Clinical Reasoning: A 60-Year-Old Diabetic Woman With Fluctuating Visual Disturbances

Visual disturbances are a common presenting complaint in neurology, and the characteristics of these complaints combined with the examination findings are important in localization and then the generation of a complete differential diagnosis. Patients with diabetes, particularly in the setting of hyperglycemia, can have multiple reasons for vision changes localized throughout the visual pathways, including ophthalmic manifestations such as diabetic retinopathy, early development of nuclear sclerotic cataracts, and macular edema, as well as increased risk of ischemic optic neuropathies and retrochiasmal ischemia. Assessing the visual fields of these patients is crucial in localizing the abnormality. Occipital cortical lesions causing contralateral homonymous hemianopic visual field defects can result from a wide variety of underlying etiologies, including ischemia, mass effect, demyelination, and inflammation/infection, as well as electroclinical seizures. In addition, homonymous hemianopic visual field defects have been attributed both to direct manifestations of hyperglycemia and to hyperglycemic-induced electroclinical seizures with both ictal and postictal visual changes. We describe a patient with both bilateral homonymous visual field defects and fluctuating positive visual phenomena in the setting of poorly controlled diabetes mellitus. This case highlights the importance of localization of visual field defects and allows readers to generate a complete differential diagnosis and arrive at the most likely pathophysiology and diagnoses.