Biomedical subjects

D W Droste

Publications and source records attributed to D W Droste.

At least 55 records · Page 3Linked to original sources

PubMed1997

Oscillations of cerebrospinal fluid pressure in nonhydrocephalic persons.

Spontaneous cerebrospinal fluid (CSF) pressure oscillations with a wavelength of 0.5-2/min (B-waves) are used as a criterion for shunt insertion in hydrocephalic patients. We describe CSF pressure oscillations in two nonhydrocephalic patients with normal baseline CSF pressure. Intracranial pressure was recorded via a ventricular drainage in a 54-year-old male who had a lumber CSF leak after surgery for lumbar spinal stenosis and disc herniation after the leak was closed. In the second patient, a 42-year-old male, CSF pressure was monitored via a lumbar drainage which was placed for treatment of a subcutaneous CSF effusion after resection of a recurrent temporal meningioma. CSF pressure oscillations of a wavelength of 0.5-2/min were observed with a relative frequency of 50% (patient 1) and 60% (patient 2) of the recorded time. Also longer waves were observed. Our data suggest that CSF pressure oscillations are not confined to hydrocephalic patients with raised intracranial pressure.

Adult↗

PubMed1997

Comparison of ultrasonic and histopathological features of carotid artery stenosis.

Besides the degree of carotid artery stenosis, the composition of the plaque may help to predict the thromboembolic risk. Low echogenicity on ultrasound and hemorrhage into the atheroma demonstrated histopathologically have been shown to be associated with a higher risk of embolism. Twenty-nine consecutive patients with carotid artery stenosis and scheduled for carotid endarterectomy were investigated preoperatively by B-mode ultrasound. Post-operatively the endarterectomy specimens were examined histopathologically. Neither atheroma with hemorrhage nor atheroma without hemorrhage were significantly associated with echolucent ultrasound presentation. Out of the 10 lesions echolucent and homogeneous on ultrasound, six corresponded to atheroma with hemorrhage, two corresponded to atheroma with hemorrhage plus thrombus, two corresponded to fibrous plaque plus thrombus, and one corresponded to pure thrombus. Out of the 4 lesions heterogeneous and predominantly echolucent, one corresponded to atheroma without hemorrhage plus thrombus, one corresponded to atheroma with hemorrhage, one corresponded to atheroma with hemorrhage plus thrombus, one corresponded to atheroma with hemorrhage plus fibrous plaque. Seven out of the 18 atheromas with hemorrhage did not present as purely or predominantly echolucent lesions, six of them were even homogeneously echogenic. Plaque surface could not reliably be predicted by ultrasound. In our study, there was no significant correlation between ultrasound and histology of the lesion.

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PubMed1997

Flow void of cerebrospinal fluid in idiopathic normal pressure hydrocephalus of the elderly: can it predict outcome after shunting?

OBJECTIVE: We investigate the predictive value of cerebrospinal fluid (CSF) flow void on outcome after shunting in a prospective series of patients with idiopathic normal pressure hydrocephalus (NPH). METHODS: The degree and extension of CSF flow void were examined on T2-weighted magnetic resonance imaging scans of 37 elderly patients with idiopathic NPH who underwent subsequent shunting. The degree of flow void was assessed in comparison with the signal of large cerebral arteries. The extension was evaluated via the calculation of sum scores for the occurrence of flow void in different locations of the ventricular system. Those parameters were not considered in the decision to perform shunting. CSF flow void in the aqueduct and the adjacent third and fourth ventricles of the 37 patients with idiopathic NPH was compared with that of 37 age-matched control patients. CSF flow void scores in patients with idiopathic NPH were investigated for correlations between postoperative outcome scores and ventricular width indices. RESULTS: No difference was found between the occurrence of aqueductal CSF flow void in patients with idiopathic NPH and the control group. A significant difference, however, was noted for the extension of the CSF flow void, which was greater in the NPH group. Postoperative improvement was found in 33 of 37 patients with idiopathic NPH at a mean follow-up of 15.6 months. Only small, statistically not significant correlations were found between CSF flow void and postoperative outcome. Flow void sum scores, however, correlated significantly with ventricular width indices. CONCLUSION: The degree and extension of CSF flow void on T2-weighted magnetic resonance imaging scans have little predictive value for outcome after shunting in patients with idiopathic NPH. The greater extension of the CSF flow void in patients with NPH is most likely related to increased ventricular width. It is not useful to consider CSF flow void findings on conventional magnetic resonance imaging scans in making the decision to offer shunting in patients with idiopathic NPH.

