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R Töpper

Publications and source records attributed to R Töpper.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cortical activation patterns during complex motor tasks in piano players and control subjects. A functional magnetic resonance imaging study.

We performed functional magnetic resonance imaging (MRI) in professional piano players and control subjects during an overtrained complex finger movement task using a blood oxygenation level dependent echo-planar gradient echo sequence. Activation clusters were seen in primary motor cortex, supplementary motor area, premotor cortex and superior parietal lobule. We found significant differences in the extent of cerebral activation between both groups with piano players having a smaller number of activated voxels. We conclude that, due to long-term motor practice a different cortical activation pattern can be visualized in piano players. For the same movements lesser neurons need to be recruited. The different volume of the activated ortical areas might therefore reflect the different effort necessary for motor performance in both groups.

Adult↗
PubMed2000

Influence of stimulus control on the excitability of the electrically elicited blink reflex in patients with schizophrenia.

BACKGROUND: In humans, the excitability of the electrically evoked blink reflex is influenced by the subject's attention to the stimulus. The early reflex component R1 has been found to be facilitated in conditions of increased selective attention, whereas the late components R2 and R3 exhibited a marked suppression. Distraction from the stimulus leads to enhanced R2 and R3 magnitudes. METHODS: We investigated the excitability of the distinct reflex components in 19 patients with schizophrenia and 19 healthy control subjects. In the control condition (EE), stimulation was elicited by the experimenter; in a second condition (SE), subjects released a key to evoke the reflex themselves. RESULTS: The SE patients with schizophrenia exhibited an abnormally increased R1 facilitation and an impaired R2 inhibition in comparison with normal control subjects. An R3 component could be registered in EE in 13 of 19 patients but only in one control subject; SE resulted in a complete suppression of this component in all but two patients with schizophrenia. CONCLUSIONS: The abnormal R1 facilitation and the impaired R2 inhibition may be regarded as neurophysiological markers of defective information processing in a condition of increased selective attention to a self-controlled stimulus in patients with schizophrenia. The enhanced excitability of the R3 component under standard conditions indicates defective attentional mechanisms in patients with schizophrenia in an uninstructed passive condition attending a stimulus triggered by the experimenter.

Adult↗
PubMed2000

Sleep stage dependant changes of the high-frequency part of the somatosensory evoked potentials at the thalamus and cortex.

OBJECTIVES: It is known that the high-frequency oscillations (above 400 Hz) of the somatosensory evoked potentials (SEPs) diminish during sleep while the N20 persists (Neurology 38 (1988) 64; Electroenceph clin Neurophysiol 70 (1988) 126; Electroenceph clin Neurophysiol 100 (1996) 189). We investigated possible differential effects of sleep on the 600 Hz SEPs at the thalamus and cortex. METHODS: SEPs from 10 subjects were recorded using 64 channels following electric stimulation at the wrist during awake state and sleep stages II, IV and REM. Dipole source analysis was applied to separate brain-stem, thalamic and cortical activity in the low-frequency (20-450 Hz) and the high-frequency (450-750 Hz) part of the signal. RESULTS: The low-frequency SEPs showed a non-significant increase of the latency of the N20 and a bifid change of the waveform in 3 subjects. The high-frequency SEPs showed a significant decrease of their amplitude at the level of the thalamus and cortex but not at the brain-stem. This decrease in amplitude at the thalamus and cortex were significantly correlated. There was no effect on the latency of the signal. In addition, at the cortex, differential effects on early and late parts of the 600 Hz oscillations were found by time-frequency analysis using a wavelet transformation. CONCLUSIONS: Sleep dependent decrease of the high-frequency SEPs were first observed at the thalamus pointing to the known function of the reticular thalamic nucleus regulating arousal. The results presented here provide further evidence for a thalamic origin of the 600 Hz oscillations. In addition, on the basis of the differential effects on early (up to the N20 peak) and late (between 20 and 25 ms) parts of the signal, at least one intracortical generator of these oscillations is proposed. In general, the high-frequency SEPs (600 Hz oscillations) are supposed to reflect activity of a somatosensory arousal system.

Adult↗
PubMed2000

[Recurrent dreams as migraine aura symptoms].

Elementary geometric imagery seen in the visual aura of migraine can be experienced as incorporated into the content of a dream which precedes the awakening with a migraine headache. Furthermore, recurrent dreams featuring complex visual imagery, often terrifying nightmares, can occur as migraine aura symptoms. The said phenomena are illustrated by two original case reports and discussed against the background of a review of the literature.

