Disorders of memory follow damage to the medial surfaces of both temporal lobes and their brainstem connections – the hippocampi, fornices and mammillary bodies. Bilateral lesions are necessary to cause amnesia. It is characteristic of all organic memory disorders that more recent events are recalled poorly, in contrast to the relative preservation of distant memories.

Memory loss (the amnestic syndrome) is part of dementia, but also occurs as an isolated entity (see Table 21.4).