• Llewellyn Padayachy, Reidar Brekken, Graham Fieggen, and Tormod Selbekk.
• Division of Neurosurgery, University of Cape Town, Cape Town, South Africa.
• Oper Neurosurg (Hagerstown). 2019 Jun 1; 16 (6): 726-733.

BackgroundMeasurement of optic nerve sheath diameter (ONSD) is a promising technique for noninvasive assessment of intracranial pressure (ICP), but has certain limitations. A recent study showed that the deformability index (DI), a dynamic parameter quantifying the pulsatile nature of the optic nerve sheath, could differentiate between patients with high vs normal ICP.ObjectiveTo further evaluate the diagnostic accuracy of the DI, when interpreted together with ONSD.MethodsThis prospective study included children undergoing invasive ICP measurement as part of their clinical management. Ultrasound images of the optic nerve sheath were acquired prior to measuring ICP, the images were further processed to obtain the DI. Patients were dichotomized into high (≥20 mm Hg) or normal ICP groups and compared using the Mann-Whitney U-test. Diagnostic accuracy was described using area under the receiver operating characteristic curve (AUC), sensitivity and specificity, correlation between DI, ONSD, and ICP was investigated using linear regression.ResultsA total of 28 patients were included (19 high ICP). The DI was lower in the high ICP group (0.105 vs 0.28, P = .001). AUC was 0.87, and a cut-off value of DI ≤ 0.185 demonstrated sensitivity of 89.5% and specificity of 88.9%. Diagnostic accuracy improved when combining DI with ONSD (AUC 0.98, sensitivity 94.7%, specificity 88.9%) and correlation with ICP improved when combined analysis of DI and ONSD was performed (Pearson correlation coefficient: 0.82 vs 0.42, respectively, P = .012).ConclusionThe DI was significantly lower for patients with high vs normal ICP. This relationship improved further when the DI and ONSD were interpreted together.Copyright © 2018 by the Congress of Neurological Surgeons.

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