Aged↗
PubMed1999

Facilitation of picture naming after repetitive transcranial magnetic stimulation.

OBJECTIVE: To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on picture naming. BACKGROUND: Previous studies have shown that rTMS disrupts ongoing speech processes when delivered over frontal or parietal areas of the dominant hemisphere. METHODS: In 15 healthy right-handed male individuals, rTMS trains of 20 Hz with a duration of 2 seconds and an intensity of 55% of maximum stimulator output were delivered either to Wernicke's area, to the right-hemisphere homologue of Wernicke's area, to Broca's area, or to the primary visual cortex. Twenty black-and-white line drawings, which the individuals had to name as quickly as possible, were shown immediately after the completion of rTMS and again 2 minutes later. RESULTS: Immediately after the end of a train over Wernicke's area a shortening of naming latency was observed compared with naming without rTMS (p < 0.001). No significant effects on picture naming were observed 2 minutes later or at any time after stimulation of the right-hemisphere homologues of Wernicke's area, Broca's area, or the visual cortex. CONCLUSION: Repetitive transcranial magnetic stimulation over Wernicke's area leads to a brief facilitation of picture naming by shortening linguistic processing time.

Adult↗
PubMed1999

Pathophysiology of chorea and bradykinesia in Huntington's disease.

This article reviews the neurophysiological abnormalities described in Huntington's disease. Among the typical features of choreic movements are variable and random patterns of electromyographic (EMG) activity, including cocontraction of agonist and antagonist muscles. Studies of premotor potentials show that choreic movements are not preceded by a Bereitschaftspotential, therefore demonstrating that choreic movement is involuntary. Early cortical median-nerve somatosensory-evoked potentials have reduced amplitudes and the reduction correlates with reduced glucose consumption in the caudate nucleus. Long-latency stretch reflexes evoked in the small hand muscles are depressed. These findings may reflect failed thalamocortical relay of sensory information. In Huntington's disease, the R2 response of the blink reflex has prolonged latencies, diminished amplitudes, and greater habituation than normal. These abnormalities correlate with the severity of chorea in the face. Patients with Huntington's disease perform simple voluntary movements more slowly than normal subjects and with an abnormal triphasic EMG pattern. Bradykinesia is also present during their performance of simultaneous and sequential movements. Eye movements show abnormalities similar to those seen in arm movements. In Huntington's disease, arm movement execution is associated with reduced PET activation of cortical frontal areas. Studies using transcranial magnetic stimulation show that patients with Huntington's disease have normal corticospinal conduction but some patients have a prolonged cortical silent period. Bradykinesia results from degeneration of the basal ganglia output to the supplementary motor areas concerned with the initiation and maintenance of sequential movements. The coexisting hyperkinetic and hypokinetic movement disorders in patients with Huntington's disease probably reflect the involvement of direct and indirect pathways in the basal ganglia-thalamus-cortical motor circuit.

Basal Ganglia↗
PubMed1999

Localization of the motor hand area using transcranial magnetic stimulation and functional magnetic resonance imaging.

OBJECTIVE: The anatomical location of the motor area of the hand may be revealed using functional magnetic resonance imaging (fMRI). The motor cortex representation of the intrinsic hand muscles consists of a knob-like structure. This is omega- or epsilon-shaped in the axial plane and hook-shaped in the sagittal plane. As this knob lies on the surface of the brain, it can be stimulated non-invasively by transcranial magnetic stimulation (TMS). It was the aim of our study to identify the hand knob using fMRI and to reveal if the anatomical hand knob corresponds to the hand area of the motor cortex, as identified by TMS, by means of a frameless MRI-based neuronavigation system. METHODS: Suprathreshold transcranial magnetic stimuli were applied over a grid on the left side of the scalp of 4 healthy volunteers. The motor evoked potentials (MEPs) were recorded from the contralateral small hand muscles, and the centers of gravity (CoG) of the MEPs were calculated. The exact anatomical localization of each point on the grid was determined using a frameless MRI-based neuronavigation system. In each subject, the hand area of the motor cortex was visualized using fMRI during sensorimotor activation achieved by clenching the right hand. RESULTS: In all 4 subjects, the activated precentral site in the fMRI and the CoG of the MEP of all investigated muscles lay within the predicted anatomical area, the so-called hand knob. This knob had the form of an omega in two subjects and an epsilon in the other two subjects. CONCLUSIONS: TMS is a reliable method for mapping the motor cortex. The CoG calculated from the motor output maps may be used as an accurate estimation of the location of the represented muscle in the motor cortex.

