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Biomedical subjects

W Paulus

Publications and source records attributed to W Paulus.

At least 145 records · Page 8Linked to original sources
PubMed1998

Demonstration of facilitatory I wave interaction in the human motor cortex by paired transcranial magnetic stimulation.

1. Transcranial magnetic stimulation (TMS) of the human motor cortex results in multiple discharges (D and I waves) in the corticospinal tract. We tested whether these volleys can be explored non-invasively with paired TMS. The intensity of the first stimulus (S1) was set to produce a motor-evoked potential (MEP) of 1 mV in the resting contralateral abductor digiti minimi (ADM) muscle; the second stimulus (S2) was set to 90 % of the resting motor threshold. At interstimulus intervals of 1.1-1.5, 2.3-2.9 and 4.1-4.4 ms the MEP elicited by S1 plus S2 was larger than that produced by S1 alone. 2. Varying the S1 intensity between 70 and 130 % resting motor threshold with S2 held constant at 90 % resting motor threshold showed that the threshold for the first MEP peak was <= 70 % resting motor threshold. The second and third MEP peaks appeared only at higher S1 intensities. The latency of all peaks decreased with increasing S1 intensity. 3. Varying the S2 intensity with S1 held constant to produce a MEP of 1 mV on its own showed that the amplitude of all MEP peaks increased with S2 intensity, but that their timing remained unchanged. 4. Paired TMS in the active ADM (S1 clearly suprathreshold, S2 just above threshold; interstimulus interval, 1 ms) produced strong MEP facilitation. The onset of this facilitation occurred later by about 1.5 ms than the onset of the MEP evoked by S2 alone. No MEP facilitation was seen if the magnetic S2 was replaced by anodal or cathodal transcranial electrical stimulation. 5. It is concluded that the MEP facilitation after paired TMS, at least for the first MEP peak, is due to facilitatory interaction between I waves, and takes place in the motor cortex at or upstream from the corticospinal neurone.

Adult↗
PubMed1998

Ichthyosis follicularis, alopecia, and photophobia (IFAP) syndrome: clinical and neuropathological observations in a 33-year-old man.

The syndrome of ichthyosis follicularis, alopecia, and photophobia (IFAP) is an uncommon neuroichthyosis described in only 10 males so far. We report on a man with congenital ichthyosis and alopecia with apparently normal development in early infancy. Photophobia and generalized myoclonicastatic seizures began during or after the first year of age and were associated with progressive impairment of motor skills and mental abilities. He died at 33 years of age. Neuropathological findings showed an unusual deformation of the temporal lobes and olivocerebellar atrophy. Cytogenetic and molecular studies did not uncover deletions in either Xp22.2 to 3 or in Xq27.3 to qter.

Abnormalities, Multiple↗
PubMed1998

Selective activation of human cortical area V5A by a rotating visual stimulus in fMRI; implication of attentional mechanisms.

The human homologue of area V5A of rotation-selective cells in the monkey medial superior temporal area (MST) was identified using functional magnetic resonance imaging (fMRI). It was located within the border region of occipito-temporo-parietal cortex, in four of 10 subjects on both sides, and on the right or left side in three subjects each. The stimulus was a black-and-white sine-modulated windmill presented either stationary or in rotation phases of 1 s duration. Areas V1-V3 did not show up with this paradigm. Focusing attention by mentally counting the number of rotation phases ensured high signal intensity in V5A, whereas moving attention away by counting electric stimuli to the wrist diminished it despite persistent fixation of gaze to the centre of the windmill.

Adult↗
PubMed1998

Spatial-frequency-related efficacy of visual stabilisation of posture.

The present study investigates the efficacy of visual stabilisation of posture for different spatial frequencies of a visual stimulus. Circular sine wave gratings were used to analyse the correlation between perception of motion in depth and stabilisation of fore-aft sway by the mechanism of detecting changes in target size. Body sway was recorded by a force-measuring platform (series A) and, in addition, by simultaneous tracking of infrared markers fixed to the subject's body (series B). Mean velocity and amplitude (RMS) of body sway were calculated in both sagittal (a-p) and lateral (l-r) planes. Sagittal sway was of least magnitude when viewing contrast gratings with lowest thresholds, whereas higher thresholds resulted in increasing sway parameters. As intended by the design of the stimuli, sagittal sway was correlated closer with the stabilising effect exerted by the different stimuli than was lateral sway. Sway velocity was reduced more efficiently, however, with a lower correlation with the psychophysical transfer function, than was RMS sway. Since sway velocity measured by the platform is suggested to depend to a greater extent on dynamic muscle forces generated at each individual body site the results indicate that visual information can be used to reduce and thereby optimise dynamic muscle action (sway velocity) even though static body sway is either not or less reduced. A comparable economisation of sway velocity but not of RMS sway was also seen at the end of posture investigations, indicative of positive training effects.

