M.J.G. Harrison

Estimation of cerebrovascular reactivity using transcranial Doppler, including the use of breath-holding as the vasodilatory stimulus.

Background and Purpose A proportion of individuals with carotid artery stenosis show a reduced cerebrovascular reserve as measured by a reduced cerebral arterial vasodilatory response to carbon dioxide. Two methods of quantifying this vasodilatory response, using transcranial Doppler ultrasonography, have been in general use: the total range of vasodilation between hypocapnia, induced by hyperventilation, and hypercapnia induced by breathing carbon dioxide, and the response to breathing a fixed concentration of 5% carbon dioxide. We studied whether it is possible to use the rise in carbon dioxide occurring during breath-holding as the vasodilatory stimulus. Methods Using transcranial Doppler, cerebral reactivity to carbon dioxide was measured in 23 subjects undergoing intravenous digital subtraction angiography of their carotid arteries for symptoms of cerebrovascular disease. A breath-holding method was compared with the two previous methods, which required administration of carbon dioxide. Results All three methods gave results that correlated highly significantly with the degree of carotid stenosis, although the correlation was highest when the full vasodilatory range was measured. This method was adopted as the gold standard, and the other methods were compared with it The breath-holding method correlated at least as well (p=0.67) as the 5% CO2 method (p=0.64). It identified a similar group of low reactors to our gold standard method, whereas the 5% CO2 method gave some discrepant results. Conclusions The breath-holding method offers potential as a convenient, well-tolerated screening method of assessing carbon dioxide reactivity not requiring the administration of carbon dioxide, although further validation against more established methods of measuring cerebrovascular reserve is first required.

Multi-infarct dementia

Abstract Fifty-two patients presenting with dementia were divided into a group in whom clinical features suggested an ischaemic basis (multi-infarct dementia) and a group in whom a primary degenerative process seemed more likely. Focal EEG changes and angiographic evidence of ischeamic areas and atheromatous disease of intracranial vessels were more common in the “ischaemic” than in the primary degenerative group. CBF was significantly reduced in the former but the regional pattern was equally distorted in the two groups. These findings strengthen the belief that the ischaemic score can identify those patients whose dementia is associated with vascular disease.

EFFECT OF HAEMATOCRIT ON CAROTID STENOSIS AND CEREBRAL INFARCTION

Carotid angiograms in 187 patients presenting with transient ischaemic attacks and minor completed strokes were reviewed. A haematocrit of 50% or more was encountered more frequently in those found to have carotid occlusion. The severity of vessel-wall disease showed no relationship to the level of haematocrit. Computerised axial tomographic to the level of haematocrit. Computerized axial tomographic measurements of the volume of the cerebral infarct seen in 23 patients with carotid occlusion and completed strokes showed a correlation between the size of the infarct and the height of the haematocrit. It is suggested that reduced blood flow resulting from increase blood viscosity associated with a high haematocrit adversely affects collateral flow, thereby increasing the size of the infarct.

Impact of carotid endarterectomy upon cognitive functioning - A systematic review of the literature

Background and Purpose: The extent to which carotid endarterectomy (CEA) influences cognitive functioning has been the subject of a number of studies often with conflicting conclusions. This paper systematically reviews the literature in an attempt to clarify this issue. Results: Although the majority of studies (16/28) reported an improvement in cognition after surgery, a substantial minority (12/28) found no change. Studies before 1984 tended to report an improvement, while later studies tended to report no change in cognition. Cognitive improvement was also more likely the longer the time interval between CEA and assessment. The studies were found to differ on many methodological factors, e.g. sample size, type of patient and control group, severity and side of carotid stenosis, the range of cognitive tests and timing of postoperative assessment. Conclusion: Given the conflicting findings, and the methodological issues, it is not possible to draw a clear conclusion regarding the impact of carotid endarterectomy upon cognition. Future research which pays attention to these methodological factors is needed in order to adequately resolve the current debate.

EFFECT OF ASPIRIN IN AMAUROSIS FUGAX

Abstract Two patients with amaurosis fugax were treated with 600 mg. of aspirin daily. In both patients the frequency of attacks decreased, and this response appeared to be due to the drug.

Current management of amaurosis fugax

We present a consensus on the pathophysiology, etiology, diagnosis, and treatment of amaurosis fugax. The phenomenon is defined and described, and the roles that extracranial and ocular vascular diseases play are discussed. Nonvascular ophthalmic and neurologic disorders that can be confused with amaurosis fugax are listed, and an algorithm for evaluation (which includes ophthalmic examination, laboratory studies, and noninvasive carotid artery studies) is given. Treatment of atherosclerosis, carotid artery disease, and other causes of amaurosis fugax are also discussed.

