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Biomedical subjects

E B Ringelstein

Publications and source records attributed to E B Ringelstein.

At least 109 records · Page 6Linked to original sources
PubMed1999

Echocontrast-enhanced ultrasound of extracranial internal carotid artery high-grade stenosis and occlusion.

BACKGROUND AND PURPOSE: Proper assessment of extracranial internal carotid artery high-grade stenosis and occlusion by extracranial color-coded duplex sonography (ECCD) is occasionally made difficult by shadowing, an unfavorable insonation angle, low flow velocity or volume, or a deep insonation depth. In these cases, echocontrast could be helpful to quantify the degree of stenosis and to diagnose occlusion. METHODS: We investigated 17 arteries with poor precontrast investigation conditions and suspected high-grade stenosis or occlusion by contrast-enhanced ECCD. RESULTS: Compared with the precontrast scans, echocontrast allowed for significantly more segments to be evaluated by pulsed Doppler sonography (P<0.001) and for longer lumen segments to be displayed on color mode (P<0.001). Because it was now possible to place the sample volume right into the jet of the stenosis, the maximal flow velocity registered increased in all patients with stenosis. CONCLUSIONS: Echocontrast-enhanced ECCD of the carotid arteries is helpful for stenosis classification in a small group of preselected patients with poor original examination conditions.

Adult↗
PubMed1999

Neuropsychological impairment correlates with hypoperfusion and hypometabolism but not with severity of white matter lesions on MRI in patients with cerebral microangiopathy.

BACKGROUND AND PURPOSE: Cerebral microangiopathy, indicated on MRI by lacunar infarctions (LI) and deep white matter lesions (DWML), is said to lead to vascular dementia. METHODS: Fifty-seven patients with proven cerebral microangiopathy were assessed for changes in regional cerebral blood flow (rCBF) and glucose metabolism (rMRGlu) and compared with 19 age-matched controls. The findings were correlated with results of extensive neuropsychological testing, as well as with MRI findings. A special head holder ensured reproducibility of positioning during rCBF (single-photon emission CT [SPECT]), rMRGlu (positron emission tomography [PET]), and MR imaging. White matter and cortex were quantified with regions of interest defined on MRI and superimposed to corresponding PET/SPECT slices. LI and DWML were graded by number and extent. RESULTS: Even with severe DWML and multiple LI, rCBF and rMRGlu values were not reduced. ANOVAs identified brain atrophy and neuropsychological deficits as the main determinants for reduced rCBF and rMRGlu values in both cortex and white matter. Neuropsychological deficits correlated well with decreased rCBF and rMRGlu, whereas MRI patterns such as LI and DWML did not. Factor analysis revealed no correlation of LI and DWML with rCBF, rMRGlu, atrophy, and neuropsychological deficits, showing instead positive correlations between rCBF, rMRGlu, and neuropsychological performance and negative correlations of the latter 3 with brain atrophy. CONCLUSIONS: From these data, we conclude that LI and DWML are epiphenomena that may morphologically characterize cerebral microangiopathy but do not in themselves indicate cognitive impairment. Dementia or neuropsychological deficits, by contrast, are reflected exclusively by functional imaging parameters (rCBF, rMRGlu) and cerebral atrophy.

Adult↗
PubMed1999

Automatic embolus detection by a neural network.

