Are ultrasonography measurements of optic nerve sheath diameter an alternative to funduscopy in children with syndromic craniosynostosis?

OBJECT: Children with syndromic or complex craniosynostosis are evaluated for increased intracranial pressure (ICP) using funduscopy to detect papilledema. However, papilledema is a late sign of increased ICP. Because papilledema might be preceded by an increase in optic nerve sheath (ONS) diameter, the authors conducted a prospective study to establish the validity and applicability of measuring the ONS using ultrasonography.

METHODS: From January 2007 to December 2009, 175 bilateral ultrasonography ONS measurements were performed in 128 patients with syndromic or complex craniosynostosis during the daytime. The measurements were correlated with ONS diameter assessed on CT and simultaneous funduscopy, when available. Furthermore, results were compared by using thresholds for ONS diameters on ultrasonography that are available in the literature.

RESULTS: The mean ONS diameter on ultrasonography was 3.1 ± 0.5 mm. The CT measurement was significantly correlated with the ultrasonography measurement (r = 0.41, p < 0.001). The mean ONS diameter in 38 eyes with papilledema was 3.3 ± 0.5 mm, compared with 3.1 ± 0.5 mm in the eyes of patients without papilledema (p = 0.039). Relative to the age-related thresholds, the ONS diameter was too large in 11 eyes (3%), particularly in patients with Crouzon syndrome. Compared with funduscopy, ultrasonography sensitivity was 11%, specificity was 97%, and positive and negative predictive values were 40% and 86%, respectively.

CONCLUSIONS: Ultrasonography is a valid and easy way of quantifying the ONS. Although the ONS diameter is larger in children with papilledema, it cannot be used as a daytime screening tool instead of funduscopy. The ONS diameter is possibly a more real-time indicator of ICP.