He died in October 2000 and there was no postmortem analysis. He progressively developed behavioural abnormalities including motor and verbal stereotypies, coprolalia, with poor self control, although he remained able to discontinue them momentarily. He performed very poorly on the frontal battery test and failed to improve under various drug regimens. Brain MRI remained generally atrophic. We suggest that the pathological process underlying his progressive loss of behavioural control was already at work when the patient became unable to read silently.
Inner speech is an understudied phenomenon giving rise to mentation under internal control.
Silent reading could be an externally triggered inner speech as opposed to an internal production of inner speech linked to the thinking process. Besides the generating mechanisms producing inner speech at the interface of thought and language, an endogenous control must exist to inhibit the utterance of inner speech. A pathological process involving this inhibitory control may unmask inner speech. We speculate that such an inhibitory control of inner speech may be pathologically involved in our patient, underlying both initial loss of silent reading, and the most recent vocal compulsive stereotypies. Prefrontal cortical dysfunction may be the underlying pathophysiological mechanism explaining the inability to inhibit the vocalisation of inner speech in our patient, as assumed by the final clinical diagnosis.