Assessment of Intracranial Hypertension With Noninvasive Subharmonic-Aided Pressure Estimation: A First-in-Humans Trial.

OBJECTIVES: Idiopathic intracranial hypertension (IIH) is a major cause of elevated intracranial pressure (ICP) typically diagnosed by lumbar puncture (LP) with an opening pressure ≥18 mmHg; however, LPs are invasive and variable. Subharmonic-aided pressure estimation (SHAPE) is an ultrasound-based technique that relies on the subharmonic signal of contrast microbubbles to detect surrounding pressure changes. This study investigated the utility of SHAPE for noninvasive assessment of ICP. METHODS: This IRB-approved, two-center study enrolled subjects undergoing LP for suspected IIH. SHAPE data were obtained pre- and post-LP from the ophthalmic artery and vein. The SHAPE gradient, defined as the difference between ophthalmic artery (OA) and ophthalmic vein (OV) subharmonic signal intensities, was calculated offline and the change in the SHAPE gradient between pre- and post-LP scans was correlated with the measured reduction in ICP following LP. Intracranial elastance (E), pressure-volume index (PVI), and optic nerve sheath diameter (ONSD) were also compared with LP pressures. RESULTS: A total of 20 patients were enrolled. A significant negative correlation was observed between the SHAPE gradient and the reduction in ICP following drainage (r = -0.61, p = 0.01). Individual SHAPE values pre- and post- LP did not correlate with the individual OP and CP pressures (p = 0.72). Neither ONSD, E, nor PVI correlated significantly with LP pressures (p ≥ 0.05). CONCLUSION: SHAPE demonstrated responsiveness to intracranial pressure changes and may have potential for noninvasive monitoring of ICP trends.