Twenty-four patients of comparable age, blood pressure, and degree of dementia were classified by an "Ischemic Score" based on clinical features into "multi-infarct" and "primary degenerative" dementia. Regional cerebral blood flow (CBF) was measured by the intracarotid xenon 133 method. Both groups showed a decreased proportion of rapidly clearing brain tissue (largely gray matter). Cerebral blood flow per 100 gm brain per minute was normal in the primary degenerative group but low in the multi-infarct group. This suggests the blood flow is adequate for metabolic needs of the brain in patients with primary degenerative dementia but inadequate for those with multi-infarct dementia. There was no correlation between degree of dementia and CBF in the primary degenerative group but an inverse relationship existed in the multi-infarct group. Reactivity of blood vessels to reduction of arterial carbon dioxide pressure was normal in both groups.

The cerebral blood flow, oxygen extraction and oxygen utilization has been measured regionally in 22 dements, and 14 aged normal volunteers. Ten demented patients were studied twice at a six-month interval from initial measurements. The use of a steady-state 15O technique and positron tomography for measuring regional cerebral blood flow, regional oxygen extraction fraction and mean cerebral oxygen utilization is discussed. The limitations of measurements are reviewed in the light of the present results and the current state of technological development in positron emission tomography is discussed. A decline in cerebral blood flow and mean cerebral oxygen utilization was correlated with increasing severity of dementia in both degenerative and vascular dements. The decline was coupled, both for the cerebral hemisphere as a whole and regionally. There was no increase in oxygen extraction ratio globally, and therefore no evidence to support the existence of a chronic ischaemic brain syndrome. Focal abnormalities in oxygen utilization were observed for both vascular and degenerative groups. In the vascular group, parietal defects were the most pronounced. Individual derangements of the regional pattern varied, reflecting the different unique patterns of ischaemic damage in these patients. In the degenerative group, parietal and temporal defects were seen in the less severe group, but a profound depression in the frontal regions with relative sparing of occipital area characterized the severe degenerative dements.

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Using pneumoencephalography and computerized axial tomography (EMI scanning) Polaroid pictures, the relationship between ventricular size and cerebral size was investigated in 35 patients. Evans' index was used for pneumoencephalograms, and planimetric measurement of the ventricular and cerebral cross-sectional areas was used for EMI scanning. The percentage ratio for the latter technique is termed VBR. The correlation coefficient between the two methods was 0.9510 (p less than 0.001).

S Y N 0 P S I S Patients suffering from severe migraine, usually for many years, have been examined by the EMI scanner between attacks. Judged by criteria validated originally by comparison with pneumoencephalography, about half of the patients showed evidence of cerebral atrophy. Perhaps of more significance than generalised atrophy was the frequency of areas of focal atrophy and of evidence of infarction.Although migraine is a common disease afflicting between 5% and 10% of the population (Friedman, 1971), little is known about either the underlying pathological changes which are present during an attack or the structural changes, if any, which may occur in the brain after one or many episodes. This difficulty in obtaining information arises from the fact that migraine is rarely a fatal illness, and such information as we have is derived from studies of those vessels which are visible in the retina, from the very small number of postmortem studies which have been reported in patients dying from migraine and its complications, and from a few angiographic and cerebral blood flow studies.Computerised axial tomography (CAT) (EMI scanning) offers a new opportunity for the visualisation of pathological changes in the brain occurring in the course of non-fatal illness.Symonds (1951) suggested that slight, but cumulative structural damage may result from repeated attacks of migraine. We have therefore analysed the results of CAT in a group of patients suffering from severe migraine in an attempt to determine whether structural damage does occur.

SYNOPSIS Cerebral blood flow (CBF) has been measured in 26 patients liable to cluster headaches. Of four patients studied during spontaneous attacks CBF fell in three and rose in one. Attacks could not be induced by nitroglycerine, alcohol or histamine except when patients were currently experiencing a bout of cluster headaches. The CBF rose during some induced attacks and fell during others. It is concluded that CBF changes do occur in cluster headache but the pattern is not consistent and does not at present suggest a mechanism for cluster headache.

The frequency with which patients presenting with acute or chronic noncompressive cord syndromes subsequently develop multiple sclerosis is uncertain. Magnetic resonance imaging (MRI) was performed on 121 patients with such syndromes to determine the frequency of asymptomatic brain lesions and to assess the sensitivity of MRI in detecting the local cord lesion. MRI findings were compared with those from visual, brainstem, and somatosensory evoked potentials (VEPs, BAEPs, SEPs), and cerebrospinal fluid electrophoresis. Lesions were seen in the appropriate cord region in 47 of 73 patients (64%) with a cervical syndrome, and in 7 of 25 patients (28%) with a thoracic or lumbar syndrome. MRI demonstrated more cervical lesions than did SEPs, but fewer thoracic or lumbar lesions. Cord swelling was seen in 6 patients and atrophy in 10. Of those with acute syndromes, abnormalities were seen with brain MRI in 18 of 32 patients (56%), with VEPs in 2 of 30 patients (7%), and with BAEPs in 2 of 24 patients (8%). In patients with chronic syndromes, abnormalities were seen with brain MRI in 73 of 89 patients (82%), with VEPs in 22 of 80 patients (28%), and with BAEPs in 12 of 62 patients (19%). Brain MRI was thus more sensitive than evoked potentials were in establishing multiplicity of lesions. However, in acute syndromes, it was not possible to diagnose multiple sclerosis from a single abnormal brain scan in chronic syndromes, a diagnosis of clinically probable multiple sclerosis could be made from one scan, provided there was no better explanation for the abnormalities: the added presence of oligoclonal bands allows a diagnosis of laboratory-supported, definite multiple sclerosis as was the case in 28 patients in this series.