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

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 verba l and visual memory, naming, knowledge and executive ability. In addition, structural (CT and MRI) and functional (HMPAO-SPECT) brain scans were perfo rmed. Results-Both patients presented with fairly sudden onset of profound and persistent memory loss in the absence of other neurological symptoms. T heir subsequently diagnosed small cell lung cancer was treated with a combi nation of radiotherapy and chemotherapy, leading to remission of the tumour . The memory of patient 1 recovered fully and he died from an unrelated cau se I year later; neuropsychological testing showed a severe, but isolated, anterograde amnesia, brain MRI was normal and HIMPAO-SPECT showed left medi al temporal hypoperfusion. Patient 2 remained densely amnesic despite regre ssion of her lung tumour; neuropsychological testing disclosed both anterog rade and extensive retrograde amnesia together with more generalised cognit ive deficits including anemia and executive impairments, MRI showed gross a trophy 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 associate d with pure anterograde amnesia without evidence of structural hippocampal damage in MRI. By contrast, cognitive deficits beyond severe anterograde am nesia and evidence of destructive medial temporal lobe pathology on MRI see m to be poor prognostic features.