THE EXTRAin'RAMIDAL MOTOR SYSTEM 



86 T 



spinal fiber systems traversing the pyramids in tlie 

 medulla originate from extrapyramidal cortical areas, 

 whereas many efferent fibers from area 4 gamma do 

 not appear in the medullary pyramids but go to sub- 

 cortical nuclei, in particular to the striatum and 

 pallidum. Thus every cortical motor area appears to 

 have mixed pyramidal and extrapyramidal functions. 

 That the pyramids contain fibers of various diameters 

 and origins has been a well-known fact since the 

 studies of Haggqvist (74), Lassek (157) and others. 

 Still inadequate is our knowledge of those efferent 

 fibers from cortical motor areas which follow routes 

 not passing through the pyramids. However, in spite 

 of fundamental changes in our knowledge of the 

 pyramidal tract, we do not favor a complete abandon- 

 ment of the concept — in contrast to many other 

 authors such as Bucy (23). Since all these different 

 fibers constitute a tight bundle at the medullary level, 

 the pyramidal tract remains a well-defined and ex- 

 perimentally accessible structure. Many of the earlier 

 concepts remain valid if restricted to the largest fibers 

 in the pyramids, because the great majority of the 

 large pyramidal fibers have their origin in the Betz 

 cells of area 4 gamma. 



The concept of 'striate" or 'extrapyramidal motor' 

 mechanisms has its origin in human pathology. 

 'Striate' or 'extrapyramidal motor' diseases are charac- 

 terized by one or more of the following: an excess of 

 spontaneous, aimless and unintentional movements, 

 a lack of associated and synergistic movements, a 

 persistent increase of muscle tone but with no spastic 

 pareses, and absence of essential changes in the 

 reflexes (84). It was the great merit of the pathological 

 studies of Anton (7), Vogt & Vogt (269), Alzheimer, 

 Wilson (294), Tretiakoff (258) and many others to 

 have shown that diseases with these signs occur as a 

 result of lesions in the striatum (the caudate nucleus 

 and putamen), the pallidum, the subthalamic 

 nucleus, the red nucleus or the nucleus niger. There 

 is general agreement that these latter subcortical 

 structures belong to the extrapyramidal motor system 

 in the narrow sense or to the 'striatal system.' To what 

 extent, however, other structures and fiber systems 

 should be included in this system, will be discussed 

 later. 



Survey of Clinical Exlrapyramidal Sxndromes 



Clinically two major groups of extrapyramidal 

 motor phenomena may be distinguished : the hyper- 

 kinetic-dystonic syndromes characterized by an excess 

 of motor activity, and the hypokinetic-rigid syndrome 



or Parkinson's disease showing a lack of spontaneous 

 motor manifestations. The resting tremor of the 

 parkinsonian syndrome certainly is an involuntary 

 movement and therefore also belongs to the amyostatic 

 phenomena described by Kleist (150) and Herz (97). 

 On the other hand, it is very closely related to the 

 hypertonic syndromes, is controlled largely by anterior 

 horn mechanisms and therefore cannot be considered 

 as a genuine hyperkinetic phenomenon. Thus, to 

 consider the resting tremor as an aspect of the hypo- 

 kinetic-rigid syndrome is not in conflict with the 

 classification just given. 



The hyperkinetic-dystonic syndromes will now be 

 described briefly. 



a) The choreic syndrome is characterized by rapid, 

 involuntary jerks or fragments of movements occurring 

 at irregular intervals and unexpectedly involving any 

 muscle group of the extremities, the trunk or the head. 

 Both the localization and degree of violence of these 

 movements are variable and cannot be foreseen. Each 

 single hyperkinetic episode being of short duration, 

 the different episodes remain separated from each 

 other. Like all other hyperkinetic phenomena they 

 are considerably enhanced by sensory stimuli, 

 emotional stress or voluntary movements. Further- 

 more, voluntary movement is impaired by diflticulties 

 in finding correct innervation, by lack of static support 

 and by poor coordination (asynergism). It is impos- 

 sible for an affected patient to keep the same posture 

 quietly over any considerable period of time. Fre- 

 quently muscle tone is definitely decreased. The 

 anatomical defect responsible for the choreic syndrome 

 is a destruction involving especially the small cells in 

 the putamen and caudate nucleus. 



/)) The ballistic syndrome receives its name from 

 its violent tossing movements which always begin in 

 proximal muscle groups, spread all over the limb and 

 last without interruption for a long time (fig. i). The 

 peripheral joints are affected by much .slower alter- 

 nating stretching and bending movements. The face 

 also is usually involved. The movements are so rapid, 

 violent and unexpected that the patient often falls 

 down or gets hurt by the wide swinging excursions. 

 When lying down, he is rolled back and forth Ijy the 

 movements. The limbs can hardly l)e moved \-oluntar- 

 ily as every movement initiates hyperkinetic episodes 

 which may also ije started by surprise or by emotion. 

 Pathological reflexes and increased abdominal re- 

 flexes are seen on the hyperkinetic side. Scratching of 

 the sole of the foot evokes a very definitely enhanced 

 flexion reflex. Disorders of sensibility due to simul- 

 taneous lesions in the major sensory pathways or in 



