Tuesday, July 31, 2018

Anatomoclinical understanding in psychiatry

In the introduction to The birth of the clinic, Michel Foucault contrasts the views of Pomme from the middle of the eighteenth century and Bayle less than a hundred years later. Pomme believed that baths for ten or twelve hours a day for 10 whole months desiccated the nervous system and its sustaining heat, and observed in a patient after this treatment that:-
‘membranous tissues like pieces of damp parchment… peel away with some slight discomfort, and these were passed daily with the urine; the right ureter also peeled away and came out whole in the same way’. The same thing occurred with the intestines, which at another stage, ‘peeled off their internal tunics, which we saw emerge from the rectum. The oesophagus, the arterial trachea, and the tongue also peeled in due course; and the patient had rejected different pieces either by vomiting or by expectoration’. 
Such “language of fantasy” was not used by Bayle when he described the encephalitic lesions of general paralysis. Foucault describes such new pathological understanding as a “mutation in discourse”.

Such anatomoclinical understanding, relating symptoms to their underlying physical pathology, was a major advance for medicine in the first half of the nineteenth century and still underlies our modern understanding of disease. But the enthusiastic search for anatomical localisation in psychiatry still led to fanciful notions later in the nineteenth century. For example, Theodor Meynert (1833-1892) delineated various ‘fibre-systems’ in the brain and deduced functions for these ‘pathways’. Despite his skills in brain dissection, his theories were not based on empirical findings. They were eventually attacked and labeled as ‘brain mythology’, particularly after his death. To quote from Auguste Forel, who studied with him:
He [Meynert] was certainly brilliant and full of ideas, but his imagination made leaps that were ten times as bold as mine. The longer I remained, the more I lost faith in his encephalogical schemata, and the fibrous connections which he perceived in the brain. … I could not always see what Meynert saw.

Modern neuroimaging studies also have the tendency to be interpreted as facts despite the inconsistencies and confounders in the data (eg. see previous post). Meynert’s research may have appeared so successful because it seemed to give a material explanation of the basis of mental illness, in the same way as brain scanning does for us now. Its empirical truth is a lesser concern in whether the results are believed or not.

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