Agraphia

Definition and Overview

Agraphia or dysgraphia is an acquired loss or disturbance of the ability to write or spell, resulting from neurological injury. Since the act of writing is complex, depending on language, motor control, visuospatial skills, and kinesthetic function, many different types of deficits can lead to agraphia. A key distinction is made between central agraphias, which affect the linguistic content of writing, and peripheral agraphias, which affect the motor or spatial aspects of writing.

Central (Aphasic) Agraphias

These are linguistic dysgraphias, usually associated with aphasia and alexia. Oral spelling is also impaired. Two main types of paragraphia (writing errors) are distinguished:

• Surface/Lexical Dysgraphia: Misspelling of irregular words, producing phonologically plausible errors (e.g., writing "simtums" for "symptoms"). This is seen with left temporoparietal lesions, as in Alzheimer’s disease.
• Deep/Phonological Dysgraphia: Inability to spell unfamiliar words and nonwords, often with semantic errors (e.g., writing "cat" instead of "dog"). This is seen with extensive left hemisphere damage.

Peripheral (Non-Aphasic) Agraphias

These agraphias result from deficits outside the core language system. Oral spelling is often spared.

• Mechanical Agraphia: Impaired motor control of writing due to weakness (paresis), dyspraxia, or movement disorders like dystonia or parkinsonism (see Micrographia).
• Neglect (Spatial) Dysgraphia: Associated with visuospatial neglect from a non-dominant hemisphere lesion. Patients may neglect the left side of the page, or miss or misspell the left side of words.

Pure Agraphia

This is a rare syndrome in which writing ability is lost in isolation, while oral language, reading, and motor praxis remain normal.

Clinical Significance and Syndromes

Agraphia is a component of Gerstmann syndrome, which also includes alexia, acalculia, finger agnosia, and right-left disorientation, and is caused by lesions in the dominant parietal lobe.

Furthermore, a disturbance in the mechanics of writing is often the most sensitive language abnormality in delirium, likely because writing is a complex task that depends on the integration of multiple cognitive and motor functions.

 

References

Benson DF, Ardila A. Aphasia: a clinical perspective. New York: OUP, 1996: 212-234

Roeltgen DP. Agraphia. In: Heilman KM, Valenstein E (eds.). Clinical neuropsychology (4th edition). Oxford: OUP, 2003: 126-145

 

Cross References

Alexia; Allographia; Aphasia; Apraxia; Broca’s aphasia; Fast micrographia; Gerstmann syndrome; Hypergraphia; Macrographia; Micrographia; Neglect; Wernicke’s aphasia