Clinical Characteristics and Clinical Course of Body Lateropulsion in 47 Patients with Brainstem Infarctions.

BACKGROUND: In patients with lower lateral medullary infarction (LMI) located under the vestibular nucleus, proprioceptive impairment due to dorsal spinocerebellar tract (DSCT) is considered a pathological condition for body lateropulsion. In patients with brainstem infarction located at or above the level of the vestibular nucleus, other pathways, such as the crossed vestibulothalamic tract (CVTT), are considered responsible. RESEARCH QUESTION: The clinical course of body lateropulsion between each anatomical level of infarction remains unclear. Further, whether body lateropulsion refers to a static or a dynamic symptom also remains unclear. METHODS: We examined 47 patients who exhibited body lateropulsion and categorized them into four groups: lower LMI under the vestibular nucleus, LMI at the level of the vestibular nucleus, pontine infarction, and midbrain infarction. The patients' time to acquire static upright standing position and gait in a straight line were statistically analyzed by a log-rank test using the Kaplan-Meier method. RESULTS: Body lateropulsion in the static upright position was less frequent in the lower LMI group than in the other groups. SIGNIFICANCE: Lower LMI primarily affected body lateropulsion in gait. DSCT damage could affect ipsilateral hip joint or leg coordination, causing body lateropulsion in dynamic situation.

Neurophysiological monitoring of brainstem function in a patient with Wallenberg syndrome, using Vestibular Evoked Myogenic Potentials.

PURPOSE: We evaluated the use of Vestibular Evoked Myogenic Potentials (VEMPs) in the assessment of neural function, following medullary lesions. METHODS: A 54-year-old male presented with symptoms and signs typical of right lateral medullary (Wallenberg) syndrome. He underwent brain MRI and three successive neurophysiological investigations, which included VEMPs, Brainstem Auditory Evoked Responses (BAERs) and the blink reflex. RESULTS: VEMPs amplitude on the left (unaffected) side was 256.8 microv in the first investigation and remained approximately equal to that value in the following two ones. Their amplitude on the right (affected) side was 37.9 microv, 154.2 microv and 235.2 microv correspondingly. At the same time vertigo, diplopia and nystagmus gradually improved. Right blink reflex comprised a normal R1, but delayed R2 ipsilateral and R2 contralateral responses, which remained unaltered during the follow-up period. Brain MRI disclosed a right dorsolateral medullary infarct. CONCLUSIONS: VEMPs amplitude progressively increased, parallel to the improvement of vestibular symptoms. The blink reflex evolved differently, while BAERs were not affected. As the three evoked responses are mediated by separate neural circuits, they provide information on different aspects of brainstem function. Thus, VEMPs seem to be a useful method that complements existing ones in the assessment of brainstem lesions.

Rotational vertebral artery syndrome: oculographic analysis of nystagmus.

In four patients with rotational vertebral artery syndrome (RVAS), the initial nystagmus was mostly downbeat, with the horizontal and torsional components beating toward the compressed vertebral artery side (n = 3) or directed away (n = 1). Three patients showed spontaneous reversal of the nystagmus and two exhibited no or markedly diminished responses on immediate retrial of head rotation (habituation). The patterns of nystagmus suggest that RVAS may result from differing mechanisms.

Medial medullary infarction: abnormal ocular motor findings.

In 20 consecutive patients with isolated medial medullary infarction, abnormal ocular motor findings included nystagmus (n = 8), ocular contrapulsion (n = 5), and contralesional ocular tilt reaction (n = 2). The nystagmus was ipsilesional (n = 4), gaze-evoked (n = 5), upbeating (n = 4), and hemiseesaw (n = 1). The ocular motor abnormalities may be explained by involvements of the nucleus prepositus hypoglossi, medial longitudinal fasciculus or efferent fibers from the vestibular nuclei, climbing fibers, and cells of the paramedian tracts.

Diagnosis of vestibular imbalance in the blink of an eye.

BACKGROUND: In a recent study, the authors found that blinks in healthy volunteers always triggered ocular torsion quick phases during dynamic roll movements of the head. On the basis of this observation, they hypothesized that blinks in patients with a vestibular tone imbalance would also trigger torsional quick phases. METHODS: Using video-oculography with a fixation target, the authors recorded the ocular torsion position of the left eye of 37 participants while they made voluntary blinks once every 6 to 10 seconds. The participants were recruited from four groups: two age groups of healthy volunteers with a mean +/- SD age of 32 +/- 4 (n = 9) and 65 +/- 11 y (n = 9); patients with a unilateral vestibular disorder in an acute state (n = 12, 53 +/- 17 y); and those in a persisting state in which spontaneous nystagmus had already faded (n = 9, 65 +/- 13 y). RESULTS: In the control groups of healthy volunteers, blinks triggered no or only small quick phases on the order of 0.1 deg. In both patient groups blinks always triggered quick phases with significantly higher amplitudes of 1.85 +/- 1.02 deg and were followed by exponentially decaying slow-phases with time constants on the order of 1 to 2 seconds. Patients in the persisting state clearly differed from patients in the acute state in that their torsional spontaneous nystagmus had already vanished due to vestibular compensation. But surprisingly, these two groups did not show a large difference in terms of the effect of blinks on ocular torsion. The authors always observed torsional quick phases with the upper pole of the eye beating away from the side of the lesion. CONCLUSIONS: Blinks are able to trigger torsional quick phases in patients with both acute and persisting vestibular disorders. The side of the impairment can be determined from the direction in which the eye is rotated after a blink. Thus, ocular torsion recordings during blinks can be used as a simple clinical test for a vestibular tone imbalance, particularly during a persisting failure in which spontaneous nystagmus has resolved and can therefore no longer be used for diagnosis.

