267

MEAN VALUES AND VARIABILITY OF tcPCO, IN PRE-PVH, PVH, ANDPOST-PVH EPOCHS

1 kPa=7-5mm Hg.

variability of tcPC02 during PVH epochs (see table). Events such asendotracheal tube suction, handling, and pneumothorax causesignificant increases in the variability of tcPC02 in critically ill

infants. In association with changes in systemic arterial bloodpressure the risk of PVH is considerable. Continuous tcPC02monitoring allows the early detection of such increases in PC02.In the early days of transcutaneous oxygen monitoring,

previously unrecognised hypoxic episodes were detected, and thisled to the modification of nursing and medical routines to avoid suchepisodes. Maintenance of PaC02 within narrow limits is also

important. The early detection of hypercapnia by use of continuoustcPC02 analysis will have as much impact on neonatal intensivecare as did continuous tCP02 monitoring in the past.Newcastle Mater Misericordiae Hospital,Waratah, New South Wales 2298,Australia G. J. REYNOLDS

HANDEDNESS IN 47,XXY MALES

SIR,-Cerebral dominance may be atypical in individuals with Xchromosome aneuploid states. We and others have reported that45,X Turner syndrome females do not show the normal degree ofright ear advantage in reporting dichotically presented verbalmaterial, 1,2 suggesting that their left-hemisphere based

specialisation for language is attenuated. 47,XXY males showstronger leftward biases than chromosomally normal males in testsrequiring the recognition of letters and the enumeration of dotspresented to the left and right visual fields. These results also pointto a disturbance of hemispheric organisation characterised by morethan normal degrees of right hemisphere involvement in verbal andnon-verbal problem solving in these individuals. Since 45,X Turnersyndrome females have selective impairments of spatial ability4 andsince 47,XXY males have specific disorders in verbal aptitudes5 thequestion arises whether anomalies in hemispheric organisationunderlie their intellectual disorders.Thus far, the evidence for anomalous cerebral dominance has

been based on behavioural measures which are not only imperfectlyvalid but also distinctly unreliable. Handedness is also not

completely valid but, unlike results obtained from bilaterallypresented stimuli, is undeniably reliable. The relationships ofhandedness to hemispheric organisation is complex but it can beconcluded that within non-right-handed samples there is a higherproportion of subjects who do not conform to the rule that languageis predominantly represented in the left cerebral hemisphere.8 Thequestion addressed in the present report is whether there is a lowerthan normal incidence of right-handers in an unselected group of47,XXY males. If so, this would be consistent with our laboratorybased results and also with the view that cerebral dominance isatypical in these individuals.

1. Netley C Dichotic listening of callosal agenesis and Turner’s syndrome patients. NewYork: Academic Press, 1975; 134-43.

2. Waber D. Neuropsychological aspects of Turner syndrome. Develop Med Child Neurol1979; 21: 5-70.

3. Stewart D, Bailey J, Netley C, Park E, Rovet J. Growth and development of childrenwith X and Y chromosome aneuploidy from infancy to pubertal age: the Torontostudy Birth Defects Orig Art Ser (in press).

4 Garron D. Sex linked recessive inheritance of spatial and numerical abilities andTurner’s syndrome. Psychol Rev 1977; 77: 147-52.

5. Robinson A, Lubs H, Nielsen J, Sorensen K. Summary of clinical findings: Profiles ofchildren with 47,XXY, 47,XXX and 47,XYY karyotypes. Birth Defects Orig Art Ser1979; 15: 261-66.

6. Bryden P. Strategy effect in the assessment of hemispheric asymmetry. In: Strategies ofinformation processing. New York: Academic Press, 1978: 117-49.

7 Annett M A coordination of hand preference and skill replicated. Br J Psychol 1976;67: 587-92.

8 Morgan M, Corballis M On the biological basis of human laterality II: Themechanisms of inheritance. Behav Brain Sci 1978; 2: 270-77.

