Involvement of Onuf's nucleus in ALS. Demonstration of intraneuronal conglomerate inclusions and Bunina bodies.

Onuf's nucleus of 3 ALS cases was examined histologically, morphometrically and for metal content. Case 1 showed conglomerate inclusions (CIs), cases 2 and 3 showed Bunina bodies in Onuf's nucleus. Electron microscopy showed that CIs were intracytoplasmic accumulations of 10 nm neurofilaments with discrete borders. Onuf's neurons in ALS showed a significant decrease (P less than 0.001) in the cytoplasmic, nuclear and nucleolar areas in comparison with neurons of age-matched controls and elderly controls. Metal analysis of the sacral spinal cords by alpha particle-excited X-ray fluorescence analysis (PIXE) showed relatively high Al levels in the ALS cases compared with controls. Morin staining revealed intense green fluorescence (indicating Al) in the nucleoli and cytoplasm of the CI-containing neurons, but not in the CIs themselves. The appearance of CIs or Bunina bodies and neuronal atrophy in Onuf's nucleus seems to indicate that this structure is also involved in the disease process of ALS, although it is less vulnerable than most other motor ganglia.