ABSTRACT: A 29-year-old man was admitted because of sudden onset of retrograde amnesia. The patient was unable to recall events having occurred during the past 2 years. The impairment was especially serious with regard to personal memories during the 5 months prior to admission, while he had first been working as a full-time employee under stressful circumstance. A diagnosis of dissociative amnesia was made on the basis of absence of any systemic or neurological diseases that could cause amnesia, the inadaptable character of the patient, the nature of amnesia, and presence of stressful condition possibly related to the amnesia. Visual event-related potential (ERP) studies recorded with human face discrimination tasks demonstrated a P3a wave in response to a face of his superior in the office, whom he said that he had never seen before. The similar P3a wave was observed in response to a face quite familiar to the patient, his mother, but not to a face "truly" unknown to him. These findings suggest that the visual memory of his superior's face exists in the brain, but the patient is unable to retrieve it by some psychogenic mechanism. 131I-IMP SPECT revealed decreased perfusion in the left medial temporal lobe and the basal forebrain, suggesting the association between dissociative amnesia and focal brain dysfunction. While dissociative amnesia has been understood as psychogenic nature, both ERPs and SPECT are quite important tools to understand the association between the psychological phenomenon and biological changes of the brain in this disorder.
Rinsho shinkeigaku = Clinical neurology 02/2004; 44(1):14-9.