Biomedical subjects

J Zeitlhofer

Publications and source records attributed to J Zeitlhofer.

At least 73 records · Page 4Linked to original sources

PubMed1991

Neuromagnetic investigation of somatotopy of human hand somatosensory cortex.

In order to investigate functional topography of human hand somatosensory cortex we recorded somatosensory evoked fields (SEFs) on MEG during the first 40 ms after stimulation of median nerve, ulnar nerve, and the 5 digits. We applied dipole modeling to determine the three-dimensional cortical representations of different peripheral receptive fields. Median nerve and ulnar nerve SEFs exhibited the previously described N20 and P30 components with a magnetic field pattern emerging from the head superior and re-entering the head inferior for the N20 component; the magnetic field pattern of the P30 component was of reversed orientation. Reversals of field direction were oriented along the anterior-posterior axis. SEFs during digit stimulation showed analogous N22 and P32 components and similar magnetic field patterns. Reversals of field direction showed a shift from lateral inferior to medial superior for thumb to little finger. Dipole modeling yielded good fits at these peak latencies accounting for an average of 83% of the data variance. The cortical digit representations were arranged in an orderly somatotopic way from lateral inferior to medial superior in the sequence thumb, index finger, middle finger, ring finger, and little finger. Median nerve cortical representation was lateral inferior to that of ulnar nerve. Isofield maps and dipole locations for these components are consistent with neuronal activity in the posterior bank of central fissure corresponding to area 3b. We conclude that SEFs recorded on MEG in conjunction with source localization techniques are useful to investigate functional topography of human hand somatosensory cortex non-invasively.

Brain Mapping↗

PubMed1991

The sensitivity of transcranial cortical magnetic stimulation in detecting pyramidal tract lesions in clinically definite multiple sclerosis.

We determined central motor conduction time (CMCT) (motor cortex to root C-8 and motor cortex to root S-1) as well as the amplitude of the compound muscle action potentials in the hypothenar and the abductor hallucis muscles on both sides in 44 patients with definite MS. We compared the values with standards obtained from 86 healthy controls and correlated them with the degree of clinical deficit of the limbs examined. Thirty-nine patients (88.6%) showed a prolonged CMCT. By comparison, only 74.4% of patients had abnormal visual evoked potentials.

Action Potentials↗

PubMed1991

[The prognostic value of evoked potentials in early neurologic rehabilitation of patients with the apallic syndrome].

In 22 patients with apallic syndrome brainstem auditory and somatosensory evoked potentials were recorded, in 8 patients the course during rehabilitation was observed. Clinically the patients were scored with Glasgow-coma scale, Karnofsky-index and Goldenberg-scale. The outcome of rehabilitation was estimated by the "Glasgow-outcome scale". No correlation was found between results of evoked potentials and clinical state. First evoked potentials measurements of apallic patients allowed no prognosis. Evoked potentials are an important prognostic factor after severe head trauma, but have no value for the prognosis of apallic patients.

Adolescent↗

PubMed1991

[Sleep and epilepsy].

The frequency of epileptiform discharges shows a wide intraindividual variability; it is influenced by the sleep-waking cycle and by the different stages of sleep: generalized seizures (tonic-clonic, tonic and myoclonic) are activated in nonrapid eye movement sleep, partial seizures tend to have more complex relationships with sleep states. Generally, sleep stages I and II and transit stages have an activating effect on discharges. Rapid eye movement sleep has an "anticonvulsive" effect and focalizes paroxysmal activity. Sleep recordings are useful for localizing a focus in temporal lobe seizures and for differentiation of epileptic seizures from non-epileptic seizure-like sleep disturbances. EEG after sleep deprivation should be used in patients suspected of suffering from epilepsy whose prior EEGs (including hyperventilation, photic stimulation and short sleep) were normal or yielded borderline abnormalities. Epileptiform discharges can--without clinical seizures--produce arousal reactions and sleep disturbances.

Cerebral Cortex↗

PubMed1990

Improvement of brain function in hemodialysis patients treated with erythropoietin.

