Introduction

Reading and writing are increasingly important in society. More transactions and communications take place over the internet each day. Stroke or other focal brain injuries can selectively impair reading and/or writing, causing important deficits in these daily interactions. Although not immediately apparent on the traditional neurological examination, alexia and agraphia can be disabling and dehumanizing. Furthermore, these deficits may be the only functional sequel of certain types of stroke, such as posterior watershed infarct, embolism to the left posterior parietal cortex, or occlusion of the left posterior cerebral artery. Therefore, assessment of reading and writing is an essential component of a complete neurological examination in cases of suspected stroke.

Presentations of disordered reading and writing

Reading and spelling are complex tasks with a number of processing components, each of which can be individually impaired by focal brain lesions. It is possible to determine the component of the task that is disrupted by evaluating performance across a variety of tasks and by considering the types of error made by the patient.

In order to read a printed word, the sequence of letters must first be seen and attended to. This early visual processing involves computation of a sequence of increasingly abstract spatial representations of the visual stimulus. In this process, specific letter shapes must be converted to graphemes (abstract letter identities), so that the word chair written in lower-case script in the left-hand corner of the page is recognized as the same word as the stimulus CHAIR written in upper-case block letters at the bottom of the page.