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PubMed1997

White matter lesions in patients with idiopathic normal pressure hydrocephalus and in an age-matched control group: a comparative study.

OBJECTIVE: To compare the occurrence of periventricular lesions (PVLs) and deep white matter lesions (DWMLs) in elderly patients with idiopathic normal pressure hydrocephalus (NPH) and in an age-matched control group. METHODS: PVLs and DWMLs were evaluated using T2-weighted magnetic resonance scans of 37 patients with idiopathic NPH and 35 participants from an age-matched control group. All patients with idiopathic NPH included in this study improved after shunting. The control group consisted of 16 healthy elderly persons and 19 patients with depression. To allow quantitative assessment and comparison, scores for PVLs and DWMLs were calculated. Furthermore, possible correlations between white matter lesion scores, ventricular width, and age were investigated. RESULTS: There was a significantly higher incidence of PVLs and DWMLs in patients with idiopathic NPH. The mean total PVL was 12.1 (range, 2-24) in the NPH group and 3.9 (range, 0-10) in the control group (P < 0.001). The mean total DWML score was 12.9 (range, 3-24) in the NPH group and 4.5 (range, 0-16) in the control group (P < 0.001). There were significant correlations between the severity of PVL and DWML scores in both groups. Only a weak positive correlation between the severity of DWMLs and age was found in the NPH group, whereas this correlation was significant in the control group. There was a significant negative correlation between the width of the anterior horns and the severity of both PVLs and DWMLs in patients with NPH; however, positive correlations were found in the control group. CONCLUSION: Elderly patients with idiopathic NPH have more frequent and more severe PVLs and DWMLs than people in age-matched control groups. Our data suggest a frequent co-occurrence of idiopathic NPH and vascular subcortical encephalopathy; however, they do not support a direct causal relationship.

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PubMed1997

Oxygen inhalation can differentiate gaseous from nongaseous microemboli detected by transcranial Doppler ultrasound.

BACKGROUND AND PURPOSE: Clinically silent circulating microemboli can be detected by transcranial Doppler sonography. The composition of these emboli in different clinical conditions is unclear. METHODS: We performed 1-hour transcranial Doppler sonographic recordings from the middle cerebral or posterior cerebral artery in 20 patients with mechanical prosthetic heart valves, in 78 patients with an arterial embolic source, and in 20 control subjects. During 30 minutes of this recording, the patients inspired room air and 6 L of oxygen per minute via a loosely fitting facial mask; during the remaining 30 minutes, they breathed room air only. RESULTS: There was a significant decline of embolic signals (ES) under oxygen in the patients with mechanical prosthetic cardiac valves (144 ES without oxygen versus 63 ES with oxygen; P = .002) but not in the patients with arterial embolic sources (145 ES without oxygen versus 135 ES with oxygen; P = NS). In the control subjects, no ES were found. CONCLUSIONS: ES in patients with mechanical prosthetic cardiac valves correspond mainly to gas bubbles. Oxygen inhibits the cavitation process of mechanical prosthetic heart valves or speeds up redissolution of gas bubbles generated by cavitation. In contrast, solid microemboli originating from thrombus or atheroma cannot be suppressed by oxygen inhalation. This simple method of oxygen inhalation should help to clarify the composition of microemboli in various clinical and experimental settings.

Administration, Inhalation↗

PubMed1997

Clinically silent microemboli in patients with artificial prosthetic aortic valves are predominantly gaseous and not solid.

