B-scan ultrasound in papilledema.
A. Diameter of the optic nerve sheath in a normal person.
B. Diameter of the optic nerve sheath in a patient with IIH.
C. Diameter of the optic nerve sheath in the same patient as (B) following lumbar puncture with therapeutic removal of CSF.
Image credit: Bäuerle J, Nedelmann M. B-mode sonography of the optic nerve in neurological disorders with altered intracranial pressure. Perspectives in Medicine 2012;1:404-407. Available online.
30° test.
A-scan (figure) or B-scan (not shown) ultrasonography is used to measure the optic nerve sheath diameter in primary (left) and eccentric gaze (right). A reduction in the nerve sheath diameter >20% is considered a positive result, strongly suggesting increased fluid around the optic nerve.
Image credit: Wang R, Kini A, Al Othman B, Lee AG. Pseudotumor cerebri and papilledema: an overview of this perplexing syndrome and its hallmark presentation. Glaucoma Today. 2019 Jan/Feb:34-46. Available online.