BACKGROUND AND PURPOSE: Embolus detection using transcranial Doppler ultrasound is a useful method for the identification of active embolic sources in cerebrovascular diseases. Automated embolus detection systems have been developed to reduce the time of evaluation in long-term recordings and to provide more "objective" criteria. The purpose of this study was to evaluate the critical conditions of automated embolus detection by means of a trained neural network (EMBotec V5.1 One, STAC GmbH, Germany). METHODS: In 11 normal volunteers and in 11 patients with arterial or cardiac embolic sources, we performed simultaneous recordings from both middle or both posterior cerebral arteries. In the normal subjects, we produced 1342 additional artifacts to use the latter as false-positives. Detection of microembolic signals (MES) was done offline from digital audiotapes (1) by an experienced blinded investigator used as a reference and (2) by a trained 3-layer-feed-forward neural network. RESULTS: From the 1342 provoked artifacts the neural network labeled 216 events as microemboli, yielding an artifact rejection of 85%. In microembolus-positive patients the neural network detected 282 events as emboli, among these 122 signals originating from artifacts; 58 "real" events were not detected. This result revealed a sensitivity of 73.4% and a positive predictive value of 56.7. The spectral power of the detected artifact signals was 16.5+/-5 dB above background signal. MES from patients with artificial heart valves had a spectral power of 6.4+/-2.1 dB; however, in patients with other sources of emboli, MES had an averaged energy reflection of 2.7+/-0.9 dB. CONCLUSIONS: The neural network is a promising tool for automated embolus detection, the formal algorithm for signal identification is unknown. However, extreme signal qualities, eg, strong artifacts, lead to misdiagnosis. Similar to other automated embolus detection systems, good signal quality and verification of MES by an experienced investigator is still mandatory.

Adult↗
PubMed1999

Contrast transcranial Doppler ultrasound in the detection of right-to-left shunts. Reproducibility, comparison of 2 agents, and distribution of microemboli.

BACKGROUND AND PURPOSE: Cardiac right-to-left shunts can be identified by transcranial Doppler ultrasound (TCD) with the use of different contrast agents and by transesophageal echocardiography (TEE). Systematic data are available on neither the reproducibility of contrast TCD, the comparison of different contrast agents, nor the comparison of simultaneous bilateral to unilateral recordings. Furthermore, we assessed the side distribution of thus provoked artificial cardiac emboli. METHODS: Fifty-four patients were investigated by TEE and by bilateral TCD of the middle cerebral artery. The following protocol was performed twice: injection of 9 mL of agitated saline without Valsalva maneuver, injection of 9 mL of agitated saline with Valsalva maneuver, injection of 5 mL of a commercial galactose-based contrast agent without Valsalva maneuver, and injection of 5 mL of the galactose-based contrast agent with Valsalva maneuver. RESULTS: In 18 patients, a right-to-left shunt was demonstrated by TEE and contrast TCD (shunt positive). Twenty-nine patients were negative in both investigations, 1 was positive on TEE and negative on TCD, and 6 patients were only positive on TCD. Both bilateral and repeated recordings increased the sensitivity of contrast TCD. There was a symmetrical distribution of microembolic signals in the right and left middle cerebral artery. CONCLUSIONS: TCD performed twice and with the use of saline or a galactose-based contrast agent is a sensitive method in the identification of cardiac right-to-left shunts also identified by TEE. The cardiac microemboli in this study did not show any side preference for one of the middle cerebral arteries.

Adult↗
PubMed1999

Contrast transcranial Doppler ultrasound in the detection of right-to-left shunts: comparison of different procedures and different contrast agents.

BACKGROUND AND PURPOSE: Cardiac right-to-left shunts can be identified by transesophageal echocardiography (TEE) and by transcranial Doppler ultrasound (TCD) with the use of different contrast agents and different provocation procedures. Currently, data on an appropriate time window for the appearance of contrast bubbles in the TCD recording after the injection of the contrast medium and the comparison of different provocation maneuvers to increase right-to-left shunting are insufficient. METHODS: Forty-six patients were investigated by both TEE and bilateral TCD of the middle cerebral artery. The following protocol with 6 injection modes was applied in a randomized way: (1) injection of 10 mL of agitated saline without Valsalva maneuver, (2) injection of 10 mL of agitated saline with Valsalva maneuver, (3) injection of 10 mL of a commercial galactose-based contrast agent (Echovist) without Valsalva maneuver, (4) injection of 10 mL of Echovist with Valsalva maneuver, (5) injection of 10 mL of Echovist with standardized Valsalva maneuver, and (6) injection of 10 mL of Echovist with coughing. RESULTS: In 20 patients, a right-to-left shunt was demonstrated by TEE and contrast TCD (shunt-positive). Sixteen patients were negative in both investigations, no patient was positive on TEE and negative on TCD, and 10 patients were only positive on at least 1 TCD investigation but negative during TEE. The amount of microbubbles detected in the various tests decreased in the following order: Echovist and Valsalva maneuver, Echovist with coughing, Echovist and standardized Valsalva maneuver, saline with Valsalva maneuver, Echovist, and saline. With a time window of 20 to 25 seconds for the bubbles to appear in the TCD recording and with a sequence of first Echovist and Valsalva maneuver and then Echovist with coughing, all shunts were reliably identified with a specificity of 65% compared with TEE as the traditional gold standard. The time of first microbubble appearance was not helpful to distinguish between shunts detected on TEE and other shunts. CONCLUSIONS: TCD performed twice with 2 provocation maneuvers using Echovist is a sensitive method to identify cardiac right-to-left shunts also identified by TEE.

