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At least 1,261 records · Page 70Linked to original sources
PubMed2003

Effect of posture on blood and intraocular pressures in multiple system atrophy, pure autonomic failure, and baroreflex failure.

BACKGROUND: Intraocular pressure (IOP) may be partially under systemic vascular control. This study examined whether a correlation exists between blood and intraocular pressures in patients with autonomic dysfunction. METHODS AND RESULTS: Eleven patients with 3 types of confirmed autonomic dysfunction (multiple system atrophy, pure autonomic failure, and baroreflex failure) were compared with age- and gender-matched controls and had IOP, systolic blood pressure, diastolic blood pressure, heart rates, and calculated mean arterial pressures (MAP) and mean ocular perfusion pressures (MOPP) measured in the supine, sitting, and standing positions. Data were analyzed with a general linear model repeated-measures ANOVA. All pressures for patients showed a dramatic decline (P<0.001) from supine to standing (MAP -31+/-14 mm Hg; IOP -6+/-3 mm Hg; MOPP -25+/-14 mm Hg) compared with controls (MAP +4+/-7 mm Hg; IOP -1+/-2 mm Hg; MOPP +6+/-7 mm Hg). There was no significant change in heart rate from supine to standing for patients compared with controls (P=0.648). Within both the multiple system atrophy (n=5) and pure autonomic failure (n=4) groups, all initial pressures were similar to control pressures in the supine position, whereas patients with baroreflex failure (n=2) had higher mean pressures than respective controls in the supine position. CONCLUSIONS: In autonomic dysfunction, a large decrease in MAP correlated with a large decrease in IOP. These data suggest that the autonomic nervous system, perhaps through an influence on systemic blood pressure, has a significant role in IOP regulation.

Adult↗
PubMed2004

Ocular rotation axes during dynamic Bielschowsky head-tilt testing in unilateral trochlear nerve palsy.

PURPOSE: To explain the positive Bielschowsky head-tilt (BHT) sign in unilateral trochlear nerve palsy (uTNP) by the kinematics of three-dimensional eye rotations. METHODS: Twelve patients with uTNP monocularly fixed on targets on a Hess screen were oscillated (+/- 35 degrees, 0.3 Hz) about the roll axis on a motorized turntable (dynamic BHT). Three-dimensional eye movements were recorded with dual search coils. Normal data were collected from 11 healthy subjects. RESULTS: The rotation axis of the viewing paretic or unaffected eye was nearly parallel to the line of sight. The rotation axis of the covered fellow eye, however, was tilted inward relative to the other axis. This convergence of axes increased with gaze toward the unaffected side. Over entire cycles of head roll, the rotation axis of either eye remained relatively stable in both the viewing and covered conditions. CONCLUSIONS: In patients with uTNP, circular gaze trajectories of the covered paretic or unaffected eye during dynamic BHT are a direct consequence of the nasal deviation of the rotation axis from the line of sight. This, in turn, is a geometrical result of decreased force by the superior oblique muscle (SO) of the covered paretic eye or, according to Hering's law, increased force parallel to the paretic SO in the covered unaffected eye. The horizontal incomitance of rotation axes along horizontal eye positions can be explained by the same mechanism.

Adolescent↗
PubMed1991

The venoarteriolar response in diabetics.

Resting skin blood flow and the venoarteriolar response (VAR) were studied in 40 patients with diabetic microangiopathy and neuropathy, in 40 diabetics with microangiopathy, and in 30 normal subjects by means of laser-Doppler flowmetry. In patients with microangiopathy and neuropathy, resting flow (RF) was increased and the VAR was impaired to a greater extent than in patients without neuropathy. There was also a significant delay in the VAR in diabetics, particularly in patients with neuropathy. The microangiopathy index (VAR/RF) was on the average 71.3 in normal subjects, significantly lower (p less than 0.05) in diabetics without neuropathy (34.8), and even lower in those with neuropathy (13.6). The VAR was evaluated with different postural changes; The authors observed that in the passage from supine to standing the VAR is more evident. In conclusion these results confirm that the postural control of blood flow in the skin of the foot is impaired in diabetic microangiopathy, particularly in patients with neuropathy. The increased skin blood flow and the impaired VAR are causes of edema and may contribute to the thickening of capillary basement membranes observed in diabetes.

Blood Flow Velocity↗
PubMed1990

Results of microvascular decompression of the eighth nerve as treatment for disabling positional vertigo.

A total of 41 patients who underwent microvascular decompression to relieve disabling positional vertigo in one 12-month period were studied. At follow-up examinations 2 1/2 to 3 1/2 years after the operation, 30 patients had total relief of their symptoms or were considerably improved, to the point that they could resume normal work or other activities in which they were not able to engage before the operation. Two of the 41 patients had mild improvement, and the final 9 patients had no change in their symptoms. One patient, who had had a previous vestibular nerve section without improvement, underwent microvascular decompression of the stump as well as decompression of the opposite side with no relief: 3 of these 9 patients had clear signs of bilateral vestibular nerve compression, but elected not to undergo a second procedure at that time. One patient lost hearing as a result of the operation, and 1 who had a second operation suffered a hearing loss and subsequently underwent vestibular nerve section with improvement of the symptoms. Two patients had transient deficits related to cranial nerves IV and X. The remaining patients had no complications from the operation.

