Objectives: Most abnormalities on magnetic resonance imaging (MRI) in limbic encephalitis involve the medial temporal lobes and are associated with memory impairment. Recent neuroimaging studies have shown that not only the medial temporal lobes, but also the prefrontal lobes, contribute to cognitive functions.
Methods: We describe a case of limbic encephalitis with abnormalities in the medial temporal lobes on MRI and decreased accumulation of radionuclide in the prefrontal regions on SPECT.
Results: The patient had persistent retrograde amnesia, particularly affecting remotely acquired memories including public events and autobiographical memories.
Conclusion: Disruption of the prefrontal-medial temporal circuitry by intense inflammation may have initiated the metabolic changes in the prefrontal cortices, which may exacerbate amnesia.