PubMed Health⌕ Search

Biomedical subjects

B Sperling

Publications and source records attributed to B Sperling.

18 recordsLinked to original sources

The effect of i.v. L-NG methylarginine hydrochloride (L-NMMA: 546C88) on basal and acetazolamide (Diamox) induced changes of blood velocity in cerebral arteries and regional cerebral blood flow in man.

The aim of this study was to estimate the effect of Nitric Oxide synthase (NOS)-inhibition (L-NMMA) on the diameter of the middle cerebral artery (MCA) and on regional cerebral blood flow (rCBF). Furthermore, to assess the effect of L-NMMA on acetazolamide induced increases in MCA blood velocity (Vmean) and rCBF. In an open crossover design 12 healthy subjects attended the laboratory twice. The first day 6 mg/kg L-LNMMA i.v. over 15 min preceded 1 g acetazolamide i.v. over 5 min. Eight days later only acetazolamide was given. V(mean) in MCA was determined with transcranial Doppler (TCD) and rCBF with Xe-133 inhalation SPECT at baseline, after L-NMMA and 25 and 55 min after acetazolamide infusion. After L-NMMA the decrease in rCBF(MCA) was 6.8% (+/- 7.4) (P < 0.019, n = 12), whereas V(mean) was not affected (P = 0.83, n = 8). The change in MCA diameter was estimated to - 1.3% (P = 0.44, n = 8). L-NMMA did not affect acetazolamide increases in Vmean (P = 0.67, n = 8) nor rCBF (P = 0.29, n = 12). The percentage increase of V(mean) was 1.5 times that of rCBF (n = 8). Our data suggest that the basal tone of human cerebral arterioles but not of conduit arteries is NO-dependent. The action of acetazolamide in man is not NO-dependent.

Acetazolamide↗

CGRP may play a causative role in migraine.

Calcitonin gene-related peptide (CGRP) has been detected in increased amounts in external jugular venous blood during migraine attacks. However, it is unknown whether this is secondary to migraine or whether CGRP may cause headache. In a double-blind crossover study, the effect of human alphaCGRP (2 microg/min) or placebo infused intravenously for 20 min was studied in 12 patients suffering from migraine without aura. Headache intensity was scored on a scale from 0 to 10. Two patients were excluded due to severe hypotension and one because she had an infection. In the first hour median peak headache score was 1.0 in the halphaCGRP group vs. 0 in the placebo group (P < 0.01). During the following 11 h all patients experienced headaches after halphaCGRP vs. one patient after placebo (P = 0.0004). The median maximal headache score was 4 after CGRP and 0 after placebo (P = 0.006). In three patients after halphaCGRP, but in no patients after placebo, the delayed headache fulfilled the IHS criteria for migraine without aura. As intravenous administration of halphaCGRP causes headache and migraine in migraineurs, our study suggests that the increase in CGRP observed during spontaneous migraine attacks may play a causative role.

Adult↗

Transcranial Doppler sonography and internal jugular bulb saturation during hyperventilation in patients with fulminant hepatic failure.

Mechanical hyperventilation is often used to postpone or ameliorate intracranial hypertension in patients with fulminant hepatic failure (FHF). Because such treatment may critically reduce cerebral blood flow (CBF), bedside techniques to monitor CBF are warranted. In this study, we evaluated the efficacy of transcranial Doppler (TCD) sonography of the middle cerebral artery (MCA) and internal jugular bulb saturation (svJO(2)) to determine relative changes in CBF during mechanical hyperventilation in 8 patients with FHF (median age, 40 years; range, 20 to 54 years). We found that TCD and svJO(2) decreased during hyperventilation in parallel with CBF, determined by the xenon 133 ((133)Xe) washout technique. Quantitatively, the TCD method was less accurate to determine carbon dioxide (CO(2)) reactivity compared with svJO(2) and the (133)Xe technique. This indicates a slight change in MCA diameter during hyperventilation. We conclude that TCD and svJO(2) monitoring may give valuable information on relative changes in CBF during hyperventilation. However, the TCD method appears less accurate for quantitative estimation of CO(2) reactivity in patients with FHF.

Adult↗

MR-visible brain water content in human acute stroke.

