Optic nerve sonography: A noninvasive means of detecting raised intracranial pressure in a resource-limited setting

ABSTRACT Objective: The aim was to assess the use of optic nerve sonography (ONS) as a quick, noninvasive diagnostic test tool for detecting raised the intracranial pressure (ICP). Materials and Methods: A prospective blinded observational study was conducted at Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC), Ile-Ife, Nigeria. The study population consisted of 160 adult patients referred to the radiology department for cranial computed tomography (CT) scan. There were 80 subjects and 80 controls. Optic nerve sheath diameter (ONSD) was measured by a radiologist using a 7.5 Megahertz ultrasound probe while cranial CT was reviewed by other radiologists blinded to the ONSD. Results: Sixty-nine subjects (86.3%) had intracranial space occupying lesions (SOL) with cranial CT confirmed features of increased ICP, mean binocular ONSD of 5.7 ± 0.59 mm while 11 (13.7%) had intracranial SOL without any cranial CT evidence of increased ICP, mean binocular ONSD of 4.8 ± 0.39 mm. The difference of mean ONSD of the two groups was statistically significant (P = 0.0001). The controls had a mean binocular ONSD of 4.5 ± 0.22 mm and the difference in mean binocular ONSD for subjects with raised ICP and the controls were also statistically significant (P = 0.0001). A cut-off value of 5.2 mm (sensitivity 81.2% [95% confidence interval (CI): 69.9–89.6], specificity 100% [95% CI: 71.5–100]) was obtained from the receiver operator characteristics curve as the mean binocular ONSD that best predicts raised ICP confirmed by at least a sign on cranial CT. Conclusions: Optic nerve sonography can differentiate between normal and elevated ICP and may serve as a useful screening tool in resource-limited practice.

Optic Nerve Sonography in the Diagnostic Evaluation of Pseudopapilledema and Raised Intracranial Pressure: A Cross-Sectional Study

Introduction. Differentiating pseudopapilledema from papilledema which is optic disk edema and a result of increased ICP (intracranial pressure) is important and can be done with noninvasive methods like orbital ultrasound examination.Method. This was a cross-sectional study in which patients with optic nerve head swelling were referred for LP exam after optic nerve head swelling diagnosis confirmation and having normal brain imaging (CT scan). Before LP (lumbar puncture) exam the patients were referred for optic nerve ultrasound test of both eyes.Results. Considering 5.7 mm as the upper limit for normal ONSD (optic nerve sheath diameter), sensitivity and negative predictive value of optic sonography in diagnosis of pseudopapilledema are 100% for both eyes. Calculated accuracy validity of ONSD measurement in detecting pseudopapilledema is 90% for the right eye and 87% for the left eye.Conclusion. Our study demonstrated a close correlation between optic nerve sheath dilation on ocular ultrasound and evidence of elevated ICP with optic disk swelling. With the aid of noninvasive diagnostic tests we can avoid unnecessary concerns along with expensive and invasive neurological investigations while targeting the correct diagnosis in bilateral optic disk swelling. Our study showed optic nerve sonography as a reliable diagnostic method for further usage.