Adult↗
PubMed1999

Middle cerebral artery blood flow velocity, end-tidal pCO2 and blood pressure in patients with obstructive sleep apnea and in healthy subjects during continuous positive airway pressure breathing.

There is conflicting evidence in the literature as to the potential effect of continuous positive airway pressure (CPAP) on cerebral perfusion. Compromising cerebral perfusion could possibly outweigh the benefit of improved oxygenation. Patients with the obstructive sleep apnea syndrome (OSAS) have been claimed to have a higher cerebrovascular reactivity to changes in end-tidal pCO2. In this study, we investigated 23 patients with OSAS and 16 healthy young adults in the waking state. Both groups performed a series of 10 min of normal breathing, 20 min with 9 cmH2O nasal CPAP, and then 10 min of normal breathing while wearing a nasal CPAP mask. The following parameters were assessed: bilateral transcranial Doppler signal of the middle cerebral artery, systolic and diastolic blood pressure assessed manually, and cerebrovascular reactivity to changes in pCO2 during hyperventilation and rebreathing into an airbag. Continuous end-tidal pCO2 measurements were performed in 14 subjects. As compared with normal breathing middle cerebral artery blood flow velocity and pCO2 remained unchanged during CPAP. Systolic and diastolic blood pressure increased slightly by 1.2 mmHg (p = 0.015) and 1.1 mmHg (p = 0.007), respectively. Cerebrovascular reactivity did not differ in the two groups. Nasal CPAP of 9 cmH2O is a safe treatment with respect to the maintenance of cerebral blood flow. Our study gives further evidence for the autoregulation's capacity to maintain cerebral blood flow velocity constant during different levels of intrathoracic pressure and different cerebral perfusion pressures. We could not demonstrate any difference in cerebrovascular reactivity between patients with OSAS and healthy persons.

Adult↗
PubMed1998

Cerebral hemodynamics during electrically induced seizures.

Electroconvulsive therapy (ECT) is an appropriate clinical model to investigate blood flow during seizures. In this study cerebral blood flow velocity (CBFV) was measured during 40 ECTs in 10 patients by means of transcranial Doppler sonography. EEG was recorded continuously. Under general anesthesia, the pre-convulsive blood flow velocity (Vmean) decreased significantly. After ECT, we measured a dramatic increase in Vmean which was significantly greater in the left MCA than in the right MCA. After termination of seizures, flow velocities returned to baseline levels. The striking increase in cerebral blood flow velocity reflects excessive cerebral metabolism during convulsive neuronal activation. The left hemisphere seems to be more sensitive to electrical stimuli as was indicated by its predominant augmentation of CBFVs.

Adolescent↗
PubMed1998

Absence of mutations in peripheral myelin protein-22, myelin protein zero, and connexin 32 in autosomal recessive Dejerine-Sottas syndrome.