BACKGROUND AND PURPOSE: Microembolic signals (MES) are frequently observed by transcranial Doppler ultrasound after prosthetic heart valve implantation. Whether these MES are due to solid or gaseous particles is uncertain. We hypothesized that MES are gaseous and that if they are due to cavitation effects, their occurrence should respond to changes of dissolved oxygen concentration in the blood. METHODS: Transcranial monitoring of MES was performed in five patients with prosthetic aortic valves, who inspired 100% oxygen through a facial mask. In one patient 100% oxygen was administered under hyperbaric (2.5 kPa) conditions in a hyperbaric chamber. RESULTS: Inspiration of 100% oxygen reduced the total number of MES from 96/30 min to 2/30 min. Increasing the concentration of dissolved oxygen in the hyperbaric chamber led to an increase from 0.3 MES per minute (1.0 kPa) to 0.9 MES per minute (2.5 kPa). CONCLUSIONS: The dependence of occurrence of MES in patients with prosthetic cardiac valves on the oxygen partial pressure in blood provides strong evidence that these microemboli are gaseous.

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PubMed1997

Bigated transcranial Doppler for the detection of clinically silent circulating emboli in normal persons and patients with prosthetic cardiac valves.

BACKGROUND AND PURPOSE: Detection of clinically silent circulating microemboli by transcranial Doppler sonography is now being widely investigated in the hope of identifying patients at increased risk for stroke. Automatic detection by bigated Doppler, which uses sampling from two different depths in the artery under study and considers the motion of the embolus, may help to define "periods of interest" that can be evaluated off-line. METHODS: In 12 normal volunteers and 10 patients with prosthetic aortic valves, we performed 1-hour recordings from one middle cerebral artery. In the normal subjects, we produced additional artifacts to use them as false-positives. Detection of microemboli was done off-line from digital audiotapes by an experienced blinded investigator (used as the gold standard) and was compared with on-line detection using specially designed software. RESULTS: With the setting used, 91.5% of all recorded artifacts could correctly be identified as such with the software. Embolic signals were detected by the software with a specificity of 59.9% and a sensitivity of 74.3%. CONCLUSIONS: Bigated Doppler adds a new dimension to the definition and detection of microembolic signals. It constitutes an important step forward toward automatic screening of stroke-prone patients. Assessing on-line periods of interest during the recording and going over the recorded data again off-line helps to save time for the discrimination of embolic signals from both the normal Doppler spectrum background and artifacts.

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PubMed1996

Variability in occurrence of embolic signals in long term transcranial Doppler recordings.

Albeit still unproven, it is supposed that the presence and number of asymptomatic circulating cerebral microemboli detected by transcranial Doppler ultrasound (TCD) may be an indicator of stroke risk. Little research has been done to assess the reproducibility of these data and the required time for recording. We examined one middle cerebral artery in 7 subjects with carotid, aortic or cardiac embolic source for 24 h by TCD. Analysis for embolic signals was done off line completely blinded to the diagnosis and the time of the day during the recording. Embolic signals were found in all 7 subjects varying from 0 per h to 13 per h. Embolic signals occurred throughout the day with a nonsignificant tendency towards higher values in the early morning hours. Half an hour recording would not have been suitable to rule out or to confirm the presence of embolic signals as there were too many gaps between embolic signals of more than 1/2 h. One hour is the required minimum. Concerning the number of embolic signals, even a recording of four hours yielded variabilities of 0.25 and 8 embolic signals per hour in the same person. We recommend to perform follow-up studies the same time of the day. In patients with a low number of embolic signals longer recordings or a lower detection threshold with a higher number of detected embolic signals are necessary to compare frequencies of embolic signals.

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PubMed1996

Asymptomatic circulating cerebral emboli and cerebral blood flow velocity under aspirin and ticlopidine in patients with cerebrovascular disease.

