A randomised double-blind, cross-over trial of 4-aminopyridine for downbeat nystagmus--effects on slowphase eye velocity, postural stability, locomotion and symptoms.

Objective: The effects of 4-aminopyridine (4-AP) on downbeat nystagmus (DBN) were analysed in terms of slow-phase velocity (SPV), stance, locomotion, visual acuity (VA), patient satisfaction and side effects using standardised questionnaires.

Methods: Twenty-seven patients with DBN received 5 mg 4-AP four times a day or placebo for 3 days and 10 mg 4-AP four times a day or placebo for 4 days. Recordings were done before the first, 60 min after the first and 60 min after the last drug administration.

Accessing escalators: a central vestibular disorder after posterior fossa tumor removal.

About 20% of childhood tumors originate within the central nervous system. Progress in assessment and treatment of these lesions has led to improved survival rates. We describe a patient with a posterior fossa ependymoma who despite a remarkable recovery following treatment has been frustrated by difficulty in using escalators.

Visual dependence and BPPV.

The increased visual dependence noted in some vestibular patients may be secondary to their vertigo. We examine whether a single, brief vertigo attack, such as in benign paroxysmal positional vertigo (BPPV), modifies visual dependency. Visual dependency was measured before and after the Hallpike manoeuvre with (a) the Rod and Frame and the Rod and Disc techniques whilst seated and (b) the postural sway induced by visual roll-motion stimulation.

A new device to quantify ocular counterroll using retinal afterimages.

Background: The integrity of vertical semicircular canal and otolith function remains difficult to assess in the clinical setting, partly due to difficulties in recording ocular counterroll. Here, we quantify static ocular counterroll from head tilt using a new head-mounted device.

Methods: The device consists of an LED positioned 42 cm in front of one eye and a striated lens which produces a streak of light on the retina.

The effect of repeated visual motion stimuli on visual dependence and postural control in normal subjects.

Patients with vestibular dysfunction, migraine and/or anxiety may experience visual vertigo (VV), whereby symptoms are provoked by disorienting visual environments (e.g. supermarkets).

Adaptation of ventilation to 'buffeting' in vehicles.

Objectives: Short exposures to buffeting in a vehicle driving over rough terrain induce an increase in the frequency of respiration resulting in hyperpnoea and hypocapnia. The present study investigates the adaptation to buffeting-induced hyperpnoea.

Methods: We monitored ventilation and cardiovascular function in nine healthy young adults prior to, throughout and post a 30 minute simulation of buffeting.

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.

Reduced self-motion perception in patients with midline cerebellar lesions.

Vestibular input to the cerebellum mediates balance and eye movement control. Recent functional MRI studies, however, show midline cerebellar activation during visually induced illusions of self-rotation, thus suggesting that the cerebellum may also contribute to self-motion perception. Here, we investigate self-motion perception directly in patients with vermal (or midline) cerebellar ataxia.

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.

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.

Vestibular perception in patients with acquired ophthalmoplegia.

Using a perceptual technique it is shown that patients with chronic external ophthalmoplegia have shortened vestibular responses. It is postulated that this is secondary to the retinal image slip experienced by these patients during head movements and a useful compensatory mechanism to suppress motion-induced sickness and spatial disorientation.

Influence of target size on vertical gaze palsy in a pathologically proven case of progressive supranuclear palsy.

We document a new oculomotor phenomenon in a patient with pathologically proven progressive supranuclear gaze palsy (PSP), namely that vertical gaze excursion improves with larger pursuit targets. We used computerised video-oculography during vertical smooth pursuit eye movements (SPEM) of circular targets of diameter 0.16 degrees and 16 degrees, sinusoidally oscillating at 0.

Effect of semicircular canal stimulation on the perception of the visual vertical.

Unlabelled: The subjective visual vertical (SVV) is usually considered a measure of otolith function. Herewith we investigate the influence of semicircular canal (SCC) stimulation on the SVV by rotating normal subjects in yaw about an earth-vertical axis, with velocity steps of +/- 90 degrees /s, for 60 s. SVV was assessed by setting an illuminated line to perceived earth vertical in darkness, during a per- and postrotary period.

Short-latency eye movements evoked by near-threshold galvanic vestibular stimulation.

To investigate whether the primary planes of eye and body responses to galvanic vestibular stimulation (GVS) are congruent, we have measured the binocular, three-dimensional eye movements (scleral coil technique) to bilateral bipolar GVS in six normal human subjects. Stimulation intensities were kept deliberately low in order to characterize the response to near-threshold intensities of stimulation (0.1-0.