To evaluate the effects of recombinant human erythropoietin (rHuEPO) on brain function, 15 chronic hemodialysis patients were studied by event-related P300, stimulus-related evoked potentials, and trailmaking before (hematocrit 22.7%) and after rHuEPO (hematocrit 30.6%). P300 peak latency elicited by a tone discrimination paradigm improved (391 before vs. 366 ms after; Cz = vertex; P less than 0.01) confirming beneficial effects on cerebral cognitive processing. P300 amplitude (13.6 vs. 15.8 microV; P = 0.06) and trailmaking tended to improve (55 vs. 43 s). P300 measures were influenced by low hemoglobin levels before rHuEPO (P less than 0.01), suggesting that severe anemia may contribute to uremic brain dysfunction. Furthermore, decrease of stimulus-related auditory brainstem I-V interpeak latency (4.28 before vs. 4.17 ms after; P less than 0.05) and increase of somatosensory N20/P25 amplitude (4.8 vs. 7.0 microV; P less than 0.05) pointed to improvement of sensory pathways by mechanisms unrelated to cognition. Brain dysfunction in chronic hemodialysis patients may, beside other factors, in part be caused by severe anemia and can be improved by rHuEPO treatment.

Anemia↗

PubMed1990

The influence of temperature on somatosensory-evoked potentials during cardiopulmonary bypass.

Somatosensory-evoked potentials (SEPs) after median nerve stimulation were recorded in 10 neurologically normal patients during cardiopulmonary bypass and hypothermia. In all patients the changes of the latencies (spinal N13, cortical N20 and N35) and the central conduction time during cooling, and the decrease in latencies during rewarming was described by a gamma function. The analytic discussion of pooled data of all patients led to another SEP-latency-temperature relationship than the observation of each single patient. In 6 of 10 patients there was found a maximum of latency increase before the minimal temperature was reached. The cooling and the rewarming curve had to be considered separately. Latency changes of SEPs during hypothermia are discussed as a very complex phenomenon influenced by many technical and patient factors. This reduces the value of SEPs as an index of central nervous system integrity during open heart surgery and hypothermia.

Adult↗

PubMed1990

[The value of evoked potentials in brain death diagnosis].

At the moment evoked potentials in Austria are not admitted for diagnosing brain death. Brainstem auditory evoked potentials are proving the loss of the brainstem function, if a primary supratentorial lesion is excluded and if they disappear bilaterally and stepwise. The early components of somatosensory evoked potentials after median nerve stimulation allow the examination of the brainstem and the cortical function, if medullary lesions are excluded. In our study evoked potentials were recorded in 23 patients with bulbar brain syndrome and isoelectric EEG: In 21 (47%) of the 45 examined hearing pathways a component I and in 3 pathways (7%) a component II was found. In 41 examined pathways of median nerve a complete loss of the spinal response was observed in 12 pathways, whereas in 29 pathways (71%) the spinal response was preserved.

Adolescent↗

PubMed1990

[Possibilities and limitations of the automatic analysis of sleep stages using the Oxford system].

34 ambulatory polygraphic sleep-records of young adults were carried out using the Oxford Medilog 9000 recorder. All of the records underwent automatic evaluation by the Oxford Sleep Stager. 10 cases were, in addition, evaluated visually. 4 records could not be analyzed because of artifacts. Thus, 30 subjects were used in the end for establishing standard values of sleep parameters. Automatic versus automatic comparisons and automatic versus visual comparisons of ten polysomnograms were performed epoch-by-epoch. The automatic versus automatic comparison showed agreement in 85.5% of epochs, and the automatic versus visual comparison in 70.4% of epochs. The Sleep Stager showed the best agreement with the visual evaluation in epoch-by-epoch comparison in the REM-stage (93.9%), the worst in stage 1 (32.4%). In calculating the percentages of total night sleep for the respective sleep stages, the automatic analysis showed strongest disagreement with visual evaluation in the REM-stage (plus 7.5%) and in stage 2 (minus 5.2%).

Adult↗

PubMed1990

[The significance of EMG artefacts in isoelectric EEG].

Five potential organ donors showed muscle artefacts during isoelectrical EEG recording. The electromyographic examination revealed MUAP activity occurring as doublets, triplets and quadruplets. All patients had normal blood chemistry except reduced CO2 and increased O2 partial pressures. We assume that the recorded "tetaniform" muscle activity is due to hyperexcitability of the nerve membrane caused by artificial hyperventilation.

