Features of Idiopathic Intracranial Hypertension on MRI With MR Elastography: Prospective Comparison With Control Individuals and Assessment of Postintervention Changes

Abstract

BACKGROUND. Understanding of dynamic changes of MRI findings in response to intracranial pressure (ICP) changes in idiopathic intracranial hypertension (IIH) is limited. Brain stiffness, as assessed by MR elastography (MRE), may reflect changes in ICP. OBJECTIVE. The purpose of this study was to compare pituitary height, ventricular size, and brain stiffness between patients with IIH and control individuals and to evaluate for changes in these findings in patients with IIH after interventions to reduce ICP. METHODS. This prospective study included 30 patients (28 women, two men; median age, 29.9 years) with IIH and papilledema and 21 control individuals (21 women, 0 men; median age, 29.1 years), recruited from January 2017 to July 2019. All participants underwent 3-T brain MRI with MRE; patients with IIH underwent additional MRI examinations with MRE after acute intervention (lumbar puncture with normal closing pressure; n = 11) and/or chronic intervention (medical management or venous sinus stenting with resolution or substantial reduction in papilledema; n = 12). Pituitary height was measured on sagittal MP-RAGE images. Ventricular volumes were estimated using unified segmentation, and postintervention changes were assessed by tensor-based morphometry. Stiffness pattern score and regional stiffness values were estimated from MRE. RESULTS. In patients with IIH, median pituitary height was smaller than in control individuals (3.1 vs 4.9 mm, p < .001) and was increased after chronic (4.0 mm, p = .05), but not acute (2.3 mm, p = .50), intervention. Ventricular volume was not different between patients with IIH and control individuals (p = .33) and did not change after acute (p = .83) or chronic (p = .97) intervention. In patients with IIH, median stiffness pattern score was greater than in control individuals (0.25 vs 0.15, p < .001) and decreased after chronic (0.23, p = .11) but not acute (0.25, p = .49) intervention. Median occipital lobe stiffness was 3.08 kPa in patients with IIH versus 2.94 kPa in control individuals (p = .07) and did not change after acute (3.24 kPa, p = .73) or chronic (3.10 kPa, p = .83) intervention. CONCLUSION. IIH is associated with a small pituitary and increased brain stiffness pattern score; both findings may respond to chronic interventions to lower ICP. CLINICAL IMPACT. The "partially empty sella" sign and brain stiffness pattern score may serve as dynamic markers of ICP in IIH.

Keywords: IIH; MR elastography; MRE; brain stiffness; idiopathic intracranial hypertension; pituitary gland; ventricular size.

Fig. 1—

Flowchart shows patient selection. Patients with idiopathic intracranial hypertension (IIH) in acute intervention subgroup underwent large-volume diagnostic lumbar puncture after enrollment with closing pressure of less than 250 mm H₂O. Patients with IIH in chronic intervention subgroup underwent medical management or venous sinus stenting with resolution or substantial improvement in papilledema. ICP = intracranial pressure.

Fig. 2—

Dot plots of quantitative MRI metrics across study groups and subgroups. A–D, Dot plots of pituitary height (A), ventricular size (B), MR elastography (MRE) stiffness pattern (C), and MRE occipital region stiffness (D). Each dot represents one participant, and horizontal lines mark medians of groups and subgroups. Acute intervention refers to large-volume diagnostic lumbar puncture, and chronic intervention refers to medical management or venous sinus stenting. IIH = idiopathic intracranial hypertension.

Fig. 3—

28-year-old woman with idiopathic intracranial hypertension. A and B, Sagittal T1-weighted MP-RAGE images at baseline (A) and after chronic intervention by venous sinus stenting (B). Measurement of pituitary height (vertical line between horizontal lines marking top and bottom of pituitary) is depicted on both images. Pituitary height increased from 3.2 mm at baseline to 4.6 mm after chronic intervention.

Fig. 4—

28-year-old patient with idiopathic intracranial hypertension. A and B, Stiffness maps from MR elastography at baseline (A) and 6 months after venous sinus stenting (B) visually show increased occipital lobe stiffness bilaterally at baseline and reduction in occipital lobe stiffness after intervention. Occipital lobe stiffness measured 3.20 kPa at baseline and 3.06 kPa after chronic intervention.

Fig. 5—

26-year-old woman with idiopathic intracranial hypertension. A and B, Baseline MRI. Axial source image (A) and 3D maximum-intensity-projection (MIP) image (B) from phase-contrast MR venography (MRV) show marked narrowing of lateral aspect of transverse sinuses bilaterally (arrows), consistent with transverse sinus stenosis. C and D, Postintervention MRI. Patient underwent medical management with substantial improvement of papilledema. Axial source image (C) and 3D MIP image (D) from phase-contrast MRV show resolution of transverse sinus stenosis (arrows).