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The classification of aphasias: a brief history Volume 7, issue 1, Janvier-Février-Mars 2015

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Author
1 UNICAEN, UMR_S 1077, Caen, France
2 Inserm, U1077, Caen, France
3 EPHE, UMR_S 1077, Caen, France
4 CHU de Caen, Service de neurologie, 14033 Caen, France
* Correspondance

The variety of aphasia types was immediately sensed by Paul Broca himself, shortly after he had described his first case. He then distinguished “alogia”, “verbal amnesia”, “aphemia” and “mechanic alalia”. The classification of aphasias has ever since appeared as an obvious need to generations of neurologists. In 1874, Carl Wernicke was the first to propose a classification of aphasias based on the anatomical correspondence of the various aspects of language impairment, with a posterior center and an anterior center connected by an anatomical pathway, the damage to which would give rise to sensory, motor and conduction aphasia, respectively. This concept was further elaborated, to culminate in the well-known Lichtheim's “house” scheme. In addition to the three aforementioned types, this model included “transcortical” (motor, sensory or mixed) and “pure” (caused by impairment of a single linguistic ability, e.g. agraphia, alexia or pure verbal deafness) aphasias. This view was supported by generations of neurologists throughout the 20th century, from Jules Dejerine to Norman Geschwind, despite strong criticism from advocates of the holistic conception of language, such as Pierre Marie or Kurt Goldstein, who did not agree with the idea that language could be split into multiple functions, which in turn would depend on multiple cerebral structures. As Pierre Marie put it, “There is only one aphasia, Wernicke's, and Broca's aphasia is nothing but Wernicke's aphasia without speech”. Despite occasional attempts to modify it, the “connexionist” model came to us virtually unchanged, and is still present in neurology textbooks. The emergence of CT and MRI scans from the 1980s on brought about new concepts, e.g. “subcortical aphasias”, which were called “dissident” because they did not fit the clinical profile of the classical aphasic syndromes. This is an example of how better anatomical lesion analysis can help refining the clinical approach. A completely new time in aphasia classification has come with the intervention of first, linguistics and second, cognitive neuropsychology. The linguist Roman Jakobson stressed the importance of the paradigmatic/syntagmatic dichotomy, corresponding to selection and combination, respectively, of linguistic elements (phonemes/morphemes/words). The target of the linguistic analysis is only the language disorder, regardless of any anatomical correlation. Cognitive neuropsychology individualizes cognitive syndromes with the aim of finding double dissociations in order to infer modular models of normal cerebral functioning. Contrary to pure linguistics, cognitive neuropsychology (and therefore neuropsycholinguistics) aims at uncovering the brain areas that support specific speech processes. In the field of aphasia, some well-known achievements of neuropsycholinguistics include reading and writing disorders such as deep and surface dyslexia for example. Although the ancient classifications inherited from the 19th century are still in use in everyday neurology, the continuous advances in brain imaging together with the new methods of linguistic analysis will no doubt result in further refinements in the aphasia nosology.