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  • Updated 06.06.2018
  • Released 07.14.1997
  • Expires For CME 06.06.2021

Cortical blindness

Introduction

This article includes discussion of cortical blindness, Anton syndrome, Anton-Babinski syndrome, cerebral blindness, cortical visual impairment, and geniculocalcarine dysfunction. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Cortical blindness refers to visual loss due to bilateral lesions of the geniculocalcarine pathways in the brain. Patients with cortical blindness may or may not be aware of their visual deficits. When they are unaware of the extent of visual loss (often confabulating their responses), the clinical presentation is termed “Anton syndrome.” Etiologies of cortical blindness are numerous and diverse. In this article, the author discusses the diagnosis of cortical blindness and its various causes.

Key points

• Cortical blindness is a term used to encompass visual loss from lesions of the retrogeniculate pathways. Pupillary responses are spared in a patient with cortical blindness because they rely on synaptic reflexes through the brainstem and do not require cortical inputs.

• Patients with cortical blindness due to occipital lesions may be unaware of their visual deficits. If so, the clinical presentation is termed “Anton syndrome.”

• Brain MRI is an important diagnostic test to determine the cause of cortical blindness, but not all causes produce MRI abnormalities.

• When infarction is suggested by MRI, the diagnostic work-up should be aimed at identifying cardioembolism and other causes of stroke.

• Posterior reversible encephalopathy syndrome may cause cortical blindness and is associated with severe preeclampsia or eclampsia, hypertension, and use of certain medications.

• Nonorganic visual loss should be considered a diagnosis of exclusion but can be suggested by examination findings that violate physiological patterns of visual loss.

Historical note and terminology

"Cortical blindness" is generally used to refer to visual loss due to bilateral dysfunction of the occipital visual cortex (“striate cortex” or V1). Some patients will exhibit unawareness of the extent of visual loss; this remarkable clinical state is termed "Anton syndrome" in reference to Gabriel Anton, who described this phenomenon in 1899 (04). For lesions not isolated to the cortex, including the subcortical visual pathways, the term "cerebral blindness" may be more appropriate. The term "cortical visual impairment" has also been introduced (particularly in the pediatric population) when visual deficits are incomplete (22). Nevertheless, because the term "cortical blindness" continues to be in common use, it will be retained in this discussion.

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