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Biomedical subjects

D Kömpf

Publications and source records attributed to D Kömpf.

At least 55 records · Page 3Linked to original sources
PubMed1996

[See-saw nystagmus. Clinical aspects, diagnosis, pathophysiology: observations in 2 patients].

See-saw nystagmus is an uncommon but characteristic kind of nystagmus. Typically there is intorsion and elevation of one eye and simultaneous extorsion and depression of the other eye. The nystagmus can be of pendular-waveform or jerk-waveform. The pendular-waveform see-saw nystagmus is commonly due to a midline meso-diencephalic, bilaterally compressing mass. The jerk-waveform see-saw nystagmus is mostly due to a unilateral lesion in the meso-diencephalic junction. For explanation, a current theory assumes a unilateral lesion of the interstitial nucleus of Cajal sparing the rostral interstitial nucleus of the medial longitudinal fascicle. Another concept suggests a lesion of the vertical vestibulo-ocular-reflex. We report two patients with jerk-waveform see-saw nystagmus. In both patients an internuclear ophthalmoplegia was found additionally. The origin was a unilateral brainstem infarction in both cases. We explain the symptomatology of see-saw nystagmus and discuss the actual theories of its origin.

Brain Mapping↗
PubMed1995

Double-blind crossover study with levorotatory form of hydroxytryptophan in patients with degenerative cerebellar diseases.

OBJECTIVE: To determine whether treatment with the levorotatory form of hydroxytryptophan (L-5-hydroxytryptophan), a controversial experimental drug, can improve the conditions of patients with ataxia. DESIGN: A double-blind crossover study with the levorotatory form of hydroxytryptophan was performed in 39 patients with degenerative cerebellar diseases. SETTING: Patients were selected from an ongoing prospective follow-up study at two university hospitals. PATIENTS: We studied 19 patients with Friedreich's ataxia, 13 with cerebellar atrophy, and seven with olivoponto-cerebellar atrophy. INTERVENTION: The levorotatory form of hydroxytryptophan was given orally in a dose of 1000 mg/d. Each treatment phase, with the levorotatory form of hydroxytryptophan or the placebo, lasted 10 months, after which the treatment of patients was crossed over to the other phase. MAIN OUTCOME MEASURES: Ataxia was documented and quantified by using a clinical score, posturography, and measurement of grip force and the rapid-syllable repetition rate. RESULT: The levorotatory form of hydroxytryptophan had no significant effect on cerebellar symptoms. CONCLUSION: Long-term treatment with a high dose of the levorotatory form of hydroxytryptophan does not improve the conditions of patients with ataxia.

5-Hydroxytryptophan↗
PubMed1995

Cortical control of double-step saccades: implications for spatial orientation.

To accurately localize a visual target in space despite eye movement-induced shifts of its retinal image, the brain must take into account both its retinal location and information about current eye position or at least the preceding eye displacement. We examined this ability with respect to saccadic eye movements by applying "double-step" stimuli, where the locations of two sequentially flashed target lights have to be fixated by two successive saccades performed after their disappearance. As the 2nd saccade will not start at the spatial location from which the 2nd target was seen, a dissonance arises between its retinal coordinates and the motor coordinates of the required 2nd saccade. Nevertheless, these saccades were performed quite accurately by 32 healthy human adults. To investigate the contribution of the cerebral cortex, we recorded horizontal double-step saccades in 35 patients with focal unilateral hemispheric lesions. Whereas frontal lesions impaired temporal properties, posterior parietal lesions caused spatial dysmetria or failure of even ipsiversive 2nd saccades following contraversive 1st saccades. This reflects an inability to compensate for retinospatial dissonance by using nonretinal information (corollary discharge) about eye displacement associated with a previous saccade into the contralesional hemifield. In conclusion, the parietal cortex is crucial for spatial constancy across saccades.

Adult↗
PubMed1995

Ultrasound for the assessment of the embolic risk of carotid plaques.