Quantification of metabolite concentrations by proton magnetic resonance spectroscopy (1H-MRS) in the human brain using water as an internal standard is based on the assumption that water content does not change significantly in pathologic brain tissue. To test this, we used 1H-MRS to estimate brain water content during the course of cerebral infarction. Measurements were performed serially in the acute, subacute, and chronic phase of infarction. Fourteen patients with acute cerebral infarction were examined as well as 9 healthy controls. To correlate with regional cerebral blood flow (rCBF) SPECT-scanning using 99mTc-HMPAO as flow tracer was performed in the patients. Mean water content (SD) in the infarct area was 37.7 (5.1); 41.8 (4.8); 35.2 (5.4); and 39.3 (5.1) mol x [kg wet weight](-1) at 0-3; 4-7; 8-21; and >180 days after stroke, respectively. Water content increased between Day 0-3 and Day 4-7 (p = 0.034) and decreased from Day 0-3 to Day 8-21 (p = 0.028). Water content at Day 4-7 was significantly higher than in controls (p < or = 0.05). At the same time intervals, mean rCBF (SD) was 76 (23); 94 (31); 106 (35); and 64 (26)%, respectively. There was a significant increase in rCBF from Day 0-3 to Day 4-7 (p = 0.050) and from Day 0-3 to Day 8-21 (p = 0.028). No correlation between rCBF and water content was found. Water content in ischemic brain tissue increased significantly between Day 4-7 after stroke. This should be considered when performing quantitative 1H-MRS using water as an internal standard in stroke patients.

Acute Disease↗

Incomplete brain infarction of reperfused cortex may be quantitated with iomazenil.

BACKGROUND AND PURPOSE: [123I]Iomazenil is a specific radioligand for the central benzodiazepine receptor that may be useful as an indicator of the intactness of cortical neurons after focal cerebral ischemia. We evaluated the binding of this receptor in reperfused cortex among patients with ischemic stroke to detect viable neurons in cortex that appeared structurally intact on conventional neuroimaging studies. METHODS: Fourteen patients were selected by (1) angiography within 24 hours of onset showing embolic occlusion of an intracranial artery, (2) cerebral blood flow showing ischemia of moderate severity in 12 cases and spontaneous reflow in 2 cases, and (3) thrombolysis with reperfusion within 24 hours in most cases. Thirty reperfused cortical areas that remained structurally intact, 7 infarcted cortical areas, and 6 contralateral cerebellar areas with reduced blood flow were selected as regions of interest to estimate receptor binding 5 days to 23 months after the stroke. A two-compartment model was used to compute the distribution volume (Vd) of iomazenil in relative units, with Vd proportional to benzodiazepine receptor concentration. The side-to-side asymmetry ratio of Vd was calculated. RESULTS: The mean asymmetry ratio was 0.89 +/- 0.11 (range, 0.64 to 1.05), 0.50 +/- 0.15 (range, 0.23 to 0.67), and 0.97 +/- 0.05 (range, 0.90 to 1.04) in reperfused cortex, infarcted cortex, and contralateral cerebellum, respectively. Compared with unity, both reperfused cortex and infarcted cortex showed significant decrease of Vd (P < .001). Contralateral cerebellum showing diaschisis had no reduction of Vd. On MRI, obtained 3 or 6 months after the stroke, mild cortical atrophy was observed in two reperfused areas where the asymmetry ratio was moderately reduced (0.64 and 0.80). CONCLUSIONS: The reduction of benzodiazepine receptor concentration in reperfused cortex that remained structurally intact is likely to be the result of injury involving only a limited number of neurons (ie, incomplete infarction). Our data suggest that the degree of viability of ischemic cortex apparently salvaged by early reperfusion can be quantified by iomazenil.

Aged↗

Augmented hypoxic cerebral vasodilation in men during 5 days at 3,810 m altitude.