Adult↗
PubMed1998

Acquired colour deficiency in patients with Parkinson's disease.

The blue cone pathway is reported to be affected early in Parkinson's disease (PD) and acquired type three (tritan) defects may occur. Sixty-one patients attending a treatment and rehabilitation centre for PD were examined with clinical colour vision tests. Seven of 13 patients, for whom the diagnosis of PD was equivocal or who had other medical conditions, were identified as having tritan colour deficiency. Results for the remaining 44 PD patients were compared with 40 age matched controls. Ten PD patients (22.7%) had tritan defects. Tritan defects were not found in the control group but performance on some tests was age related. We conclude that clinical tests for tritan colour deficiency are unlikely to be helpful in identifying PD.

Aged↗
PubMed1998

Colour discrimination thresholds in Parkinson's disease: results obtained with a rapid computer-controlled colour vision test.

A dysfunction of dopaminergic retinal neurons is thought to occur in Parkinson's disease, manifesting itself in impaired performance on various visual discrimination tasks. We have investigated whether differences in colour discrimination could readily be detected between a normal group and a Parkinsonian group, using a computer-controlled test of colour vision. Although some individual Parkinsonian patients showed an abnormal elevation of colour discrimination thresholds, there was no significant difference between the normal group and the Parkinsonian group.

Age Factors↗
PubMed1998

Transcranial magnetic stimulation: its current role in epilepsy research.

This paper reviews the current role of transcranial magnetic stimulation (TMS) in epilepsy research. After a brief introduction to the technical principles, the physiology and the safety aspects of TMS, emphasis is put on how human cortex excitability can be assessed by TMS and how this may improve our understanding of pathophysiological mechanisms in epilepsy and the mode of action of antiepileptic drugs (AEDs). Also, potential therapeutical applications of TMS are reviewed. For all aspects of this paper, a clear distinction was made between single-/paired-pulse TMS and repetitive TMS, since these two techniques have fundamentally different scopes and applications.

Anticonvulsants↗
PubMed1998

Pharmacological control of facilitatory I-wave interaction in the human motor cortex. A paired transcranial magnetic stimulation study.

A novel paired transcranial magnetic stimulation (TMS) paradigm with a suprathreshold first and a subthreshold second stimulus was used in healthy volunteers to investigate the acute effects of a single oral dose of various CNS-active drugs on short-interval motor evoked potential (MEP) facilitation. MEPs were recorded from the relaxed abductor digiti muscle. Three peaks of MEP facilitation were consistently observed at interstimulus intervals of 1.1-1.5 ms, 2.3-2.7 ms, and 3.9-4.5 ms. The size of these MEP peaks was transiently suppressed by drugs which enhance gamma-aminobutyric acid (GABA) function in the neocortex (lorazepam, vigabatrin, phenobarbital, ethanol), while the GABA-B receptor agonist baclofen, anti-glutamate drugs (gabapentin, memantine), and sodium channel blockers (carbamazepine, lamotrigine) had no effect. The interstimulus intervals effective for the production of the MEP peaks remained unaffected by all drugs. The MEP peaks are thought to be due to a facilitatory interaction of I-(indirect) waves in the motor cortex. Therefore, the present results indicate that the production of I-waves is primarily controlled by GABA related neuronal circuits. The potential relevance of this non-invasive paired TMS protocol for the investigation of I-waves in patients with neurological disease will be discussed.

Acetates↗
PubMed1998

The lateralizing value of ictal clinical symptoms in uniregional temporal lobe epilepsy.

In order to assess the lateralizing value of several ictal and postictal clinical symptoms in temporal lobe epilepsy (TLE), we analyzed 89 seizures of 20 left dominant patients with intractable left (n = 9) versus right (n = 11) TLE who had undergone successful anterior temporal lobectomy. In left TLE, movement arrest at seizure onset, postictal dysphasia > 120 s and postictal dyslexia > 180 s were the most typical findings and associated with a sensitivity of 94, 94, and 100%, respectively. The highest specificity of 100% each was evident for contralateral versions of eyes and head and dystonic posturing. In right TLE, the highest sensitivity was seen for whole-body movements at seizure onset, postictal dysphasia < 120 s and postictal dyslexia < 180 s with figures of 82, 87, and 93%, respectively. As compared to left TLE, contralateral version and dystonic posturing, ictal speech, and postictal dyslexia < 180 s each had a specificity of 100%. The careful combined analysis of certain ictal clinical signs combined with consistent findings of interictal EEG and neuroimaging studies may be often sufficient to proceed with epilepsy surgery without invasive recordings even if ictal scalp EEG is not unambiguous.

