Alzheimer's disease affects limbic nuclei of the thalamus

Sensitive silver techniques for amyloid and neurofibrillary changes were applied to examine the pathological changes revealed by limbic nuclei of the thalamus in Alzheimer's disease. Large numbers of extracellular amyloid deposits occurred in almost all thalamic nuclei. The antero-ventral nucleus harbored numerous large globular patches, other areas contained more densely packed and smaller deposits, while narrow zones of gray matter subjacent to the ependymal lining of the third ventricle remained virtually devoid of amyloid. Intraneuronal neurofibrillary changes were encountered in the form of distended argyrophilic processes covering the medial convexity of the antero-ventral nucleus. Similar structures, although in considerably lesser density, occurred in the laterally adjoining reticular nucleus. The anterior nuclear complex, the latero-dorsal nucleus, portions of the intralaminar complex, the paraventricular and reuniens nucleus contained numerous neurofibrillary tangles and neuropil threads. The antero-dorsal nucleus showed the most severe involvement. At first glance, the thalamus appeared to be only mildly affected by Alzheimer's disease. Closer inspection revealed that severe changes were confined to only a few limbic nuclei. These changes were virtually identical in amount, type and location in all cases of severe Alzheimer's disease studied. It is assumed that these changes considerably hamper the transport of information through limbic circuits.