 months. Of 83 treated patients, 56 (67%) reported clinically significant improvement compared with 33 of 87 (38%) usual care patients (relative risk, 1.78 [95% CI, 1.31 to 2.42]).

LIMITATIONS

Psychological elements of the therapy may have contributed to outcomes, and the treatment may be effective only for well-motivated patients.

CONCLUSIONS

Vestibular rehabilitation delivered by nurses in general practice improves symptoms, postural stability, and dizziness-related handicap in patients with chronic dizziness.

Influence of whole-body pitch tilt and kinesthetic cues on the perceived gravity-referenced eye level

We investigated the effects of whole body tilt and lifting the arm against gravity on perceptual estimates of the Gravity-Referenced Eye Level (GREL), which corresponds to the subjective earth-referenced horizon. The results showed that the perceived GREL was influenced by body tilt, that is, lowered with forward tilt and elevated with backward tilt of the body. GREL estimates obtained by arm movements without vision were more biased by whole-body tilt than purely visual estimates. Strikingly, visual GREL estimates became more dependent on whole-body tilt when the indication of level was obtained by arm lifting. These findings indicate that active motor involvement and/or the addition of kinesthetic information increases the body tilt-induced bias when making GREL judgements. The introduction of motor/kinaesthetic cues may induce a switch from a semi-geocentric to a more egocentric frame of reference. This result challenges the assumption that combining non-conflicting multiple sensory inputs and/or using intermodal information provided during action should improve perceptual performance.

Vestibular function interferes in cardiovascular reflexes [corrected]

BACKGROUND

Experimental work indicates that the vestibular system participates in autonomic reflexes during body movement and postural changes. However, there are no studies of cardiovascular reflexes during vertigo due to human acute vestibular lesions.

METHODS

We assessed the response to active change of posture and hand immersion in cold water in seven patients with unilateral peripheral vestibular failure (vestibular neuritis) and seven age/sex-matched healthy subjects in acute phase (72 h from vertigo onset) and at 2 weeks of follow-up.

RESULTS

During acute phase, patients showed decreased blood pressure response during cold hand test (p < 0.05). Upright stance induced deficient decrease of the respiratory component of heart rate variability (p < 0.05) with lack of increase in low frequency/high frequency (LF/HF) ratio. At 2 weeks of follow-up, these abnormalities improved.

CONCLUSIONS

Results suggest that acute vestibular lesions can interfere with cardiovascular autonomic responses in humans. This may reflect disruption of normal vestibulo-autonomic reflexes.

The integration of multiple proprioceptive information: effect of ankle tendon vibration on postural responses to platform tilt

Previous studies have looked at co-processing of multiple proprioceptive inputs but few have investigated the effect of separate dynamic and tonic predominantly proprioceptive disruptions applied concurrently at the same segment. The purpose of the present study was to investigate how simultaneous ankle tendon vibration, a tonic stimulus, with a dynamic toes-up (TU) or toes-down (TD) platform perturbation (1) affects postural stability and (2) influences the adaptation process. Sixteen normal subjects (ten male, six female, mean age 26 +/- 4.8 years) stood blindfolded on a moving platform with vibrators attached bilaterally over the Achilles tendons. Participants were tested in quiet stance (QS), and with five successive TU and TD tilts. All tests were conducted both with (QS+V, TU+V, TD+V) and without vibration. Centre of pressure (CoP) displacements and pitch angular trunk velocity were recorded. Results for QS+V showed a significant 1.02-cm backward CoP displacement (P<0.01) and a significant increase in trunk velocity (peak-to-peak amplitude, P<0.05; SD of trunk velocity, P<0.05). TU+V resulted in a non-significant increase of maximum backwards CoP displacement when compared to TU alone. In addition, no notable effect of vibration on other measures of CoP (pre-tilt position, SD and area of sway) and trunk velocity (peak-to-peak, SD and area of sway) indicates that TU+V does not introduce significantly greater instability compared to tilt alone. In the TD condition, vibration was found to be a stabilising influence, causing a significant shift of the mean pre-tilt position 0.85 cm backwards (P<0.01) and a substantial decrease in the area of forward CoP displacement (P<0.01). However, maximum forwards CoP displacement and trunk velocity measures were not significantly altered during TD+V. Furthermore, in neither TU nor TD was the time-course or pattern of adaptation disrupted by the additional application of vibration. In conclusion, although vibration significantly affects postural measures when applied in isolation, this finding does not hold when it is applied in combination with a more dynamic stimulus. Instead it seems that once postural stability has been disrupted the central nervous system can rapidly assess information from a weaker tonic input and utilise or suppress it appropriately, depending on its effect towards overall postural control. It can be concluded that postural responses to the concurrent application of different predominantly proprioceptive stimuli are dependent upon the type of stimulus and the ability of the central nervous system to rapidly assess and re-weigh available sensory inputs.

