>9'4 



IIVMJBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY III 



ment of the eyes in the severe head defects seen in 

 some experimental animal malformations simply 

 reflects a slight difference in developmental patterns 

 between man and other vertebrates involving the 

 prechordal mesoderm. 



Ballantvnc (4) collected information about a con- 

 siderable number of these monsters. Although they 

 often no to term, they usually die soon after birth. 

 Some survive for hours or, rarely, weeks. They live 

 in uteri), obviously, and move there. Respiratory, 

 sucking and successful swallowing movements have 

 been described, and some have passed urine and 

 feces. It is remarkable how little nervous parenchyma 

 seems to be necessary for some of the basic movements 

 mentioned above to be carried out even though, from 

 the descriptions given, they are rather crude and 

 not always successful (as respiration or swallowing 

 movements). On the other hand, in one case, a male 

 ( ited by Ballantyne (4), there was no trace of cerebral 

 hemispheres or cerebellum, the midbrain, medulla 

 and pons were incomplete, but the cord was appar- 

 ently normal. The infant lived 39 hr., his rectal tem- 

 perature was 95°F, respirations were of the Cheyne- 

 Stokcs type at a rate of 9 per min., and his pulse rate 

 was 138 per min. but intermittent during inspiration. 

 His skin was cyanotic. Patellar reflexes were elicited 

 despite flexed limbs, forearm reflexes were exagger- 

 ated, and some odd muscular reflexes were present. 

 The pupils of his eyes were inalterably dilated even in 

 bright light. He sucked, swallowed and cried out, and 

 withdrew his body when the skin was pinched or 

 heated. Quinine and camphor elicited no taste re- 

 sponse, but ammonia vapor caused withdrawal of 

 die head. He began to have convulsions about 20 

 hr. after birth. These were described as starting in 

 the left arm and then becoming general. 



Anencephaly illustrates a gross structural devia- 

 tion from normal pathways of development mani- 

 festing itself early in embryogenesis. The functional 

 disturbances are for .ill practical purposes the conse- 

 quence of gross anatomic delect 



Hereditary Ataxias 



This group of disorders illustrates the fact that 

 anatomic developmental disorders can appear in a 

 tissue after it has 'grown up' to the adult stage. These 



diseases of the neiit c imusculai system of man are 



collectively called hereditary ataxias by Bell (6) 

 .ind Schu) (38), .md muscular atropines by Aring & 

 1 bb ee also Cobb inn, .md they are more 



closely id. ited genetically than their neurophysio- 



logic disturbances would suggest. The term 'heredi- 

 tary ataxia' is a fairly useful generic term because it 

 implies the two major features present in so many of 

 the syndromes. The diseases, which show several pat- 

 terns of inheritance and expression, may be inter- 

 related by the action of several genes or groups of 

 genes on more than one chromosome. These genes 

 may normally govern the integrity and longevity of a 

 specific constellation of adult neuromuscular struc- 

 tures perhaps by providing specific enzymes essential 

 for these seemingly unrelated tissues. If the enzymes 

 were absent or 'mutated,' they could affect those 

 structures profoundly. 



Some of the major patterns of the group of diseases 

 that have received distinct names arc Friedreich's 

 ataxia, hereditary cerebellar ataxia, hereditary spastic 

 paraplegia, progressive peroneal muscular atrophy 

 of Charcot-Marie-Tooth, and progressive muscular 

 atrophy. These may be combined in several ways 

 and degrees, or one may appear in fairly pure form 

 and some other findings such as optic atrophy may 

 be prominent. The heredity may be recessive or 

 dominant, and sometimes sex-linked, and in different 

 pedigrees the patterns may develop distinctive 

 characteristics. 



The disturbances of function in the hereditary 

 ataxia group are directly related to the degenerative 

 changes in the particular fiber tracts, neuron bodies, 

 peripheral or cranial nerves, or muscles involved 

 When the posterior columns of deep sensations and 

 the cerebellar pathways arc chiefly involved, ataxic 

 patterns predominate. In a given family the age of 

 onset, progress and pattern of the disorder may be 

 very uniform among the siblings 



The hereditary ataxias and related muscular dis- 

 orders are included here to emphasize the futility of 

 describing congenital abnormalities without also 

 trying to understand their ontogeny. Cobb 110) has 

 s.ii.l recently: "Several authors have tried to describe 

 new 'dtse.ises' without pathological data and without 

 understanding th.it in hereditary diseases the geno- 

 type (abnormality of the genes) may be relatively con- 

 stant, whereas the phenolvpe (clinical manifesta- 

 tion) in. iv vary greatly according to developmental 

 and environmental influences. It is this kind of making 

 of new -disease entities' .uu\ 'syndromes' which has 

 so ((implicated neurological literature that 'one can- 

 not see the forest lor the trees.' This group of neural 

 myopathies should be looked on as one disease with 

 many variants Many have been already described, 

 but many more will arise and should not then be 