33 males with a supernumerary X born between 1967 and 1972and identified in a neonatal screening survey of 76 399 births wereavailable for study.9 Of these, 2 were 47,XXY/46,XY mosaics.Handedness was assessed by a ten-item questionnaire dealing withsuch issues as which hand was used in writing and brushing teeth.Individuals with seven right-handed responses were classified asright-handed and the remainder as non-right-handed. Controls were97 male schoolchildren drawn from Toronto public schools. Themean age of the extra X males was 10-9 9 years and of the controls10 - 6. 8 of the aneuploids were non-right-handed (24%) comparedwith 10 controls (10%). A chi square test between these proportionswas significant (p<0 - 05), supporting the conclusion that extra Xmales show a higher than normal incidence of non right-handedness. This finding is consistent with the view that theseindividuals have anomalies in hemispheric organisation. Thesepossibly are related to their specific intellectual disorders.

Department of Psychology,Hospital for Sick Children,Toronto, Ontaria, Canada M5G 1X8

C. NETLEY

JOANNE ROVET

SUBACUTE MYELO-OPTIC NEUROPATHY IS NOT ASPECIAL FORM OF MULTIPLE SCLEROSIS

SIR,-Dr Inoue and Dr Nishibe (May 15, p. 1125) stressed thesimilarity between subacute myelo-optic neuropathy (SMON) andmultiple sclerosis (MS), and stated that it is impossible to differen-tiate clinically both conditions. However, it was only in the initialstage of SMON studies that this unusual disorder was suspected tobe a form of MS or optic neuromyelitis. Subsequent clinical andpathological studies have demonstrated that SMON is a new diseaseentity entirely different from MS.In SMON there are no focal neurological signs (such as mono-

ocular visual loss or asymmetric paresis or sensory level), no focaldemyelinating plaques, and no gammaglobulin production in thecerebrospinal fluid. SMON shows only diffuse degeneration ofsome systems in the CNS and the peripheral nerves, withoutinflammatory appearances. MS in Japan is not essentially differentfrom Western MS.1,2 The prevalence of MS in Japan has notchanged over the past two decades,3,4 while rise and fall in SMONwas synchronous with consumption of clioquinol in Japan andSMON disappeared when the drug was withdrawn.

Several workers have produced in dogs and other animals givenoral clioquinol, pathological - changes compatible with those ofSMON.5 On the one hand, comparable results have never beenachieved in animals inoculated with the so-called Inoue virus, andthe very existence of this virus has been questioned. 6, Isolation of asimilar virus from such pathognomonically different conditions asamyotrophic lateralising sclerosis and MS suggests that the virusmight be non-specific. 8

National Institute of Health,Tokyo 190-12, Japan,and Saitama Medical School

Neurological Institute,Kyushu University

REISAKU KONO,Former chairman of SMONResearch Commission

YOSHIGORO KUROIWA,Former chairman of MultipleSclerosis Research Committee

9. Bell A, Corey P. A sex chromatin and Y body survey of Toronto newborns. Can J GenetCytol 1974; 16: 239-50.

1. Kuroiwa Y, Kurland LT, eds. Symposium: Multiple sclerosis in Asia. (Tenth Congressof Japanese Society of Neurology, May, 1969). Clin Neurol(Tokyo) 1970; 10: 18-46.

2. Kuroiwa Y, Igata A, Itahara K, et al. Nationwide survey of multiple sclerosis in Japan.Neurology 1975; 25: 845-51.

3. Okinaka S, McAlpine D, Miyagawa K, et al. Multiple sclerosis in Northern andSouthern Japan. World Neurol 1960; 1: 22-42

4. Kuroiwa Y, Hung T-P, et al. Multiple sclerosis in Asia. Neurology 1977; 27: 188-92.5. Tateishi J, Kuroda S, Ikeda H, et al. experimental subacute myelo-optico-neuropathy.

In: Neurotoxicology: Vol I. Roizin L, Shiraki N, Grocevic N, eds New York: RavenPress, 1977: 658.

6. Kono R. The SMON virus theory. Lancet 1975; ii: 370.7. Yoshino K, Toba M, Hashimoto M, et al. failure to reproduce the cytopathic effect and

chorioallantoic membrane reactions of the so-called SMON herpesvirus. Jap JMicrobiol 1975; 19: 407-10.

8. Melnick JL, Seidel E, Inoue YK, et al. isolation of virus from the spinal fluid of threepatients with multiple sclerosis and one with amyotrophic lateral sclerosis Lancet

1982; i: 830-33.