Adult↗
PubMed1999

[Spontaneous intracranial hypotension: a rare cause of chronic headache].

Spontaneous intracranial hypotension is a rare cause of chronic postural headache. We report the case of a 58-year-old woman with a 1.5 year history of chronic headache in upright position, nausea and vomiting. Neurological examination was normal. The Gd-enhanced MRI of the brain showed an abnormal meningeal enhancement over the cerebral convexity. The CSF was normal. Opening pressure during lumbar puncture was 6 cm H2O in the lateral recumbent position. No evidence of underlying systemic, infectious or neoplastic diseases could be detected. The headache was alleviated under theophylline therapy. Spontaneous intracranial hypotension should be considered in the differential diagnosis of chronic postural headache. MRI revealing meningeal enhancement and low opening pressure in lumbar puncture are important findings for the diagnosis of spontaneous intracranial hypotension.

Brain↗
PubMed1999

Clinical significance of intracranial developmental venous anomalies.

OBJECTIVES: Venous angiomas, or developmental venous anomalies (DVAs), represent the most often occurring cerebral vascular malformation. The clinical significance of a DVA is, however, at present unclear. METHODS: A retrospective analysis was carried out on two series of consecutive cranial MRIs performed between January 1990 and August 1996 in a university department of neuroradiology and in a large radiological private practice. The medical records of all patients in whom a DVA was diagnosed were screened to identify the specific complaint which necessitated the imaging procedure. RESULTS: A total of 67 patients with DVA could be identified. In 12 patients an associated cavernoma was found. The main reason for performing the MRI was the evaluation of seizures or of headaches. In all patients with DVA in whom an intracerebral haemorrhage was diagnosed an associated cavernoma was present at the site of the haemorrhage. None of the 67 patients showed an association between the complaints that led to the MRI and the location of the DVA. CONCLUSIONS: DVAs do not seem to be associated with a specific clinical presentation. In a significant percentage of cases, however, coexisting cavernomas are found which have a defined bleeding potential and should be treated independently of the DVA. This study supports the hypothesis that DVAs are a congenital abnormality of venous drainage without clinical significance.

Adult↗
PubMed1999

The electrically elicited startle blink reflex in patients with schizophrenia: A threshold study of different reflex components.

The electrically elicited blink reflex consists of three components (R1, R2, R3). In humans the excitability of these components is influenced by attentional states. In particular, distraction from the stimulus leads to facilitation of the bilateral R2 and R3. The present study was performed in order to investigate the excitability of the different components of the electrically evoked blink reflex in 13 patients with schizophrenia and 13 normal controls under standard conditions. Therefore, the thresholds of the distinct components were determined without any inhibitory or facilitatory procedure. There was no significant difference in R1 and R2 thresholds between patients and controls. In contrast, the R3 threshold was significantly reduced in schizophrenic patients (R3 threshold = 17.5 mA in normal subjects, 10.5 mA in patients, p = 0. 0001). In recent studies the R3 magnitude was found to be highly susceptible to changes in the attentional state of normal subjects. The lower threshold of R3 in patients with schizophrenia might therefore be a neurophysiological marker of attentional dysfunctions in schizophrenia.

Adult↗
PubMed1999

Transcallosal inhibition and motor conduction studies in patients with schizophrenia using transcranial magnetic stimulation.

BACKGROUND: Transcranial magnetic stimulation of the motor cortex may not only elicit excitatory responses in hand muscles contralateral to the stimulated hemisphere, but may also suppress tonic voluntary electromyogram activity in muscles ipsilateral to the stimulation. This inhibition is mediated between the motor cortices via the corpus callosum. AIMS: To investigate motor excitability and interhemispheric (transcallosal) connections in patients with schizophrenia. METHOD: Transcallosal inhibition and motor conduction parameters were investigated in ten patients with schizophrenia and in ten age- and gender-matched healthy subjects. RESULTS: Transcallosal conduction time (TCT) and duration of the inhibition were significantly longer in patients with schizophrenia (mean (s.d.)): TCT, 12.4 (2.9) ms in normal subjects and 15.3 (2.6) ms in patients (P = 0.03); mean duration, 34.1 (4.9) ms in normal subjects and 51.9 (16.8) ms in patients (P = 0.01). CONCLUSIONS: Magnetic motor conduction parameters are unaltered in schizophrenia, but transcallosal inhibition is significantly delayed and prolonged. This may indicate abnormal function of the corpus callosum in these patients.

