PubMed Health⌕ Search

Biomedical subjects

M Daffertshofer

Publications and source records attributed to M Daffertshofer.

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

Simultaneous assessment of brain tissue oxygenation and cerebral perfusion during orthostatic stress.

Simultaneous registration of cerebral tissue oxygenation parameters obtained by near infrared spectroscopy (NIRS), intracranial blood flow velocity (CBFV) measured by transcranial Doppler sonography (TCD) and basic cardiovascular parameters was carried out during a passive 80 degrees head-up tilt table test in 15 patients with a history of orthostatic syncope and 20 control subjects. In normals, the cardiovascular parameters showed a specific course after changing to a vertical position: the heart rate increased, the mean arterial blood pressure remained unchanged, and the CBFV decreased. The NIRS measurements showed an increase in deoxyhemoglobin (HHb) and a decline in oxyhemoglobin (O(2)Hb) and the regional oxygen saturation (RSAT). Patients had a significantly more prominent decline in arterial blood pressure (p < 0.001), CBFV (p < 0.001) and RSAT (p = 0.04). Five patients experienced symptoms of (pre)syncope during the experiment, which were associated with a further sudden and marked (>10%) drop of O(2)Hb. The results indicate that the combination of TCD and NIRS increases the understanding of hemodynamic and metabolic changes during orthostatic stress, which may lead to individually suited therapeutic procedures.

Blood Flow Velocity↗
PubMed1999

Vasoneuronal coupling in migraineurs after subcutaneous sumatriptan: a TCD study.

According to the trigeminovascular model of pain in migraine, sterile neurogenic inflammation of dural vessels stimulates nociceptive fibres of the trigeminal nerve. Sumatriptan, a 5-HT1 receptor agonist, blocks this reaction and mediates vasoconstriction of meningeal arteries. However, it is uncertain, whether sumatriptan also has a vasoconstrictive effect on cerebral arteries, which may influence vasoneuronal coupling and induce secondary cerebral blood flow changes. We studied changes of cerebral blood flow velocity (CBFV) and the pulsatility index (PI) in the posterior cerebral artery (PCA) after stimulus activation before, 10 min and 30 min after subcutaneous application of 6 mg sumatriptan, in order to assess potential vasoactive effects on cerebral circulation. CBFV was recorded from both PCAs simultaneously in 27 migraineurs (twenty women, seven men, mean age 29 years), and arterial blood pressure (BP), heart rate (HR) and respiration rate (RR) were monitored. Although the mean diastolic blood pressure rose significantly from 75 mm Hg to 81 mm Hg (P<0.05) and systolic blood pressure and respiration rates remained constant, average CBFV values remained constant. Similarly, the relative increase of CBFV by visual stimulation, which is clearly higher compared to controls in other studies (55.0% before, 52.6% after 10 min, and 52.4% after 30 min), and absolute mean values for CBFV and PI did not change after visual stimulation. These results provide evidence against the hypothesis that sumatriptan produces vasoconstriction in the intracranial human arterial circulation as a potential risk of cerebral ischemia.

Adult↗
PubMed1999

Arterial gas embolism after decompression: correlation with right-to-left shunting.

Paradoxical gas embolism is a possible cause of neurologic sequelae after decompression in divers. The authors detected arterial bubbles after decompression from chamber dives in two of six divers using transcranial Doppler sonography (TCD). Arterial bubbles correlated with the size of right-to-left shunting as diagnosed by contrast TCD. The pathway of spontaneous paradoxical embolism was tracked for the first time, supporting the concept of paradoxical gas embolism as a cause of early neurologic sequelae after decompression in at-risk divers.

Adult↗
PubMed1999

Low-frequency, low-intensity ultrasound accelerates thrombolysis through the skull.

