Noninvasive Assessment of Intracranial Pressure Status in Idiopathic Intracranial Hypertension Using Displacement Encoding with Stimulated Echoes (DENSE) MRI: A Prospective Patient Study with Contemporaneous CSF Pressure Correlation

Abstract

Background and purpose: Intracranial pressure is estimated invasively by using lumbar puncture with CSF opening pressure measurement. This study evaluated displacement encoding with stimulated echoes (DENSE), an MR imaging technique highly sensitive to brain motion, as a noninvasive means of assessing intracranial pressure status.

Materials and methods: Nine patients with suspected elevated intracranial pressure and 9 healthy control subjects were included in this prospective study. Controls underwent DENSE MR imaging through the midsagittal brain. Patients underwent DENSE MR imaging followed immediately by lumbar puncture with opening pressure measurement, CSF removal, closing pressure measurement, and immediate repeat DENSE MR imaging. Phase-reconstructed images were processed producing displacement maps, and pontine displacement was calculated. Patient data were analyzed to determine the effects of measured pressure on pontine displacement. Patient and control data were analyzed to assess the effects of clinical status (pre-lumbar puncture, post-lumbar puncture, or control) on pontine displacement.

Results: Patients demonstrated imaging findings suggesting chronically elevated intracranial pressure, whereas healthy control volunteers demonstrated no imaging abnormalities. All patients had elevated opening pressure (median, 36.0 cm water), decreased by the removal of CSF to a median closing pressure of 17.0 cm water. Patients pre-lumbar puncture had significantly smaller pontine displacement than they did post-lumbar puncture after CSF pressure reduction (P = .001) and compared with controls (P = .01). Post-lumbar puncture patients had statistically similar pontine displacements to controls. Measured CSF pressure in patients pre- and post-lumbar puncture correlated significantly with pontine displacement (r = 0.49; P = .04).

Conclusions: This study establishes a relationship between pontine displacement from DENSE MR imaging and measured pressure obtained contemporaneously by lumbar puncture, providing a method to noninvasively assess intracranial pressure status in idiopathic intracranial hypertension.

Fig 1.

DENSE imaging with ROI placement and measured displacement across the cardiac cycle from a 44-year-old woman with IIH (Patient 9). A, Sagittal magnitude image from pre-LP DENSE encoded for motion in the foot-to-head direction. An ROI has been placed in the midpons to avoid partial volume effects from CSF flow. B, Corresponding phase image from the pre-LP DENSE encoded for motion in the foot-to-head direction with ROI transferred from the magnitude image into the midpons for measurement to be propagated to all 12 images acquired across the cardiac cycle. C, Graph showing DENSE displacement in the foot-to-head direction across the cardiac cycle divided into 12 phases. The solid line shows the pre-LP displacements across the cardiac cycle, and the dotted line shows post-LP displacements across the cardiac cycle. Maximum displacement is calculated by subtracting the lowest value from the highest across the cardiac cycle for both the pre-LP and post-LP states. Note the increased displacement in the post-LP state.

Fig 2.

Comparison of maximum pontine displacement in pre-LP, post-LP, and control groups. The maximum pontine displacement of an ROI in the central pons in the pre-LP IIH group was significantly lower than in the post-LP state within subjects (P < .001) and significantly lower than the control group (P = .01). The maximum pontine displacement in post-LP patients with IIH did not significantly differ from control subjects (P = .10). Values are shown in mean ± SD.

Fig 3.

Correlation of measured CSF pressure and pontine displacement by DENSE. The maximum pontine displacement measured by DENSE correlates moderately with measured pressure (opening pressure or closing pressure) by CSF manometry (r = 0.49; P = .04).