ISI values and interhemispheric differences in patients with ischemic cerebrovascular disease; correlations with clinical and angiographic findings

Impaired quantitative cerebral blood flow in scleroderma patients

Systemic Sclerosis (SSc) is a multisystem disease characterised by proliferation of vascular tissue, obliterative microvascular lesions and diffuse organ fibrosis. Despite widespread vascular disease, Central Nervous System complaints are only infrequently reported and it is uncertain whether they merely derive from systemic complications or whether they may be also caused by a primary vascular process within the brain. Regional cerebral blood flow (rCBF) was quantitatively measured by the 133Xenon clearance technique in twenty-seven consecutive SSc patients without relevant systemic complications and with different severity of vascular involvement, as staged by nailfold capillary videomicroscopy (NCV). Absolute, percent, and asymmetry rCBF values were compared (z-statistics) with age- and sex-matched healthy controls. Cerebral MRI and Mini-Mental State Examination (MMSE) were also performed. Doppler sonography of neck vessels and Transcranial Doppler sonography (TCD) were performed in patients presenting rCBF reduction. Cerebral hypoperfusion was found in the 52% of patients, i.e.: in 33% of patients with the 'early' NCV pattern, in 56% of patients with the 'active' pattern, and in 67% of patients with the 'late' NCV pattern. Thirty percent were the MRIs showing focal and/or diffuse signal abnormalities in the white matter of both hemispheres with the highest rate (44%) in the 'late' NCV pattern. MMSE disclosed mild dementia in one patient in the 'late' NCV group and some mistakes in 6 more patients, in the 'active' or 'late' NCV groups, whereas TCD failed to find significant stenosis of Willis' arteries. Cerebral hypoperfusion is shown for the first time in a substantial part of SSc patients without either neurological symptoms or relevant systemic complications. It is suggested that the rCBF reduction might be related to the systemic scleroderma microangiopathy although, probably due to the paucity of connective tissue in cerebral vessels, the vast majority of patients remains in a subclinical phase.

Blood flow asymmetry in carotid occlusive disease

Patterns of anterior border zone (ABZ) and middle cerebral artery (MCA) cerebral blood flow (CBF) asymmetry were readily seen during both normocapnic room air (RA) and induced hypercapnic (CO2) inhalation using fluoro-methane and a multislice, high-resolution positron scanner. Wilcoxon two-sample rank testing showed symptomatic-over-nonsymptomatic CBF ratios for unilateral greater than 75% carotid stenosis patients (n = 8) to be 1.05 +/- 0.07 (p less than 0.008 as compared with control of 0.97 +/- 0.02) ABZ RA, 0.98 +/- 0.11 ABZ Co2, 0.98 +/- 0.04 MCA RA, and 0.98 +/- 0.06 MCA CO2. Unilateral carotid occlusion patients (n = 8) had ratios of 0.90 +/- 0.16 ABZ RA, 0.81 +/- 0.19 (p less than 0.002) ABZ CO2, 0.90 +/- 0.12 and 0.89 +/- 0.13 for MCA RA and CO2, respectively (both p less than 0.008 as compared with control 0.99). These preliminary results suggest an upgrade of autoregulation (ie, very high ratio) in the ABZ of high-grade stenosis patients during normocapnia. CBF was preferentially higher on the symptomatic side and then either did not increase or paradoxically fell in response to hypercapnia. In comparison, carotid occlusion patients had low ABZ and MCA ratios during normocapnia, also unable to increase with hypercapnia. The fall in ratios from normocapnia to hypercapnia indicates that these areas, already subject to maximal vasodilation, fail to increase CBF or actually become hypoperfused following induced hypercapnia. These results aid in understanding the concept of "hemodynamic significance."

Regional cerebral blood flow asymmetries in a group of 189 normal subjects at rest

Regional cerebral blood flow (rCBF) asymmetries were studied in 189 subjects (96 males and 93 females) at rest with the 133Xenon inhalation method using a fixed detector system. rCBF asymmetries in the resting condition were very small, nevertheless a significant (p less than 0.001) effect for their topographical distribution was present, reflecting higher rCBF in the right fronto-temporal and left parieto-occipital regions. rCBF asymmetries were not correlated with age, and there were no significant differences between males and females. Asymmetries are therefore useful from a statistical point of view in detecting rCBF abnormalities in the resting condition: they are more stable than absolute values in normal subjects and no matching according to age or sex is required when statistical comparisons are performed.

CBF side-to-side asymmetries in stenosis-occlusion of internal carotid artery. Relevance of CT findings and collateral supply

Cerebral blood flow (CBF) was studied at rest by 133-Xenon inhalation method in 15 normal subjects, in 10 patients with cerebral infarction and normal angiograms of major cerebral arteries and in 28 patients with unilateral stenosis-occlusion of the internal carotid artery (ICA), with or without cerebral infarction. All the normals and 20 patients with ICA stenosis-occlusion were tested again after cerebral vasodilatation induced by an intravenous bolus of acetazolamide. At rest the patients with cerebral infarction, irrespective of whether ICa stenosis-occlusion was present or not, showed abnormal side-to-side CBF asymmetry. After cerebral vasodilation variations in side-to-side asymmetry were shown to depend on the inefficiency of the collaterals and not on the degree of ICA obstruction or on the presence of cerebral infarction. These data indicate that at rest side-to-side CBF distribution is influenced more by the presence of an ischemic zone than by a ICA stenosis-occlusion and that under these circumstances the hemodynamic effect of the vascular stenosis cannot be assessed. After cerebral vasodilatation a subset of patients--irrespective of the degree of ICA obstruction and of whether or not cerebral infarction is present--with true cerebrovascular insufficiency can be isolated.