The fractional increase in cerebral blood flow (CBF) velocity (VCBF) from the control value with 5-min steps of isocapnic hypoxia and hyperoxic hypercapnia was measured by transcranial Doppler in six sea-level native men before and during a 5-day sojourn at 3,810 m altitude to determine whether cerebral vasoreactivity to low arterial O2 saturation (SaO2) gradually increased [as does the hypoxic ventilatory response (HVR)] or diminished (adapted, in concert with known slow fall of CBF) at altitude. A control resting PCO2 value was chosen each day during preliminary hyperoxia to set ventilation at 140 ml.kg-1.min-1 for this and the parallel HVR study, attempting to establish control cerebrospinal fluid (CSF) and brain extracellular fluid pH values unaltered by acclimatization. The relationship of CBF to SaO2 was nonlinear, steepening at a lower SaO2. A hyperbolic equation was used to describe hypoxic cerebrovascular reactivity: fractional VCBF = x[60/ (SaO2-40)-1], where X is the fractional increase of VCBF at 70%.X rose from 0.346 +/- 0.104 (SD) at sea level to 0.463 +/- 0.084 on altitude day 5 (P < 0.05 by paired t-test, justified by the a priori experimental plan). For comparison with CO2 sensitivity, from these X values, we estimate the rise in CBF in response to a 1% fall in SaO2 at 80% to be 1.30% at sea level and 1.74% after 5 days at altitude. CBF sensitivity to increased end-tidal PCO2 rose from 4.01 +/- 0.62%/Torr at sea level to 5.12 +/- 0.79%/Torr on day 5 (P < 0.05), as expected, at the lower PCO2 due to the logarithmic relationship of PCO2 to CSF pH. This change was not significant after correction to log PCO2. We conclude that the cerebral vascular response to acute isocapnic hypoxia may increase during acclimatization at high altitude. The mechanism is unknown but is presumably unrelated to the parallel carotid chemosensitization that, in these subjects, increased the HVR by 60% in the same 5-day period from 0.91 +/- 0.38 to 1.46 +/- 0.59 l.min-1.% fall in SaO2-1).

Adult↗

Ischemic stroke and incomplete infarction.

BACKGROUND: The concept of selective vulnerability or selective loss o f individual neurons, with survival of glial and vascular elements as one of the consequences of a systemic ischemic-hypoxic insult (eg, transient cardiac arrest or severe hypotension), has been recognized for decades. In contrast, selective neuronal death as one of the lesions that may develop in the brain after occluding an intracranial artery is an idea not readily acknowledged in the current medical literature dealing with human stroke. SUMMARY OF REVIEW: A review of pertinent publications reveals that selective neuronal injury after middle cerebral artery occlusion was observed in autopsy specimens over 40 years ago, although its pathogenesis remains unclear. Recent observations in both humans and animals suggest that selective neuronal necrosis (rather than infarct) is the consequence of either a short-term arterial occlusion or permanent occlusion accompanied by ischemia of moderate severity. During the acute and subacute states of an ischemic stroke, the loss of a limited number of neurons (ie, incomplete infarction) does not result in structural changes discernible by either CT or conventional MRI. However, the loss of a selected number of neurons may be demonstrable in vivo by calculating the corresponding loss of benzodiazepine receptors. The use of specific radiotracers in combination with single-photon emission CT or positron emission tomography allows demonstration of a decrease in gamma-aminobutyric acid-ergic receptor sites at places where many neurons have been lethally injured. CONCLUSIONS: We aim to alert physicians to the potential development of incomplete brain infarctions in patients with intracranial arterial occlusions. Recognizing incomplete infarcts is particularly important in the context of stroke therapy with thrombolytic and neuroprotective agents. This brain lesion is likely to be the consequence of an arterial occlusion with a resultant ischemia of moderate severity (eg, regional blood flows in the range of 15 to 20 mL x 100 g-1 x min-1).

Animals↗

Spontaneous reperfusion of cerebral infarcts in patients with acute stroke. Incidence, time course, and clinical outcome in the Copenhagen Stroke Study.

OBJECTIVE: To determine the incidence, time course, and clinical importance of spontaneous reperfusion of cerebral infarcts in patients with acute stroke. DESIGN: Prospective, community based. SETTING: Department of Neurology, Bispebjerg Hospital, Copenhagen, Denmark. PATIENTS: Included in the incidence and time course study were 354 unselected patients with acute ischemic stroke. Clinical outcome was studied in a subgroup of 36 patients admitted on the day of stroke onset and in whom it was known whether spontaneous reperfusion occurred within the first week after stroke onset. MEASUREMENTS: Computed tomography and single photon emission computed tomography, with technetium Tc 99m exametazime used as a flow tracer. The Scandinavian Stroke Scale neurologic score was determined on admission, 1 and 2 weeks after stroke, and at discharge. RESULTS: The incidence of spontaneous reperfusion was 77% in patients with cortical infarcts. The frequency of reperfusion increased rapidly from zero at the time of onset to 60% on day 7 after stroke, reaching a maximum on day 14, at which time 77% showed reperfusion. Marked clinical improvement was observed in patients with spontaneous reperfusion (P = .001), while no improvement occurred in patients without reperfusion. Reperfusion was not observed in subcortical infarcts. CONCLUSIONS: The rate of spontaneous reperfusion increases gradually with time and occurs within the first 2 weeks after stroke onset in approximately four of five patients with cortical infarcts. Spontaneous reperfusion seemed to improve clinical outcome.

