Bedside optic nerve sheath diameter ultrasound for the evaluation of suspected pediatric ventriculoperitoneal shunt failure in the emergency department.

OBJECTIVE: To determine the feasibility and test characteristics of optic nerve sheath diameter (ONSD) measured by ocular ultrasound as a screening tool for ventriculoperitoneal shunt (VPS) failure.

METHODS: Prospective observational study using a convenience sample of children 6 months to 18 years of age, presenting to an academic pediatric emergency department for evaluation of possible VPS failure between September 2008 and March 2009. ONSD was measured by anterior transbulbar and lateral transbulbar techniques. Mean ONSD was compared between subjects with and without shunt failure, as determined by neurosurgical decision to operate.

RESULTS: A total of 39 encounters were completed, including 20 VPS failures. The mean ONSD was 4.5 ± 0.9 and 5.0 ± 0.6 mm among encounters with and without shunt failure (p = 0.03), respectively. The mean ONSD was not statistically different when obtained by the anterior transbulbar vs. the lateral transbulbar approach (4.8 ± 1.0 vs. 4.7 ± 0.8 mm, p = 0.12). ONSD ultrasound had a sensitivity of 61.1 % (95 % CI 35.7-82.7) and specificity of 22.2 % (95 % CI 6.4-47.6 %) for detecting shunt failure in this sample.

CONCLUSIONS: ONSD ultrasound does not appear to be a useful primary screening tool in emergency department evaluation of VPS failure. There was no difference between the anterior transbulbar approach and the lateral transbulbar approach. Children with VPS in our sample have larger ONSD measurements than in previously reported studies.