Is memory loss without anatomical damage tantamount to a psychogenic deficit? The case of pure retrograde amnesia

Following a car accident, a patient remained unconscious for approximately 20 min and confused for a few hours. When he could be questioned, he was found to have lost all past memories. The retrograde amnesia covered his whole life and concerned autobiographic events as well as famous facts and encyclopaedic knowledge. It also partially involved the verbal and visual lexicon. Reading, writing and counting were no longer possible. The profound impairment of retrograde memory contrasted with the preservation of anterograde memory, which permitted the patient to reacquire some of the notions he had lost, without, however, recovering the feeling of a personal experience of autobiographical information. Four years later, the retrograde deficit was unmodified, except for what had been relearnt. The search for data in support of an organic or psychological aetiology was negative. No signs of brain damage were apparent at the neurological examination and on CT, MRI and SPECT. On the other hand, there was no evidence of a psychiatric history, psychological stress or emotional precipitants that could substantiate the hypothesis that the patient derived a primary or secondary gain from amnesia. We propose that cases of focal retrograde amnesia, similar to the present one, deserve to be classified separately from organic and psychogenic forms under the label of `functional' retrograde amnesia, a syndrome in which the threshold of activation of premorbid memories is abnormally raised by the trauma, leaving the encoding and retrieval of new memories unaffected.