Perceptual and nystagmic thresholds of vestibular function in yaw

A technique for simultaneous measurement of conscious (perceptual) and reflex (nystagmus) thresholds of vestibular function is described. We used an automated modified binary search algorithm with simultaneous infrared oculography in determining perceptual and VOR nystagmic thresholds respectively, during discrete whole body rotations in the dark. In a young group of 14 normal subjects (mean age 23 years) angular acceleration thresholds were significantly higher for perceptual detection (1.18 deg/s/s) than for nystagmus generation (0.51 deg/s/s). Only nystagmic thresholds were slightly raised (0.87 deg/s/s) in an older group of 9 normal subjects (mean age 63 years). The finding that nystagmic thresholds are lower than perceptual ones indicates a higher sensitivity of brainstem than cortical vestibular mechanisms. This technique would be of particular value in clinical situations where a dissociation between reflex and conscious vestibular mechanisms is expected, e.g. in patients with cortical lesions or in elderly patients with falls.

The moving platform aftereffect: limited generalization of a locomotor adaptation

We have recently described a postural after-effect of walking onto a stationary platform previously experienced as moving, which occurs despite full knowledge that the platform will no longer move. This experiment involves an initial baseline period when the platform is kept stationary (BEFORE condition), followed by a brief adaptation period when subjects learn to walk onto the platform moving at 1.2 m/s (MOVING condition). Subjects are clearly warned that the platform will no longer move and asked to walk onto it again (AFTER condition). Despite the warning, they walk toward the platform with a velocity greater than that observed during the BEFORE condition, and a large forward sway of the trunk is observed once they have landed on the platform. This aftereffect, which disappears within three trials, represents dissociation of knowledge and action. In the current set of experiments, to gain further insight into this phenomenon, we have manipulated three variables, the context, location, and method of the walking task, between the MOVING and AFTER conditions, to determine how far the adaptation will generalize. It was found that when the gait initiation cue was changed from beeps to a flashing light, or vice versa, there was no difference in the magnitude of the aftereffect, either in terms of walking velocity or forward sway of the trunk. Changing the leg with which gait was initiated, however, reduced sway magnitude by approximately 50%. When subjects changed from forward walking to backward walking, the aftereffect was abolished. Similarly, walking in a location other than the mobile platform did not produce any aftereffect. However, in these latter two experiments, the aftereffect reappeared when subjects reverted to the walking pattern used during the MOVING condition. Hence, these results show that a change in abstract context had no influence, whereas any deviation from the way and location in which the moving platform task was originally performed profoundly reduced the size of the aftereffect. Although the moving platform aftereffect is an example of inappropriate generalization by the motor system across time, these results show that this generalization is highly limited to the method and location in which the original adaptation took place.

A new paradigm to investigate the roles of head and eye movements in the coordination of whole-body movements

Although previous studies have demonstrated the existence of coordinated eye and head movements during gaze shifts, none has studied the temporal and spatial characteristics of the various body segments during gaze transfers that require whole body movements. Without this information it is not possible to determine the extent of the interaction between the oculomotor control system and the motor control systems responsible for moving other body parts. Presented here is a detailed analysis of the timing and kinematic characteristics of participants' ( N = 5) eye, head, upper body and feet during rotation of their body to align with light cues positioned at eccentric locations (45, 90, and 135 degrees, left and right of centre). For all rotation amplitudes there was a clear sequence of body segment orientation (eye, head, upper body and feet) consistent with previous studies of locomotor steering and significant correlations between the onset latency times of the eyes and all body segments. There were also significant correlations between temporally aligned kinematic profiles of the feet and the eye in space for all movement amplitudes. The extent of correlation was significantly lower for displacement profiles of the feet versus head and of the feet versus upper body. These findings demonstrate substantial eye-foot coordination during a novel whole-body rotation paradigm and provide evidence that the output of the motor systems responsible for moving the feet is heavily influenced by the motor systems responsible for generating and coordinating eye and head movements to peripheral targets.