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    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 illinfants. 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 alsoimportant. 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


    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 basedspecialisation 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 notcompletely 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 Turners 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 andTurners 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


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