812 . THE NERVOUS SYSTEM. 



DEGENERATION OF THE CORTICO-SPINAL MOTOR NEURONES. 



Spastic Paraplegia Spastic Spinal Paralysis. This may be described as 

 a primary lesion of the upper or cortico-spinal motor neurones. It is 

 probable that the lesion affects the entire neurone. As a distinct patho- 

 logical entity the condition is extremely rare. Whether it 'originates in 

 a degeneration of the cell bodies of these neurones in the cortex is not 

 known. The clinical picture of spastic paraplegia, due to compression, 

 to a transverse myelitis, or to a multiple sclerosis, is not uncommon. 

 Marie 1 considers spastic paraplegia as a disease appearing in childhood, 

 and due to a faulty development of the cortico-spinal motor neurones, 

 rather than to their degeneration. 



DEGENERATION OF BOTH PERIPHERAL AND CORTICO-SPINAL MOTOR 



NEURONES. 



Amyotrophic Lateral Sclerosis. This is a primary progressive degener- 

 ation involving both cortico-spinal and spino-peripheral motor neurones. 

 The appearance of the transverse section of the cord is a combination of 

 that in spastic paraplegia and in progressive muscular atrophy. There 



Degeneration of the crossed pyramidal and of the direct pyramidal tracts. In this case there was but 

 little atrophy of the anterior horns. Very few cells, however, were present in the anterior horns and there 

 was an increase in the connective tissue of the horns. 



is a degeneration of the cells of the anterior horn with atrophy of the 

 horn itself, and a degeneration of the fibres of the direct and of the 

 crossed pyramidal tracts (Fig. 531). The lesion in the horns is usually 

 most pronounced in the cervical region. The extent of involvement of 

 the motor tracts of the cord is extremely variable. The degeneration 

 which is the initial lesion is accompanied by a replacement connective - 

 tissue hyperplasia, and the picture presented on section of the cord is 

 that of a sclerosis of the motor tracts and of the anterior horns. Quite 

 1 Marie, "Lectures on Diseases of the Spinal Cord," London, N. S. Soc., 1895. 