Aspirin and ticlopidine are two commonly used drugs in the prevention of cerebral embolic ischemic events. No direct comparisons in a cross-over design of the effects of ticlopidine and aspirin on asymptomatic circulating cerebral microemboli are available. We investigated 53 patients with cerebrovascular disease. Twenty-six patients were dosed for 2 weeks, 300 mg aspirin once daily and then for 2 weeks, 250 mg ticlopidine twice daily. In 27 other patients the scheme was reversed. Transcranial Doppler monitoring (both middle cerebral arteries simultaneously for 1 h were performed at the end of the two weeks. The signal was recorded on digitalised audio tapes and analyzed blinded off-line. The number of embolic signals per hour and vessel was 15.7 under aspirin and 11.7 under ticlopidine (difference not significant). The correlation between the number of emboli under the two medications was high. The highest number of embolic signals was found in high grade carotid stenosis. In patients with a low number of embolic signals, reproducibility was low. A minimum of 7 embolic signals in one treatment group is required for further therapeutic drug trials to allow reasonable comparisons. This study may help to plan further therapeutic trials using emboli detection.

Adult↗

PubMed1996

Hemostaseologic and hematologic parameters with aspirin and ticlopidine treatment in patients with cerebrovascular disease: a cross-over study.

No direct comparisons of the effects of ticlopidine and aspirin on platelet aggregability, clotting parameters, and blood count are available in a cross-over study design in humans. We investigated 45 patients with cerebrovascular disease. Twenty-one patients received 300 mg aspirin once daily for 2 weeks and then for 2 more weeks received 250 mg ticlopidine twice daily. In 24 other patients, the scheme was reversed. ADP-induced aggregability was lower during ticlopidine treatment; epinephrine- and collagen-induced aggregabilities were lower with aspirin treatment. Platelet counts were higher during ticlopidine than during aspirin treatment (199.6/ nl with aspirin, 213.0/nl with ticlop dine, p = 0.008), probably reflecting less platelet activation and degradation and a longer platelet survival time induced by ticlopidine treatment.

Adenosine Diphosphate↗

PubMed1996

Cerebrospinal fluid shunting in idiopathic normal-pressure hydrocephalus of the elderly: effect of periventricular and deep white matter lesions.

OBJECTIVE: We investigated the effect of periventricular and deep white matter lesions (DWMLs) on outcome after cerebrospinal fluid shunting in a prospective series of elderly patients with idiopathic normal-pressure hydrocephalus. METHODS: White matter lesions were assessed with T2-weighted magnetic resonance scans according to a standard protocol in 41 patients with idiopathic normal-pressure hydrocephalus of the elderly who underwent subsequent shunting. In all patients, the diagnosis of idiopathic normal-pressure hydrocephalus had been established preoperatively by clinical and diagnostic investigations. RESULTS: At a mean follow-up of 16 months, clinical improvement was observed in 37 of 41 patients (90%). There was no persistent morbidity related to surgery. The degree of overall clinical improvement was negatively correlated with the extension of periventricular lesions (correlation coefficient r = -0.324 [P = 0.04]) and DWMLs (correlation coefficient r = -0.373 [P = 0.02]). This negative correlation was also noted when the analysis was conducted separately for each of the cardinal symptoms (gait disturbance, cognitive impairment, and urinary incontinence). There was no consistent pattern of periventricular and DWMLs in the four patients who failed to respond to shunting. CONCLUSION: Periventricular and DWMLs of varying degrees are common findings on magnetic resonance scans of patients with idiopathic normal-pressure hydrocephalus of the elderly. After careful preoperative selection of patients with idiopathic normal-pressure hydrocephalus, individuals with DWMLs suggestive of concomitant vascular encephalopathy may also benefit from cerebrospinal fluid diversion. Although, in general, the degree of improvement depends on the severity of periventricular and DWMLs, patients with more extensive WMLs still may derive clinical benefit from the operation.

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PubMed1996

Periodic leg movements are part of the B-wave rhythm and the cyclic alternating pattern.

Periodic leg movements (PLM) in sleep are supposed to constitute a frequent cause of insomnia. There is some controversy whether PLM are the cause of insomnia by provoking microarousals or whether they are simply and epiphenomenon not casually related to the insomnia. We examined four patients with PLM by overnight polysomnography and concomitant transcranial Doppler sonography (TCD) monitoring, 13 patients with suspected normal pressure hydrocephalus by concomitant overnight polysomnography and intracranial pressure recording, and 10 healthy volunteers by concomitant overnight polysomnography and TCD monitoring. EEG arousals occurred more frequently before than after the PLM. PLM were associated with increase in heart rate, breathing amplitude, and cerebral blood flow velocity assessed by TCD. PLM occurred with a mean wavelength of 40.5 s. This mean wavelength corresponded to similar values calculated for intracranial pressure B-waves (43.3 s) in 13 patients with suspected normal-pressure hydrocephalus, TCD B-wave equivalents (42.2 s) in 10 healthy young adults and the frequency of the cyclic alternating pattern in EEg recordings (40 s). Our date suggest that these cyclic variations with a wavelength of about 40 s are part of a common endogenous rhythm. PLM seem to be an epiphenomenon of this rhythm and not the cause of insomnia.