Adult↗
PubMed1998

Expression of interleukin 6 in the rat striatum following stereotaxic injection of quinolinic acid.

Stereotaxic intrastriatal injection of the naturally occurring N-methyl-D-aspartate (NMDA) agonist quinolinic acid (QA) serves as a valuable in vivo model to study excitotoxic cell damage in the central nervous system (CNS). Although morphological changes such as neuronal loss, glial activation and remote reactions following QA injection have been described in some detail, much less is known about the molecular mechanisms mediating the accompanying glial response. Cytokines are known to play a crucial role in almost all kinds of CNS alterations. We now demonstrate that IL-6, a multifunctional glycoprotein which belongs to the family of neurokines, is expressed endogenously in the rat striatum following QA injection. Using Northern blot analysis, a massive but transient upregulation of IL-6 mRNA could be detected. This started 3 h after QA injection, reached a maximum at 6 h and disappeared within 24 h. That activated microglia are the most likely cellular source of the observed corresponding IL-6 protein expression could be concluded by comparing the immunocytochemical pattern of IL-6 expression and microglial activation. Interestingly, astrocytes initially downregulate their expression of glial fibrillary acidic protein (GFAP) in the excitotoxically injured striatum, but show a delayed increase in GFAP immunoreactivity starting in the periphery of the striatum, subsequently expanding to the core. The early transient IL-6 expression may play an important role in initiating the delayed astrocytic response following excitotoxic cell injury.

Animals↗
PubMed1998

Neurophysiological abnormalities in the Westphal variant of Huntington's disease.

The Westphal variant of Huntington's disease (HD) is a distinct clinical entity of HD characterized by a rigid-hypokinetic syndrome and is often associated with a juvenile onset of disease. Definite genetic differences between the subtypes of HD have not been delineated so far. Here we present the results of a battery of neurophysiological tests including somatosensory-evoked potentials, blink reflexes, long-latency reflexes, and measurement of saccadic velocities in a Westphal HD patient. Although quantitative assessment of his motor performance showed a severe hypokinetic syndrome resembling Parkinson's disease, the results of somatosensory-evoked potentials and blink reflexes were indistinguishable from results obtained in hyperkinetic HD patients. Long-latency reflexes, however, which are typically absent in hyper-kinetic HD patients, were retained in this patient. It is concluded that neurophysiology in HD patients is not a mere reflection of the patient's symptomatology but can give insight into the underlying pathophysiological process.

Adult↗
PubMed1998

Facilitation of picture naming by focal transcranial magnetic stimulation of Wernicke's area.

On the basis of an evolutionary concept of language it was postulated that activation of the motor systems for arm movements, which are phylogenetically older, should facilitate language processes. In aphasic subjects picture naming can be improved by a concomitant movement of the dominant arm. In the present study it was investigated whether a similar facilitation can be observed in normal subjects by studying the effects of transcranial magnetic stimulation (TMS) on picture naming latencies. Suprathreshold focal TMS was applied to the left motor cortex for proximal arm muscles in right-handed subjects. The effects were compared with TMS of Wernicke's area. While TMS of the motor cortex and the non-dominant temporal lobe had no facilitatory effects, TMS of Wernicke's area decreased picture naming latencies significantly when TMS preceded picture presentation by 500 or 1000 ms. The observed effects depended on the intensity of the stimulus used. While clearly present with intensities of 35% and 55% of maximum output the facilitation disappeared with higher stimulation intensities. It is concluded that focal magnetic stimulation is able to facilitate lexical processes due to a general preactivation of language-related neuronal networks when delivered over Wernicke's area.

Adult↗
PubMed1998

Interhemispheric inhibition in patients with multiple sclerosis.

