Dynamic changes of the optic nerve sheath and pituitary gland with treatment of idiopathic intracranial hypertension

Abstract

Purpose : Optic nerve sheath dilation and partially empty sella are two of the most common indirect signs of raised intracranial pressure (ICP) seen on MRI. These findings can support the diagnosis of conditions of raised ICP, including idiopathic intracranial hypertension (IIH). The dynamic nature of these findings in response to acute and chronic changes in ICP is largely unknown. We assessed changes in optic nerve sheath diameter (ONSD) and pituitary to sella (pit/sella) ratio after lumbar puncture (LP) and after chronic treatment in patients with IIH.

Methods : Patients with papilledema from IIH underwent MRI at baseline, immediately after large volume LP, and after resolution of the papilledema by medical or surgical treatment. The ONSD was measured on high resolution T2-weighted axial images 3 mm posterior to the sclera. The pit/sella ratio was defined on T1 sagittal views as the vertical height of the middle 1/3 of the gland divided by the sella height. The pituitary gland measurements were performed with the Analyze imaging software system.

Results : Twelve IIH patients underwent baseline and post-LP MRIs. The mean baseline ONSD was 6.09mm, and the immediate post-LP ONSD was 5.33mm (p=0.03). The mean baseline pit/sella ratio was 39%; post-LP, 40% (p=0.81). MRI was available after resolution of papilledema by treatment with medication (n=3) or venous sinus stenting (n=3) in 6 patients. The final mean ONSD was 5.24mm (p=0.04), and the pit/sella ratio was 47% (p=0.01).

Conclusions : In patients with IIH, the optic nerve sheath is dynamic and a reduction in ONSD was noted immediately after high volume LP, which remained decompressed after chronic treatment of the ICP. In contrast, the pituitary gland size changes more slowly, with enlargement after chronic treatment but not immediately after LP.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.