Adolescent↗
PubMed1998

Volumetric measurements of the brachial and carotid arteries in dialysis grafts: is there evidence of a subclavian-carotid artery steal syndrome?

Dialysis grafts may lead to major hyperperfusion in the graft arm and to hypertrophic, hypervolemic cardiomyopathy. No data have been published concerning the impact of dialysis grafts on the cerebral perfusion in relation to a potential carotid steal syndrome, possibly causing neurologic or neuropsychologic symptoms. In 30 patients (32 to 74 years old) with dialysis grafts we studied the following hemodynamic parameters in the brachial and common carotid arteries bilaterally: Flow velocities (spectral Doppler sonography), diameter (B-mode) and volume flow (color M-mode) with a color duplex system (Philips P700). Volume flow in the brachial arteries of the graft arm averaged 1032 ml/min (range, 158 to 2854 ml/min) as compared to 42 ml/min (range, 15 to 108 ml/min) in the nongraft arm. Almost identical volume flow data could be seen in both common carotid arteries (418 versus 421 ml/min) with no evidence of reduced flow in the carotid arteries in patients with high flow in the graft arm. A tendency toward higher volume flow in both carotid arteries in patients with high volume flow in the graft arm was noted. We found no evidence of shunt-induced cerebral hypoperfusion. Cerebral autoregulation appears to be patent even with high brachial artery shunt volume.

Adult↗
PubMed1998

Imaging of nonmotor symptoms in Parkinson syndromes.

Neuroimaging modalities in Parkinson's Disease (PD) are primarily used for the differential diagnosis of Parkinson syndromes and to understand pathophysiological mechanisms in PD. Neuroimaging of nonmotor dysfunctions in PD mostly consist of functional studies in neuropsychologically impaired PD patients using PET or SPECT techniques. Various studies controversially discuss the probable frontal versus temporal hypometabolism in demented PD patients. Functional studies of PD patients with depression are limited to case reports showing an involvement of left frontal regions. To investigate the pathophysiology of hallucinations with functional imaging may be a promising field of future research.

Brain↗
PubMed1998

[External fetal version from breech presentation to cephalic presentation: modifying factors, reliability and risks].

External cephalic version (ECV) was performed in 524 single pregnancies. The version was successful in 38.4%. Success is mainly influenced by parity, quantity of amniotic fluid and maternal weight. An emergency cesarean section was necessary in 0.6% because of fetal bradycardia. Compared to controls the ECV was not associated with the increase of a premature rupture of membranes, complications with umbilical cord or transfer of the child to the paediatric department. Also there was no difference in the pH or Apgar-ranges. One fetal death was diagnosed 17 days after ECV, the reason therefore remained unclear. There are existing a few other reports with similar cases. We conclude that ECV is a appropriate trial to convert the fetus into cephalic presentation, but because of possible complications precautions must be taken, e.g. that means to carry out the trial under conditions which allow immediate cesarean section and a frequent follow up of the woman until delivery.

Adult↗
PubMed1997

XX-agonadism in a fetus with multiple dysraphic lesions: a new syndrome.

We report on a 19-week-old fetus with a 46,XX karyotype, normal female external genitalia, complete gonadal agenesis, large encephalocele, spina bifida, and omphalocele. We postulate a new syndrome. Hitherto no consistent malformation patterns have been observed in agonadism patients. True agonadism, including even the unusual finding of an XX gonosomal status, is obviously not as rare as suggested.

Abnormalities, Multiple↗
PubMed1997

Parallel increase of heterochromatic increment threshold and postadaptation thresholds in Parkinson's disease and in neuroleptic treatment.

Following reports on a predominant loss of blue/yellow contrast sensitivity in Parkinson's disease, we revisited the physiological phenomenon of transient tritanopia. Normative data were collected from 33 healthy individuals using different colour and time combinations. Stimuli of 440 nm wavelength (blue) proved optimal, if flashed for 50 msec within the early phase of a 2 sec pause in the 600 nm adaptation light. These conditions were then applied to 15 patients with Parkinson's disease. We found a parallel increase of increment threshold (P < 0.001) and postadaptation thresholds (P < 0.01), with little change in the extent of transient tritanopia. The same tendency at a lower significance level was found in 15 psychiatric patients under chronic treatment with depot neuroleptics.