Systemic thrombolysis of acute ischemic stroke with recombinant tissue plasminogen activator (rt-PA) has been established recently. Whereas the delay to and the rate of vessel recanalization are unknown, they are likely slower and smaller than for local application of rt-PA. This may contribute to the small benefits of recovery reported and stimulate further investigations to improve clot lysis. Pilot studies indicate that continuous-wave low-frequency ultrasound (US) can accelerate rt-PA-mediated recanalization of peripheral thrombotic vessel occlusion. For the hypothesized therapeutical purpose in stroke treatment, we measured the attenuation of ultrasound through the skull at different frequencies and intensities (33.3 and 71.4 kHz; 0.5 and 3.4 W/cm2), and investigated thrombolysis in vitro (n = 125 clots). Attenuation was lowest by transtemporal insonation of 33.3 kHz, 0.1 dB (0.9). Thrombolysis (artificial fibrin-rich clots) was significantly increased after 1 h (p < 0.025) and after 3 h (p < 0.01) for US treatment in combination with rt-PA vs. rt-PA alone. Results suggest that US increases rt-PA-mediated thrombolysis through the skull and may improve benefits of thrombolytic stroke treatment in vivo.

Brain Ischemia↗
PubMed1999

Comparison of transcranial Doppler flow velocity and cerebral blood flow during focal ischemia in rabbits.

The predictive value of transcranial Doppler (TCD) cerebral blood flow velocity (CBFV) measurements for cerebral blood flow (CBF) calculations in humans is still controversial, and experimental correlative studies are lacking. The aim of the present study was to validate TCD signals of CBFV during focal cerebral ischemia. Therefore, CBFV determined in the middle cerebral artery (MCA) was compared with values of CBF obtained from autoradiograms of ischemic brain areas. To determine CBFV, a transcranial Doppler ultrasound probe (TCD) adapted to small sample volumes was used in 9 rabbits. CBF was quantified after a final infusion of [14C]-iodoantipyrine in the same animals. For focal cerebral ischemia induction, two threads were flushed upward simultaneously into the internal carotid artery, resulting in a flow reduction in the ipsilateral MCA. After thread occlusion, mean systolic CBFV in the MCA decreased from 49 +/- 9 cm/s to 22 +/- 3 cm/s. CBF in the caudate nucleus was reduced (19 +/- 8 mL/100 g/min) compared to the contralateral nonischemic side (52 +/- 18 mL/100 g/min). The decrease in hemispheric CBF correlated well with the decrease in both mean systolic (r = 0.97) and diastolic (r = 0.94) CBFV in the MCA (p < 0.01). The decrease in CBFV determined by transcranial Doppler ultrasound in the MCA appears to reflect the reduction in CBF in the affected brain hemisphere and can be used as a quantitative in vivo parameter for tissue perfusion.

Animals↗
PubMed1999

Age and stimulus dependency of visually evoked cerebral blood flow responses.

BACKGROUND AND PURPOSE: During visual stimulation, the increased metabolic demand is coupled with an increase of cerebral blood flow velocity (pCBFV) in the posterior cerebral artery (PCA). Investigation of the visually evoked flow responses (VEFR, expressed as percentage of increase from baseline pCBFV values) was suggested for different conditions of vasoneuronal disorders in the absence of any systematic investigation in healthy subjects. METHODS: We investigated VEFRs from both PCAs to various increasingly complex paradigms (diffuse light, alternating checkerboard patterns, and a color video movie stimulation; 5, 10, 20, and 30-second intervals) in 60 healthy volunteers (mean age, 41.5+/-14.9 years; range, 24 to 80 years; 28 male, 32 female) at different recording sites (P1 versus P2 segments of PCAs). RESULTS: With increasing complexity of stimulation, the VEFRs increased significantly (24.3+/-10.3%, 28.5+/-13.5%, and 43.4+/-10.7%, respectively). Twenty-second stimulation intervals yielded maximal responses (41.5+/-13.2%) compared with 5-, 10-, and 30-second intervals (22.6+/-14.1%, P=0.001; 34.4+/-11.7%, P=0.0042; and 35.5+/-9.9%, P=0.0032, respectively). Significantly higher responses were gained from P2 segments than from P1 segments (42.7+/-7.2% versus 28.2+/-7.1%). Although VEFRs tended to decrease in amplitude with age (mean, 41. 7+/-10.5% [20 to 40 years], 35+/-9.2% [40 to 60 years], and 33.9+/-8.6% [60 to 80 years]); without significant sex-related differences, only the percentage decrement of the pulsatility indices during stimulation were significant (mean, 24+/-10.7% [20 to 40 years], 20+/-7.3% [40 to 60 years], and 13+/-11.2% [60 to 80 years]). CONCLUSIONS: For optimal stimulus conditions for maximum VEFRs, a colored video stimulation of 20-second intervals should be used to combine responses not only from the primary visual projection fields (V1 and V2) but also from temporal lobe areas (V3 through V5) often supplied by the PCA.

