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Agraphia is an acquired neurological disorder causing a loss in the ability to communicate through writing, whether the ability to write has been lost due to some form of motor dysfunction or just the ability to spell . The loss of writing ability may or may not present with other language or neurological disorders. Common disorders appearing with apraphia are alexia, aphasia, dysarthria, agnosia, and apraxia. The study of individuals with agraphia may provide more information about the pathways involved in writing, both language related and motoric.

Broadly speaking, agraphia can be divided into aphasic agraphias and nonaphasic agraphias. Aphasic agraphias tend to involve language areas of the brain, causing difficulty spelling or spontaneous communication, and are often accompanied by other language disorders . Nonaphasic agraphias usually target motor and visuospatial skills in addition to language and tend to involve motoric areas of the brain, causing difficulty in the movements associated with writing.

Forms of Agraphia

Gertsmann's Syndrome Agraphia

Gerstmann's syndrome is a rare syndrome defined by three of the following symptoms: difficulty discriminating between one's own fingers, agraphia, difficulty distinguishing let from right, and difficulty performing calculations. This tetrad of symptoms has been shown to be structural, not functional, as all four symptoms result from pathway lesions. Gerstmann's syndrome may additionally present with alexia and mild aphasia.

Lexical/Surface Agraphia

Lexical agraphia is caused by damage to the orthographic memory; these individuals cannot visualize the spelling of a word, though they do retain the ability to sound them out. This impaired spelling memory can imply the loss or degradation of the knowledge or just an inability to efficiently access it. There is a regularity effect associated with lexical agraphia in that individuals with this form of agraphia are less likely to correctly spell words without regular, predictable spellings; for example, they would spell "night" as "nite". Additionally, spelling ability tends to be less impaired for common words. Individuals with lexical agraphia also have difficulty with homophones; they would tend to spell both night and knight the wrong way (as "nite"). Language competence is terms of grammar and sentence writing tends to be preserved.

Phonological Agraphia

Phonological agraphia is largely the opposite of lexical agraphia in that the ability to sound out words is impaired, but the orthographical memory of words may be intact. Phonological agrapia is associated with a lexicality effect in that there is a difference in the ability to spell words versus nonwords because individuals with this form of agraphia are depending on their orthographic memory. Additionally, it is often harder for these individuals to access more abstract words without strong semantic representations (i.e., it is more difficult for them to spell prepositions than concrete nouns).

Deep Agraphia

In individuals with deep agraphia, both phonological ability and orthographic memory are affect. They can neither remember how the words look when they are spelled correctly, nor sound them out to determine spelling. These individuals attempt to spell using the damaged orthographic memory. Errors are common and usually semantic in nature; for example, one might be asked to write "ship" and write "boat" instead. These individuals have more difficulty with abstract concepts and uncommon words. Reading and spoken language are often impaired as well.

Global Agraphia

Though the same types of memories are impaired, global agraphia is worse than deep agraphia; in global apraxia, spelling knowledge is lost to such a degree that the patient cannot write any words at all or only a very few meaningful words. Reading and spoken language are also markedly impaired.

Apraxic Agraphia

Apraxic agraphia is a nonaphasic form of agraphia and consists of distorted, slow, effortful, incomplete, and/or imprecise letter formation. Though written letters are often so poorly formed that they are almost illegible, the ability to spell aloud is often retained. This form of agraphia is caused specifically by a loss of specialized motor plans for the formation of letters and not be any dysfunction affecting the writing hand. Apraxic agraphia may present with or without ideomotor apraxia.

Visuospatial Agraphia

Visuospatial agraphia is a form of nonaphasic agraphia and is defined as a tendency to neglect one portion (often an entire side) of the writing page, slanting lines upward or downward, and abnormal spacing between letters, syllables, and words. The orientation and correct sequencing of the writing will also be impaired. Visuospatial agraphia is frequently associated with left hemispatial neglect, difficulty in building or assembling objects, and other spatial difficulties.

Causes

Diagram of human brain showing surface gyri and the primary auditory cortex

  Angular gyrus

  Supramarginal gyrus

  Broca's area

  Wernicke's area

  Primary auditory cortex

Phonological agraphia is linked to damage to areas of the brain involved in phonological processing skills (sounding out words), specifically to the left perisylvian language areas such as Broca's area, Wernicke's area, and the supramarginal gyrus.

Lexical agraphia is associated with damage to the left angular gyrus and/or posterior temporal cortex. The damage is typically posterior and inferior to the perisylvian language areas.

Deep agraphia involves damage to the same areas of the brain as lexical agraphia plus some damage to the perisylvian language areas as well. More extensive left hemisphere damage can lead to global agraphia.

Gerstmann's syndrome is caused by a lesion of the dominant (usually the left) parietal lobe; usually these are left angular gyrus lesions.

Apraxic agraphia with ideomotor apraxia is typically caused by damage to the superior parietal lobe (where graphomotor plans are stored) or the premotor cortex (where the plans are converted into motor commands). Additionally, some individuals with cerebellar lesions (more typically associated with non-apraxic motor dysfunction) develop apraxic agraphia. Apraxic agraphia without ideomotor apraxia may be caused by damage to either of the parietal lobes, the dominant frontal lobe, or to the dominant thalamus.

Visuospatial agraphia typically has a right hemisphere pathology.

Treatment

• usually aimed at strengthening impaired processes and promoting the use of residual abilities
• use of written language in conjunction with other types of communication is likely to enhance overall success

Lexical Agraphia

• two major approaches to treating patients with lexical agraphia

Copy and Recall Treatment (CART)

• repeated copying of target words to re-establish the ability to spell those specific words
  • required repeated practice and is more likely to be successful when a few words are trained to mastery than when a large group of unrelated words is trained

Problem-Solving Approach to Spelling

• this strategy is intended to promote interaction between the undamaged phonological and the damaged lexical-semantic spelling routes by writing out multiple plausible spellings and finding the one that looks right
  • phonologically plausible spellings can help trigger recall of correct spellings
  • may improve access to memory of spellings or strengthen orthographic representations or both

Phonological Agraphia

• treatments strengthen sound-to-letter correspondences by using single words whose spellings are remembered (orthographic memory not damaged) as keys for specific consonants (e.g. Kim for that k sound)
  • allows patients to generate plausible spellings for words

Deep or Global Agraphia

• likely to have significant aphasia and alexia with their agraphia, so writing can be even more important to them as it can cue spoken language

Anagram and Copy Treatment

• patients are asked to arrange component letters into the target word and then to repeatedly copy the target word
  • similar to CART, which can also be used with pictures to link words and meanings
• facilitates the relearning of a set of personally relevant written words for communication

Apraxic Agraphia

• positive treatment outcomes are less common
• if copying skills are preserved, repeated copying may result in a shift from the highly intentional and monitored hand movements indicative of apraxic agraphia to a more automated graphomotor control