Direct demonstration of transsynaptic degeneration in the human visual system: A comparison of retrograde and anterograde changes

Abstract

Transneuronal degeneration of retinal ganglion cells was directly demonstrated in a patient who had unilateral removal of the striate cortex forty years prior to necropsy. For comparison, another case is presented showing anterograde transneuronal atrophy forty years after enucleation of one eye. Transsynaptic retrograde degeneration (TRD) has been described in several neuronal systems. Previous studies have indicated that the severity of TRD was inversely proportional to the age of the subject at the time of injury and directly proportional to the time elapsed following the injury. The authors present two case reports in which paraphenylene diamine (PPD) was used to stain degenerated axons and axon terminals. This technique has been shown to be a highly sensitive and reliable method for identifying degenerated axons in human brain material. PPD has been shown to stain degenerated axons following lesions that occurred more than five years before death. The resolution achieved by this technique is better than can be obtained with silver impregnation; it thus allows the identification of very small numbers of fibres.