Adaptation, Ocular↗
PubMed1997

Pleomorphic xanthoastrocytoma: report of six cases with special consideration of diagnostic and therapeutic pitfalls.

BACKGROUND: Pleomorphic xanthoastrocytoma (PXA) is a rare clinicopathologic entity that occurs typically in young patients. Improved neuroradiologic techniques, especially gadolinium-enhanced magnetic resonance imaging (MRI), reveal a characteristic tumor appearance. METHODS: We present six cases of PXA operated on with unusual clinical course, elucidating different clinical implications. RESULTS: Two patients showed subsequent progression into a malignant glioma, one case was a primary anaplastic PXA. The latter case had not previously been reported in the literature. Increased mitotic activity seems to indicate a worse clinical course; whereas focal infiltration of the brain does not necessarily lead to malignant transformation. CONCLUSIONS: Surgical removal is the treatment of choice. A consequent follow-up is mandatory in order to detect a potentially malignant recurrence as early as possible and to select patients who need additional therapy.

Adolescent↗
PubMed1997

The influence of established and new antiepileptic drugs on visual perception. 1. A placebo-controlled, double-blind, single-dose study in healthy volunteers.

The influence of single oral dosages of carbamazepine (CBZ), valproic acid, vigabatrin (VGB), lamotrigine (LTG), gabapentin (GBP), and losigamone (LSG) on visual perception was investigated in ten healthy volunteers according to a double-blind, placebo-controlled, cross-over study design. The test battery comprised visual acuity, the Lanthony-D-15-désaturé colour perception test, increment, postadaptation and transient tritanopia threshold measurements, perception threshold assessment for monochromatic and chromatic gaussian dots, monochromatic gratings and gratings of differing spatial frequency, and critical flicker fusion tests with various stimuli. The only consistent and partly significant effects were seen after VGB and GBP. After VGB, increment, postadaptation and transient tritanopia thresholds and the critical flicker fusion increased, whereas GBP led to a somewhat converse profile. The other tests were not influenced consistently by any antiepileptic drug (AED). We conclude that: (i) gamma-amino-butyric acid-(GABA)-related properties as under the prototype drug VGB result in specific alterations of the transient tritanopia phenomenon which is consistent with the physiological hypothesis for this retinal paradigm based on extracellular recordings in primates. The possible mechanisms why VGB improved critical flicker fusion as the only AED in this trial are discussed. The profile of GBP indicates a unique mechanism of action. We have not observed specific influences on visual perception under AEDs which act mainly via alterations of ion membrane conductance. The transient tritanopia and flicker fusion paradigms we used appear to be promising to investigate antiepileptic drugs with hitherto unknown modes of actions in human noninvasively.

Adaptation, Ocular↗
PubMed1997

The influence of established and new antiepileptic drugs on visual perception. II. A controlled study in patients with epilepsy under long-term antiepileptic medication.

In this study, we investigated visual performance under chronic antiepileptic drug treatment. Patients were under carbamazepine (CBZ) (n = 18), valproic acid (VPA) (n = 9), CBZ and vigabatrin (VGB) (n = 4), CBZ and gabapentin (GBP) (n = 8), and under CBZ and topiramate (TPR) (n = 6), respectively. Seven untreated patients with epilepsy and 42 healthy volunteers served as controls. The test battery comprised the Lanthony-D15-désaturé colour perception test, increment, postadaptation and transient tritanopia (TT) threshold measurements, visual perception threshold assessments for monochromatic and chromatic gratings and gaussian dots, and critical flicker fusion (CFF) tests. No differences were seen between naive patients and healthy controls. Patients under drug treatment always showed alterations of visual perception. Postadaptation and TT thresholds were altered under each drug regimen after short delays between switching off the adaptation light and switching on the blue test light. Threshold elevations were maximum under the combination of CBZ and TPR and lowest under CBZ and GBP. Consistent impairment of the CFF was seen under combined CBZ and TPR whereas VPA as well as combined CBZ and VGB led to ameliorations the mechanisms of which are discussed. The other tests were less sensitive. In conclusion, alterations of visual function were apparent under chronic antiepileptic drug treatment both with established and new agents. However, it may be difficult to distinguish between effects based on specific modes of action and nonspecific retino- and neurotoxicity.

Adaptation, Ocular↗