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.

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.

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.

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.

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.

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.

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.

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.

The effect of velocity on the appearance of embolic signals studied in transcranial Doppler models

BACKGROUND AND PURPOSE

Transcranial Doppler ultrasound can be used to detect circulating cerebral emboli. Recent studies have demonstrated that embolus size is significantly related to both the relative intensity increase and duration of an embolic signal. This may allow information about embolus size to be obtained by analysis of Doppler embolic signals. However, theoretically duration will be inversely related to velocity, and therefore velocity may need to be accounted for if information on embolus size is to be derived from the duration of Doppler embolic signals.

METHODS

The relation between velocity and both relative intensity increase and duration of embolic signal was investigated in an in vitro flow model, a sheep carotid artery model, and in patients with prosthetic heart valves. The same standard transcranial Doppler ultrasound machine was used for all studies. Embolic signals resulting from 99 glass microspheres (size, 210 to 250 microns) were studied in the in vitro model, as were those from 64 glass microspheres (size, 105 to 150 microns) in the sheep model. Embolic signals recorded from the six middle cerebral arteries of three patients with prosthetic cardiac valves were also studied.

RESULTS

There was a significant (P < .001) inverse relation between velocity and duration of high-intensity signal (in vitro model, r = -.82; sheep model, r = -.43); the exact relations were described using best-fit equations. Correlation coefficients for this relation in patients varied between -.30 and -.55. There was also an unexpected significant positive relation between velocity and intensity in the sheep model (r = .44, P < .001) but not in the in vitro model (P > .05). This relation was also seen in some, but not all, patients.

CONCLUSIONS

When the duration of embolic signals is used to provide information about the relative size of an embolus, the velocity of the embolic signal should be taken into account. A relation between velocity and relative intensity increase was found in the sheep model and in some patient recordings. It is suggested this relation may result from greater power being supplied to emboli traveling at higher velocities in the center of the vessel; this may occur under certain recording conditions.

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.

Middle cerebral artery blood flow velocity in healthy persons during wakefulness and sleep: a transcranial Doppler study

In 10 normal young adults, middle cerebral artery blood flow velocity was measured continuously over one night by transcranial Doppler sonography. Polysomnography was used to assess the different sleep stages and waking state. During rapid eye movement (REM) sleep, middle cerebral artery blood flow velocity was higher than in any other sleep stage and wakefulness. During the waking state the velocity was higher than in sleep stage 2. Spontaneous rhythmic oscillations of cerebral blood flow velocity were found related to different stages of sleep. A fast Fourier's transformation of the Doppler wave forms revealed a periodicity of 20-75 seconds, which was most prominent during REM sleep and to a lesser degree during sleep stages 1, 2 and 3 and the waking state. These waves may correspond to intracranial pressure changes referred to as B-waves.

Simultaneous recording of cerebrospinal fluid pressure and middle cerebral artery blood flow velocity in patients with suspected symptomatic normal pressure hydrocephalus

CSF pressure (intracranial pressure, in one patient lumbar pressure) was monitored continuously for one night in 23 patients with suspected symptomatic normal pressure hydrocephalus (NPH) to identify patients who might benefit from subsequent shunt surgery. In 20 patients middle cerebral artery (MCA) blood flow velocity by means of transcranial Doppler sonography (TCD) and CSF pressure were recorded simultaneously. In three patients transcranial Doppler signals were insufficient. Spontaneous changes in CSF pressure always paralleled changes in the TCD signal. Equivalents of B-waves as well as intermediate waves (in between B- and A-waves), and C-waves could be identified easily and always appeared in phase. The Doppler signal, however, could not be used to evaluate the absolute changes in CSF pressure. Fast Fourier Transform of the Doppler signal was a useful tool to indicate the relative frequency of B-wave equivalents. In five patients the injection of 10ml saline into the ventricle raised intracranial pressure considerably, but hardly affected the MCA blood flow velocity. Continuous TCD monitoring might be useful as a noninvasive screening procedure in patients with suspected symptomatic NPH before continuous invasive CSF pressure measurements are performed.

