PRACTICE PARAMETER: EVALUATION OF THE CHILD WITH MICROCEPHALY (AN EVIDENCE-BASED REVIEW): REPORT OF THE QUALITY STANDARDS SUBCOMMITTEE OF THE AMERICAN ACADEMY OF NEUROLOGY AND THE PRACTICE COMMITTEE OF THE CHILD NEUROLOGY SOCIETY

PRACTICE PARAMETER: EVALUATION OF THE CHILD WITH MICROCEPHALY (AN EVIDENCEBASED REVIEW): REPORT OF THE QUALITY STANDARDS SUBCOMMITTEE OF THE AMERICAN ACADEMY OF NEUROLOGY AND THE PRACTICE COMMITTEE OF THE CHILD NEUROLOGY SOCIETY To the Editor: I read the recent practice parameter regarding microcephaly and would like to comment on the authors’ findings.1 First, microcephaly is defined by the authors as a head circumference less than 2 standard deviations below population means. This is not a neurologic sign but a physical measurement. It is of interest to neurologists only as a crude approximation of brain size. Abnormally small head size is defined by others as a head circumference of less than 3 standard deviations below the norm. Second, Ashwal et al. do not consider the important—and generally benign— determinants of familial correlation or general body size. The definition they use inflates the magnitude of the condition but distorts its importance: the majority of children with head circumferences between 2 and 3 standard deviations are normal.2 In addition, microcephaly is treated as a free-standing condition which is causally pertinent to comorbid conditions such as cerebral palsy and epilepsy, instead of the associative condition that it is. Third, the referenced studies regarding such associations are misclassified. They are based on small and highly selected populations vs representative populations of the conditions under discussion. The all too frequent practice of citing figures from these reports promotes unreflective and expensive testing. The evidence for performing neuroimaging, genetic and metabolic testing, and monitoring for epilepsy and cerebral palsy is acknowledged as weak or insufficient.1 Upgrading the level of evidence which they represent is unacceptable. More stringent vetting of practice parameters and guidelines is needed. Once a guideline is proposed, it gains momentum and acceptance by sponsoring societies. However, this is insufficient to warrant validation.