BEACHIAL PLEXUS PAEALYSIS. 233 



the plexus, when the shoulder is forcibly depressed, and the 

 neck laterally flexed towards the opposite shoulder. 



The intermediate type of paralysis corresponds to a lesion of 

 the middle part of the plexus. It is usually associated with the 

 upper arm type, but may be observed as a residual palsy 

 after the upper part of the plexus has recovered. The muscles 

 paralysed are the triceps, and the extensors of the wrist and 

 fingers. The attitude is characteristic, the elbow being flexed, 

 the wrist dropped, the fingers somewhat bent, and the hand 

 lying midway between pronation and supination. The seventh 

 cervical root is the one chiefly involved. 



The distal type of paralysis is known as Klumpke's. The 

 lesion involves the lower fibres of the plexus, corresponding 

 to the eighth cervical and first dorsal nerves. The small muscles 

 of the hand and the flexors of the fingers are paralysed. This 

 type of paralysis is accompanied by myosis, narrowing of the 

 palpebral fissure and retraction of the eyeball, phenomena 

 referred to implication of the oculo-pupillary fibres which pass 

 into the cervical sympathetic from the upper dorsal nerves. 



The intermediate and distal types of paralysis are uncommon, 

 the corresponding nerves being protected by the fact that the 

 inner part of the clavicle has a forward convexity, and so does 

 not so readily compress the lower part of the plexus. Or, if the 

 lesion be due to stretching and laceration, the fact that the lower 

 fibres of the plexus are not rendered taut so easily as the upper 

 will account for their comparative immunity. 



The brachial plexus may be involved by other lesions such as 

 tumours, disease of the cervical spine, cervical meningitis, local 

 pressure or wounds in the lower part of the posterior triangle of 

 the neck, and dislocations of the shoulder. It is sometimes the 

 seat of neuritis. 



Anaesthesia is not so readily produced as motor paralysis, and 

 when present, if due to a lesion of the nerve roots, will have the 

 corresponding segmental distribution. (Figs. 20 and 22, p. 226.) 



The lumbar and sacral plexuses may be involved by local 

 lesions such as malignant growths, psoas abscesses or spinal 



