Answer
The test was a spinal tap.
Our patient had bilateral chronic disc edema, which accounted for the enlarged blind spot in each eye. He had experienced transient blurred vision, and such episodes are common in idiopathic intracranial hypertension (IIH, previously known as benign intracranial hypertension or pseudotumor cerebri). Unlike many IIH patients, however, he denied having any headaches. After an MRI ruled out an intracranial mass, our patient had a spinal tap, which showed an elevated opening pressure of 30 cm H20 (normal 6-25), confirming a diagnosis of IIH. He was treated with Diamox (acetazolamide), and there was a significant reduction in disc edema but the vision did not improve.
IIH is about 20 times more frequent in women than men. The age of onset is usually between 20-50, and patients usually have a high body/mass index. Our patient had a BMI of 38. The case dramatizes the vision-threatening nature of this condition.
There were several other diagnostic considerations.
Intracranial mass: This needed to be ruled out before doing a spinal tap, because, depending on the location of the tumor, sudden lowering of intracranial pressure during the spinal tap can result in death due to herniation of the brainstem into the spine.
Diabetic papillopathy: This condition usually does not cause such severe, chronic disc edema, and there is usually no significant loss of visual acuity or a visual field defect. Diabetes likely accounted for the elevated C-reactive protein.
Optic neuritis: Our patient denied having any other neurological symptoms such as numbness, tingling, or weakness. The lack of other neurologic symptoms does not rule out this diagnosis. Bilateral, symmetrical, severe, chronic disc is atypical for optic neuritis.
Hypertensive optic neuropathy. The BP had been very elevated in the past, but it was normal when we saw the patient, and he said that his recent BP control had been good. Patients with hypertensive optic neuropathy typically also have manifestations of hypertensive retinopathy, including intraretinal hemorrhages.
Optic disc drusen: Disc drusen can result in a pseudopapilledema presentation. In our patient, there was no hyperautofluorescence (though drusen can be buried and not manifest hyperautofluorescence). Also, our patient had dilated blood vessels over the disc, which indicated true papilledema. A subtle but helpful sign distinguishing papilledema from pseudopapilledema is that, in the former case, the RPE adjacent to the disc is pushed forward and there is a convex orientation. In pseudopapilledema, the RPE has the same concave shape adjacent to the disc as elsewhere. Initially, the disc edema was so marked in our patient that there was poor visualization of the RPE adjacent to the disc. After treatment resulted in significant reduction in the disc edema and presumably in the intracranial pressure, the proper orientation of the RPE adjacent to the disc was found.
Anterior ischemic optic neuropathy. The severe and chronic disc edema is very atypical, and much greater loss of vision in both eyes would be expected in a setting of bilateral, severe disc edema in AION.
Infiltrative optic neuropathy. Leukemia or lymphoma can cause chronic disc edema, as can inflammatory processes such as sarcoidosis. Our patient’s CBC was unremarkable, and the chest X-ray was normal. Chest X-ray tends to be more sensitive than angiotensin converting enzyme or lysozyme for diagnosing sarcoidosis.
A curious finding is the deep whitish material adjacent to the disc in the left eye. Clinically it resembled an organized, fibrotic, idiopathic choroidal neovascular membrane.