Aged↗

Long-term follow-up of cerebral infarction patients with proton magnetic resonance spectroscopy.

BACKGROUND AND PURPOSE: With proton magnetic resonance spectroscopy it is possible to measure the content of various brain metabolites in vivo, including N-acetylaspartate (which may be used as a neuronal marker), creatine, choline, and lactate. The content of these brain metabolites was measured serially from the acute stage to the chronic stage of infarction. Regional cerebral blood flow was also measured within the affected areas. These factors were compared with the clinical outcome. METHODS: Six patients with ischemic stroke were examined serially from the acute stage (< or = 2 days) to the chronic stage (> 6 months) with proton magnetic resonance spectroscopy. Cerebral blood flow was measured with single-photon emission-computed tomography with 99mTc-labeled d,l-hexamethylenepropyleneamine oxime as flow tracer. RESULTS: Lactate was found in all patients in the acute stage of stroke. Lactate was also found in the 3 largest lesions in the chronic stage; in 2 of these patients lactate was not found in the subacute stage. Reduced levels of N-acetylaspartate were found in 5 patients; in the sixth patient with a small lesion no reduction was found. In all lesions reduced blood flow was found in the acute and chronic stage, whereas hyperemia was found in 4 patients in the subacute stage. CONCLUSIONS: In this preliminary study no clear correlation was found between the level of N-acetylaspartate or lactate in the acute stage of stroke and the clinical outcome; however, there does appear to be some connection between the reduction of cerebral blood flow and the spectroscopic findings in the chronic stage and to some extent the clinical outcome. Studies of larger clinical groups will be necessary to further elucidate the prognostic potential of proton magnetic resonance spectroscopy in human stroke.

Adult↗

Use of 99mTc-bicisate in activation studies by split-dose technique.

The properties of the brain single photon emission computed tomography (SPECT) tracer 99mTc-bicisate (ethyl cysteinate dimer) were examined in regard to its use in test-retest studies with short-interval, split-dose studies. The stimulus applied in these tests was a visual activation by a "flickering chessboard" pattern. We used a fast dynamic SPECT (Tomomatic 232) recording eight slices. Twelve volunteers were assigned to two groups for reproducibility control and stimulation experiments, respectively. All were examined on 2 days. On the first day, only one injection was given in the resting state (t = 0), while two recordings were performed (t = 30 and t = 100), simulating the course and timing of a full split-dose study. The average washout of 8.3 +/- 1.0% was used as a correction on the second-day study. On that day the first injection was given during rest exactly as on day 1, allowing an estimate of day-to-day reproducibility. The second injection was made either in a resting state identical to the first or during visual stimulation. All images were normalized to mean brain count value. Results were analyzed in predefined anatomical regions of interest (ROIs). The day-to-day reproducibility was fair, with only one ROI (inferior frontal cortex) showing a significant 2% decrease. The studies of day 1 revealed a regional difference in observed washout ranging in the applied cortical ROIs from 7.9 to 11.5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

99mTc-bicisate reliably images CBF in chronic brain diseases but fails to show reflow hyperemia in subacute stroke: report of a multicenter trial of 105 cases comparing 133Xe and 99mTc-bicisate (ECD, neurolite) measured by SPECT on same day.

