Alexia without agraphia: a study of a case of verbal alexia without accompanying colour-naming defect.

A 47-year-old man developed a persistent form of alexia without agraphia as the result of a haemorrhagic intracerebral lesion in the left inferior temporo-occipital region, due to the rupture of an arteriovenous malformation. Surgical evacuation of the haematoma and excision of the malformation did not produce any modification of the reading deficit, which remained unchanged during a 4-year follow-up. The reading deficit was restricted to words and the patient was able to read only letter-by-letter, so that the whole words were reconstructed from the auditory names of the letters. So far, the disconnection explanation is the standard explanation of alexia without agraphia and the present case of verbal alexia may be regarded as being within this overall category. However, this explanation meets with unanswered questions that suggest more flexible interpretations. Neurolinguistic studies have questioned the unique character of alexia without agraphia as a clinical entity and, in contrast to the disconnection hypothesis, support the notion that the different varieties of alexia that are traditionally described represent distinctive syndromes, each with its own clinical features and pathophysiological basis. In this context, the reading properties in this case seem fully compatible with a deficit of the visual word-form system postulated by Warrington and Shallice, that is, the relatively early stage of the reading process through which a word-form or equivalent unit is attained. This system might be lateralized to the left hemisphere, as suggested by the fact that this case, like other cases of verbal alexia, had sustained damage to the left hemisphere and did not show any differential preservation of the reading of concrete words.