Adult↗
PubMed1999

Changes in coagulation and fibrinolysis markers in acute ischemic stroke treated with recombinant tissue plasminogen activator.

BACKGROUND AND PURPOSE: Shifts of the balance between coagulation and fibrinolysis play a crucial role in pathogenesis and treatment of cerebral ischemia. In this study, we characterized the kinetics of hemostatic abnormalities induced by acute ischemic stroke and its thrombolytic (recombinant tissue plasminogen activator [rtPA]) or anticoagulant (heparin) treatment. METHODS: Systemic generation of molecular markers of hemostasis (fibrin monomer, D-dimer, thrombin-antithrombin complex, and fibrinopeptide 1.2) was monitored in acute ischemic stroke, and the effects of thrombolytic and anticoagulant treatments were analyzed. RESULTS: Thrombolysis with rtPA induced a massive response of markers of coagulation activation and fibrin formation that peaked after 1 to 3 hours and persisted for up to 72 hours. In contrast, only minor hemostatic changes were induced by acute ischemic stroke itself. Administration of heparin did not significantly affect these hemostatic abnormalities. CONCLUSIONS: This first characterization of the coagulation activation induced by rtPA treatment for acute ischemic stroke and the failure to abolish such hemostatic abnormalities by heparin may be of value for further refinement of the currently discussed thrombolytic therapy and the controversial adjunctive anticoagulant prophylaxis in stroke patients.

Aged↗
PubMed1998

Assessment of T2- and T1-weighted MRI brain lesion load in patients with subcortical vascular encephalopathy.

Previous cross-sectional studies in patients with subcortical vascular encephalopathy (SVE) have shown little or no correlation between brain lesion load and clinical disability, which could be due to the low specificity of T2-weighted MRI. Recent studies have indicated that T1-weighted MRI may be more specific than T2-weighted MRI for severe tissue destruction. We studied 37 patients with a diagnosis of SVE and 11 normal controls with standardised T1- and T2-weighted MRI. All patients underwent detailed clinical assessment including a neuropsychological test battery and computerised gait analysis. Both the T2- and T1-weighted total MRI lesion loads different between patients and controls different, particularly T1. The ratio of T2-/T1-weighted lesion load was lower in controls than in patients. There was no overall correlation of T1- or T2-weighted lesion load with clinical disability, but group comparison of patients with severe and mild clinical deficits showed different lesion loads. We suggest that T1- and T2-weighted MRI lesion loads demonstrate relevant structural abnormality in patients with SVE.

Aged↗
PubMed1997

Leakage of brain-originated proteins in peripheral blood: temporal profile and diagnostic value in early ischemic stroke.

The clinical value of determination of CNS-specific proteins in peripheral blood at the acute phase of ischemic stroke is unclear. S-100 protein and neurone specific enolase were serially quantified in peripheral blood at the acute and subacute phase of ischemic stroke (hours 4, 8, 10, 24 and 72 after onset of symptoms). Whereas S-100 protein was detected in none of the matched control subjects. this protein was observed in 17/24 of the stroke patients. Patients with detectable S-100 protein had significantly larger infarctions. Cortical infarctions had already significantly increased S-100 concentrations at days 1 and 3 compared to subcortical or brainstem infarctions. Patients with volumes of brain lesion of >5 ccm exhibited significantly increased serum levels of S-100 at hours 10, 24 and 72 compared to those with lesion volumes of <5 ccm. At hours 10, 24 and 72, concentrations of S-100 correlated with scores of neurological outcome. Although kinetics of release of neurone specific enolase showed a similar pattern of release in blood, no significant association to outcome or extent of brain damage was observed. These results suggest that S-100 protein and not NSE may represent a useful serum marker of brain damage in acute stroke.

Aged↗
PubMed1997

Cohort study of multiple brain lesions in sport divers: role of a patent foramen ovale.

