QUANTITATIVE ASSESSMENT OF MOTOR-NEURON LOSS IN EQUINE MOTOR-NEURON DISEASE (EMND)

The mean number of motor neurons was assessed in the C-7 spinal cord s egment of 5 EMND and 5 control horses. Mean number per section in EMND horses was reduced significantly (P<0.001). The mean neuronal loss wa s estimated at 31%. Each of the 5 affected horses had a mean neuronal count below the 95% confidence interval for control horses. The statis tically significant difference between the 3 groups was consistent in the cranial, middle and caudal thirds of the C-7 segment (P<0.001). Th e results of regression analysis indicated an association between neur onal reduction in EMND horses and the duration of the disease when adj usted for age (P<0.001). This is the first quantitation of the neurode generative loss in EMND and it provides a clearer explanation for resi dual deficits in horses that survive EMND.