Letters to the Editor
Idiopathic Intracranial Hypertension
Here we make some comments on the state-of-the-art article by Friedman and Jacobson (1) on idiopathic intracranial hypertension. The authors did not mention the echographic examination of the optic nerve as one of the most important diagnostic procedures to diagnose the presence of high intracranial pressure and to monitor the clinical course of this disease (2). With this technique, it is possible to detect an increase of subarachnoidal fluid within the optic nerve sheaths that is caused by the presence of high intracranial pressure (3-4).
The authors noted that “in some patients, papilledema never resolves completely despite resolution of symptoms and stabilization of visual function.” The reason for this was described several years ago by Hayreh (5), who implanted balloons in the brains of monkeys and showed that papilledema takes 1 to 5 days to appear after intracranial pressure elevations. Acutely elevated cerebrospinal fluid pressure for up to 2 hours or sudden lowering of the pressure to normal does not produce immediate resolution of papilledema. This is caused by the slow process of axoplasmic accumulation, the cause of swelling of the axons in the optic nerve head.
Echography is much more sensitive than optic nerve ophthalmoscopic examination, because it can detect a sudden increase or decrease of intracranial pressure by measuring the diameter of the optic nerve sheath. This diameter depends on the amount of perineural subarachnoid fluid, which increases during high pressure and returns to normal when there is a normalization of intracranial pressure. Echography can thus avoid the need for frequent intracranial pressure measurements that are not risk-free.
Nicola Rosa, MD
Luigi Capasso, MD
Michele Lanza, MD
Department of Ophthalmology Second University of Naples Naples, Italy
1. Friedman DI, Jacobson DM. Idiopathic intracranial hypertension. J Neuro Ophthalmol
2. Rosa N, Giamundo A, Jura A et al. Mesalazine-associated benign intracranial hypertension in a patient with ulcerative colitis. Am J Ophthalmol
3. Green R, Frazier Byrne S. Ultrasound of the eye and orbit
. St Louis: Mosby Publishing; 2002:419-22.
4. Ossoinig KC. Standardized echography of the optic nerve. In: Till P, ed. Ophthalmic Echography 13
. Dordrecht, The Netherlands: Kluwer Academic Publishers; 1993:3-99.
5. Hayreh MS, Hayreh SS. Optic disc edema in raised intracranial pressure: I. Evolution and resolution. Arch Ophthalmol