Quantitative Study of Synaptophysin Immunoreactivity of Cerebral Cortex and Spinal Cord in Motor Neuron Disease

Abstract

Synaptophysin immunoreactivity can be quantified by image analysis to evaluate loss of presynaptic terminals in human neurodegenerative diseases. The extent and regional distribution of such loss is reported in motor neuron disease (MND). Autopsy samples of spinal cord and cerebral cortex were examined from 28 cases of MND and 28 age and sex matched controls. The MND group included individuals with amyotrophic lateral sclerosis (17[ALS]), and progressive muscular atrophy (11[PMA]). In the spinal cord, there was significant reduction of presynaptic terminals in the lateral ventral horn (15%) in both the ALS (p < 0.01) and PMA (p < 0.05) groups. Perisomatic synaptophysin profiles on lower motor neurons are preserved late in the disease and are not related to corticospinal innervation. Less marked presynaptic loss was demonstrable more widely in the medial ventral, intermediate and dorsal spinal grey matter (10%) in both ALS (p = 0.03) and PMA (p = 0.05). In the cerebral cortex no synaptic loss was demonstrated in motor or anterior cingulate regions in any of the MND cases. Spinal degeneration in MND is associated with loss of presynaptic terminals in all grey matter regions. It is most marked in the limb motor neuron area and is independent of corticospinal tract degeneration. The cerebral pathology of ALS is not associated with significant loss of presynaptic terminals in the cortical areas studied.