Motor and sensory neuropathies with the clinical features of HMSN III (Dejerine-Sottas syndrome, DSS) are etiologically related to heterozygous mutations in either peripheral myelin protein-22 (PMP22) or myelin protein zero (MPZ). Heterozygous mutations in either of these two genes are also responsible for other hereditary peripheral neuropathies (HNPP, CMT1A, CMT1B or CH). In two families DSS was related to the homozygous presence of a MPZ mutation while heterozygosity showed a much milder phenotype. It has therefore been suggested that the clinical phenotype in peripheral neuropathies is related to the mutated gene, the type of mutation and confounding effects from other sources. In this study we describe a family with recessive DSS in which mutations were absent from the PMP22, MPZ, and connexin 32 (Cx32) genes. We conclude that DSS also exists as a distinct genetic entity with autosomal recessive inheritance as originally defined by Dejerine and Sottas in 1893.

Child, Preschool↗
PubMed1998

Recurrent brachial plexus palsies as the only clinical expression of hereditary neuropathy with liability to pressure palsies associated with a de novo deletion of the peripheral myelin protein-22 gene.

There is phenotypic heterogeneity in patients with hereditary neuropathy with liability to pressure palsies. In rare cases, recurrent brachial plexopathy is the only expression of the disease. We describe a patient with three episodes of plexus brachialis palsy and a de novo deletion of the peripheral myelin protein-22 gene. We conclude that DNA analysis is a key issue not only for the differentiation of peripheral neuropathies but also in the diagnosis of recurrent plexopathies.

Adult↗
PubMed1998

[Recommendation for organization of special stroke departments (stroke units). 1997 implementation].

Stroke units are hospital-based special wards aiming at optimal care by a specialized team with an integrated concept for patients with acute strokes. Following the initial neurological and neuroradiological evaluation, early treatment will be initiated based on the assumed pathophysiology of the stroke. Acute management includes monitoring of physiological, parameters, care by specialized nurses, and early implementation of physiotherapists, speech therapy and occupational therapy. Despite the increased initial costs, the long-term burden for the health system is decreased by shorter hospital stay and reduced morbidity and disability.

Cerebrovascular Disorders↗
PubMed1998

Prevalence of factor V Leiden mutation in young adults with cerebral ischaemia: a case-control study on 225 patients.

Cerebral ischaemia in young adults is a well-recognised disease, and approximately half of the cases remain aetiologically unclear despite extensive investigations. Thrombophilias are known to cause a subset of ischaemic strokes in this population. The factor V Leiden (FVL) mutation, causing resistance to activated protein C, has recently been recognised as the most important genetic thrombophilia in the Western population. Carriers of this gene mutation have a sevenfold increased risk of phlebothrombosis. We undertook this study to evaluate whether the FVL mutation constitutes a risk factor for juvenile cerebral ischaemias. A total of 225 patients aged < or = 45 years at onset of cerebral ischaemia and 200 age-matched healthy controls were investigated. The overall frequency of heterozygosity for the FVL mutation did not differ significantly between patients (8.4%) and controls [6.0%; odds ratio (OR) 1.4, 95% confidence interval (CI) 0.7-3.1]. In the subgroup of patients with cryptogenic cerebral ischaemia (n = 94), however, a significantly higher frequency of this gene defect (15.9%) was found compared with the controls (OR 3.0, CI 1.3-6.6). Further trends towards higher frequencies of the FVL mutation were found in patients with patent foramen ovale (OR 1.9), individual (OR 2.1) or family history of previous thrombembolisms (OR 2.0), and in those aged 25 years at onset of disease (OR 1.9, all not significant). In conclusion, the FVL mutation is not a risk factor for cerebral ischaemia of the young. However, our results suggest that this gene mutation plays an aetiological role in the subgroup of patients suffering from 'cryptogenic' ischaemic events.

Adolescent↗
PubMed1998

Cerebral and systemic embolization during left ventricular support with the Novacor N100 device.