OBJECTIVE: To investigate the role of a patient foramen ovale in the pathogenesis of multiple brain lesions acquired by sport divers in the absence of reported decompression symptoms. DESIGN: Prospective double blind cohort study. SETTING: Diving clubs around Heidelberg and departments of neuroradiology and neurology. SUBJECTS: 87 sport divers with a minimum of 160 scuba dives (dives with self contained underwater breathing apparatus). MAIN OUTCOME MEASURES: Presence of multiple brain lesions visualised by cranial magnetic resonance imaging and presence and size of patent foramen ovale as documented by echocontrast transcranial Doppler ultrasonography. RESULTS: 25 subjects were found to have a right-to-left shunt, 13 with a patent foramen ovale of high haemodynamic relevance. A total of 41 brain lesions were detected in 11 divers. There were seven brain lesions in seven divers without a right-to-left shunt and 34 lesions in four divers with a right-to-left shunt. Multiple brain lesions occurred exclusively in three divers with a large patent foramen ovale (P = 0.004). CONCLUSIONS: Multiple brain lesions in sport divers were associated with presence of a large patent foramen ovale. This association suggests paradoxical gas embolism as the pathological mechanism. A patent foramen ovale of high haemodynamic relevance seems to be an important risk factor for developing multiple brain lesions in sport divers.

Brain Injuries↗
PubMed1997

Combined electroencephalography and measurements of transcranial blood flow velocity during orthostatic testing--a new approach to assess syncope of unknown origin?

Differential diagnosis of syncope and seizures frequently imposes a major problem, particularly if interictal examinations are normal. We performed orthostatic testing combined with surface electroencephalography (EEG) and non-invasive measurements of cerebral blood flow velocity. Ten healthy controls, ten patients with confirmed diagnosis of epilepsy and 25 patients with history of syncope of unknown origin were examined. The following parameters were evaluated continuously and simultaneously during orthostatic challenge: computerized EEG with synchronous video-monitoring, transcranial Doppler sonography (TCD), heart rate and blood pressure. Isolated cerebrovascular dysregulation (i.e. a drop in cerebral perfusion despite the absence of a significant drop in peripheral blood pressure) occurred in 2/10 controls, 3/10 patients with epilepsy and 11/25 patients with syncope of unknown origin. The combined EEG and TCD measurements represent a new approach to the work-up of patients with otherwise unexplained syncope, helping us to understand the interdependence of neuronal activity and peripheral/cerebrovascular autoregulation under postural stress.

Adolescent↗
PubMed1997

Cerebrovascular involvement in the acute phase of bacterial meningitis.

Cerebral ischaemia is a common complication of bacterial meningitis. Although cerebrovascular involvement in the acute phase of inflammation may be particularly important for the still unacceptably high morbidity and mortality, only, a few studies have investigated cerebrovascular changes in bacterial meningitis. We prospectively investigated changes of intracranial cerebral blood flow velocities (CBFV) in 22 patients (12 men, 10 women, mean age 48 years, 19 years, SD) with bacterial meningitis, by means of transcranial Doppler sonography (TCD). According to previously published criteria the degree of arterial narrowing was assessed and related to the patients' outcome. Elevated CBFVs in the middle cerebral artery were documented in 18/22 patients with markedly increased systolic peak velocities (CBFV of > 210 cm/s) in 7 patients. Serial examinations performed in 11 patients showed elevated CBFV as early as day 1, reaching peak CBFV between day 3 and day 6 after onset of symptoms in most cases. Furthermore, cerebrovascular involvement was also documented by disturbances of physiological slow spontaneous oscillations of blood flow velocities in 5/10 patients examined with TCD. Low Glasgow Coma Scales (< 7) on admission (29% vs 0%), focal cerebral ischaemic deficits (29% vs 7%) and, seizures (43% vs 7%) were more frequent in patients with CBFV of > 210 cm/s. Finally, a poor clinical outcome was significantly related to severe vascular involvement (P < 0.05). In conclusion, cerebrovascular complications are frequently found in patients with bacterial meningitis. TCD is an easily applicable technique for revealing vascular changes non-invasively, even in severely ill patients. Since our data suggest an unfavourable course of the disease in association with increased CBFV in intracranial arteries, probably indicating vasospasm, TCD could potentially be used to identify high-risk patients who could benefit from adjuvant therapeutic interventions.

Adult↗
PubMed1996

High intensity transient signals (HITS) in patients with carotid artery disease.

