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  • Updated 10.07.2020
  • Released 05.04.2001
  • Expires For CME 10.07.2023

Alexia without agraphia

Introduction

Overview

Alexia without agraphia is a dramatic disorder of higher visual function in which patients can still write but are unable to read. This has been variably conceptualized as a disconnection syndrome or a word-form agnosia. In this article, the author reviews the clinical features, causes, and pathophysiologic arguments of this condition.

Key points

• Alexia without agraphia is due to the language cortex being cut off from visual input. It usually associated with visual agnosia and prosopagnosia but may also occur in isolation.

• Unlike other agnosias, alexia without agraphia occurs strictly from left hemisphere lesions. Most common localization is left occipitotemporal and splenium of corpus callosum.

• Alexia without agraphia is often but not always accompanied by right hemianopia.

• Alexia without agraphia may be either a disconnection syndrome or a selective word form visual agnosia.

• The differential diagnosis of alexia without agraphia includes reading problems due to hemianopia, attentional deficits, eye movement abnormalities, and linguistic problems.

Historical note and terminology

Acquired alexia is the loss of efficient reading for comprehension, despite adequate visual acuity. Alexia without agraphia refers to a specific form, in which the ability to write is preserved, as are auditory and verbal aspects of language.

In the late 19th century, Déjérine first described this entity in a man with associated incomplete right homonymous hemianopia from a lesion of the left fusiform and lingual gyri. He subsequently deduced that the left angular gyrus stored the visual representation of words (needed for reading and writing), and that disconnecting the visual inputs of both hemispheres from the left angular gyrus could disrupt reading but leave writing intact (28). These conclusions were affirmed in 1965 by Geschwind in his series of cerebral disconnection theories (39).

Alexia without agraphia is also known as pure alexia or word blindness. More severe cases are sometimes referred to as global alexia, whereas milder forms constitute spelling dyslexia or letter-by-letter reading.

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