Loss of thalamic intralaminar nuclei in progressive supranuclear palsy and Parkinson's disease: clinical and therapeutic implications.

Whilst many reports mention neurofibrillary tangle pathology in the thalamus in progressive supranuclear palsy, there has been little detailed regional analysis of the distribution and density of thalamic pathology in this disease or in other parkinsonian syndromes. The caudal intralaminar thalamic nuclei are the major thalamic regulators of the caudate nucleus and putamen, areas known to be dysfunctional in progressive supranuclear palsy and Parkinson's disease. We investigated whether these thalamic nuclei degenerate in patients with these disorders compared with age-matched, neurologically normal controls. Neurofibrillary tangle and Lewy body pathology was assessed and unbiased optical disector methods were used to quantify total neuronal number. Despite different thalamic pathology, there was a dramatic reduction in the total neuronal number in the caudal intralaminar nuclei in both progressive supranuclear palsy and Parkinson's disease (40-55% loss). In contrast, there was no loss of volume or total neuronal number in the limbic thalamic nuclei in either disease group, indicating selective degeneration of the caudal intralaminar nuclei. In Parkinson's disease, Lewy bodies were found in these regions, while in progressive supranuclear palsy abundant intracellular neurofibrillary tangles and glial tangles concentrated in the caudal intralaminar nuclei. However, tangle formation accounted for only a small proportion of cell loss (