Agraphia is a neurological term of Greek origin (A + Greek graphein). It designates an impairment of the ability to write occurring in the setting of cerebral damage. The term is almost always used for the acquired variety of the disturbance, although there is a developmental form of agraphia which is an integral part of developmental dyslexia and is generally referred to as dysgraphia or spelling difficulty (see Alexia). Patients with agraphia may be entirely unable to write any words or even single letters, or they may be able to write words but with numerous spelling mistakes. In some patients the disorder may be confined to an inability to place the written material in the appropriate horizontal alignment from the left to the right side of the page. (This is known as spatial agraphia and is seen in superior parietal lesions of the dominant hemisphere.) In other patients the disorder is limited to an inability to maintain the size of the letters which become miniscule by the end of the line. (This is known as micrographia and is characteristic of parkinsonism, especially of the idiopathic variety.) Agraphia rarely occurs in isolation, although cases of pure agraphia have been reported. The anatomical substrate of such cases has not been identified.