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Biomedical subjects

A Straube

Publications and source records attributed to A Straube.

At least 19 recordsLinked to original sources
PubMed1999

Orbital position dependency is different for the gain of externally and internally triggered saccades.

The gain of visually triggered saccades depends on orbital position. Centrifugal saccades have smaller gains and are slower than centripetal saccades elicited by the same target amplitude. We determined whether internally triggered saccades, e.g. scanning or memory saccades, exhibit the orbital position dependency evident in visually guided saccades. The search coil technique was used to record eye movements of healthy subjects while they performed horizontal 12.5 degree saccades under three paradigms (gap, scanning and memory saccades). Orbital position influenced externally triggered gap saccades but not the gain or peak eye velocity of scanning or memory saccades. These findings do not support the idea that position dependency caused by orbital mechanics is compensated for at the level of the common brainstem burst generator. Instead our results are consistent with the view that cortical output reflects the differences evident in the gain of visually triggered centrifugal and centripetal saccades.

Adult↗
PubMed1999

Influence of visual and proprioceptive afferences on upper limb ataxia in patients with multiple sclerosis.

Our objective was to investigate how cooling of the arm and vision influence pointing movements in healthy subjects and patients with cerebellar limb ataxia due to clinically proven multiple sclerosis. An infrared video motion analysis system was used to record the unrestricted, horizontal pointing movements toward a target under three different conditions involving a moving, stationary, or imaginary target; a visual, or acoustic trigger; and vision or memory guidance. All three tasks were performed before and after cooling the arm in ice water. Patients had more hypermetric and slower pointing movements than controls under all tested conditions. Patients also had significantly larger three-dimensional finger sway paths during the postural phase and larger movement angles of the wrist joint. Memory-guided movements were the most hypermetric recorded in both groups. Cooling of the limb had no effect on amplitude or peak velocity of the pointing movement in either group under all tested conditions, but significantly reduced the three-dimensional finger sway path during the postural phase in patients with limb ataxia. Cooling-induced reduction of the finger sway was largest in those patients with the largest finger sway before cooling. In conclusion, the cooling-induced reduction of the proprioceptive afferent inflow, most probably of group I spindle afferents, reduces postural tremor of patients with cerebellar dysfunction.

Adult↗
PubMed1999

[A rare headache syndrome. SUNCT syndrome, hemicrania continua and red ear syndrome].

Rare headache syndromes that are so fare not yet admitted to the classification system of the International Headache Society are the SUNCT syndrome (short-lasting, unilateral, neuralgiform headache attacks with conjunctival injection and tearing), the hemicrania continua and the red ear syndrome. The clinical characteristics, differential diagnoses and therapeutic strategies of these pathophysiologically unclarified diseases are presented with three casuistic reports.

Aged↗
PubMed1999

Intrasaccadic target steps during the deceleration of primary saccades affect the latency of corrective saccades.

This study investigates how visually guided saccades and subsequent corrective saccades are affected by a secondary target step occurring at different times during the primary saccade. Eye movements of human subjects were measured by means of a differential infrared light reflection technique while the subjects performed visually guided saccades to a laser spot in darkness. The target was stepped backward or onward during the targeting saccade. While the intrasaccadic target step did not influence gain, peak velocity or skewness of the primary saccade, it had a significant effect on the subsequent corrective saccade when the secondary target step occurred during the deceleration phase of the primary saccade: the latency of the corrective saccade was significantly increased compared with the one performed under the single-step control condition. This increase also occurred when single target steps were presented randomly intermixed with backward and onward double target steps and even between selected sub-samples of saccades with identical postsaccadic visual error. If the target step occurred early during the primary saccade, the latency of the corrective saccade was not changed. This indicates that visual information sampled during the deceleration phase of a saccade can lead to a cancellation of the normal trigger mode of corrective saccades.

Deceleration↗
PubMed1999

Internally and externally guided voluntary saccades in unmedicated and medicated schizophrenic patients. Part I. Saccadic velocity.