In a prospective study we compared duplex-ultrasound characteristics of symptomatic internal carotid artery (ICA) stenoses with cranial computerized tomographic (CCT) findings in 82 patients suffering from completed or transient middle cerebral artery symptoms. The aim was to assess the pathogenic role of ICA plaque morphology and the potential embolic risk of ICA plaques. The degree of carotid stenosis was estimated by spectral analysis of the pulsed Doppler signal. The CCT findings were classified as being either normal, lacunar lesions, hemodynamically induced low-perfusion infarctions, or territorial embolic infarctions. According to their ultrasonic features we characterized the ICA plaque surface as smooth or irregular and their structure as homogeneous or heterogeneous. Plaques with an irregular surface and heterogeneous echogenicity dominated significantly in CCT-territorial infarctions (p < 0.01), whereas hemodynamically induced low-perfusion infarctions showed no relationship with any plaque characteristic. High degree ICA stenoses (> 50%) dominated in both territorial infarctions and low-perfusion infarctions, as compared to ipsilateral normal CCT or lacunes (p < 0.05). Normal CCT and lacunar infarctions were associated with homogeneous and smooth plaques (both p < 0.05). We conclude that > 50% ICA stenoses can cause both hemodynamically induced low-perfusion infarctions as well as thromboembolic territorial infarctions, whereas ulcerated and heterogeneous plaques constitute a high risk factor for arterio-arterial embolic stroke. Furthermore, carotid ultrasound may help to estimate the clinical significance of carotid lesions.

Adult↗
PubMed1994

The presaccadic cortical negativity prior to self-paced saccades with and without visual guidance.

The presaccadic negativity (PSN) of the scalp EEG potential prior to self-initiated saccades aimed either at a visual target or at the remembered position of that target in total darkness was analysed in 10 normal subjects. Under both conditions a PSN with a negligible EOG contamination was found, showing 4 characteristics: (1) In both conditions, the PSN maximum is localized at the vertex, probably containing the activity of the supplementary motor area. (2) At an electrode placed over the frontal eye field (FEF) contralateral to the saccade direction, there is a temporary, circumscribed maximum prior to saccades to the visual target, thus probably reflecting activity of the FEF. (3) Prior to saccades to the visual target, there is a statistically significant interhemispheric difference of the PSN over the parietal cortex with a larger amplitude over the hemisphere contralateral to the saccade direction; this might be attributed to directed visual attention. (4) Prior to saccades without visual guidance in darkness there is a statistically significant interhemispheric difference of the PSN over the frontal cortex with a larger amplitude over the hemisphere contralateral to the saccade direction. The amplitude of the PSN decreased in the course of the experiment, probably due to psychological factors such as attention and motivation. Our results suggest that the PSN is a readiness potential preceding voluntary saccades, containing activity related both to unspecific psychological processes and to specific movement preparation in the frontal and parietal ocular motor areas.

Adult↗
PubMed1994

Movement-related cortical potentials preceding sequential and goal-directed finger and arm movements in patients with cerebellar atrophy.

To determine the influence of cerebellar involvement on the preparatory state of the cerebral cortex for voluntary movements, we studied the movement-related cortical potentials (Bereitschaftspotential, BP) preceding sequential and goal-directed finger and arm movements in patients with cerebellar atrophy (CA). The first task (paradigm 1) consisted of a sequential finger movement at a self-paced rate of every 3 sec or longer, in which patients and control subjects pushed rapidly 7 keys on a keyboard in a sequence visually predetermined on a screen. The second task (paradigm 2) consisted of a goal-directed self-paced movement with visual feedback on a screen. In both paradigms, control subjects and patients had distinct movement-related cortical potentials, but peak amplitudes (close to movement onset) were reduced in the patient group (paradigm 2), whereas in the overall analysis the mean amplitude 600-800 msec before movement onset (NS1) was larger in the patient group (paradigms 1 and 2). Accordingly, the difference (NS2) between peak amplitude and NS1 was smaller in the patient group (paradigms 1 and 2). Whereas control subjects' peak amplitude (paradigm 2) and NS2 (paradigm 1) were focused at Cz, this topographical differentiation was abolished in the patient group. The onset of the BP was earlier in the patients than in the control subjects (paradigms 1 and 2). Our results suggest that pathways from the cerebellum to the cortex do play a role in generating movement-related cortical potentials. A strong input from the cerebellum seems to be crucial for the generation of a normal motor potential close to the movement onset, reflecting a specific deficit in patients with CA. Patients with CA may try to compensate for their motor deficits by a longer cortical activation preceding voluntary movements (earlier onset of the BP). The increased NS1 could be the result of larger effort, by which patients try to compensate for their motor deficits as well.