Interest in the Doppler ultrasound phenomenon of "High Intensity Transient Signals" (HITS) is based on the, thus far, unproven hypothesis, that these signals may to some extent represent silent cerebral microembolism ahead of a TIA/stroke and hence identify patients at risk for stroke. We prospectively investigated 80 patients with 102 moderate/severe internal carotid artery lesions. Patients with additional potential sources of cerebral ischemia were excluded. Bilateral transcranial Doppler monitorings of the middle cerebral arteries (MCA) were performed for =>30 min. HITS occurred more often in patients with completed stroke (21.9%) than in patients with transient ischemic deficits (12.5%), but significantly less in asymptomatic subjects (4.3%) (p<0.05). The incidence was maximal in patients examined within the first week after the onset of stroke. HITS were significantly more often associated with severe (> 70%) (23.5%) than with moderate (50 - 70%) internal carotid artery stenosis (3.4%) (p<0.05). These figures are closely related to annual stroke risk estimates recently reported about patients evaluated in multi-centre trials for carotid endarterectomy, and support the concept that HITS associated with carotid disease represent an important individual risk predictor.

Carotid Artery Diseases↗
PubMed1996

High-intensity transient signals in patients with cerebral ischemia.

BACKGROUND AND PURPOSE: This study investigated the diagnostic relevance of transcranial Doppler monitoring for the detection of high-intensity transient signals (HITS) in patients with recent cerebral ischemic events of various origins. METHODS: We prospectively performed bilateral transcranial Doppler monitoring (mean, 48 +/- 8 minutes) from both middle cerebral arteries in 280 patients with an acute (< 4 weeks) cerebral ischemic event in the middle cerebral artery territory and in 118 asymptomatic control subjects. HITS were analyzed according to a standardized protocol. RESULTS: Symptomatic patients had a significantly (P < .001) higher rate (9.3%) of HITS than asymptomatic control subjects (1.7%). Patients with reversible ischemia (4.2%) and patients with suspected small-vessel syndromes (4.5%) had lower rates of HITS (P < .05) than those with large-vessel territory strokes (14.2%). Brain imaging (CT/MRI) results corresponded with this observation: the occurrence of HITS was significantly higher (P < .001) in patients with a pattern of large-vessel territorial brain infarction (19.0%) than in those with lacunar lesions (0%) or unidentified ischemic lesions (3.4%). Patients with identified sources of potential embolism (12.9%) had HITS (P < .001) more frequently than those without (0%). Patients with cardiac sources of embolism (excluding artificial heart valves) showed fewer HITS (6.2%) than patients with vascular sources (17.1%). CONCLUSIONS: The results indicate that HITS occur predominantly in patients with large-vessel territory stroke patterns and persisting deficits that are most likely due to artery-to-artery or cardiogenic embolism. In contrast, patients with small-vessel disease and rapid recovery only occasionally present with HITS. Thus, the detection of HITS may substantially support the classification of the individual pathogenesis of cerebral ischemia, particularly when multiple risk constellations for stroke coexist.

Adult↗
PubMed1995

Cerebrovascular regulation and vasoneuronal coupling.

Maintenance of cerebral perfusion pressure is a prerequisite for the prevention of cerebral ischemia. Physiological fluctuations in systemic perfusion pressure are compensated by cerebrovascular autoregulation. Cerebral hypoperfusion could result from (1) systemic hemodynamic failure (eg, distal to severe arterial stenosis), overcharging the vasoregulatory capacity; (2) dysfunction and exhaustion of cerebrovascular autoregulation; or (3) both. Ultrasound offers an excellent temporal resolution, is noninvasive, and is easily applicable for follow-up investigations. Despite its poor spatial resolution, transcranial Doppler sonography has been used for determination of cerebral perfusion reserve studies measuring cerebral blood flow velocity (CBFV) during hypercapnia or application of vasoactive agents (eg, acetazolamide). This approach evaluates vasomotor regulation in patients with hemodynamic compromise distal to severe stenosis or occlusion of the brain supplying arteries. Monitoring CBFV during tilt table examinations directly measures cerebral autoregulation. In patients with systemic orthostatic hypotension, maintainance or failure of cerebrovascular compensation and, even more importantly, cerebrovascular dysautoregulation, despite normal systemic blood pressure regulation, may be demonstrated. Vasoneuronal coupling is reflected by CBFV variations during appropriate neuronal stimulation. Neuronal dysfunction is associated with CBFV abnormalities as exemplified by preconditions of focal cerebral dysfunction in the posterior cerebral artery (PCA) in migraineurs with aura, where massive alteration of vasoneuronal coupling and ischemia is threatening during spreading depression. A highly significant asymmetric gain of vasoneuronal coupling in the interictal state may act as a trigger mechanism in these patients. Testing for vasoneuronal coupling within the middle cerebral artery (MCA) territory is more difficult due to the poor spatial resolution with various neuronal stimuli (eg, motorsensory or cognitive paradigms), only eliciting local neuronal areas underrepresented in the MCA CBFV global changes. However, motor stimulation evoked CBFV may be used to indicate dysintegration of vasoneuronal coupling in the course of acute cerebral ischemia with sensorimotor hemiparesis and, moreover, seems to be of prognostic value regarding the motor deficit.

