LESIONS OF THE SPINAL MEDULLA 47 



in the motor tract and spread to the anterior column of grey 

 matter in the spinal medulla, or it may commence in the 

 anterior column and spread to the motor tract. In the first 

 case, the initial symptoms are those of an upper neurone 

 affection (p. 3), whereas in the second case they belong to 

 the lower neurone type (p. 3). 



The lesion usually commences in the first thoracic segment 

 of the spinal medulla, and, in consequence, the small muscles 

 of the hand (p. 156) are the first to undergo atrophic changes. 

 The disease gradually spreads upwards and downwards along 

 the spinal medulla, and the muscles of the forearm, arm and 

 trunk become similarly affected. The sterno-mastoid and the 

 upper part of the trapezius (accessory nerve, p. 103) are 

 attacked late in the disease, and their involvement indicates 

 that the lesion is spreading to the medulla oblongata, where it 

 affects the nuclei of the ninth, tenth, eleventh and twelfth 

 cerebral nerves, causing bulb *ar paralysis (p. 108). It should 

 be noted that the muscles of the face and the platysma, 

 which are supplied by the facial nerve, are practically never 

 involved. 



In Syringomyelia- the lesion is situated near the base of the 

 posterior column (cornu) of the grey matter. The cells in 

 which the fibres of the pyramidal tract end (p. 37) may be 

 affected, but the most characteristic symptoms are due to 

 interference with the sensory path. Thermal and painful 

 sensations are lost, since the fibres are interrupted as they 

 traverse the grey matter to reach the other side of the spinal 

 medulla. Tactile sensation, as a rule, is not affected, because 

 many of the tactile fibres ascend in the posterior columns, 

 without first crossing the median plane (p. 43). The motor 

 paralysis is always of the upper neurone type (p. 3), since the 

 cells in the anterior column (cornu) are not involved. 



Complete Transverse Lesions of the spinal medulla neces- 

 sarily produce both motor and sensory paralysis. If the lesion 

 is placed in the thoracic region, spastic paraplegia results, 

 although the paralysed muscles may be flaccid, in the case of 