Adult↗
PubMed1994

Reduction of P3b in patients with temporo-parietal lesions.

By recording event-related EEG potentials from patients with frontal, parietal, or temporo-parietal lesions, we wanted to determine the cortical area that is relevant to the P3b component, replicating the approach used by Knight and associates who found reduced P3bs in patients with temporo-parietal lesions. They used auditory and somatosensory stimuli. We wanted to replicate their findings in auditory and visual oddball tasks and analysed potentials evoked by targets and by standard stimuli. Temporo-parietal patients' P3bs were reduced with auditory targets and lacked a distinct Pz maximum with visual targets. Further, auditory N1 was reduced both with targets and standards, P3 to visual standards and P2 to auditory standards were reduced. Parietal patients' P3bs differed only slightly from the control group, being somewhat reduced over the lesioned hemisphere with visual stimuli. Their P3 to visual standards was, however, reduced to the same extent as was the temporo-parietal patients'. Frontal patients did not differ from the control group both in their P3b and in their P3 to standards but had a number of conspicuous features in modality-specific components. In sum, our results on P3b (as well as on N1) replicate Knight's findings, confirming his conclusion that integrity of the temporo-parietal junction is critical for P3b. Implications for hypotheses on P3 are discussed.

Acoustic Stimulation↗
PubMed1994

Auditory selective attention is impaired in Parkinson's disease--event-related evidence from EEG potentials.

Selective attention refers to the ability to focus on one channel of information in the presence of distracting other channels. For the visual modality, results on impairments of selective attention have been conflicting in patients with idiopathic Parkinson's disease (PD). Independent of possible interferences from visual or movement disturbances selective attention can be measured as the so-called 'processing negativity' (PN) using auditory evoked potentials. Therefore, auditory selective attention with the PN was measured in 14 patients with PD and 16 control subjects. Subjects had to attend to tones presented to one ear (i.e. to press a button to occasionally presented longer tones) and ignore tones presented to the other ear. Tones were presented at a rate of 1/s ('slow') or 2/s ('fast'). PN was measured as the difference of the potentials evoked by attended minus ignored standard tones. PN was significantly smaller in the PD patients than in the controls with slow presentation. There was no difference between both groups with fast presentation. PN remained unchanged when patients had a 12-h withdrawal of their usual anti-Parkinsonian drug therapy. PD patients and controls did not differ in their P3 component evoked in the usual 'oddball' task nor in the mismatch negativity evoked by the occasionally longer tones in the PN task. The results provide evidence for an impairment of auditory selective attention that is specific for patients with PD (i.e. independent of the P3 component).

Acoustic Stimulation↗
PubMed1994

Thalamic stroke: correlation of clinical symptoms, somatosensory evoked potentials, and CT findings.

We studied 18 patients with a single ischemic thalamic lesion, who had somatosensory disturbances and/or central pain in the opposite hemibody, by correlating their clinical symptoms, somatosensory evoked potentials (SEPs), and computed tomography (CT) findings. Patients were divided into three groups: (1) those with somatosensory deficits, central pain, and abnormal SEPs, which comprised two thirds of the patients (classic thalamic pain syndrome), (2) those with somatosensory deficits, no central pain, and abnormal SEPs (analgetic thalamic syndrome), and (3) those with almost normal sense perception, central pain, and normal SEPs (pure algetic thalamic syndrome). CT evidence of a paramedian or anterolateral thalamic lesion might be an indicator for the development of central pain, because these types of infarctions occurred only in patients with the classic thalamic syndrome or the pure algetic thalamic syndrome. The differentiation of the thalamic syndrome into three subtypes is of prognostic value, because patients with a loss of cortical SEPs and a posterolateral ischemic thalamic lesion on the CT scan probably will not exhibit central pain.

Aged↗
PubMed1994

Differences in P3 amplitudes between schizophrenics and healthy controls vary between the different events presented in a guessing task.