Saccadic eye movements were elicited in 30 schizophrenic patients before and in 17 of these 30 during antipsychotic treatment with neuroleptics, and compared with those of 12 age-matched controls under three different conditions: (a) the gap paradigm, which tests the visually triggered and visually guided saccades; (b) the anti-task paradigm, which tests the internally guided, visually triggered saccades; and (c) the memory paradigm, which tests the internally triggered and guided saccades. Eye movements were recorded by DC electro-oculography, and the peak eye velocities for the different saccades were calculated. We found that antipsychotic treatment with neuroleptics reduces the peak saccadic eye velocity. This effect is larger for internally guided saccades than for externally triggered and guided eye movements. The saccadic velocity of the unmedicated schizophrenic patients did not differ from that of the controls. Since patients with diseases of the basal ganglia primarily show abnormalities of the internally guided and triggered saccades, our findings indicate that neuroleptics influence the oculomotor loop through the basal ganglia and that this loop, by means of neuroleptic influence on the brainstem saccadic burst generator, also influences the peak velocity of the internally guided saccades. This contradicts the current idea of the role of the cortical input to the brainstem saccadic burst generator, which is thought to not be involved in the determination of saccadic velocity.

Adult↗
PubMed1999

Internally and externally guided voluntary saccades in unmedicated and medicated schizophrenic patients. Part II. Saccadic latency, gain, and fixation suppression errors.

Saccades were elicited in 30 schizophrenic patients before medication, in 17 of them during medication with neuroleptics, and in 12 healthy controls using six paradigms that tested different types of saccades: (a) the externally triggered and visually guided saccades; (b) the externally triggered and internally guided saccades (anti-saccades); and (c) the internally triggered and internally guided saccades (memory-guided saccades). Latency of the primary saccade, gain (eye amplitude to target amplitude), and percentage of unwanted saccades (fixation suppression errors) were calculated. The externally triggered and externally guided saccades were only slightly affected in the patients, indicating that the function of parieto-tectal pathways was preserved. In contrast, the internally guided and externally triggered saccades showed abnormally long latencies, slightly smaller gains, and an increased rate of suppression errors regardless of the medication status. These findings were even more pronounced in the internally triggered and internally guided saccades such as memory-guided saccades. According to animal experiments and studies on patients with disorders of the basal ganglia, the performance of these saccades is based on the function of the pre- and dorsolateral frontal cortex and its connections to the basal ganglia. The minimal improvement of some of the parameters after clinical improvement and during treatment with neuroleptics suggests that the eye-movement deficits are associated with abnormalities of schizophrenia, which do not basically change under medication with neuroleptics. The observed effects of neuroleptics also argue against a primary abnormality in the dopaminergic input to the frontal cortex - basal ganglia oculomotor loop and support the view that there is a primary disturbance of the cortical input to the oculomotor loop through the basal ganglia in schizophrenics.

Adult↗
PubMed1999

The criteria of the International Headache Society for Tolosa-Hunt syndrome need to be revised.

In 1988 the International Headache Society defined the diagnostic criteria of Tolosa-Hunt syndrome (THS) to include episode(s) of unilateral orbital pain for an average of 8 weeks if untreated, with associated paresis of one or more of the third, fourth, and sixth cranial nerves. Cranial nerve paresis may coincide with the onset of pain or follow it within a period of up to 2 weeks, and the pain must be relieved within 72 h after the initiation of corticosteroid therapy. Other causative lesions must be excluded by neuroimaging. On the basis of the history and neuroradiological findings of six patients we show the pitfalls in diagnosing THS with these criteria. We propose a revision of the criteria: Other causative lesions must be excluded by neuroimaging, especially of the region of the cavernous sinus and the orbita, and by blood and CSF examinations. Since imaging techniques have dramatically improved, it is now possible to visualize the inflammatory tissue in THS. Positive magnetic resonance imaging or computed tomography findings compatible with inflammatory tissue neither exclude nor confirm THS and remain suspect until a malignant tumor or inflammation other than THS is excluded. Clinical and radiological follow-up examinations must be performed for at least 2 years, even in patients with negative findings on magnetic resonance imaging at onset.