BACKGROUND: Patients undergoing implantation of left ventricular assist systems (LVAS) are prone to thromboembolic complications. We analyzed the incidence, clinical findings, and outcome of neurologic and systemic thromboembolic events (TE) in patients with the Novacor N100 LVAS. In a subset of patients, transcranial Doppler sonography was used to detect microembolic signals. METHODS: Thirty-six patients underwent implantation of a Novacor N100 LVAS for various reasons. The surgical procedure was elective in 18 patients and scheduled on an urgent or emergency basis in another 18 patients. The assist period lasted from 17 to 336 days (109 +/- 88 days); 22 patients were forwarded to heart transplantation after being supported for 140 +/- 87 days. RESULTS: Clinical cerebral embolism was evident in 17 patients (47%). Thromboembolic events were singular in 8 and multiple in 9 patients; in the latter up to 10 TE occurred (mean +/- SD, 1.4 +/- 2 TE). Leading neurologic symptoms were unilateral hemiplegia in 11, as well as ocular symptoms and aphasia in 12 patients each. Noncerebral TE were detected in 4 patients, 2 of whom underwent an emergency operation for intestinal and iliac artery occlusion. The incidence of TE did not correlate strongly with the interval of LVAS support. Cerebral computed tomography confirmed lesions in 58% of patients. Transcranial Doppler sonography detected microembolic signals on 67% of all recordings, with the microembolic signals being more frequent on days with clinically manifest TE. The outcomes were good, as only 2 patients suffer from neurologic sequelae. CONCLUSIONS: Thromboembolism is still a major threat for patients with LVAS implantation. Neurologic sequelae are frequent but have a favorable prognosis, and systemic complications occur considerably less often. Patient selection, adequate anticoagulation, and transcranial Doppler sonography may help to reduce the incidence of TE.

Adult↗
PubMed1998

The photic driving EEG response and photoreactive cerebral blood flow in the posterior cerebral artery in controls and in patients with epilepsy.

OBJECTIVES: Instantaneous changes in blood flow velocities during visual stimulation can be assessed by transcranial Doppler sonography (TCD). METHODS: We investigated the possible relationship between the characteristics of photic driving in the EEG elicited by repetitive intermittent photic stimulation and the photoreactive flow changes in the posterior and middle cerebral artery (PCA, MCA) of 25 normal controls and 25 patients with focal epilepsy. Cerebral blood flow velocities (CBFV) of the right PCA (P2 segment) and the left middle cerebral artery (MCA) were measured using a 2 Hz transcranial Doppler device. Simultaneously, scalp EEGs were recorded. RESULTS: During photic stimulation the mean CBFV increase was 20.4 +/- 9.5% in the PCA of the controls (n = 132 stimulations) and 16.0 +/- 10.8% in epileptic patients (n = 150 stimulations, P < 0.01). During those stimulation series with a good EEG driving response (n = 203), the mean increase of CBFV in the PCA was 19.7 +/- 10.0%, as opposed to 14.4 +/- 10.5% during the stimulations with a poor EEG response (n = 79, P < 0.01). A good photic driving response was associated with a higher increase of CBFV in the PCA than a poor one. The increase in CBFV of the PCA in normal controls was higher than in patients with focal epilepsy. CONCLUSIONS: This may indicate that epileptic patients have a reduced coupling between neuronal activation and blood flow.

Adolescent↗
PubMed1998

Detection of high intensity transient signals (HITS): how and why?

HITS (high intensity transient signals) in transcranial Doppler recordings reflect either microemboli, both gaseous and solid, or artefacts. Various frequencies in number of microembolic signals (MES) have been reported in the same clinical condition. A possible explanation for these discrepancies may be different device settings and algorithms for embolus detection. For reproducibility of data, we suggest that studies on MES report the following parameters: (1) Ultrasound device; (2) transducer type; (3) insonated artery; (4) insonation depth; (5) algorithms for signal intensity measurement; (6) scale settings; (7) detection threshold; (8) axial extension of sample volume; (9) fast Fourier transform (FFT) size (number of points used); (10) FFT length (time); (11) FFT overlap; (12) transmitted ultrasound frequency; (13) high pass filter settings; and (14) recording time. No current system of automatic embolus detection has the full sensitivity and specificity required for clinical use. Therefore, each of the signals detected by these devices needs to be checked and verified by an experienced investigator. MES will help to identify the site and activity of the embolizing lesion. Microembolus detection might reduce the observation time and the number of patients needed to perform interventional trials. First, however, MES needs to be validated as a meaningful prognostic parameter. Microemboli originating from prosthetic cardiac valves are mainly gaseous. Therefore, they cannot serve as an indicator of the valves thromboembolic activity or the patient's stroke risk.