A multicenter study was performed in seven European centers comparing 99mTc-bicisate with 133Xe as a means of evaluating bicisate as a tracer of CBF distribution in humans. The same type of single photon emission computed tomography (SPECT) instrument (Tomomatic) was used in all centers. A total of 115 cases were collected, and of these 105 were considered technically adequate, comprising 18 normal subjects, 18 senile dementia, eight epilepsy, one brain tumor, eight chronic head trauma, and 52 stroke cases. As expected, bicisate gave better spatial resolution than Xe. Agreement between the results of the two methods was noted in 98 cases, but not in the remaining 7, all belonging to the stroke group. These seven all suffered from a subacute stroke (11-23 days after onset), and the disagreement in all cases consisted of bicisate showing low count rate in the area of the infarct and Xe a normal or elevated flow (luxury perfusion) as sign of spontaneous thrombolysis with reperfusion; in fact, these seven cases comprised all the reperfusion cases in the series. The results validate bicisate as a tracer of CBF in normal humans and in chronic brain diseases. Only in a subgroup of subacute stroke cases does bicisate not follow CBF, as it fails to show reperfusion hyperemia. This suggests the usefulness of bicisate in stroke cases, particularly in the subacute phase, where other SPECT methods often present difficulties due to reflow masking the size and the severity of the lesion.

Aged↗

Reduced contralateral hemispheric flow measured by SPECT in cerebellar lesions: crossed cerebral diaschisis.

Four patients with clinical signs of cerebellar stroke were studied twice by SPECT using 99mTc-HMPAO as a tracer for cerebral blood flow (CBF). When first scanned 6 to 22 days after onset, all had a region of very low CBF in the symptomatic cerebellar hemisphere, and a mild to moderate CBF reduction (average 10%) in contralateral hemispheric cortex. In all four cases clinical signs of unilateral cerebellar dysfunction were still present when rescanned 1 to 4 months later and the relative CBF decrease in the contralateral cortex of the forebrain also remained. The basal ganglia contralateral to the cerebellar lesion CBF showed variable alterations. A relative CBF decrease was seen in upper part of basal ganglia in all four cases, but it was not a constant phenomenon. A relative CBF increase in both early and late SPECT scans was seen at low levels of neostriatum in two cases. The remote CBF changes in cerebellar stroke seen in the forebrain are probably caused by reduced or abolished cerebellar output. The term "Crossed Cerebral Diaschisis" may be used to describe these CBF changes that would appear to reflect both decreased and increased neuronal activity.

Aged↗

Thrombolytic therapy in acute ischemic stroke. A Danish pilot study.

BACKGROUND AND PURPOSE: In a feasibility and safety study of thrombolytic therapy in acute ischemic stroke, we explored the usefulness of measurements of regional cerebral blood flow. METHODS: Twenty-three patients with acute ischemic stroke were treated with 100 mg recombinant tissue plasminogen activator infused intravenously over 1 hour. Thrombolytic therapy was initiated 78 to 355 minutes after onset of symptoms. RESULTS: Angiography 16 to 24 hours after treatment in 17 patients showed patient intracranial arteries in 12, partial occlusion of the middle cerebral artery in 3, and total occlusion of the middle cerebral artery in 2. rCBF with 99mTc-hexamethylpropyleneamine oxime intravenously was measured 5 minutes before and within 24 hours after thrombolytic therapy in 12 patients. 10 of the 12 patients showed brain tissue reperfusion and 2, with angiographically documented middle cerebral artery occlusion, showed no reperfusion, thus documenting a relationship between reperfusion measured by regional cerebral blood flow and angiographic patency (P = .015). Three patients died. Patients who were reperfused within 24 hours (documented by repeated regional cerebral blood flow measurements) showed greater clinical improvement on the Scandinavian Stroke Scale the sooner their thrombolytic therapy was started and the more severe their neurological deficits. CONCLUSIONS: Acute cerebral ischemia can be documented by rCBF measurements without delay of thrombolytic therapy, and repeated rCBF measurements can reveal whether cerebral reperfusion has occurred. In our study, early reperfusion was associated with clinical improvement.

Adult↗

Alteplase therapy in acute ischemic stroke: a Danish pilot study.OFF.

In the period from October 1990 to December 1991, 23 patients with acute ischemic stroke were treated with recombinant tissue plasminogen activator (rt-PA) at a median of 205 min (range 78-355 min) after symptom onset. In this open pilot study rt-PA was given intravenously after an acute CT scan had not shown acute changes. In 12 patients regional cerebral blood flow was measured intravenously using 99mTc-HMPAO before and within 24 h after thrombolytic therapy. Reperfusion of the ischemic area was obtained in 10 patients. In these patients clinical improvement was greater the shorter the delay from symptom onset to initiation of treatment. Three of the 23 patients died, one of a parenchymatous hematoma, one of a large middle cerebral artery infarct, and one of acute myocardial infarction.