P3 amplitudes were often found to be reduced in schizophrenics, but in varying degree. We studied in a guessing task whether variations of group differences could even be obtained within the same task, by measuring P3 in the potentials evoked by the three qualitatively different events that occurred in each trial. We hypothesized that such variations were due to variations of subjective task relevance associated with each event. In each trial, a light or a sound was presented. Subjects had to confirm this 'primary event' by a delayed response, and then the current amount of money earned by correct responses was displayed. In the certain condition, the primary event was preceded by the appropriate cue on the screen ('light' or 'sound') whereas in the uncertain condition, the word 'guess' appeared. The task-relevance hypothesis predicted that schizophrenics would have smaller P3s than the control group with the primary event in the uncertain condition, but that the groups would not differ for the P3s evoked by the other events (certain primary event, cue and earnings display in uncertain and certain conditions). Essentially, this predicted pattern of results was obtained, but additional assumptions are needed for the task-relevance hypothesis to account for the precise pattern of results. Analysis of subjects' guessing behavior showed that control subjects' guesses were affected by the outcome of their preceding guesses while schizophrenics' guesses were not. This result provides some additional support for the hypothesis that the guessing task is less relevant to schizophrenics than to control subjects.

Adult↗
PubMed1994

[Psychiatric comorbidity in dissociative disorders in neurology].

We studied consecutively 50 neurologic inpatients of a university neurological department with dissociative (conversion) disorders with regard to their associated psychopathologic features as well as to their comorbidity. The study involved both self-measuring instruments and a standardized psychiatric interview. As a result patients with conversion disorders appeared as a psychopathologic highly disturbed group. We found that although the dissociative symptoms are phenomenological very predominant and were the reason for hospital admission in all cases, they must be interpreted as accompanying features in the context of complex psychiatric disorders. Diagnostic and therapeutic consequences are discussed with regard to the neurology.

Adolescent↗
PubMed1994

[Stiff-man syndrome. Report of 4 cases].

Four patients are presented who exhibited progressive muscular rigidity in both legs, the thoracolumbar, paraspinal and the abdominal muscles. In only one patient, there was an initial involvement of the shoulder girdle muscles. Electromyography in all four patients at rest recorded continuous electric activity resembling an interference pattern. Following sudden exteroceptive stimuli the activity increased in amplitude and density this corresponded clinically to painful spasms. All patients had oligoclonal banding in CSF. In the serum and CSF of three patients IgG subtype autoantibodies were detected. These have been found to be directed against GABAergic nerve terminals in the rat and human cerebellum and, more specifically, to glutamic acid decarboxylase. All patients improved on clonazepam. Trials of intermittent high-dose methylprednisolone administration gave relief from rigidity in one patient and permitted reduction of clonazepam in another. Intravenous immunoglobulins however had no effect in one patient.

Adult↗
PubMed1994

[Effect of low dose alcohol concentration on saccadic eye movements. Infrared reflection technique for recording oculomotor reactions with reference to dangerous traffic situations].

Saccadic eye movements were registered under different ethanol concentrations (0 g/kg, 0.5 g/kg, 1.0 g/kg) using an infrared reflexion method. On the basis of photographic pictures conflict situations of a car driver were simulated. 12 young car drivers were exposed for 10 sec to four pictures, all under different ethanol concentrations. The eye movements were registered and analyzed by a computer. The amplitude of saccades, their number, duration and velocity as well as the points of fixation and the scanning of the pictures were qualitatively and quantitatively analyzed. All persons demonstrated deficits in all parameters under 1 g/kg blood ethanol concentration. Nearly all results were reduced under 0.5 g/kg in comparison to 0 g/kg situation. In conclusion, low dose ethanol influence the saccadic eye movements. On the other hand the study could demonstrate a new technique (infrared reflexion technique), which allows the qualitative and quantitative recording of the influence of ethanol as well as peripheral as cortical structures of the brain. The exposition to photographic pictures demonstrating dangerous traffic situations simulate real traffic situations and allows to transfer the laboratory results to real situations.

Adult↗
PubMed1993

Thrombosis of the right vein of Labbé: radiological and clinical findings.

A rare case of aseptic thrombosis of the right vein of Labbé in a young woman is reported. Cerebral venous thrombosis was suggested by computed tomography and confirmed by angiography. Mild left-sided neurological deficits resolved almost completely. The combination of a nonspecific clinical picture with an atypical lesion on CT may favour the diagnosis of cortical venous thrombosis.

Adult↗