In this chapter we consider a number of diverse pathological conditions that may occasionally give rise to a clinical picture in which dementia predominates (Table 23.1). Other neurological features are also likely to be present at some stage in the course of these diseases. In some, perhaps most, such cases these other clinical features may have led to the correct diagnosis being established before clinical dementia develops, but in a few the diagnosis may be impossible to achieve before death. Therefore, a pathologist can expect to encounter these diseases occasionally among cases of dementia presenting at autopsy. Full treatment of pathological aspects of these diseases and their illustration is beyond the scope of this chapter and for details a more general textbook of neuropathology should be consulted, e.g. Greenfield's Neuropathology (Graham & Lantos, 2002) or Davis and Robertson's Textbook of Neuropathology (1996).

Neurodegenerative conditions

Neuronal intranuclear hyaline inclusion disease (NIHID)

Neuronal intranuclear hyaline inclusion disease (NIHID) is a rare neurodegenerative disorder characterized by the presence of large eosinophilic inclusions in neuronal nuclei in a wide distribution (Sung et al., 1980; Funata et al., 1990). Whilst most cases present clinically with predominantly motor or other non-cognitive problems, some cases have had dementia (Weidenheim & Dickson, 1995). The neuronal inclusions are present in peripheral ganglionic neurons as well as at all levels of the CNS from cerebral cortex to spinal cord. In addition to the presence of neuronal inclusions, there may be somewhat smaller inclusions in astrocytic nuclei. Neuronal inclusions consist ultrastructurally of haphazardly arranged 10 nm diameter straight filaments without any surrounding membrane.