Abstract
This case study addresses episodic memory impairment or focal retrograde amnesia related to limbic encephalitis. The patient in question was a right-handed man in his 60s who developed focal retrograde amnesia due to limbic encephalitis. An abnormal MRI signal was observed in the right medial temporal lobe. Immediately after the encephalitis onset, mental symptoms—including impaired consciousness, disorientation, hallucinations, and delusions—appeared; however, his condition improved with medical treatment. After transfer to a convalescent and rehabilitation hospital, various neuropsychological tests were conducted but no apparent functional decline was observed in intellectual function, attention, memorization, or retention. However, the patient exhibited impairments related to autobiographical memory and memory of events 4 - 5 years before the onset of limbic encephalitis. Based on these observations, the patient was considered to exhibit focal retrograde amnesia due to limbic encephalitis. Despite exhibiting retrograde amnesia, he had no difficulty in his daily life in the ward. Moreover, after discharge from hospital, smooth work reinstatement was possible. This case demonstrates that, even after exhibiting retrograde amnesia, if its duration is relatively short and physical function and other higher-order brain functions are sustained, social rehabilitation—including work reinstatement—is feasible.
Highlights
Episodic memory impairment is classified as anterograde or retrograde amnesia in accordance with the time of onset
During the trial overnight stay, when taking the route he had often used before disease onset, he reported not knowing it. These two points are observations that points toward topographic disorientation; it is necessary to consider the period of retrograde amnesia in this case study, which is about 4 - 5 years
We report on a patient who exhibited retrograde amnesia involving memory spanning a period of 4 - 5 years as a result of limbic encephalitis
Summary
Episodic memory impairment is classified as anterograde or retrograde amnesia in accordance with the time of onset. Following the H.M. case report [1], it was elucidated that the medial temporal lobe is an important neural structure related to episodic memory and that patients with injury to this region may exhibit both anterograde and retrograde amnesia. Retrograde amnesia without the accompanying anterograde amnesia is known as focal retrograde amnesia and illustrates the importance of understanding the neurological basis of episodic memory. This report addresses a case in which the patient exhibited focal retrograde amnesia as a result of limbic encephalitis and describes the head MRI findings, symptoms, neuropsychological test results, the mechanism of appearance of focal retrograde amnesia, and the feasibility of social rehabilitation
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