A 9-year-old boy, with a history of repair of severe coarctation of the aorta through balloon angioplasty 2 weeks ago, presented in the emergency paediatric department with symptoms consistent with transient cerebral ischaemia. MRI revealed an area of cerebral infarction in the right frontal lobe. Causes of cerebral ischaemia after aortic coarctation repair are briefly discussed.

Cerebral infarction, as the result of atheroma in large blood vessels, was one of the first explanations for dementia in older people. However, this was a relatively uncommon finding in those presenting with dementia and it was soon realized that subcortical infarctions due to non-atheromatous changes in small blood vessel walls were more important factors in cognitive decline. Furthermore, small vessel disease (SVD) producing lacunar infarcts (LI) and white matter changes increased dementia severity in individuals with only moderate Alzheimer's disease (AD) pathology. Magnetic resonance imaging (MRI) found subcortical (lacunar) ‘silent infarcts’ and white matter changes were surrogate markers for SVD and increased significantly the likelihood of developing dementia. Detailed histopathological studies of SVD showed it was in fact a range of pathologies, but the aetiology of the most common type (arteriosclerosis/lipohyalinosis) is difficult to explain. Theories to explain SVD include effects of hypertension, a leaky blood–brain barrier (BBB), amyloid accumulation, microbleeds, venous changes and endothelial inflammation. Endothelial expressed inflammatory molecules could represent potential biomarkers of SVD. Many of the risk factors associated with SVD are also present in AD, such as diabetes, systemic hypertension and ageing; all of these can target the endothelium with the potential to initiate SVD, resulting in ischaemic changes and neurodegeneration, including AD pathology.

Cognitive deficits were produced in rats by different methods of damaging the brain: chronic ingestion of alcohol, causing widespread damage to diffuse cholinergic and aminergic projection systems; lesions (by local injection of the excitotoxins, ibotenate, quisqualate, and AMPA) of the nuclei of origin of the forebrain cholinergic projection system (FCPS), which innervates the neocortex and hippocampal formation; transient cerebral ischaemia, producing focal damage especially in the CA1 pyramidal cells of the dorsal hippocampus; and lesions (by local injection of the neurotoxin, colchicine) of the granule cells of the dentate gyrus. Following chronic alcohol or lesions of the FCPS, transplants of cholinergically rich fetal brain tissue into the terminal areas (neocortex and/or hippocampus) restored performance almost to control levels, with a time course consistent with growth of the transplants and integration with host tissue; transplants of cholinergically poor fetal tissue (hippocampus) were without effect, as were transplants of cholinergically rich tissue into the region containing the nuclei of origin of the FCPS. Grafts of primary cells enriched in glia and cultured neuroblastoma cells into the terminal areas of the FCPS were equally effective, suggesting that there are multiple mechanisms by which neural transplants can restore cognitive function following diffuse cholinergic damage. In contrast, after ischaemia- or neurotoxin-induced damage to CA1 or dentate granule cells respectively, cholinergically rich fetal transplants into the damaged hippocampal formation were ineffective in restoring performance. After ischaemic damage, however, performance was restored by suspension grafts of CA1 cells but not by transplants containing CA3 pyramidal cells or granule cells; and after colchicine damage it was restored by solid grafts containing granule but not CA1 pyramidal cells. Furthermore, electrophysiological evidence has demonstrated functional, graft type-specific host-graft functional neuronal connectivity. Thus, restoration of cognitive function by neural transplants is possible after damage to either diffuse (cholinergic) or point-to-point (intrahippocampal) forebrain systems, but the transplant must be appropriate to the damage to be repaired. Because the different types of brain damage studied provide analogues of human alcoholic dementia, Alzheimer's disease, and heart attack, these results are encouraging with regard to the eventual application of neural transplant surgery to the treatment of cognitive deficits in humans.

Sometimes progress is hard to see, when looking at the big picture, because there is very little of it. But sometimes progress is hard to see because the big picture is out of focus. When perioperative deaths ascribed to anaesthesia are in the order of 1 in 20 000 operations and even changes in major morbidity require massive sample sizes to detect, neuroanaesthesia's most emphatic yardstick of progress is too crude to measure advances that have occurred over the most recent decade. We clearly need to become more familiar with neuropsychological tests that can detect subtle changes. Today, for elective neurosurgery, we are primarily in the business of doing two things – pushing the envelope for surgical intervention to include cases that would have been considered too risky 15 years ago, and reducing the frequency of “Uncle-Joe-has-never-been-the-same-since-they-operated-on-his-brain syndrome”. Both of these areas of progress are empirically measurable, but we have not made much progress towards measuring them. Of course, this measurement problem plagues anaesthesiology generally, and we need to attend to it in general. Meanwhile, saying where we are relative to the recent past and the near future involves a lot of guesswork. What follows is my guesswork about progress in neurosurgical anaesthesiology.