Paroxysmal alternating skew deviation and nystagmus after partial destruction of the uvula.

A patient with suspected brain stem glioma involving the area of the left vestibular nuclei and cerebellar peduncle, developed paroxysmal alternating skew deviation and direction changing nystagmus after biopsy of the inferior cerebellar vermis resulting in destruction of the uvula. Between attacks she had right over left skew deviation with asymptomatic right beating horizontal nystagmus. Slow phases of the resting nystagmus showed increasing velocity, similar to congenital nystagmus.

Horizontal ocular vergence and the three-dimensional response to whole-body roll motion.

We evaluated the human binocular response to roll motion in the dark and during visual fixation with horizontal convergence. Six normal human subjects were exposed to manually driven, whole-body rotation about an earth-vertical, naso-occipital axis, under two conditions: (I) oscillation at 0.4 Hz (peak velocity 69+/-3.

The incidence and waveform characteristics of periodic alternating nystagmus in congenital nystagmus.

Purpose: To investigate the incidence and waveform characteristics of periodic alternating nystagmus, (PAN) in congenital nystagmus (CN).

Methods: In a prospective study, 18 patients with CN without associated sensory defects agreed to undergo eye movement documentation using binocular infrared oculography. Two of the 18 had a diagnosis of suspected PAN before entering the study.

Visual and oculomotor responses induced by neck vibration in normal subjects and labyrinthine-defective patients.

Three-dimensional scleral search coil eye movement recordings were obtained in five normal subjects and four patients with absent vestibular function, during unilateral vibration of the neck in the supine position. The purpose of the experiments was to investigate any role played by eye movements in the illusion that a small fixation target, viewed in an otherwise dark room, moves when vibration is applied to the neck (propriogyral illusion). Vibration was applied to the right dorsal neck muscles in three visual conditions: total darkness, fixating a light-emitting diode (LED) in an otherwise totally dark room and LED fixation in the normally lit room.

Fast eye movement initiation of ocular torsion in mesodiencephalic lesions.

Three patients with episodic ocular torsion and skew deviation due to mesodiencephalic lesions were studied by using binocular three-dimensional scleral search coils. The conjugate ocular torsion (upper pole of each eye rotating toward the side of the brainstem lesion) was initiated by a torsional fast eye movement. During prolonged episodes, torsional nystagmus was also present.

Otolith and semicircular canal contributions to the human binocular response to roll oscillation.

Three normal human subjects were oscillated about their naso-occipital axis in a supine position at 0.4 Hz and 0.1 Hz, both in darkness and in the light with a structured fixation target.

Evaluating 3D semicircular canal function by perception of rotation.

Objective: We aimed to develop a clinical test of 3D canal dysfunction by perceptual matching of motion stimuli as an alternative to vestibular ocular reflex assessment.

Study Design: The study was a comparison with age-matched controls.

Setting: The study was performed in a clinical neurophysiology laboratory.

Motion detection deficits in infantile esotropia without nystagmus.

Purpose: To investigate whether adults with infantile strabismus but without latent nystagmus have abnormalities of horizontal motion detection.

Methods: Eleven adult subjects with infantile esotropia but without latent nystagmus and 15 control subjects were required to detect the onset of motion and drift direction of a sinusoidal, spatial frequency grating that moved with linearly increasing velocity. The grating was presented monocularly in paracentral vision at an eccentricity of 16.

Skew deviation following vestibular nerve surgery.

Eighteen consecutive patients undergoing vestibular nerve surgery underwent pre- and postoperative examination of ocular motility. Five patients developed a skew deviation following surgery, with the lower eye on the operated side and an incomitant pattern of deviation in all cases. Three patients experienced diplopia lasting from 1 day to 6 months.

Visual and vestibular factors influencing vestibular "navigation".

In order to elucidate the role of the "starting point" in path integration, normal subjects underwent a self-rotational task in a motor-driven turntable rotating around an earth-vertical axis. They were passively rotated ("stimulus") and had to return to the starting point, controlling the direction and velocity of the turntable by means of a joystick ("response"). The test included conditions with an earth-fixed target (EFT) as starting point, shown before the stimulus, and conditions without EFT presentation.

Optically induced plasticity of the cervico-ocular reflex in patients with bilateral absence of vestibular function.

The horizontal cervico-ocular reflex (COR) was examined in five labyrinthine-defictive subjects (LDS), during both passive oscillations of the head on the trunk (HTexam) and of the trunk under the earth-fixed head (THexam) at 0.1-0.5 Hz, peak angular displacement +/- 30 degrees.