Fig. 3
CNS lesions in atypical primate infections. a Bilateral, medial pseudo-necrotic lesions of the anterior horns with neuronal loss in the lower cervical spinal cord extended in some cases up to C4 (Primate R8. C6 spinal cord. Klüver–Barrera/KB stain). Wallerian degeneration of the posterior spinal tracts (mainly gracilis) was also observed along the whole length of the spinal cord and in parts of the optic tracts (Supplementary Fig. 4). Atrophic ganglion cells were noted in dorsal root ganglia. b At higher magnification, lesions appeared as a loss of ground substance filled with macrophages and surrounded by glial cells with few preserved neurons (haematoxylin–eosin/H&E stain). There were no infiltrates of lymphocytes or granulocytes, haemorrhages, fibrin deposits, vascular obstructions or thickened vessels. c The same type of bilateral pseudo-necrotic lesion was observed in the brainstem within the spinal nuclei of the trigeminal nerve and extended in some cases to the inferior cerebellar peduncles (Primate R6, H&E stain). d Those lesions (arrows) might be visualised with MRI analysis (primate R16, terminal stage of the disease). Coronal T2-weighted images were acquired using a fast spin-echo sequence (TE/TR = 60/4000, 450 × 450 µm in plane resolution, 1 mm slice thickness, 40 slices, 14 min acquisition time). In these foci, involvement of the nervous tissue was of different degrees, ranging from status spongiosus like (e) (primate R16, H&E) to cavitation with myelin debris and axonal loss (f) (primate R6, H&E). g At the periphery of the lesions, intracellular vacuoles were detected in some neurons (primate R17, KB stain)
