Abstract
BackgroundUltrasonographic (USG) measurement of optic nerve sheath diameter (ONSD) has been proposed as a non-invasive, bedside method to detect raised intracranial pressure (ICP) in various clinical settings. We aimed to correlate the ONSD obtained from ultrasonography with the gold standard, intraventricular ICP, and to find out the cut-off point which predicts ICP accurately at different levels.MethodologyA prospective double-blind study was carried out by performing ocular ultrasounds in 30 adult patients with features of intracranial hypertension. The ONSD was measured by USG intraoperatively along with direct intraventricular pressure measurement. The ONSD was compared with the intraventricular ICP and correlations were derived. The optimum cut-off of ONSD to predict ICP > 20 mm Hg, 25 mm Hg, 30 mm Hg, and 35 mm Hg was sought.ResultsThere was a significant correlation of ONSD with ICP (r = 0.532, p = 0.002). An ONSD threshold of 5.5 mm predicted ICP > 20 mm Hg with high sensitivity (100%) and specificity (75%) (area under receiver operating characteristic [ROC] curve = 0.904, p=0.01). The optimum ONSD cut-off predicting ICP at values of 25 mm Hg, 30 mm Hg, and 35 mm Hg was 6.3 mm, 6.5 mm, and 6.7 mm, respectively.ConclusionOur study confirms the utility of optic nerve ultrasound in the diagnostic evaluation of patients with known or suspected intracranial hypertension. We recommend an ONSD cut-off of 5.5 mm for predicting ICP > 20 mm Hg.
Highlights
Diagnosis and management of raised intracranial pressure (ICP) is a critical aspect of patient care in neurological and neurosurgical cases [1]
There was a significant correlation of optic nerve sheath diameter (ONSD) with ICP (r = 0.532, p = 0.002)
Ultrasonographic measurement of ONSD has been correlated with CT and MRI findings suggestive of raised ICP, intracranial pressure measured by intraparenchymal probes, bolts, external ventricular drainage (EVD) catheters and cerebrospinal fluid (CSF) pressures measured by lumbar puncture [3, 14,15,16, 17,18,19]
Summary
Diagnosis and management of raised intracranial pressure (ICP) is a critical aspect of patient care in neurological and neurosurgical cases [1]. Its association with various complications like infection, trauma, hemorrhage, and the inability to cannulate or perform it as a rapid bedside method is a significant limitation of the invasive method [8,9] This has led to an intense search for non-invasive methods of measuring intracranial pressure [10]. Known methods of non-invasive ICP measurement like tympanic membrane displacement techniques, transcranial doppler ultrasonography, magnetic resonance imaging, computerized tomography scans, quantitative pupillometry, and optic nerve sheath diameter measurements eliminate the aforementioned complications related to invasive methods [10]. They have limited accuracy and reproducibility, limiting their routine and widespread use in clinical practice [10]. We aimed to correlate the ONSD obtained from ultrasonography with the gold standard, intraventricular ICP, and to find out the cut-off point which predicts ICP accurately at different levels
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