gms | German Medical Science

Objective: In pediatric neurosurgery many pathologies are associated with raised intracranial pressure (ICP). Because of the need for diagnosing children non-invasively and radiation-free, ultrasonography is highly appreciated. Regarding detection of a possible ICP increase, ultrasound based measurement of the optic nerve sheath diameter (ONSD) has been proven to be a reliable method in children of any age group. This pediatric study aims to investigate a) the relationship between ONSD and invasively measured ICP and b) if ONSD values can guide the neurosurgeon in clinical situations with potentially increased ICP in pediatric neurosurgical patients.

Methods: The presented prospective study investigates 49 patients aged 1 month to 17 years (median age 6 years). Diagnoses included hydrocephalus (n=29), tumor (n=9), craniosynostosis (n=5), and other intracranial pathologies (n=6). ONSD was measured using 11 Mhz transducers, standardized 3 mm behind the globe, for a total of 3 measurements per eye. Dependent on diagnosis, the investigation was performed pre- and post-operatively or longitudinally over a period of time, respectively. In 12 patients the mean binocular ONSD was compared to invasively measured ICP.

Results: 12 patients underwent ultrasonography of the ONSD during invasive measurement of ICP. ONSD revealed dynamic changes that were directly proportional to ICP (e.g. ONSD 7.2/6.7/5.7/5.25 mm at ICP 20/14/8/4 mmHg). The correlation between ONSD and ICP was satisfactory, especially regarding the relatively small number of cases (r= 0.61, p< 0.01). 25 patients with clear symptoms of increased ICP underwent surgery to decrease ICP. All patients showed increased ONSD values before surgery (mean 5.89 ± 0.82mm). Post treatment ONSD significantly (p< 0.001) decreased to a mean of 5.14 ± 0.8 mm. In 16 patients with moderate clinical signs of raised ICP, normal ONSD values (mean 4.78 ± 0.38 mm) were found. In those a wait-and-see strategy was applied and none needed a therapeutic intervention during follow-up. In four patients with mild or absent symptoms of raised ICP, increased ONSD values were found (mean 5.4 ± 0.29 mm). In those further invasive diagnostics were pursued. The ONSD cut-off value with the highest diagnostic accuracy for detecting clinically relevant situations of increased ICP was 5.3 mm, with a sensitivity of 76%, specificity of 94% and odds ratio (OR) of 47.5.

Conclusion: In pediatric neurosurgical patients high-resolution ultrasound measurement of the ONSD appears to be a reliable, non-invasive and radiation-free technique to identify patients with potentially raised ICP. ONSD reacts quickly to changes of ICP and demonstrates a high diagnostic accuracy for detecting increased ICP. The potential role of ONSD is already promising as a first line screening tool in daily routine.