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Biomedical subjects

A M Bronstein

Publications and source records attributed to A M Bronstein.

At least 109 records · Page 6Linked to original sources
PubMed1995

Body sway and vibration perception thresholds in normal aging and in patients with polyneuropathy.

Body sway and vibration perception in the lower limbs were measured in 32 normal subjects and 25 patients with peripheral neuropathies; nerve conduction studies were also performed in the patients with neuropathies. Body sway was measured by means of force-plate posturography, and three methods were used to assess vibration perception: a neurothesiometer, a semiquantitative tuning fork, and the bone vibrator of a conventional audiometer. Body sway and vibration perception were increased in the patients with peripheral neuropathies and there was significant correlation between these measures.d These findings, together with the lack of correlation between sway and muscle strength, indicate that the main source of unsteadiness in these patients is the loss of proprioceptive information. Vibration perception and body sway did not correlate with the electrophysiological variables, indicating that these measures assess different aspects of peripheral nerve function. In all subjects there was close correlation between vibration perception as assessed by the neurothesiometer and the audiometer could be used to screen proprioceptive function in patients with balance disorders. In normal subjects age correlated with vibration perception (measured with the neurothesiometer and audiometer) and also with body sway standing on foam. This suggests that the increased body sway in elderly people may partly be due to redue proprioception in the lower limbs.

Adult↗
PubMed1995

Visual vertigo syndrome: clinical and posturography findings.

Neuro-otological and posturography findings in 15 patients with visually induced vertiginous symptoms (visual vertigo) are reported. Thirteen patients were considered to have a peripheral vestibular disorder; seven had abnormal caloric or rotational test results. Two patients had CNS disorder--a cerebellar degeneration and a brainstem stroke. Posturography testing showed that five patients showed abnormally large body sway induced by full field visual motion stimulation. This group included the two patients with CNS disease and four with strabismic symptoms (diplopia, squint surgery, and ocular muscle weakness). It is concluded that visual vertigo is a heterogeneous syndrome with peripheral or central aetiologies and may occur if patients with balance disorders show high visual field dependence. In patients with visual vertigo, the presence of additional CNS or strabismic symptoms may cause inappropriate postural reactions in environments with conflicting or disorienting visual stimuli, probably by reducing the ability to resolve the sensory conflict.

Adult↗
PubMed1995

Repetitive paroxysmal nystagmus and vertigo.

A 55-year-old woman had paroxysms of vertigo and visual blurring associated with complex combined torsional, horizontal, and vertical nystagmus. These episodes occurred regularly at 2-minute intervals, each attack lasting for 15 seconds. Between attacks, there was a much finer asymptomatic nystagmus whose components were in the opposite direction to those associated with the paroxysmal attacks. A brain MRI revealed an arteriovenous malformation in close proximity to the left vestibular nucleus, with evidence of previous bleeding. Caloric testing demonstrated a left-sided vestibular paresis. We suggest that neurons in this patient's damaged left vestibular nucleus are usually underactive but regularly produce pathologic brief bursts of hyperactivity causing episodic reversal and gross exacerbation of her resting nystagmus. Treatment with low-dose carbamazepine was successful in abolishing both the paroxysms of nystagmus and the symptoms of vertigo and visual disturbance.

Arteriovenous Malformations↗
PubMed1995

The visual vertigo syndrome.

Neuro-otological and posturography findings in 15 patients with visually induced vertiginous symptoms (visual vertigo, VV) are reported. Most patients were considered to have peripheral vestibular disorders but one had cerebellar degeneration and another a brainstem stroke. Five patients showed abnormally large body sway induced by full-field visual motion stimulation; including the 2 patients with CNS disease. Four of these 5 patients had additional strabismic symptoms (diplopia, squint surgery and ocular muscle weakness). VV may occur if patients with balance disorders show high visual field dependence. The presence of additional CNS or strabismic symptoms, probably by reducing the ability to resolve conflicting visual stimuli, may lead to inappropriate postural reactions.

