Selective loss of nigral neurons in Pick's disease: a morphometric study.

Loss of neurons from the substantia nigra (SN), which is often encountered in Pick's disease, was quantitatively analyzed in 13 cases of Pick's disease and 19 age-matched controls. On sections from the upper and lower portions of the SN, the pigmented zone (zona compacta) and the non-pigmented zone (zona reticulata) were delineated, and these zones were partitioned into quarters: medial, mid-medial, mid-lateral and lateral. Neuronal loss was fairly severe and more evident in the upper section of the SN (-40%), especially in the mid-medial and lateral quarters. In the lower section (neuronal loss: -28%), the medial quarter was most severely affected. Non-pigmented neurons were preserved. Fibrillary gliosis was denser in the zona reticulata, where neuronal loss was minimal. These findings revealed a selective vulnerability of nigral neurons according to their topography and pigmentation and suggests the primary involvement of some neuronal groups (especially the pigmented neurons) of the SN in Pick's disease.