APHASIA. - Difficulty or impossibility of speaking due to alteration of particular areas of the cerebral cortex (speech centers), on the left in right-handed people, on the right in left-handed people. The destruction or functional blocking of these centers makes it impossible to articulate speech or to recognize the sounds and signs (v. ASYMBOLIA) by which others communicate their thoughts. Two forms of aphasia are distinguished: motor and sensory.
A person affected by motor aphasia hears as a healthy person does, recognizes sounds, retains the memory of heard words, and understands their meaning; however, he lacks the faculty of forming the word itself, even though the innervation and musculature of the nasobuccopharyngeal-laryngeal apparatus are intact (v. DYSARTHRIA). In other words, he has lost the ideation of the movements by which the word is articulated. There is a form of "complete motor aphasia of Broca" (cortical form) in which the faculty of speaking is completely suppressed, and since written language depends largely on articulated language, the ability to write is also lost; comprehension of language remains preserved. In "pure verbal mutism" (transcortical form), on the other hand, the patient, while not speaking at all, retains the faculty of reading and writing.
In sensory aphasia, patients can speak and even hear, but they no longer understand words and grasp nothing of what is said to them; they behave toward the language as if it were an unknown tongue. In "complete sensory aphasia" (cortical form of Wernicke) the sick hear, but do not understand the meaning of words. In this form there occur, as secondary manifestations, paraphasias and paragraphs (that is, in speaking and writing they use one word for another). "Pure verbal deafness" (subcortical form) is the same as the preceding, but paraphasia and paragraphia are absent. In total aphasia, a combination of the two preceding forms, both speaking and understanding are completely abolished and the disorder reaches its highest degree through the simultaneous loss of internal speech (the reasoning development of ideas) and external speech (language).
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Giuseppe de Nanno