What's in a name? Everything

Field: Medicine (Health Sciences)

I read with interest the systematic review by D'Antonio et al.1 and would like to point out some apparent inconsistencies between the data provided in the review, and those in the source publications from which they have been drawn, that may bias the review conclusions. Although the authors state that they defined vermian hypoplasia (VH) as ‘a normally formed vermis but of smaller size, with an otherwise normal size and anatomy of the posterior fossa’, they included amongst their cases of VH fetuses that had imaging findings consistent with a persistent Blake's pouch cyst (BPC). The series of 19 patients with inferior vermian hypoplasia (IVH) reported by Limeroupoulos et al. in 20062, although diagnostic criteria for IVH were not explicitly provided, were evaluated at a mean age of 19.8 ± 4.9 months. Three of 13 with ‘confirmed’ IVH on postnatal imaging had motor and language delays and two of 13 had behavioral problems. The single image provided in this paper (Figure 1) demonstrates findings consistent with a BPC as defined by D'Antonio et al. This study was not included in the systematic review. However, D'Antonio et al. did include in their VH subgroup 20 children from a later follow-up study by Tarui et al.3 that included 17 of the original 19 children studied by Limeropoulos et al.2 as well as a further three children, all said to have IVH. Once again, the criteria for a diagnosis of IVH were not provided and, in this paper, nor were any images. At follow up the children were a mean ± SD age of 6.1 ± 1.9 years and all cases with ‘isolated’ IVH had normal neurodevelopmental outcome. It seems highly likely that some, if not all, of these subjects had a persistent BPC instead of IVH or VH. The review states that only one of the 86 cases with BPC had aneuploidy and this was trisomy 21, however one of the included studies4 indicates that two of their 19 subjects with antenatally diagnosed BPC had trisomy 21. This would change the conclusion of the review with regard to the prevalence of aneuploidy in fetuses with BPC. One of the six cases (Case 4 in the series) with ‘isolated’ Dandy–Walker malformation (DWM) reported by Guibaud et al.5 was reclassified as BPC on review of the fetal magnetic resonance image (MRI) (Figure 2). This child had a normal neurological outcome at 23 months. When analyzing Table 1 of the review, D'Antonio et al. appear to have included this series of six patients as cases of DWM. This has the potential to bias their conclusions about the likelihood of important outcomes (additional congenital abnormalities, postnatal confirmation and chromosomal abnormalities) in DWM. BPC and DWM exist as somewhat well-defined points on a continuum. VH, that is generalized and not necessarily ‘inferior’, frequently coexists with BPC particularly as the cyst size and thus tegmentovermian angle increase. Isolated VH, as defined by D'Antonio et al., without vermis rotation and thus without BPC, is likely to be a completely different entity from BPC with associated VH. Greater rigor and sophistication are required with regard to defining ‘enlarged posterior fossa’, ‘elevated torcular’, ‘vermian hypoplasia’, ‘inferior vermian hypoplasia’ and ‘normally foliated vermis’ in future studies of both ultrasound and MRI before we can understand better the relationship of these imaging findings, whatever we call them, to patient outcomes, including neurodevelopment. S. K. Goergen Departments of Medical Imaging and Surgery, Monash University, Southern Clinical School, 246 Clayton Road, Clayton, Victoria, 3168, Australia (e-mail: [email protected])