THE EXTRAPYRAMroAL MOTOR SYSTEM 



867 



FIG. 2. Athetosis of the right hand. 

 Left: Maximal flexion in the wrist. 

 Middle: Pressure is appUed to the lower 

 arm. Right: A few seconds later the 

 flexion changes to an athetotic hyper- 

 extension of the fingers. [From Hassler 

 (84)-] 



their thalamic relay nuclei are present rather fre- 

 quently but are not related to the lesion of the sub- 

 thalamic nucleus. In one-fifth to one-fourth of the 

 cases, disorders of the autonomic nervous system, 

 such as hyperhidrosis, edema, vasomotor disorders 

 and the Bernard-Horner syndrome, were observed on 

 the side contralateral to the lesion; they are due to 

 injury of neighboring structures. In most of the cases 

 hemiballism is caused by a large lesion of the contra- 

 lateral subthalamic nucleus. 



c) The athetoid syndrome is characterized by in- 

 voluntary movements which are slower and to a 

 greater extent afTect the peripheral muscle segments 

 of the limbs and the face. The movements are worm- 

 like, spasmodic, repetitious and frequently lead to 

 overextention of joints, especially of the fingers (fig. 2). 

 The joints have a tendency to become fLxed in ab- 

 normal postures. The enhancing eflfect of emotional 

 influences and sensory stimuli is particularly im- 

 portant in this disorder. Normal expressions are 

 always exaggerated (the 'disease of associated move- 

 ments' of Lewandowsky). Voluntary movements are 

 impaired and partially impossible. The muscles are 

 hypotonic although the tone is exaggerated during 

 the moveinents. With athetosis there are also patho- 

 logical skin reflexes and exaggerated normal extero- 

 ceptive reflexes. In most cases there is a combined 

 lesion of the striatum and the external pallidum, 

 sometimes a progressive disease of the pallidum alone. 



/) The dystonic syndrome is also called proximal 

 athetosis because of its likeness to athetosis. Every 

 movement or even the intention to move initiates 

 strong contractions in muscle groups preventing the 

 movement originally intended. These muscular spasms 

 involve the muscles of the neck and trunk (torticollis 

 and tortipelvis). Strange postures and slow spasmodic 

 rotations of the trunk and limbs — torsions — are char- 



acteristic inotor manifestations (fig. 3). It is amazing, 

 however, how easily complicated habits — like riding 

 a bicycle or playing a ball game — as well as powerful 

 efforts are performed. The resistance of the inuscles 

 to passive movement is at times below and at times 

 above normal. The question of the anatomical sub- 

 strate is still unsettled. In most cases lesions of the 

 putamen without involvement of the caudate nucleus 

 and pallidum have been reported. Destruction of the 

 part of the centrum medianum leading to the putamen 

 has been described in one hereditary case [Vogt & 

 Vogt (272)]. 



e) The myoclonic syndrome is less homogeneous. 

 It includes disorders characterized by quick ar- 

 rhythmic contractions of single muscles or muscle 

 groups with more or less wide movements at a fre- 

 quency of less than 3 per sec. and also myorhythmic 

 disorders of the soft palate or the pharynx muscles 

 which inay persist during sleep. Myoclonic move- 

 ments may occur in any muscle, frequently leaping 

 from one muscle to the other. Voluntary movements, 

 eiBotional stress and heterogeneous sensory stimuli 

 enhance all involuntary manifestations. The anatomi- 

 cal substrate is a lesion in the system including the 

 dentate nucleus, red nucleus, central tegmental tract 

 and olives. Pathogenetically a focus of hyperexcita- 

 bility seems to exist in the brain-stem reticular forma- 

 tion which projects both rostrally to the motor cortex 

 and caudally to the anterior horn cells. 



j) In addition, there are more complex motor dis- 

 orders consisting of myoclonic manifestations or of a 

 combined variety of such phenomena. Besides con- 

 vulsive contractions in the floor of the mouth, there 

 are various types of organic tics and many extra- 

 pyramidal motor fits. In contrast to myoclonic dis- 

 orders, organic tics are arrhythmic but stereotypically 

 repeated movements of restricted muscle groups look- 