Adult↗
PubMed1995

Influence of target distance and acceleration level on eye movements evoked by lateral acceleration steps.

Lateral eye movements produced by linear acceleration along the inter-aural axis were studied in 6 normal subjects. They were seated upright, whole-body restrained, and were exposed to randomised rightward/leftward steps of 0.05 g. 0.1 g, 0.24 g of 600 ms duration. When viewing earth-fixed targets at 30, 60 or 280 cm from their eyes, mainly pure compensatory slow-phase eye movements were evoked at latencies around 50 ms measured for the closest viewing distances. At onset, slow-phase amplitude was modulated by acceleration and target distance. When the subjects were stationary and pursued moving targets at similar distances and accelerations, latencies around 140 ms were observed, and catch-up saccades were frequently made. From these experiments, we defined the dynamics of the otolith-ocular reflex for various levels of acceleration and viewing distances.

Adult↗
PubMed1995

Subjective postural vertical in peripheral and central vestibular disorders.

The perception of subjective postural vertical was assessed in normals and patients with peripheral and central vestibular disorders and spasmodic torticollis. The subjects were seated in a motorized gimbal with the head and torso restrained and their eyes closed. The gimbal executed 7-10 cycles of tilt around the vertical at 1.5 degrees/s in either pitch or roll. Subjects indicated when they began to feel upright and again when they began to feel tilted by an analogous 3-position joystick. Normal subjects felt upright within a sector of 5-6 degrees around vertical in pitch and roll. Five patients with absent vestibular function, 25 torticollis patients and 3 patients with acute unilateral peripheral vestibular lesions showed a significant increase of the sector in pitch and roll, but only the latter had a mild directional bias. Two patients with long standing complete unilateral vestibular deficit and 8 patients with up or downbeat nystagmus in the vicinity of upright had abnormally large sectors within which they felt to be upright. The results suggest that vestibular function is important for the accurate perception of the postural vertical and that a directional asymmetry in vestibulo-ocular function or a head tilt does not necessarily correlate with a directional bias of subjective verticality.

Adult↗
PubMed1995

Clinical and electrophysiological findings in the Tullio phenomenon.

A 55 year old female with idiopathic Tullio phenomenon is presented. Binocular, scleral search eye coil recordings demonstrated a predominantly torsional left-beating and vertical down-beating nystagmus in response to sound intensities over 100 dB HL to the left ear, increasing in amplitude and slow phase velocity with sound intensity and removal of visual fixation. The vertical ocular movement was conjugate, i.e. without skew deviation. Neuro-imaging, all other neuro-otological features, including ipsilateral-contralateral stapedius muscle reflexes, and surgical exploration of the middle ear, were normal. Click-evoked vestibulo-collic potentials were normal from the right ear but showed low threshold (70 dB) and increased amplitude from the left. There was no evidence that the Tullio phenomenon in this patient arises from stapes footplate hypermobility. The findings suggest that some cases of the Tullio phenomenon may be due to a hyperexcitability of the normal vestibular response to sound.

Acoustic Stimulation↗
PubMed1995

Bilateral loss of vestibular function.

The clinical findings in 53 patients with bilateral vestibular failure (BVF) seen in a neurological hospital are reported. Bilateral acoustic neuromas were excluded. Seven patients (13%) had progressive cerebellar degeneration; these patients had no hearing complaints but showed gait ataxia, abnormal eye movements and cerebellar atrophy on neuro-imaging. Referral in these patients was primarily for eye movement assessment, and BVF was usually unsuspected. Neuropathies were present in 5 patients (9%), usually with normal central (brainstem-cerebellar) ocular motor function and variable patterns of hearing loss. The single largest group was idiopathic BVF (11 patients, 21%), patients presenting with vertiginous episodes, progressive unsteadiness or brief paroxysms of oscillopsia; auditory function, eye movements, neurological examination and imaging were usually normal. Nine patients (17%) suffered ototoxicity, mostly due to gentamicin; hearing was normal or mildly impaired. In 6 patients (11%) BVF was post-meningitic, with concomitant auditory loss. Autoimmune disease was found in 5 patients (9%); other organs were involved by the disease, and hearing was impaired but eye movements were spared. Miscellaneous neurological, otological or neoplastic diseases accounted for the remaining 10 patients. This study suggests that i) in patients with cerebellar degenerations, BVF may be underdiagnosed as the unsteadiness may be attributed only to the cerebellar disorder, ii) some patients with idiopathic BVF present with only minor visual or vestibular symptoms, and iii) detailed immunological screenings should be undertaken more often, in view of the significant proportion of patients with autoimmune and idiopathic BVF.