Cerebral Infarction↗

Early time course of N-acetylaspartate, creatine and phosphocreatine, and compounds containing choline in the brain after acute stroke. A proton magnetic resonance spectroscopy study.

BACKGROUND AND PURPOSE: The early time course after acute stroke of cerebral N-acetylaspartate, creatine and phosphocreatine, and compounds containing choline was studied in vivo by means of localized water-suppressed proton magnetic resonance spectroscopy. METHODS: Eight patients with acute stroke were studied serially in the acute phase, 1 week after, and 2-4 weeks after the onset of clinical symptoms. Ten healthy volunteers served as controls. A stimulated echo (STEAM) sequence was used for measurement of the brain metabolites in a volume of interest located within the infarcted area as visualized by magnetic resonance imaging. For quantification, the unsaturated water signal was used as the internal standard. Regional cerebral blood flow in the infarcted area was measured relative to a symmetrically located unaffected area by means of single-photon emission computed tomographic scanning, using 99mTc-labeled d,l-hexamethylenepropyleneamine oxime as the flow tracer. RESULTS: Relative regional cerebral blood flow was considerably reduced in the infarcted area in the acute phase. After 1 week, hyperemia was seen in all but one patient. The N-acetylaspartate content was significantly reduced, with the loss appearing to occur between 6 and 24 hours after the stroke incident. The reduction in N-acetylaspartate content was greater in the central part than in the peripheral part of the infarcted area. Creatine and phosphocreatine were also reduced in the infarcted area, whereas no significant change was seen in the choline content. CONCLUSIONS: Assuming that N-acetylaspartate content reflects neuronal survival or loss, our results may suggest that treatment procedures with restoration of blood flow to severely ischemic areas should be initiated within the first 6 hours after stroke onset.

Acute Disease↗

Migraine pain associated with middle cerebral artery dilatation: reversal by sumatriptan.

The combination of measurements of regional cerebral blood flow (rCBF) and blood velocity in the middle cerebral arteries (MCA) by transcranial doppler sonography was used to investigate cerebrovascular involvement in migraine. Ten migraine patients with unilateral headache were studied during an attack and when they had been free of attacks for 5 days (non-attack). On both occasions they were given as intravenous infusion of sumatriptan (2 mg), a 5-HT1-like receptor agonist, which relieved the symptoms within 30 min without affecting rCBF. The MCA velocity was normal on both sides on the non-attack day and on the unaffected side during the attack. However, during the attack the MCA velocity on the headache side was significantly lower than that on the non-headache side (45 vs 61 cm/s:mean difference 16.3 [95% confidence interval 10.3-22.3]; p = 0.02). The MCA velocity on the headache side returned to normal after treatment with sumatriptan and recovery. Since rCBF in the MCA supply territory was unaffected, the lower velocity can be explained only by dilatation of the MCA. The mean MCA diameter increase was estimated to be 20%. Thus, headache was associated with intracranial large arterial dilatation on the headache side. Sumatriptan predominantly had effects on the distended artery, which suggests that the 5-HT receptor system has a role in the pathogenesis of migraine.

Adult↗

Cerebral lactate production and blood flow in acute stroke.

Eight stroke patients were examined serially in the acute phase and 1 week and 2-4 weeks after stroke with water-suppressed proton magnetic resonance spectroscopy. The time courses of lactate level and regional cerebral blood flow were studied. A high lactate level was found in the acute phase. The lactate content decreased to barely detectable levels during the following 3 weeks, while regional blood flow increased during this period. The inverse relationship between lactate level and cerebral blood flow suggests that lactate plays no substantial role in the vasodilatation underlying the hyperemia that follows reperfusion. The amount of lactate present in the acute phase reflects the severity of ischemia in the affected region. The lactate level was still above normal in the subacute phase with hyperemia, suggesting lactate production through aerobic glycolysis. Thus, the lactate level in the subacute phase probably does not reflect the degree of anaerobic glycolysis in hypoxic neuronal tissue.

Acute Disease↗