Adult↗

PubMed1990

[Transarterial EEG in superselective cerebral angiography].

Transarterial EEG-recording is a complementary method to surface and depth-techniques. In 8 patients having superselective angiography because of diagnosis or therapeutic manoeuvres transarterial EEG-recording was performed. There were only few artefacts and no clinical side effects. The value of this additional information is discussed.

Adult↗

PubMed1990

Fatal encephalitis in a patient with chronic graft-versus-host disease.

A 32-year-old male patient with chronic myelocytic leukemia in accelerated phase received a bone marrow allograft from his 42-year-old HLA/MLC-identical sister. He recovered from acute graft-versus-host disease (GVHD) grade III-IV of skin, liver and gut, but chronic GVHD of progressive onset developed. On day 556 post-graft severe thrombocytopenia was resistant to prednisolone, cyclophosphamide and high dose immunoglobulin. Splenectomy was followed by a normalization of platelet counts. The subsequent clinical course was characterized by progressive muscular atrophy and weight loss. Dysphagia, dysarthria, cachexia and ultimately recurrent pneumonic episodes ensued. The cachectic patient developed a highly abnormal breathing pattern with hypoventilation and intermittent apnea requiring mechanical ventilation. Auditory evoked potentials revealed a considerable dysfunction of the brainstem. The patient died on day 1120 post-graft from pneumonia, aggravated by thoracic muscular insufficiency. Postmortem examination revealed diffuse predominantly lymphoid perivascular infiltration in meninges and CNS tissue; proliferation of activated microglial cells expressing the HLA-DR antigen was prominent in the brainstem. These histologic changes are similar to those observed in the CNS in experimental GVHD. We suggest that this case represents the first documentation of CNS involvement in chronic GVHD.

Adult↗

PubMed1989

[The variability of the number and daily distribution of spike wave seizures in two 24-hour long-term EEG recordings made one shortly after the other].

30 patients suffering from primary generalized epileptic seizures were investigated twice in intervals of 1-7 days by means of mobile long-term-EEG monitoring. The total number of paroxysms showed a variability from 53% to 187%, the time of maximum paroxysmal activity varied in between 2.76 hours to 5.40 hours for the whole group; the results for adults, children and patients with/without antiepileptic medication did not differ much. Our findings suggest, that the results of one single 24 hours long-term-EEG investigation must be interpreted with great caution.

Adolescent↗

PubMed1989

[Evoked potentials in the follow-up and prognosis of patients with craniocerebral trauma].

The aims of this study were to find a reliable way of establishing the prognosis for the final outcome in the first week after head injury, to show the correlation between abnormalities in evoked potentials (EP) and clinical coma score, and finally, to document EP results in patients with the clinical diagnosis of brain death. We examined 46 patients, 23 in different states of coma and 23 with bulbar syndrome (complete absence of cortical and brain stem function). In the group of comatose patients brain stem auditory EP (BAEP) and somatosensory EP (SEP) were recorded in the first 48 h, 3-5 days, 1 week and 4 weeks after the head injury. The depth of coma was scaled with a scoring system devised by the authors and with the Innsbruck coma scale. Outcome was evaluated with the Glasgow outcome scale after 3, 6, and 9 months. BAEP were recorded bilaterally after stimulation with clicks; SEP were recorded from the neck (C2) and the contralateral cortex (C3', C4') after electrical stimulation of the median nerve. Evoked potentials were scored according to a four-point scale from grade 1 (normal) to grade 4 (only component I present in BAEP or absence of cortical responses on both sides in SEP). We found a significant correlation between the mean SEP score of the first week and the Glasgow outcome of the 3rd month, but no significant correlation between the BAEP score of the first week and the Glasgow outcome. There was a significant correlation between SEP (BAEP) scores and the corresponding clinical score.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1988

[Syncopal consciousness disorders and drop attacks from the neurologic viewpoint].