Adult↗

PubMed1996

Vascular risk factors and arteriosclerotic disease in idiopathic normal-pressure hydrocephalus of the elderly.

BACKGROUND AND PURPOSE: There is some evidence from previous studies that idiopathic normal-pressure hydrocephalus (NPH) of the elderly might be linked to vascular leukoencephalopathy. The purpose of this study was to examine the prevalence and impact of vascular risk factors and vascular diseases in idiopathic NPH compared with a control cohort. METHODS: The prevalence of arterial hypertension; diabetes mellitus; hypercholesterolemia; hyperlipidemia; smoking; obesity; and cardiac, cerebrovascular, and other arteriosclerotic diseases was assessed in 65 patients with idiopathic NPH. The findings were compared with those of 70 patients with comparable age distribution. To describe the differences of the prevalences of vascular risk factors, odds ratios were obtained by univariate and multivariate analyses. RESULTS: The univariate analysis revealed significant associations between idiopathic NPH and arterial hypertension (prevalence, 54 of 65 [83%]; control group, 25 of 70 [36%]; P < .001) and diabetes mellitus (prevalence, 31 of 63 [49%]; control group, 20 of 70 [29%]; P < .015) but not with other vascular risk factors. After multivariate regression analysis, only hypertension remained significantly associated with NPH (P < .0001). There was also a significant association between NPH and cardiac (P < .001), cerebral arteriosclerotic (P = .007), and other arteriosclerotic diseases (P = .001). A positive association was found between the severity of clinical symptoms of NPH and the presence of hypertension, especially for gait disturbance. The presence of hypertension was not related to the duration of NPH. CONCLUSIONS: Our data show a highly significant association between idiopathic NPH and arterial hypertension. Arterial hypertension might be involved in the pathophysiological mechanisms promoting idiopathic NPH.

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PubMed1995

The relation of intracranial pressure B-waves to different sleep stages in patients with suspected normal pressure hydrocephalus.

The interpretation of data from continuous monitoring of intracranial pressure (ICP) in patients with suspected normal pressure hydrocephalus (NPH) is the subject of controversy. Despite the fact that overnight ICP monitoring is widely used for the diagnosis of NPH, normative criteria are poorly defined. The present study demonstrates that there is a relationship between the relative frequency, the absolute amplitude, the wavelength and the morphology of B-waves and different sleep stages. Intraventricular intracranial pressure was recorded continuously overnight in 16 patients with suspected normal pressure hydrocephalus. Simultaneous polysomnography was performed to investigate the relation of spontaneous ICP oscillations to different sleep stages. A correlative analysis was done with the data of 13 patients. Three patients were excluded, one who was awake throughout the night and two in whom polysomnography was incomplete due to technical reasons. The mean resting cerebrospinal fluid (CSF) pressure was 12.87 cm CSF. B-waves were observed in the ICP recordings of all patients. They were present for a mean of 72% of the total recording time. The relative frequency of B-waves was higher during REM sleep and sleep stage 2 as compared to wakefulness (87.8% and 83.2% vs. 56. p < 0.05). The absolute amplitude was higher during REM sleep than in wakefulness (9.56 vs. 3.44 cm CSF, p < 0.05). Wavelengths were longer in REM sleep than in wakefulness and stages 1 and 2 (62.4 vs. 42, 40.7 and 44.8 sec, p < 0.05). The morphology of B-waves was also related to different sleep stages. Ramp-type B-waves were associated with REM sleep in six patients, however, were also present in sleep stage 2 in three of them. Knowledge of the relation of spontaneous ICP oscillations to different sleep stages may help to establish physiological foundations and alterations. Furthermore, polysomnography may be useful to avoid erroneous interpretation of ICP recordings due to sleep stage related variability.