Adult↗
PubMed1999

Muscle and skin biopsies are a sensitive diagnostic tool in the diagnosis of CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a microangiopathic syndrome. Although the defective gene has been identified, genetic analysis may be effort some due to its large size and various mutations. Providing a reliable diagnostic marker would therefore be helpful. Electron microscopy has revealed characteristic electron-dense granular deposits in the basal lamina of vessels of patients with CADASIL. We investigated the sensitivity of skin and muscle biopsies for diagnosing CADASIL. We examined 30 family members of three unrelated German families affected by CADASIL. In 14 of the 21 affected individuals we performed skin and muscle biopsies; two patients were clinically asymptomatic. Under electron microscopy all muscle and skin biopsy specimens showed patches of granular and electron-dense material in the basal layer of both arterioles and capillaries. These findings confirm that general microangiopathy is a typical feature of this syndrome and is present in the early phase of the disease with or without clinical manifestation. Thus, as electron microscopy of skin biopsy specimens can establish the diagnosis of CADASIL with high certainty, it may be considered the method of first choice.

Adult↗
PubMed1999

Different postural reaction patterns for expected and unexpected perturbations in patients with idiopathic Parkinson's disease and other parkinsonian syndromes.

Different postural reaction patterns after predictable and unpredictable perturbations during free stance were studied in 8 patients with idiopathic Parkinson's disease (iPD), in 4 patients with other parkinsonian syndromes (PS) and in 5 healthy controls. First, the amplitude of leaning maximally backward and forward was measured (condition I). Secondly, the body equilibrium was disturbed by self-paced, predictable, rapid arm elevations (condition II) and by sudden unpredictable toe-down and toe-up rotations of a supporting platform (condition III). Patients with PS particularly had difficulties in regaining body equilibrium after unexpected perturbations. In controls and patients with PS, unpredictable disturbances were better compensated in toe-down than in toe-up direction, whereas the opposite was true for patients with iPD. These results correspond to the fact that patients with PS had a specific leaning-backward impairment and patients with iPD, a leaning-forward impairment. The authors conclude that the differences in postural stability between patients with iPD and PS are caused by different pathophysiological mechanisms. These differences in postural stability could serve as an additional tool for differential diagnosis.

Aged↗
PubMed1999

T-cell subsets and expression of integrins in peripheral blood of patients with migraine.

Neurogenic inflammation is considered as an animal model of human migraine attacks. Using flow cytometry, we examined T-cell subsets and their integrin expression in the peripheral blood of 32 migraine patients in order to evaluate a possible inflammatory process in humans, as postulated in the migraine animal model. Our results show that migraine patients have a significant increased proportion of T-helper (47.4 +/- 6.3% vs 43.2 +/- 5.8%; p < 0.01) and T-helper memory cells (23.6 +/- 5.9 vs 20.3 +/- 6.5%; p < 0.01). Moreover, the 22 migraine patients without aura also exhibited an increase of LFA-1 expression of T-helper cells (34.7 +/- 11.5%) compared to the 35 controls (27.5 +/- 12.0%; p < 0.01). These preliminary results support the hypothesis that immunological mechanisms (such as an enhanced lymphocyte endothelium interaction) could be part of the migraine pathophysiology in humans.

Adult↗
PubMed1999

Angiitis of the central nervous system after allogeneic bone marrow transplantation?

BACKGROUND AND PURPOSE: There is only limited information about late neurological complications after bone marrow transplantation (BMT). The purpose of this study is to describe a cerebral angiitis-like syndrome after allogeneic BMT. METHODS: Clinical and diagnostic findings of 5 BMT patients with chronic graft versus host disease and neuropathological data of 1 patient were reported. RESULTS: In the described patients, focal neurological signs and neuropsychological abnormalities occurred years after BMT. MRI revealed periventricular white matter lesions, lacunar or territorial infarctions, leukoencephalopathy, and hemorrhages. Angiitis of the central nervous system was confirmed in 1 patient at autopsy, and an angiitis-like syndrome was suspected in the other patients because of the clinical course and response to treatment. Three patients received cyclophosphamide and steroids (2 improved, 1 died), 1 patient improved after steroids alone, and 1 patient without immunosuppressive therapy deteriorated further. CONCLUSIONS: We propose that an angiitis-like syndrome of the central nervous system can be a neurological manifestation of graft versus host disease, which should be considered a possible cause of cerebral ischemic episodes and pathological MRI scans in BMT patients with graft versus host disease.