A transcranial Doppler study of blood flow velocity in the middle cerebral arteries performed at rest and during mental activities

While changes in blood velocity in the middle cerebral artery relative to rest were assessed by transcranial Doppler sonography, 70 volunteers with no sign of cerebrovascular disease performed two (left and right middle cerebral artery) series of six cognitive tasks. The tasks are assumed to be processed predominantly by either the left (verbal and mathematical tests performed aloud) or the right hemisphere (dot/distance estimation, spatial perception, and face recognition performed silently). All tasks were shown to increase middle cerebral artery blood flow velocity on both sides, by 1.6-10.6%. After an initial maximum at approximately 8 seconds, velocity decreased then increased again. A steady state was reached after approximately 24-42 seconds. The initial minimum during the following rest phase was reached some seconds later, followed by a slow increase to the reference rest steady state. A difference according to side could be determined only during the three right-hemispheric tasks (right greater than left, 2.5-2.9%). Left-handedness/ambidexterity, familial sinistrality, and profession seemed to have no influence on the results. The middle cerebral artery blood flow velocity increase on both sides was higher in women than in men during the dot/distance estimation and was also higher bilaterally in older than in younger subjects during the dot/distance and the spatial perception tasks. Habituation in performing the tasks was an important factor associated with a decrease of blood flow velocity, especially in the right middle cerebral artery. The habituation more pronounced on the right side possibly reflects the role of the right hemisphere in attention and arousal. The absolute blood velocities at rest decreased bilaterally with age.

Brain activity and blood flow velocity changes: a transcranial Doppler study

Seventy volunteers with no sign of cerebral vascular disease performed two series of 6 cognitive tasks, 3 of which are assumed to be processed predominantly by the left and 3 by the right hemisphere. During the tasks, blood flow velocity changes in the middle cerebral artery were recorded every 3 seconds by the transcranial Doppler method (TCD). All tasks increased blood flow velocities in both MCAs, but only the "right hemispheric" tasks resulted in a statistically significantly higher increase than the left MCA. The time course of velocity changes reflects the increase in blood flow caused by increased brain metabolism during brain activity. During stimulation of the right and/or left visual field, blood flow velocity changes were recorded in the P2-segment of the corresponding hemisphere. In 76 volunteers, the study was performed. The time course of velocity changes was similar to that in the MCA study. Velocity rose as a result of increasing complexity of the visual stimulus. The velocity changes are similar to blood flow increases reported in the literature and rose by as much 2 to 25%. Assuming that the diameter of the large branches of the circle of Willis does not change during mental activity, blood flow velocity changes reflect blood flow volume changes. With the TCD method the close relationship among brain activity, metabolism, and blood flow can be reliably investigated. The high spatial resolution enables information to be given about the onset of autoregulation.

Two transcranial Doppler studies on blood flow velocity in both middle cerebral arteries during rest and the performance of cognitive tasks

While the middle cerebral artery (MCA) blood flow velocity changes relative to rest were assessed with transcranial Doppler sonography (TCD), 28 right-handed subjects with no sign of cerebrovascular disease performed two series of 6 cognitive tasks (two series = right and left MCA). The tasks included "reading", "finding nouns with a given first letter", and "multiplication" in four comparable versions to be performed aloud and silently in each of the two series. All of the tasks increased the MCA blood flow velocity bilaterally (2.7-12.1%). A significant left-right difference was present during "noun finding aloud" (left greater than right by 4.7%). A statistically insignificant tendency in the same direction was also present for the five other tasks. During loud reading the increase was higher bilaterally than during silent reading. Blood flow velocity changes in the right MCA for the three tasks performed aloud were lower in older than in younger people. It is posited that older people perform the tasks more slowly and under less stress requiring less right-hemispheric participation. Averaging the results for each of the four subjects involved leads to the conclusion that future TCD-lateralization studies should be done bilaterally at the same time to assess lateralization in a single person.