Blood Flow Velocity↗
PubMed1995

Modification of low-frequency spontaneous oscillations in blood flow velocity in large- and small-artery disease.

During a 30-minute period, the blood flow velocity of both middle cerebral arteries (MCAs) was measured bilaterally in 27 patients with obstructive carotid disease (n = 18, large-artery disease) or subcortical vascular encephalopathy (n = 9, small-artery disease) and in control subjects of similar age and sex distribution (n = 14). To identify low-frequency spontaneous oscillations (LFSOs), MCA envelope curves were Fourier transformed with filter application to select low-frequency spectra (0.01-0.05, 0.05-0.15, 0.15-0.50 Hz). To measure the extent of LFSO amplitudes, a coefficient of variation (CoV) was calculated. In addition, a coefficient of correlation (CoC) was calculated to assess LFSO bilateral synchronicity. Normal ranges for CoV (mean = 5.38 +/- 1.82%) and CoC (mean = 0.91 +/- 0.06) were established in control subjects. In patients with large-artery disease, a significant CoV reduction was observed ipsilateral to the carotid lesion (CoV mean = 3.91 +/- 1.10%; p < 0.05, Wilcoxon's test) with a contralateral compensatory increase (CoV mean = 5.68 +/- 1.79%). In addition, a significant desynchronization of LFSOs was found in patients with large-artery disease (CoC = 0.39 +/- 0.35, p < 0.05). This was less obvious in patients with small-artery disease, who demonstrated a marked bilateral reduction of LFSO activity (CoV mean = 3.60 +/- 0.71%, p < 0.05) and CoC values.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Variability of vascular territory in stroke. Pitfalls and failure of stroke pattern interpretation.

BACKGROUND AND PURPOSE: We investigated the efficacy and feasibility of determining infarction mechanisms and underlying embolic or hemodynamic pathologies from topographical patterns of ischemic damage seen on computed tomography or magnetic resonance imaging. METHODS: Infarction patterns from 22 patients with ipsilateral severe, hemodynamically relevant carotid stenosis (n = 6) or occlusions (n = 16) were superimposed, using two matching algorithms, onto maps showing the variability of the cerebral vascular territories as determined from recent cadaver studies. These images were used to classify the infarctions as border-zone or territorial for the two conditions of minimal and maximal middle cerebral artery distribution. RESULTS: Classification of infarction patterns resulting from carotid stenosis was independent of the territorial extension map chosen: 83% were classified as territorial. Classification of patterns due to carotid occlusion, however, varied highly; 81% of infarctions were considered territorial when the maximal middle cerebral artery distribution map was used, whereas only 19% were when the minimal territorial extension map was used. CONCLUSIONS: The current concept that stroke mechanisms can be inferred from the interpretation of stroke patterns seen on computed tomography scans or magnetic resonance imaging is significantly confounded by the demonstrated variability in intracranial vascular distributions. Stroke pattern interpretation appears to be highly dependent on the in vivo vascular tree of the individual, which is unknown to the examiner. This calls into question the reliability of classifying infarction patterns as border-zone or territorial. Determination of true underlying stroke mechanisms requires a comprehensive approach and cannot be based solely on stroke pattern interpretation.

Brain↗