Caloric Tests↗
PubMed1995

Acquired pendular nystagmus: oculomotor and MRI findings.

The clinical, oculomotor and ophthalmological features of 27 patients with pendular nystagmus were studied in whom 22 also had MR imaging of the brainstem. The nystagmus was predominately horizontal in 4 patients, torsional in 5, vertical in 3 and mixed in trajectory in 8. Fifteen patients had conjugate nystagmus. Twelve patients had disconjugate nystagmus. Eight patients had INO. In 16 patients visual acuity was 6/12 or worse. Acuity and the presence of INO were unrelated to the conjugacy of the nystagmus. The MRI cuts at the medullary, pontine and midbrain levels were analysed statistically to determine the areas where there was significant (< 0.05%) overlap between areas of abnormal signal in different patients. Significant target areas for lesions causing the nystagmus were: in the pons the medial vestibular nucleus, central tegmental and paramedian tracts; in the medulla the inferior olivary nucleus, reticular formation, dorsal accessory olivary nucleus, central tegmental tracts and olivo-cerebellar fibres; in the midbrain the red nucleus and central tegmental tracts. Horizontal pendular nystagmus was preferentially associated with pontine lesions and torsional nystagmus with medullary lesions. Patients with conjugate nystagmus had a tendency to have bilateral mirror image MRI lesions (p = 0.028). The prevalence of lesions in our patients raises a possibility that more than one neuronal mechanism must be affected to produce pendular nystagmus. The inferior olive may be responsible for the rhythm of ocular oscillation. The disruption of pathways proximal to the oculomotor nuclei may determine the instability in terms of individual eye movement.

Adult↗
PubMed1995

Vision during motion in patients with absent vestibular function.

We have measured a spatial visual response and visual velocity discrimination in 4 patients with long standing vestibular loss and 6 controls. The spatial response was measured during; i) body and visual display stationary conditions, ii) whole-body oscillation (1 Hz +/- 50 degrees/s) and iii) visual stimulus oscillation (1 Hz +/- 50 degrees/s). Velocity discrimination was assessed during conditions i) and ii). The visual tests applied were selected on the basis that the spatial response is known to reflect peripheral processes of the retina, whereas velocity processing is more central in origin. Patients had normal spatial responses under static conditions and they suffered a degradation in their spatial responses during whole-body oscillation, whereas, normals' responses remained unaltered. During oscillation of the visual display both patients and normals suffered a degradation in their spatial responses, and for patients the change was very similar to that observed during whole-body oscillation. The changes in the spatial responses were dependent on the gain of the eye movements which compensated for the whole-body or visual display oscillation. In 3 patients and all controls whole-body oscillation did not alter the discrimination of velocity of a vertically moving horizontally orientated grating compared with when the subjects were stationary. One patient suffered a severe reduction in the ability to discriminate velocity under whole-body oscillation, which suggests that central suppression of motion perception reduces oscillopsia.

Acceleration↗
PubMed1995

EMG-responses to sudden onset free fall.

