A case of subcortical dementia due to sarcoidosis of the hypothalamus and fornices

Subcortical dementia. Neuropsychology, neuropsychiatry, and pathophysiology

Subcortical dementia refers to a clinical syndrome characterised by slowing of cognition, memory disturbances, difficulty with complex intellectual tasks such as strategy generation and problem solving, visuospatial abnormalities, and disturbances of mood and affect. The syndrome was first described by Kinnier Wilson, but further progress in development of the concept has occurred only within the past ten years. Subcortical dementia occurs in degenerative extrapyramidal disorders and has also been identified in inflammatory, infectious, and vascular conditions. Histologic, metabolic, and neurochemical investigations implicate dysfunction primarily of subcortical neurotransmitter systems and subcortical structures or subcortical-frontal connections in the genesis of the syndrome. Subcortical dementia contrasts neuropsychologically and anatomically with disorders such as dementia of the Alzheimer type that affect primarily the cerebral cortex. The clinical characteristics of subcortical dementia reflect the interruption of fundamental functions (motivation, mood, timing, arousal) mediated by phylogenetically and ontogenetically early maturing structures.

The neuropathology of amnesia

Relations between brain damage and memory disturbance are outlined with emphasis on the so-called amnesic syndrome. Following a brief introduction into forms of memory and memory failures, the basic causes of brain damaage (with relevance to amnestic failures) are described. Thereafter, the two best-known forms of brain damage-amnesia relations are reviewed: the consequences of damage to medial temporal lobe structures and to diencephalic regions. For the cases with medial temporal lobe damage, evidence is reported in greater detail for H.M., who has been examined more than any other amnesic patient for more than 30 years now, as a considerable amount of literature has accumulated on his behavior in diverse situations. Other cases with more or less circumscribed damage to medial temporal lobe structures are reviewed so as to outline criteria for or against the hypothesis that there are regions within the medial temporal lobe whose damage might be critical for the amnesic syndrome. Two cases of diencephalic amnesia are summarized in particular (cases of Mair et al., 1979) as they have received extensive neuropsychological and neuropathological investigation. Other cases with, for example, Korsakoff's disease are reviewed, as well as cases with diencephalic, or combined mesencephalic-diencephalic damage without nutritional causes. A third group of patients with massive, but still selective amnesic disturbances are then described: cases of basal forebrain damage, followed by descriptions of Alzheimer's disease which has similarities in the underlying neuropathology. This leads over to cases with more generalized intellectual deteriorations (dementia), which may have developed on the basis of primarily cortical damage or damage principally to basal ganglia structures. After reviewing cases with mainly material-specific memory failures--usually as a consequence of restricted neocortical damage--a separate section follows on patients in whom retrograde amnesia is the prominent symptom. The contribution of animal models of human amnesia is critically reviewed and discrepancies are analyzed between human and animal memory disturbances. This section emphasizes the value of investigating inter-dependencies between brain structures by pointing out that relations between memory disturbances and brain damage may be more complicated than apparent from a simple structure-function assignment. This aspect is further followed up in the conclusions.