Homonymous visual field defects in patients without corresponding structural lesions on neuroimaging

Homonymous visual field defects usually occur with structural processes aff ecting retrochiasmal visual pathways. The responsible lesion is usually evi dent on magnetic resonance imaging or on other neuroimaging studies. When r esults of neuroimaging are normal, functional illness is often suspected. T he authors report four patients with homonymous visual field defects who pr esented with no evident corresponding lesion on magnetic resonance or compu ted tomography imaging. Etiologies for the visual field defects included th e Heidenhain variant of Creutzfeldt-Jacob disease, degenerative dementia, s ubtle occipital ischemia demonstrated only on positron-emission tomography scanning, and nonketotic hyperglycemia. Clinicians should be aware of the a lternative etiologies of organic homonymous visual field loss in patients w ith normal neuroimaging.