Recordings of axial and limb muscles in reaction to a free fall induced startle were performed in subjects while they were lying on a tilting couch with their eyes closed. Young normals (n = 24, aged 31.1 +/- 6.6 years) showed an activation sequence consisting of sternomastoid (N.XI: 57 ms), abdominal muscles (T10: 65 ms), quadriceps (L3: 75 ms) and deltoid (C5: 78 ms) and tibialis anterior (L4: 80 ms). The sequence of activation is not compatible with the current hypothesis of the startle being produced by a single volley spreading rostrally and caudally from the lower brainstem. Instead it is suggested that the startle is a patterned response organized by a putative reticular generator capable of spatio-temporal sequencing. Two avestibular patients had responses at mildly delayed latencies, showing that these can be elicited by non-vestibular inputs. Similar testing of 11 subjects aged 70-80 years showed a latency delay of ca. 26% in the EMG response but a similar activation sequence. The amount of delay in the elderly can only partially be attributed to age-dependent motor conduction slowing and suggests a prolongation of central processing time. In patients with advanced stages of akinetic-rigid syndromes abnormalities were seen in cases with an involvement of the brainstem reticular formation.

Accidental Falls↗
PubMed1995

Vertical and torsional VOR in posterior canal occlusion.

The vertical and torsional vestibulo-ocular reflexes (VOR) were investigated in 3 patients with surgical occlusion of the posterior semicircular canal and 1 patient with singular neurectomy, for treatment of refractory paroxysmal positional vertigo. Stimuli comprised sinusoidal oscillation in the coronal ("roll") and sagittal ("pitch") plane as well as in two oblique planes intermediate between pitch in order to stimulate left anterior + right posterior (LARP) and right anterior + left posterior (RALP) canal pairs separately. One case with left side BPPV was investigated pre and post-operatively. Depression of the vertical and torsional VOR gain was seen 1 week postoperatively when the occluded canal was placed in the optimal plane for stimulation at 1 week postoperatively and subsequently gradually recovered. Recordings in other planes suggested that the contralateral posterior canal was also hypofunctioning, a finding which may explain some residual gait unsteadiness in this case. The other 3 cases who were investigated postoperatively all showed a decrease in downward VOR gain in the "on' direction of the operated canal. The data indicate the specificity of the test procedure and underline the prognostic value of comprehensive pre-operative vestibular assessment.

Adult↗
PubMed1995

The perception of head rotation in Parkinson's disease.

The accuracy in detecting angular displacements of the head and the neck was investigated in 14 patients with idiopathic Parkinson's disease (PD) and 16 age matched normal controls by the technique of vestibular and cervical "remembered" saccades. It was found that although the remembered saccades in PD patients were multiple-step and showed low initial saccadic gain, the final eye position of the eyes matched the rotational stimulus as accurately as in normals. This indicates that perception of head/neck rotation is normal in PD which is inconsistent with views that vestibulo/proprioceptive dysfunction contributes to the postural disorder in PD. The presence of multiple-step remembered vestibular and cervical saccades agrees with reported abnormalities in visual remembered saccades in PD and indicates that the difficulty in generating saccadic movements based on memorized sensory information is not confined to visual-memory.

Adult↗
PubMed1995

Recovery from bilateral vestibular failure: implications for visual and cervico-ocular function.

We report a patient who sustained severe bilateral labyrinthine lesions during Streptococcus suis meningitis but considerably recovered vestibular function over a 7 month period. This unique case allowed us to examine the cervico-ocular reflex (COR) and visual function at various levels of activity of his vestibular system. The slow phase COR, elicited by trunk oscillation (0.2 Hz) with the head earth-stationary, was negligible immediately after the acute vestibular loss but rose to a gain of 0.51 one month after. Seven months later, when vestibular function was improved, COR gain dropped to a gain of 0.15. Measurements of spatial visual function during whole body oscillation in the acute stage and after 6 months showed marked improvement which correlated entirely with VOR measurements in the dark and during optic fixation. This patient also showed the unique feature that, in the acute stage, eye movement gain and visual function were poorer during whole body motion than during identical visual target motion. These findings suggest that: i) the COR may be inhibited by the presence of vestibular signals, ii) spatial vision measurements provide accurate assessment of the patient's visual blur during head motion, and iii) the severe oscillopsia experienced by patients in the acute stage of vestibular loss may not only be due to the absence of the VOR; additional degradation in eye movements during head motion, perhaps arising from acutely distorted labyrinthine signals, may also play a part.