The most important neurological disorders leading to syncope and/or drop attack are presented. With respect to epilepsy it is important to consider generalized absence seizures (petit mal), generalized tonic-clonic seizures (grand mal) and some types of complex partial seizures. Additionally, some sleep and arousal disorders must be mentioned, such as narcolepsy, disorders of excessive somnolence associated with sleep-induced respiratory impairment, as well as the Kleine-Levin-Critchley syndrome. Vagotonic, asympathicotonic, sympathicotonic and central autonomic disorders are comprised in the group of autonomic attacks. Among other brain diseases manifesting syncope and/or drop attack, cerebrovascular disorders are of major importance in view of their high incidence. Psychogenic seizures also have to be taken into account in the differential diagnosis.

Brain Diseases↗

PubMed1988

[Somatosensory evoked potentials following tibial nerve stimulation. Method and normal values in relation to physical variables].

Somatosensory evoked potentials were recorded in 40 healthy subjects (age: 22-63 years) with gluteal, lumbar, cervical and cortical surface electrodes after stimulation of the tibial nerve. Normal latency values were established in relationship to height and also for the amplitudes of the different components; the latencies of the cortical P40, N50 and P60 were significantly dependent on height, the latency of the cervical N33, the lumbar N22 and the gluteal Ng were dependent on the distance (stimulation--to recording point). The central conduction time showed no dependence on back length. Age dependence (in relation to normal height) was found only in the case of cortical P60.

Adult↗

PubMed1988

Single photon emission computerized tomography during and between seizures.

In three patients, patterns of brain activity were measured by 99mTc-hexamethyl-propyleneamineoxime (99mTc-HM-PAO) brain SPECT (single photon emission computerized tomography) in ictal and interictal states. Increased relative blood flow indicated the focus of partial seizures, its spreading to adjacent cortical regions and to distant brain structures via neuronal pathways. Ictal patterns of regional cerebral blood flow (rCBF) were in agreement with clinical symptomatology. Successive SPECT studies were performed after 3-7 days in the absence of electroencephalographic and clinical signs of seizures but still revealed increased relative blood flow in the focus of the seizures. SPECT studies, performed 2-6 weeks after the last clinically observable seizures, demonstrated the transition from increased to decreased relative blood flow in the focus of the seizures. In one patient, the EEG was complementary to and corresponded with the rCBF patterns in the ictal state. However, the dynamics of interictal changes could only be assessed by brain SPECT.

Adult↗

PubMed1988

Hexa-methyl-propylene-amine-oxime (HMPAO) single photon emission computed tomography (SPECT) in epilepsy.

Twenty-eight normal volunteers and 74 seizure patients were investigated with hexa-methyl-propylene-amine-oxime (HMPAO) brain single photon emission computed tomography (SPECT). Fifty-four patients suffered from partial seizures and 20 patients had generalized seizures. Indices describing regional tracer distribution (RIs) were calculated in all investigated subjects. Regions whose RI exceeded the mean normal RI +/- 3 SD were defined as abnormally perfused. In normals a significant interhemispheric asymmetry of HMPAO deposition was found, with higher RI values in the right frontal, parietal, temporal and occipital regions. In 59.3% of partial seizure patients abnormal RIs were found. Low RIs were detected predominantly in the frontal and temporal cortex, while elevated RIs were observed predominantly in the anterior basal ganglia. Only in 20% of the cases with generalized seizures, abnormal RIs were found. In one patient an ictal and 3 follow-up SPECT studies were obtained. Here SPECT results indicated transient rCBF changes between the ictal and seizure free state. EEG and SPECT foci were ipsilaterally located in 69.2% of the partial seizure cases. The results indicate that HMPAO brain SPECT is valuable for the detection of rCBF abnormalities in seizure patients and that patients with partial seizures have mostly several abnormally perfused areas in their brains.

Adult↗

PubMed1988

Brainstem auditory-evoked potentials studied with paired stimuli in multiple sclerosis patients.

In 19 patients with definite multiple sclerosis (MS) brainstem auditory-evoked potentials (BAEP) with paired stimuli were recorded. Only hearing pathways without abnormalities in usual BAEP were examined. The latencies of wave III and wave V were significantly increased with the paired-stimulus technique (using paired-click intervals of 1.5 and 4.0 ms duration) compared to single clicks. In 4 patients (21%) paired-click BAEP latencies exceeded the critical values of normal subjects. This technique might give new possibilities in detecting minor lesions in MS patients.

Adult↗