Walsh & Hoyt: "Chiasmal Syndrome" of Cushing

In 1930, Cushing described the importance of optic atrophy and bitemporal field defects in adults as indicative of tumor when the sella turcica seemed normal in the plain lateral skull x-ray. This syndrome is most often produced by suprasellar meningiomas, aneurysms, and craniopharyngiomas. This notable contribution was once of great value in eliminating, or at least reducing, misdiagnosis of sinusitis and retrobulbar optic neuritis as common causes for slowly progressive bilateral loss of vision. Optic atrophy in such cases may be very slight, or the optic discs may remain normal in appearance for months despite pronounced loss of vision and extensive defects in the visual fields. The bitemporal field defects in some cases are extremely mild and detected only by careful kinetic perimetry or automated static perimetry. Finally, the normalcy of the sella turcica may only be relative. Since Cushing described this syndrome, there have been substantial advances in neuroimaging. With the almost universal availability of computed tomography (CT) scanning and magnetic resonance (MR) imaging, most patients with progressive visual loss no longer undergo plain skull x-rays. Cushings syndrome of the chiasm is thus more important for its historical significance than for its place in current neuro-ophthalmologic diagnosis. Nevertheless, there are still some areas in the world in which skull radiographs are used as the sole or initial step in assessing patients with an optic chiasmal syndrome. In such cases, the triad that represents Cushings syndrome remains a useful clinical entity.