Dark Adaptation↗
PubMed1995

Perceptual studies in patients with vestibular neurectomy.

Twelve patients undergoing unilateral vestibular neurectomy for the treatment of refractory vertigo were investigated. Vestibular motion perception was assessed using a self-rotational task and "vestibular remembered saccades". Cervical perception was also measured with remembered saccades. The tests were performed pre- and post-operatively to examine changes in vestibular and cervical perception following an acute vestibular lesion, and to monitor the progress of vestibular compensation. These perception tests were carried out in conjunction with a conventional evaluation of the vestibular ocular reflex (VOR), using electro-oculography. The patients' subjective symptoms at each stage of testing were also quantified with questionnaires. Generally, in the vestibular tests, for stimulation to the operated side, responses became strongly hypometric directly after the neurectomy, with a partial recovery during convalescence. In the cervical test, responses were bilaterally reduced immediately after operation. Results from both of the vestibular perception tests were significantly correlated with the VOR assessment of vestibular function. Scores for the patients' subjective symptoms of "vertigo" were only significantly correlated with the vestibular perception tests, and not with the conventional measures of vestibular function. Perceptual measurements afford useful complementary information in the assessment of vestibular patients.

Adult↗
PubMed1994

Responses in neck and facial muscles to sudden free fall and a startling auditory stimulus.

EMG responses elicited by sudden onset of free fall and a startling auditory stimulus were investigated in healthy subjects while lying on a couch with their eyes closed. Muscle responses were recorded from masseter (V cranial nerve), orbicularis oculi and mentalis (VII nerve) and sternomastoid and trapezoid (XI nerve). A similar sequence of muscle activation and absolute latencies occurred in response to both stimulus modalities, consisting of a blink (30 msec) followed simultaneously by mentalis, sternomastoid and trapezoid (55 msec). Masseter could either be simultaneously activated with the latter muscles or follow after a delay of 10-20 msec. A patient with bilateral cochleo-vestibular nerve section had responses at comparable latencies in the free fall experiment. The similarities between the reaction to free fall and a startling auditory stimulus indicate that the early response to free fall constitutes a startle and that various stimuli converge onto a common response generator. The latency pattern of neck and facial muscles does not follow a sequence of innervation with increasing segmental distance from a single centre. Therefore, our data do not support the concept that the startle response is produced by a caudally and rostrally spreading volley from a putative pontomedullary centre. It is suggested that the startle response is a polysynaptically generated patterned muscle activation.

Acoustic Stimulation↗
PubMed1994

Vestibular, cervical and visual remembered saccades in Parkinson's disease.

In order to assess both vestibulo-cervical perception of head rotation and saccadic function in Parkinson's disease, 14 patients with idiopathic Parkinson's disease were subjected to discrete sigmoid-shaped rotational displacements whilst fixating a target aligned with primary gaze in an otherwise dark room. The rotational stimuli were applied to (i) the whole body (vestibular stimulus); (ii) the trunk whilst the head remained stationary in space (cervical stimulus); (iii) to the head alone whilst the trunk remained stationary (combined vestibular and cervical stimulus). The fixation target was then extinguished and the subjects had to estimate the angle travelled by the head or trunk with an ocular-pointing task using information from the preceding rotational stimulus (vestibular and cervical 'remembered' saccades). It was found that, although these saccades in Parkinson's disease patients were multiple-step and hypometric, the final position of the eyes matched the rotational stimulus as accurately as in normal subjects. A complementary experiment in six patients showed that visual remembered saccads were hypometric, but significantly less so than vestibular remembered saccades. It is concluded that (i) vestibular and cervical perception of head/neck rotation is normal in Parkinson's disease; (ii) abnormalities of 'remembered' saccades, previously reported in Parkinson's disease, are not confined to the visual modality but involve other sensory modalities as well; (iii) across different modalities of memory-guided saccades, visual input improves saccadic performance. This result demonstrates that the known increased visual dependence found in Parkinson's disease extends to memory-driven tasks.

Adult↗