Published online July 1, 2008
PEDIATRICS Vol. 122 No. 1 July 2008, pp. 220-221 (doi:10.1542/peds.2008-1237)

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LETTER TO THE EDITOR

What We Gain by Measuring Head Circumference: In Reply

Sverre Morten Zahl, MD
Department of Neurosurgery
Haukeland University Hospital
N-5021 Bergen, Norway

Knut Wester, MD, PhD
Section for Neurosurgery
Department of Surgical Sciences
University of Bergen
N-5021 Bergen, Norway
Department of Neurosurgery
Haukeland University Hospital
N-5021 Bergen, Norway

Thank you for allowing us to comment on this letter. The points raised are indeed very important; there are indications that untreated childhood hydrocephalus in some cases may remain apparently asymptomatic until adulthood and that it may predispose for later idiopathic normal-pressure hydrocephalus (INPH).

Wilson and Williams correctly assume that not all the hydrocephalic children in our study had surgery. The practice varied between departments, because there was no national consensus on if, and when, a hydrocephalic child should have surgery. This inconsistency applied, above all, to children with benign external hydrocephalus (BEH).

It is difficult, not to say impossible, to establish strict guidelines on whether a child with a somewhat pathologically increasing head circumference (HC) should have surgery. Hydrocephalus is not an "all-or-none" condition; there must be gradual transitions from the healthy child with a normal HC to the child with dramatic symptoms of increased intracranial pressure (ICP) and a rapidly increasing HC. Moreover, the symptoms and signs caused by moderately increased ICP may be vague and difficult to detect, especially for infants with a limited psychomotor repertoire.

A relatively minor delay in a child's development is often excused as trivial, and it is assumed that the development will "normalize" later in childhood. There is a surprising lack of evidence for this assumed normalization. To our knowledge, only 1 study has followed children with BEH until adulthood; apparently, they had more mental problems than would be expected in a normal population.¹ Thus, a moderate increase in ICP may, in fact, be continued beyond early childhood in these children, as suggested by Bradley et al.² According to their "2-hit" theory for the development of INPH, BEH is the first hit that makes the person susceptible to much later adverse events, such as degenerative conditions, that cause the condition to become overtly symptomatic. However, this may apply only to a subpopulation of patients with INPH.³

Finally, there is the possibility that moderately increased ICP associated with BEH may restrain the infant's brain during critical periods of its development. For years it has been known from animal experiments and from the rearing of human infants that there are critical phases early in life during which suboptimal function or deprivation of the brain may restrain the brain's acquisition of mental processes, causing permanent impairment.^4–7 Whether BEH also hampers mental development in a similar manner remains unknown, but the possibility exists.

REFERENCES

1. Muenchberger H, Assaad N, Joy P, Brunsdon R, Shores EA. Idiopathic macrocephaly in the infant: long-term neurological and neuropsychological outcome. Childs Nerv Syst.2006; 22 (10):1242 –1248[CrossRef][Web of Science][Medline]
2. Bradley WG Jr, Bahl G, Alksne JF. Idiopathic normal pressure hydrocephalus may be a "two hit" disease: benign external hydrocephalus in infancy followed by deep white matter ischemia in late adulthood. J Magn Reson Imaging.2006; 24 (4):747 –755[CrossRef][Web of Science][Medline]
3. Wilson RK, Williams MA. Evidence that congenital hydrocephalus is a precursor to idiopathic normal pressure hydrocephalus in only a subset of patients. J Neurol Neurosurg Psychiatry.2007; 78 (5):508 –511[Abstract/Free Full Text]
4. Arling GL, Harlow HF. Effects of social deprivation on maternal behavior of rhesus monkeys. J Comp Physiol Psychol.1967; 64 (3):371 –377[CrossRef][Web of Science][Medline]
5. Blakemore C, Mitchell DE. Environmental modification of the visual cortex and the neural basis of learning and memory. Nature.1973; 241 (5390):467 –468[CrossRef][Medline]
6. Bradley SJ. The relationship of early maternal separation to borderline personality in children and adolescents: a pilot study. Am J Psychiatry.1979; 136 (4A):424 –426[Web of Science][Medline]
7. Grossman ML. Early child development in the context of mothering experiences. Child Psychiatry Hum Dev.1975; 5 (4):216 –223[CrossRef][Web of Science][Medline]

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PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics

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This Article Extract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Zahl, S. M. Articles by Wester, K. Search for Related Content PubMed Articles by Zahl, S. M. Articles by Wester, K. Related Collections Neurology & Psychiatry Social Bookmarking                         What's this?