Novel and classic imaging signs of increased intracranial pressure

The arachnoid bulk ratio was recently described by Berhanu et al. on ultrasonography (US) as a potentially useful surrogate for intracranial pressure (ICP). We aimed to evaluate this novel neuroimaging index using magnetic resonance imaging (MRI) and determine the accuracy of the novel and classic imaging signs to diagnose increased ICP.

Patients with suspected increased ICP were recruited to undergo optic nerve US and MRI before invasive ICP measurement. We included a total of 23 participants and determined the correlation of the novel ratio with ICP, compared to the optic nerve sheath diameter (ONSD), and we assessed the diagnostic accuracy of the novel and classic imaging signs through receiver operating characteristic (ROC) curve analysis.

The arachnoid bulk ratio and ONSD were significantly larger in individuals with increased ICP on MRI (36% and 16%,p < 0.001) and on US (39% and 13%,p < 0.001). The ratio correlated very strongly with ICP on MRI and US (r_s = 0.89 and r_s = 0.92), outperforming the ONSD (MRI:r_s = 0.67 and US:r_s = 0.63). The Berhanu et al.'s ratio predicted increased ICP with a sensitivity of 100% and a specificity of 91% on MRI. The classic imaging signs with highest accuracy were the transverse sinus stenosis and ONSD, with a sensitivity of 89% and 91% and specificity of 100% and 92%,respectively.

This novel ratio, which selectively assesses the perineural fluid space, provides an accurate prediction of ICP on MRI. When combined with classic imaging signs, it serves as a useful non-invasive surrogate in the clinical approach to these patients.