Abstract
To evaluate and compare the performance of ocular ultrasonography (US) and magnetic resonance imaging (MRI) for detecting increased intracranial pressure (ICP) in patients with idiopathic intracranial hypertension (IIH). Twenty-two patients with papilledema from IIH and 22 with pseudopapilledema were prospectively recruited based on funduscopic and clinical findings. Measurements of optic nerve sheath diameters (ONSDs) 3 mm behind the inner sclera were performed on B-scan US and axial T2-weighted MRI examinations. Pituitary-to-sella height ratio (pit/sella) was also calculated from sagittal T1-weighted MRI images. Lumbar puncture was performed in all patients with IIH and in five patients with pseudopapilledema. Average US and MRI ONSD were 4.4 (SD ± 0.7) and 5.2 ± 1.4 mm for the pseudopapilledema group and 5.2 ± 0.6 and 7.2 ± 1.6 mm for the papilledema group (p < 0.001). Average MRI pit/sella ratio was 0.7 ± 0.3 for the pseudopapilledema group and 0.3 ± 0.2 for the papilledema group (p < 0.001). Based on receiver-operator curve analysis, the optimal thresholds for detecting papilledema are US ONSD > 4.8 mm, MRI ONSD > 6.0 mm, and MRI pit/sella < 0.5. Combining a dilated US ONSD or MRI ONSD with a below-threshold MRI pit/sella ratio yielded a sensitivity of 73% and specificity of 96% for detecting IIH. Adding the US ONSD to the MRI ONSD and pit/sella ratio only increased the sensitivity by 5% and did not change specificity. US and MRI provide measurements of ONSD that are well-correlated and sensitive markers for increased ICP. The combination of the ONSD and the pit/sella ratio can increase specificity for the diagnosis of IIH.
Highlights
Idiopathic intracranial hypertension (IIH), known as pseudotumor cerebri, is a disease characterized by increased intracranial pressure (ICP) without a mass lesion obstructing the ventricular system or other cause of raised ICP
The results of this study show that magnetic resonance imaging (MRI) and B-scan US can both be used, either independently or in conjunction with one another, to establish the likelihood of increased ICP in patients with papilledema from IIH
To the best of our knowledge, this is the first study to date to compare both MRI- and US-measured optic nerve sheath diameter (ONSD) in the same cohort of IIH patients
Summary
Idiopathic intracranial hypertension (IIH), known as pseudotumor cerebri, is a disease characterized by increased intracranial pressure (ICP) without a mass lesion obstructing the ventricular system or other cause of raised ICP. Patients can develop significant papilledema and subsequent visual loss because of the effects of the increased ICP on the optic nerve. Neuroimaging and lumbar puncture are necessary in confirming the diagnosis of IIH, as there are many other etiologies of increased ICP. The invasive nature of lumbar puncture comes with potential side effects including infection, bleeding, and over-drainage or leakage of cerebrospinal fluid (CSF) with resultant intracranial hypotension and headache. There is variability in lumbar puncture opening pressures based on patient positioning and natural physiologic variation [2, 3].
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