Memory lost, memory regained: neuropsychological findings and neuroimaging in two cases of paraneoplastic limbic encephalitis with radically different outcomes

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Abstract
OBJECTIVE To report two cases of paraneoplastic limbic encephalitis (PNLE) with similar clinical presentation, but dramatically different outcome and to highlight the role of neuropsychological and radiological evaluation in PNLE. METHODS Both patients underwent an extensive battery of neuropsychological tests designed to document general intellectual function, anterograde verbal and visual memory, naming, knowledge and executive ability. In addition, structural (CT and MRI) and functional (HMPAO-SPECT) brain scans were performed. RESULTS Both patients presented with fairly sudden onset of profound and persistent memory loss in the absence of other neurological symptoms. Their subsequently diagnosed small cell lung cancer was treated with a combination of radiotherapy and chemotherapy, leading to remission of the tumour. The memory of patient 1 recovered fully and he died from an unrelated cause 1 year later; neuropsychological testing showed a severe, but isolated, anterograde amnesia, brain MRI was normal and HMPAO-SPECT showed left medial temporal hypoperfusion. Patient 2 remained densely amnesic despite regression of her lung tumour; neuropsychological testing disclosed both anterograde and extensive retrograde amnesia together with more generalised cognitive deficits including anomia and executive impairments, MRI showed gross atrophy of the hippocampus and amygdala bilaterally, and HMPAO-SPECT showed pronounced frontal and temporal hypoperfusion. CONCLUSION Complete remission from PNLE may occur and seems to be associated with pure anterograde amnesia without evidence of structural hippocampal damage in MRI. By contrast, cognitive deficits beyond severe anterograde amnesia and evidence of destructive medial temporal lobe pathology on MRI seem to be poor prognostic features.