M M Esiri

In this review, the evidence for changes in the human brain with ageing at both the macroscopic and microscopic levels is summarized. Loss of neurons is now recognized to be more modest than initial studies suggested and only affects some neuron populations. Accompanying loss of neurons is some reduction in the size of remaining neurons. This reflects a reduced size of dendritic and axonal arborizations. Some of the likely causes of these changes, including free radical damage resulting from a high rate of oxidative metabolism in neurons, glycation and dysregulation of intracellular calcium homeostasis, are discussed. The roles of genes and environmental factors in causing and responding to ageing changes are explored.

In this study we analysed the accuracy of two sets of clinical diagnostic criteria, the NINCDS/ADRDA and DSM-III-R, in relation to the currently used pathological diagnostic criteria for Alzheimer's disease (AD), the Khachaturian criteria, the Tierney A3 criteria and the CERAD protocol. The sensitivity of the individual clinical diagnostic criteria, NINCDS/ADRDA and DSM-III-R, is poor (34-58%) irrespective of the pathological diagnostic criteria applied for the definite diagnosis of AD. The combination of the NINCDS/ ADRDA 'possible' and 'probable dementia of the Alzheimer type' (DAT) categories has a high sensitivity (91-98%). However the combination resulted in very poor specificity (40-61 %). Thus, none of the clinical diagnostic criteria is satisfactory. We found similar results when we analysed the predictive value of these clinical diagnostic criteria. The positive predictive value of NINCDS 'probable DAT' category and that of the DAT diagnosis by DSM-III-R is very high (89-100%). This makes the use of these categories suitable for research purposes. However, the negative predictive value of both diagnoses is poor (33-63%), making these criteria unsuitable for diagnostic purposes in clinical practice.

This study describes a young girl who presented with involuntary weight loss, spontaneous vomiting and behavioural change. Imaging confirmed hypothalamic and brainstem involvement. Routine investigations (including cerebrospinal fluid analysis and neuromyelitis optica IgG) were unhelpful. Biopsy of the hypothalamic lesion implicated an aggressive inflammatory aetiology. There was a response to conventional immunosuppression, while a further relapse responded to plasma exchange. She died 21 months after presentation. Postmortem examination was highly suggestive of neuromyelitis optica, which was subsequently confirmed following the identification of aquaporin 4 antibodies.

The caudate nucleus from examples of Alzheimer's disease (mean age 68, range 51-77 yr) had a mean wet weight and total protein content that were significantly lower than control. Biochemical markers of various specific nerve cells were determined. These are thought to reflect intrinsic cholinergic neurones (choline acetyltransferase activity) and corticostriatal (L-[3H]glutamate binding), nigrostriatal (dopamine and homovanillate concentrations), and ascending brain stem (serotonin, 5-hydroxyindoleacetate, and noradrenaline concentrations) tracts. There is evidence of selective vulnerability, with cholinergic, dopaminergic, and possibly glutamergic neurons being affected, but not serotonergic and noradrenergic cells. Dopaminergic neurons are probably not markedly reduced in number, but may not be fully operating. Some observations made for the monoamines, as well as the alteration in L-[3H]glutamate binding, seem to lay emphasis on the importance of cortical pathology in Alzheimer's disease.

The immunoperoxidase method has been used to demonstrate the presence of immunoglobulin-containing cells in the central nervous system in acute and convalescent phases of poliomyelitis. These cells were found in considerable numbers in the areas of damage during the acute phase, and persisted at the same sites, though in smaller numbers, during the convalescent phase for at least 8 months. Most of the positively stained cells were plasma cells. IgA was the commonest heavy chain type demonstrated, with lesser amounts also of IgG and, during the acute phase, IgM. In the acute phase more lambda than kappa light chain was demonstrated but in the convalescent phase this ratio was reversed. More light chain than heavy chain was demonstrable during the acute phase. The significance of these results is briefly discussed.