In the adult, acquired dysgraphia (or agraphia) is the partial or total loss of the ability to write. It usually occurs following brain injury (stroke, head trauma) or neurodegenerative disease. Since the components involved in the process of writing are many (the knowledge of the letters, the working memory to keep them in mind, the practical ability to write the letters) and much more, there are different types of agraphy which can originate from “central” (therefore linguistic processing) and “peripheral” (not linguistic, such as micrography in Parkinson's) problems. Even the neglect it can obviously cause writing difficulties.
A recent review by Tiu and Carter (2020)  helps us to bring order between the different types of agraphy.
There are “pure” agraphics where neither other linguistic aspects nor praxic aspects external to writing are compromised. Pure agraphias can be distinguished in linguistic agraphy pure (language and reading intact, normal handwriting, but usually phonological and lexical misspellings) and in apraxic agraphy pure (language and reading intact, handwriting deteriorated, difficulty in performing only praxis related to writing). Obviously, between these two poles, there may be mixed cadres with compromises on both sides.
In relation to the type of aphasia we can have:
|Agraphy in non-fluent aphasia||Writing usually reflects the characteristics of aphasia; production is limited and there are omissions of letters. Handwriting is often poor and agrammatism is present.|
|Agraphy in fluent aphasia||In this too, the writing reflects the characteristics of aphasia; the number of words produced can be overabundant with the production of neologisms. Grammatical elements can be overabundant with respect to nouns.|
|Agraphy in conduction aphasia||There are few studies on this; some of them refer, even in writing, to the phenomenon of the “conduit d'approche” present in the spoken word.|
The tools available to the clinician to identify the type of aphasia are:
- La calligraphy (characteristic marker of purely apraxic agrafia)
- Il dictation (compromise in linguistic agraphy, but not in apraxic)
- La copy (a writing that improves in copy may indicate a greater impairment of the linguistic level)
- Other ways of writing (for example on a computer or smartphone) can highlight specific difficulties of a practical type
- Writing of not words: allows to distinguish the level of impairment, in particular if the sublexical level has been affected