Adult↗
PubMed1999

Characteristic MR lesion pattern and correlation of T1 and T2 lesion volume with neurologic and neuropsychological findings in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathy related to a genetic defect of the notch 3 gene on chromosome 19. The purpose of this study was to evaluate lesion distribution and volume using MR imaging and to correlate the lesion volume with the neurologic and neuropsychological findings. METHODS: Twenty members of two families (14 with CADASIL as determined by linkage analysis, six healthy) were studied with MR imaging. Two observers evaluated the MR findings semiquantitatively and quantitatively. MR results were then correlated with neurologic and neuropsychological findings. RESULTS: A typical pattern of lesion distribution in patients with CADASIL was found: the frontal lobe was the site with the highest lesion load, followed by the temporal lobe and the insula. The total lesion volume on T1-weighted MR images correlated significantly with the degree of disability and the degree of impairment in neuropsychological functions (including attention, memory, and conceptual and visuospatial functions). CONCLUSION: In CADASIL patients, a common pattern of cerebral lesion distribution is found. The total T1 lesion volume is an important parameter to correlate with disability, as it may prove to be helpful in predicting the natural history of the disease.

Adult↗
PubMed1998

Neurological and neuroradiological findings in long-term survivors of allogeneic bone marrow transplantation.

The aim of this study was to assess neurological, neuropsychological, and neuroradiological findings in long-term survivors of allogeneic bone marrow transplantation (BMT) who were recruited from a hematological outpatient clinic. In addition, risk factors for the development of late neurological complications were identified. In contrast to previous studies on autopsied patients, our study design provoked a bias away from increased neurological sequelae, because patients with early complications after BMT were excluded. Fifty-nine allogeneic patients and 7 autologous BMT patients underwent clinical examination, short neuropsychological testing, and cranial magnetic resonance imaging (MRI) 34 +/- 26 months after BMT. The pathological results of the neurological examination (abnormal 64%) and the MRI examination (white matter lesions, 54%; atrophy, 11%) were associated with the occurrence of chronic graft-versus-host disease (GvHD) evolving from acute GvHD, with corticosteroid therapy and with cyclosporine medication. Neuropsychological impairment (cognitive deficits, 37%) was associated with long-term cyclosporine medication and age. No influence of pre-BMT disease, BMT donor status, or the conditioning regimen was found. These results suggest that the frequent neurological abnormalities in long-term survivors of allogeneic BMT are associated with chronic GvHD and with the resulting immunosuppression as major risk factors.

Adult↗
PubMed1998

Prediction and a stationary, structured visual background influence the dynamics of the smooth-pursuit offset in humans.

It is still not clear whether the transition from pursuit eye movements to fixation is mediated by the same system that initiates pursuit, or whether another system, a specialized fixation system, is responsible. To investigate this question we measured smooth-pursuit eye movements and smooth-pursuit termination in five normal subjects using both predictable and unpredictable step-ramp stimuli (velocities 10 degrees and 20 degrees/s) in front of a homogeneous and a structured visual background in order to compare the profile of eye velocity under these different conditions. With the predictable and/or structured visual background there was a gradual transition of eye velocity toward zero. In contrast, with the unpredictable stimulus in front of a homogeneous background, eye velocity during the offset was characterized by an overshoot (on the average, 2.2+/-1.0 degrees/s for 10 degrees/s ramps) before eye velocity settled at zero. Under this condition, steady-state velocity gain and the deceleration of the offset were significantly higher than during the other paradigm with the same target velocity. The latency of the pursuit offset was significantly shorter when a predictable stimulus was used. The duration of the offset did not depend on the experimental condition used. These findings imply that the pursuit onset and offset have some similarities and may be mediated by the same oculomotor system.

Adult↗
PubMed1998

Electrical stimulation of the posteroventral pallidum influences internally guided saccades in Parkinson's disease.

Chronic electrical stimulation of the posteroventral internal pallidum, a recently developed treatment option in advanced Parkinson's disease (PD), improves bradykinesia, rigidity and medication-induced dyskinesia. Apart from disturbances of the somatic motor system, PD is also characterized by disturbances of saccadic eye movements with hypometric and delayed internally guided saccades. We examined these internally guided eye movements (memory-guided and anti-task saccades) in a patient with bilaterally implanted stimulation electrodes, when stimulation was turned on and off. The electrical stimulation not only improved the bradykinesia and rigidity, but also the internally guided saccades by shortening the latency of the anti-saccades and increasing the gain of the memory-guided saccades. This finding supports the idea that the oculomotor pathways through the basal ganglia are organized like the somatic motor pathways and that stimulation of the posteroventral pallidum influences both.

Electric Stimulation↗