Acoustic Impedance Tests↗
PubMedDate not supplied

Posturography.

Posturography is a method of measuring a patient's ability to control his balance. Currently available testing techniques may be useful to otologists, although they have not been shown to yield information beyond that obtained from other diagnostic procedures. More powerful techniques are under development, but methodologic problems remain, and none is yet ready for routine clinical use.

Cerebellum↗
PubMed1993

Oscillopsia in patients with loss of vestibular function.

Contrary to standard teaching, many patients with bilateral vestibular loss clearly deny oscillopsia or imbalance in darkness. In an attempt to characterize these patients within the larger population of all patients with bilateral vestibular loss, the rotation and posturography test results of 22 patients with bilateral vestibular loss were reviewed. In addition, dynamic visual acuity was assessed with an eye chart test. There was a poor relationship between oscillopsia and dynamic visual acuity or rotation testing. There were three patterns of response on rotation testing, and loss of high-frequency gain was seen in as many patients who reported oscillopsia as did not. There were some patients with normal gain values at all frequencies tested who reported oscillopsia. It may be that the change in the VOR, rather than the absolute VOR loss, is responsible for the production of oscillopsia. On the basis of this and other studies, treatment strategies for patients with bilateral vestibular loss are suggested.

Adolescent↗
PubMed2003

Multimodal signal integration in vestibular neurons of the primate fastigial nucleus.

The rostral fastigial nucleus contains vestibular neurons, which presumably are involved in spinal mechanisms (neck, gait, posture) and which are not modulated with individual eye movements. Single-unit recordings in the alert behaving monkey during natural stimulus conditions reveal that virtually all neurons demonstrate integration of several sensory inputs. This applies not only for canal-canal and canal-otolith interaction, but also for otolith-otolith interaction. There is also some evidence that most neurons receive not only an utriculus but also a sacculus input. Furthermore, most neurons also respond to large-field optokinetic stimulation, reflecting visual-vestibular interaction. Neurons are also affected by the head on trunk position, which would allow these neurons to operate in a body-centered rather than a head-centered reference frame. These complex, multisensory features could permit fastigial nucleus neurons to rather specifically affect spinal motor functions.

Animals↗
PubMed2005

"Off" gait freezing and temporal discrimination threshold in patients with Parkinson disease.

OBJECTIVE: To investigate the relationship between temporal discrimination threshold (TDT) and "off" period gait freezing (OGF) in patients with fluctuating Parkinson disease (PD). METHODS: TDT values were measured at the dorsum of the toes in 11 control subjects and 22 patients with PD with a wearing-off phenomenon (16 patients with OGF and 6 patients without OGF). RESULTS: During the l-dopa "off" period, TDT values increased abnormally in both patient groups but were significantly higher in patients with OGF than in those without OGF. A positive correlation was found between the severity of OGF and TDT values measured by different point stimulation. In patients with OGF, a single dose of l-dopa treatment normalized TDT values and ameliorated OGF. CONCLUSIONS: Dopa-responsive abnormal discriminative sensory processing may be a possible cause of "off" period gait freezing observed in patients with fluctuating Parkinson disease.

Aged↗
PubMed1981

Downbeat nystagmus: a type of central vestibular nystagmus.

We used electrooculography to study horizontal and vertical eye movements in 17 patients with downbeat nystagmus (Chiari malformation, 9; multiple sclerosis, 2; olivopontocerebellar atrophy, 2; brainstem infarction, 2; and idiopathic nystagmus, 2). In all patients the velocity of slow components of the spontaneous nystagmus increased on lateral gaze, remained relatively unchanged with loss of fixation, and increased markedly after rapid positional changes in the sagittal plane. Horizontal and vertical smooth pursuit was impaired in all patients. Vertical pursuit recordings at multiple ramp velocities suggested superimposition of the spontaneous nystagmus on attempted pursuit rather than selective impairment of downward pursuit. Finally, all patients had impaired fixation suppression of vestibular nystagmus when they were rotated with a fixation point moving with their head. We conclude that downbeat nystagmus is a type of central vestibular nystagmus resulting from an imbalance in the central vertical vestibuloocular pathways.

Adolescent↗
PubMed1987

Autonomic function in parkinsonian patients relates to duration of disease.

Autonomic functions were studied after withdrawal of all medication in parkinsonian out-patients with short and long duration of disease and in age-matched healthy control subjects. Vagal heart control and noradrenergic response to standing were impaired and related to duration of symptoms of idiopathic parkinsonism. Cholinergic function of pupil motility was unchanged. The cholinergic dysfunction of heart rate variation, therefore, could be due to a specific loss of dopaminergic neurons in the vagal motor nucleus.

Aged↗