Carotid Stenosis↗
PubMed1998

Echo-enhanced ultrasound for diagnosis and management in stroke patients.

Early diagnosis of stroke and recognition of preceding transient ischemic attacks (TIAs) is important for clinical outcome. Better education of the signs and symptoms of TIA and stroke and improved diagnostic procedures will help to reduce the impact of stroke. Magnetic resonance imaging (MRI), computed tomography (CT) and single photon emission computed tomography (SPECT) are used to diagnose cerebral infarctions. MRI is the most effective diagnostic modality, however, MRI equipment is expensive and not always available. CT is therefore usually used but it has limitations, in detecting small infarctions, particularly in the posterior fossa. Ultrasound is a safe and inexpensive bedside diagnostic procedure. Ultrasound is often used in patients after TIA or stroke, however, it may be inadequate due to poor insonation conditions through the skull, or because the relevant vessel lies deep within the brain. Arteries with slow flowing blood are also difficult to image. The application of ultrasound has expanded with the development of two-dimensional transcranial color-coded sonography (TCCS) which provides both anatomical and functional information about the major cerebral vessels. In addition, the use of echo-enhancing agents now provides better images of vessels within the skull and enables ultrasound examinations to be performed even in patients with a poor transtemporal window. Echo-enhanced ultrasound can also provide images of vessels deep within the brain, which were previously non-evaluable. The echo-enhancing agent Levovist(R) has been extensively studied in patients undergoing ultrasound examination to detect cerebrovascular disease. Levovist improves diagnostic confidence without compromising safety. The improvement in images obtained of the cerebral vessels, including both arteries and veins, using echo-enhanced ultrasound may make this technique the future method of choice for patients with cerebrovascular disease.

Cerebrovascular Disorders↗
PubMed1998

Growth inhibition of newly established human glioma cell lines by leukemia inhibitory factor.

We have established three new cell lines deriving from malignant human gliomas. The cell lines were described in terms of both morphology and growth characteristics. Most cells in all three cell lines expressed the neuroepithelial marker protein GFAP. In terms of growth characteristics, the cells showed only slight differences. The cell lines showed no expression of the neural form of the c-src gene, pp60c-srcN, but did express the ubiquitous form, pp60c-src. The established glioma cell lines were also examined for expression of members of the neuropoietic cytokine family, CNTF and LIF, and their respective receptor components CNTFRalpha, LIFRbeta and gp130. With the exception of CNTFRalpha both the ligands and their receptor components were expressed in similar amounts in all three cell lines. The presence of ligand and receptor prompted us to study the effects of exogenously supplied factors on the growth of the glioma cell lines. Whereas LIF induced a high c-fos expression, only low c-fos induction was observed upon CNTF treatment. Accordingly, CNTF did not have any noticeable effects on glioma cell growth in culture, while LIF mediated an inhibiting effect on the growth of the three glioma cell lines in culture.

Aneuploidy↗
PubMed1998

Mutation analysis of a putative sialyltransferase gene, the SFRS2 splicing factor gene and the c-myb ET-locus in two families with hereditary neuralgic amyotrophy (HNA).

HNA is an autosomal dominant recurrent focal neuropathy involving the brachial plexus. The etiology of HNA is unknown but the genetic defect most likely affects a non-neuronal tissue. We previously described linkage to chromosome 17q24-q25 in two HNA-families. Here we report the mutation analysis of two candidate genes: a cDNA encoding a putative sialyltransferase and the SFRS2 splicing factor including the c-myb ET-locus which is encoded on the opposite strand of the SFRS2 gene. The complete protein coding regions of both genes were studied by direct DNA sequencing. We did not find a disease associated mutation indicating that these genes are most likely not involved in the pathogenesis of HNA. However, we identified and characterized a rare AvaII polymorphism in the SFRS2 gene and detected a sequencing error, leading to an amino acid change (Val11Leu) in the published sequence of the putative sialyltransferase.

Brachial Plexus Neuritis↗