Pure alexia is one form of alexia which makes up "the peripheral dyslexia" group. Individuals who have pure alexia suffer from severe reading problems while other language-related skills such as naming, oral repetition, auditory comprehension or writing are typically intact.

Pure alexia is also known as: "Dejerine syndrome", (after Joseph Jules Dejerine

Joseph Jules Dejerine

Joseph Jules Dejerine , was a French neurologist.Joseph Jules Dejerine was born to French parents in Geneva, Switzerland, where his father was a carriage proprietor. During the Franco-Prussian War Dejerine worked as a volunteer in a Geneva Hospital and in the spring of 1871 decided to pursue his...

, who described it in 1892, but it should not be confused with medial medullary syndrome

Medial medullary syndrome

Medial medullary syndrome, also known as inferior alternating syndrome, hypoglossal alternating hemiplegia, lower alternating hemiplegia, or Dejerine syndrome, is a type of alternating hemiplegia characterized by a set of clinical features resulting from occlusion of the anterior spinal artery...

 which shares the same eponym

Eponym

An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...

), "alexia without agraphia", "letter-by-letter dyslexia", "spelling dyslexia", or "word-form dyslexia".

Classification

Pure alexia results from cerebral lesions in circumscribed brain regions and therefore belongs to the group of acquired reading disorders, alexia, as opposed to developmental dyslexia

Dyslexia

Dyslexia is a very broad term defining a learning disability that impairs a person's fluency or comprehension accuracy in being able to read, and which can manifest itself as a difficulty with phonological awareness, phonological decoding, orthographic coding, auditory short-term memory, or rapid...

 found in children who have difficulties in learning to read.

Causes

Pure alexia almost always involves an infarct to the left posterior cerebral artery

Posterior cerebral artery

-External links: - Posterior Cerebral Artery Stroke* at strokecenter.org* at State University of New York Upstate Medical University* at psyweb.com* at neuropat.dote.hu...

 (which perfuses the splenium of the corpus callosum and left visual cortex

Visual cortex

The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....

, among other things). The resulting deficit will be pure alexia - i.e., the patient can write but cannot read (even what they have just written). This is because the left visual cortex has been damaged, leaving only the right visual cortex (occipital lobe

Occipital lobe

The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...

) able to process visual information, but it is unable to send this information to the language areas (Broca's area

Broca's area

Broca's area is a region of the hominid brain with functions linked to speech production.The production of language has been linked to the Broca’s area since Pierre Paul Broca reported impairments in two patients. They had lost the ability to speak after injury to the posterior inferior frontal...

, Wernicke's area

Wernicke's area

Wernicke's area is one of the two parts of the cerebral cortex linked since the late nineteenth century to speech . It is involved in the understanding of written and spoken language...

, etc.) in the left brain because of the damage to the splenium

Splenium

The posterior end of the corpus callosum is the thickest part, and is termed the splenium .It overlaps the tela chorioidea of the third ventricle and the mid-brain, and ends in a thick, convex, free border....

of the corpus callosum. The patient can still write because the pathways connecting the left-sided language areas to the motor areas are intact.