The spectrum of MRI findings in CNS cryptococcosis in AIDS

We retrospectively reviewed the cranial MRI appearances of 25 patients with AIDS and microbiologically proven central nervous system (CNS) cryptococcosis. Four patients had a normal scan. Ten patients had dilated perivascular Virchow-Robin spaces that were hyperintense on T2-weighted images. Nine of these patients developed progressive cryptococcomas, eight in the basal ganglia and one in the cerebral white matter. The cryptococcomas displayed high signal on T2-weighted and intermediate to low signal on T1-weighted images. None enhanced after dimeglumine gadopentetate. No abnormal dural or leptomeningeal enhancement was detected in any patient. One patient developed an acquired arachnoid cyst during treatment of CNS cryptococcosis which was thought to represent a focal collection of organisms and mucoid material within the subarachnoid space. In addition either cerebral atrophy and/or background white matter hyperintensity on T2-weighted images was present in 19/25 patients. In two patients the neuropathological findings at autopsy correlated well with the imaging abnormalities. In conclusion, this spectrum of MRI appearances in CNS cryptococcosis reflects the pathological mechanism of invasion by the fungus, but a normal scan or one with features of CNS HIV infection such as atrophy or white matter hyperintensity does not exclude the diagnosis.

The role of apolipoprotein E in cognitive decline after cardiac operation

BACKGROUND Recently, Tardiff and colleagues have suggested that the presence of the apolipoprotein E, epsilon4 allele was associated with increased likelihood of cognitive decline after coronary artery bypass grafting. The objective of the current study was to replicate this earlier work using an increased sample size. The increased sample also enabled an analysis by individual genotype in cognitive decline after coronary artery bypass grafting. METHODS Apolipoprotein E genotyping was performed on 111 individuals undergoing coronary artery bypass grafting. Each participant underwent a battery of nine neuropsychological tests before operation and 4 to 7 weeks after operation. RESULTS Cognitive decline, assessed by both continuous Z change scores and two categoric measures of cognitive deficit, was not significantly associated with either individual apolipoprotein E genotypes or categorization by the presence or absence of the epsilon4 allele. The examination of potential moderating factors did not alter this finding. CONCLUSIONS This study suggests that the epsilon4 allele is not associated with cognitive decline in the weeks after coronary artery bypass grafting.

Microembolic Signal Detection Using Ultrasound

It is 5 years since Spencer and colleagues1 described in this journal the detection of embolic signals thought to represent solid material released from carotid plaques during the dissection phase of carotid endarterectomy. There has been a rapid spread of interest in this technique. A number of reports have demonstrated the detection of embolic signals in patients with a wide variety of potential embolic sources, and it has been suggested that this detection may already form an important clinical investigational tool. Others have cautioned skepticism.2 The principles underlying ultrasonic detection of cerebral emboli are relatively simple. Being both larger than the surrounding red blood cells and of a different material with different acoustic impedance than the surrounding blood, the incident ultrasound beam is both reflected and scattered at the interface between the embolus and blood. This results in an increase in the intensity of the received signal which, as the embolus is in the sample volume for a short time only, is of short duration. It has been clearly demonstrated in both animal models3 4 and flow models5 that platelet, thrombus, atheroma, and fat emboli result in the expected short-duration, high-intensity signal, usually within the Doppler flow spectrum. In these experimental studies, emboli smaller than 200 to 400 μm could not be reliably introduced, but it is likely that much smaller emboli can be detected using this technique. The intensity increase tends to be unidirectional, and frequency or velocity focused. In contrast, artifact results in predominantly bidirectional signals that can usually, but not always, be easily distinguished.6 Preliminary studies have reported the detection of similar signals in patients with carotid stenosis,7 8 9 10 11 12 prosthetic cardiac valves,13 14 15 16 myocardial infarction,17 atrial fibrillation,18 19 and native cardiac valve …

Acute neuropsychological changes in hemodialysis and peritoneal dialysis patients

This study examined the impact of different dialysis treatments on the neuropsychological (NP) functioning of 145 end-stage renal disease patients. Hemodialysis (HD) and peritoneal dialysis (PD) patients were administered an NP test battery and measures of mood on 2 consecutive days (pre- and 24 hr postdialysis). Biochemistry was assessed at each session. Results indicated significant improvements in NP functioning (attention, concentration, verbal and visual memory, and psychomotor speed) in HD patients 24 hr postdialysis. No such fluctuations were found in PD patients. Although biochemical changes were found in the HD patients at the same time points, these were not consistently related to the NP changes.