OBJECTIVES: A single focal magnetic stimulus applied to the motor cortex of normal subjects can suppress ongoing voluntary electromyographic activity in ipsilateral small hand muscles. This inhibition is mediated from one motor cortex to the contralateral side via a transcallosal pathway. METHODS: We have investigated transcallosal inhibition in 24 patients with definite multiple sclerosis (MS) and in 24 healthy volunteers. A focal magnetic stimulus was applied to the hand area of the motor cortex and the onset latency of the inhibition of the ongoing EMG activity of the ipsilateral first dorsal interosseus muscle was evaluated. Cortico-motor conduction time to the same muscle was revealed, using a magnetic stimulus over the contralateral motor cortex. The difference between these values was calculated as transcallosal conduction time. Cerebral magnetic resonance imaging (MRI) scans including sagittal T2-weighted images were performed in 18 patients. RESULTS: The depth of inhibition (maximal inhibition as percentage of the baseline EMG) in the MS patients was comparable to normal values, but the transcallosal conduction time was significantly delayed (patients 17.2 +/- 6.4 ms; normal subjects 12.2 +/- 2.6 ms; P < 0.001). The duration of the inhibition was significantly prolonged in MS patients (patients 47.9 +/- 20.9 ms; normal subjects 38.9 +/- 10.1 ms; P = 0.02). Transcallosal conduction time was delayed in 11 (46%) of 24 patients, compared with normal subjects. It exceeded the normal range (mean +/- 2.5 SD) in one normal subject (specificity 96%). No correlation could be found between the size or extent of the lesions obtained from the MRI scan and the onset latency or the depth of the inhibition. CONCLUSIONS: We conclude that conduction over transcallosal connections is significantly slower in patients with MS.

Adult↗
PubMed1997

Epidural spinal infection. Variability of clinical and magnetic resonance imaging findings.

STUDY DESIGN: This study evaluates the magnetic resonance characteristics of spinal epidural abscesses and their associated disc space infections. OBJECTIVES: The results were correlated with history, clinical, and laboratory findings to provide guidelines for early and appropriate diagnosis of epidural spinal infections. SUMMARY OF BACKGROUND DATA: Imaging signs of spinal infections have been reported before, but not with special attention to early clinical and imaging findings. METHODS: Thirteen patients (10 men, 3 women; age range, 32-64 years) with progressive sensorimotor deficit were studied. All patients had a neurologic examination after admission and a magnetic resonance imaging scan done within the first 48 hours. In all cases, T1-weighted images before and after administration of gadolinium were obtained. T2-weighted images were acquired in eight cases as well. Ten patients subsequently underwent open surgery; in three cases, a percutaneous biopsy and drainage was performed. RESULTS: Cervical discitis was found in five patients, and thoracic discitis was seen in another five cases. Three patients had an epidural infection without a concomitant discitis. Neurologic and clinical findings varied considerably. Despite clinical signs of spinal cord involvement, a spinal cord lesion was demonstrated only once. Signal change in T2-weighted images may be the first sign of disc space infection. Because a neurologic deficit may occur before any change is visible, follow-up examinations may be required if epidural infection is suspected on clinical grounds. CONCLUSIONS: Magnetic resonance imaging is the appropriate method for diagnostic work-up of progressive neurologic deficit resulting from epidural infection.

Abscess↗
PubMed1996

Transient decrease of acetylcholinesterase in ventral horn neurons caudal to a low thoracic spinal cord hemisection in the adult rat.

Light microscopic enzyme histochemistry was employed to study the alterations of acetylcholinesterase (AChE) within lumbosacral ventral horn neurons at survival times of 1, 4, 7, 14, 28, 60, and 90 days after low thoracic spinal cord hemisection in adult rats. The intensity of histochemical staining was quantified using densitometric techniques. Virtually all ventral horn neurons of sham-operated and unoperated animals, which served as controls, displayed intense AChE staining. Hemisection of the spinal cord induced a transient ipsilateral decrease of AChE staining in most neuronal cell bodies and in the neuropil of lamina IX at all segmental levels caudal to the lesion. Quantitative analysis of representative segments revealed a reduction of AChE in the ventral horn during a postoperative (p.o.) period of 1 to 28 days followed by a phase of recovery over the next two months. AChE activity still remained slightly reduced, even at 90 days p.o. The transient decrease in AChE is a well-known metabolic response of axotomized motoneurons. However, the observed changes of AChE reactivity in intact motoneurons ipsilateral and caudal to the hemisection are presumably induced by the interruption of supraspinal descending pathways. These metabolic changes may functionally affect the whole motor unit and be involved in the disturbances of motor function following spinal cord injury.

Acetylcholinesterase↗