Fronto-temporal horn ratio: yet another marker of ventriculomegaly?

Posthemorrhagic ventricular dilatation (PHVD) continues to be a significant complication of prematurity that carries a high risk of adverse neurodevelopmental outcome.^1,2 Multiple animal and human studies have consistently demonstrated that the increase in ventricular size correlates with long-term outcome; however, it remains a matter of debate when best to treat PHVD.^3,4,5,6,7,8 Recent retrospective studies and two randomized controlled trials (RCTs) have shown beneficial effects of cranial ultrasonography (cUS)-based decisions.^{9,10,11,12,13} In these studies, deciding when to intervene mostly relied on practical and reproducible cUS measurements, such as the ventricular index (VI), anterior horn width (AHW), and thalamo-occipital distance (TOD).^14,15 In studies reported mostly by neurosurgeons, the frontal and occipital horn ratio has been shown to be a reliable surrogate for ventricular volumes,¹⁶ and more recently the fronto-temporal horn ratio (FTHR)¹⁷ has been correlated with magnetic resonance imaging (MRI) measurements by Radhakrishnan et al.¹⁸ However, until a recent study by Leijser et al.,¹⁹ no comparison was made between these different sonographic indices. The investigators explored inter-observer reliability of the sonographic indices for prediction of severe PHVD and showed a better reliability for VI and AHW measurements (intra-class correlation coefficient of 0.49–0.84 and 0.51–0.81, respectively) than for FTHR (0.41–0.82). The predictive value for neurodevelopmental outcomes after severe PHVD was also higher for the AHW than for the FTHR.¹⁹

In this issue, Obeid et al.²⁰ retrospectively assessed preterm infants with PHVD to define normative FTHR values as a marker of ventriculomegaly in cUS. The investigators found that the FTHR can be a useful quantitative biomarker of ventriculomegaly in preterm infants and it may help standardize ventricular measurements to direct intervention. While defining the normative values of FTHR is a noteworthy contribution to the literature, it should be emphasized that, due to the limited peripheral field view in cUS scans, it may be difficult to clearly visualize the parietal bone and both ends of the horizontal line indicating the biparietal width sometimes have to be estimated by judgment, as can be seen in their figure. Additionally, as there was a larger number of infants included in Obeid’s study and these infants also had a lower gestational age than that of Radhakrishnan et al.,¹⁸ it would have been a great opportunity to compare the VI, AHW, and FTHR in this large dataset. Besides, to assess additional brain injury, Obeid et al.²⁰ used the Kidokoro score²¹ but with different thresholds for the classification of white matter injury to that used by Kidokoro. In the original description, >4 was taken as the cut-off to differentiate between moderate to severe and normal to mild white matter injury, while in the present study the cut-off was ≥8, which makes it difficult to compare the extent of white injury in this cohort with previous studies that used the same scoring.

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