Adult↗

PubMed1994

Detection of asymptomatic cerebral embolic signals with Doppler ultrasound.

Can asymptomatic cerebral emboli be detected? With transcranial Doppler ultrasonography of the middle cerebral artery, short-duration high-intensity asymptomatic embolic signals were detected in 6 of 25 patients with carotid stenosis and in 9 of 24 with prosthetic cardiac valves, but not in 20 normal controls. In carotid stenosis the signals were usually unilateral and ipsilateral to the stenosis. Embolic signals were significantly more common in patients with mechanical valves than with pig xenografts (8/13 vs 1/11). With mechanical valves embolic signals were usually bilateral. Detection of asymptomatic emboli may allow identification of and preventive treatment in at-risk patients.

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PubMed1994

Predictability of intracranial pressure oscillations in patients with suspected normal pressure hydrocephalus by transcranial Doppler ultrasound.

Intracranial pressure (ICP) was monitored continuously for one night in 36 patients with suspected symptomatic normal pressure hydrocephalus (NPH) to identify patients who might benefit from subsequent shunting. In 33 of these patients middle cerebral artery (MCA) blood flow velocity by means of transcranial Doppler sonography (TCD) and ICP were recorded simultaneously. ICP B-waves always paralleled changes in the TCD signal (TCD B-wave equivalents). The relative frequency of ICP B-waves was predictable by TCD, albeit slightly underestimated due to a generally lower relative amplitude of the TCD B-wave equivalents. However, the same TCD B-wave equivalent amplitude could be accompanied by quite different ICP changes in different patients. Considering the baseline values in the absence of pressure waves, there was no significant relationship between ICP and TCD resistance index (Pourcelot) in different patients. Raising ICP by injection of 10 ml saline into the ventricle, however was accompanied by an increased TCD resistance index in the individual patient. As the relative frequency of B-wave activity is assumed to be an indicator for shunt responsiveness, continuous TCD monitoring can be used as a screening procedure to detect the presence and the relative frequency of B-wave activity in patients with suspected NPH. However, since neither the absolute ICP nor the amplitude of spontaneous oscillations can be predicted, TCD monitoring is not suitable to replace ICP monitoring.

Adult↗

PubMed1994

Rhythmic oscillations with a wavelength of 0.5-2 min in transcranial Doppler recordings.

We have studied intracranial pressure (ICP) B-waves and their association with rhythmic changes in blood flow velocity (B-wave equivalents) by transcranial Doppler sonography (TCD) monitoring. In overnight TCD recordings in 10 normal young adults, these rhythmic changes in blood flow velocity were higher and more frequent during REM sleep and sleep stage 1 than during other sleep stages. B-wave equivalents also had a longer wavelength during REM sleep. Their relative frequency in these normal subjects over one night ranged from 35 to 73%. Peripheral resistance (assessed by the Pourcelot index) was lower and heart rate was higher at the peak of these oscillations. These results support the hypothesis that ICP B-waves are caused by vasodilation. A non-linear relationship between ICP and blood flow velocity was found during B-waves in 9 of 11 patients with suspected NPH. Our results throw doubt on the suggestion that a relative frequency of less than 80% B-wave activity can be a valid indicator for shunt responsiveness in patients with suspected normal pressure hydrocephalus (NPH). ICP recordings in suspected NPH should be accompanied by polysomnography to avoid misleading results due to variability of B-wave appearance dependent on sleep pattern.

Adult↗

PubMed1994

The effect of high concentrations of inspired oxygen on middle cerebral artery blood velocity measured by transcranial Doppler.

The effects of high concentrations of inspired oxygen on cerebrovascular haemodynamics were studied in healthy human volunteers using transcranial Doppler measurements of middle cerebral artery blood velocity. If the end-tidal carbon dioxide level was kept constant, the measured blood velocity and the calculated Pulsatility Index showed no significant change when subjects were breathing 21, 40, 75 or 100% oxygen.

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