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  • Updated 07.25.2022
  • Released 07.14.1997
  • Expires For CME 07.25.2025

Cortical blindness

Introduction

Overview

Cortical blindness refers to visual loss due to bilateral lesions of the geniculocalcarine pathways in the brain. The term “cortical blindness” is used interchangeably with “cerebral blindness,” as will be the case in this discussion. Patients with cortical blindness 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.

Key points

• Cortical blindness can be confused with nonorganic visual loss because the eye examination, including pupillary responses, is normal. Nonorganic (ie, psychogenic, functional) visual loss should be considered as a diagnosis of exclusion but can be suggested by examination findings that violate physiological patterns of visual loss.

• Cortical blindness may be overlooked because symptoms of visual loss may not be expressed or may even be denied by the patient.

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

Historical note and terminology

"Cortical blindness" refers 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. Anosognosia, coined by Babinski in 1914, defines a lack of knowledge of disease. Anton syndrome (sometimes referred to as Anton-Babinski syndrome) is a form of visual anosognosia. For lesions not isolated to the cortex, including the subcortical visual pathways, the term "cerebral blindness" may be more appropriate. In strictest terms, cortical blindness is a specific subtype of cerebral blindness. The term "cortical visual impairment" has been applied in the pediatric population when visual deficits are incomplete. Nevertheless, because the term "cortical blindness" continues to be in common use, it will be retained in this article.

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