[Processing vestibular impulses in the central nervous system. Study based on positron emission tomography]. / Verarbeitung vestibulärer Impulse im Zentralnervensystem. Untersuchung anhand der Positronen-Emissions-Tomographie.

BACKGROUND AND OBJECTIVE: Functional imaging methods have opened new perspectives for vestibular research. Many authors have investigated the central connections of the system, but the differences between the reports leave further questions open. We investigated the cerebral projection of the vestibular system, using positron emission tomography in right-handed subjects. PATIENTS AND METHODS: Bilateral caloric stimulation was used in every volunteer (n = 6). This can be considered a standard method, which will make it possible to compare the results from different laboratories in the future. A detailed map of activated and deactivated brain regions is included. RESULTS: Changes caused by vestibular stimulation are portrayed. The activated regions partially correspond with previous results in the literature. We would like to point out the Brodmann 6 region as the cortical manifestation of involuntary isometric tightening of muscles. We have found many, previously unidentified regions showing decreased regional cerebral blood flow. CONCLUSIONS: We are the first to point out the functional connection between the hippocampus and the vestibular system in this report.

[Benign paroxysmal vertigo in childhood]. / Vértigo benigno paroxístico de la infancia.

Benign paroxysmal vertigo of childhood is a clinical disorder that usually begins at age 4. The child's otoneurological examination is normal in the intercrisis and the brief episodes of true vertigo are typical. In this paper we describe six new cases that had a follow-up of at least one year after diagnosis. Only a few of the patients had demonstrated vasomotor migraine, but all the children had a family history of migraine, which supports the hypothesis that this disorder is a migraine equivalent. The pathogenesis may be related with a transitory vascular disturbance that produces ischemia of the vestibular nuclei and pathways, as occurs in other vascular territories during typical migraine. One longer-than-usual episode is reported. Otherwise, the evolution of this condition is favorable.

Autoradiographic measurement of regional brainstem blood flow: occlusion of the anterior inferior cerebellar artery.

Autoradiography was used to measure regional brainstem blood flow in Wistar rats following permanent left anterior inferior cerebellar artery (AICA) occlusion. With the AICA occluded, blood flow to the left vestibular nucleus decreased 31% while flow to the left cochlear nucleus decreased 47% when compared to the right (unobstructed) side. In the rat, the median pontine branch of the basilar artery was found to provide the principal blood supply to the vestibular nucleus. Electrocochleography was also used to measure the action potential (AP), summating potential (SP) and cochlear microphonics (CM) during left AICA occlusion. The AP disappeared completely after at least 7 min, while the SP polarity changed from negative to positive. Findings also showed that CM2 did not disappear completely in pre-mortem animals.

[Reduced blood supply of the vestibular centers. Clinical and experimental studies]. / Die Mangeldurchblutung der vestibulären Zentren. Klinische und experimentelle Studien.

To explain the origin of the narrow nystagmus writing (petite écriture) selected patients with hypoxemia were examinated using the pendular rotating test and ENG. Blood gas analysis was used to determine pO2 reduction. The decreased oxygen saturation was corresponding to the decreased amplitude of nystagmus. In a second experiment with alert rabbits the inspired gas mixture was altered to obtain hypoxia (8% O2+ 92% N2, controlled with blood gas analysis). A significant reduction from the normal nystagmus reaction was observed. This reduction in the amplitude (about 50%) is immediately reversible by giving oxygen. These experiments were repeated with each animal several times, the results being reproductible. There is a significant decrease in amplitude of nystagmus through the influence of hypoxia.

Vestibular neuronal function during ischemia. Response of vestibular neurons to vertebral and carotid artery occlusion in rabbits.

The relation between ischemia experimentally produced by occlusion of arteries injecting to the brain and the changes in vestibular excitability was examined in 102 rabbit vestibular neurons responding to sinusoidal rotation. During occlusion of ipsilateral and/or contralateral vertebral and common carotid arteries, the neuronal activity took on three different patterns with respect to the frequency of neuronal discharge. The incidence of alteration of neuronal activities reflected vestibular excitability dependent on hemodynamic changes due to occlusion of the ipsilateral vertebral artery rather than due to occlusion of the contralateral artery. Occlusion of common carotid arteries caused no significant difference between the right and left vessels in the resultant change of the neuronal activity, and differed little, either, from occlusion of vertebral arteries in the incidence of the changes. A supplementary experiment, in which the four arteries were only partially occluded, clearly showed that the resultant changes in neuronal activity reflect the role of Willis' circle in the maintenance of blood flow to vestibular nuclei.