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To the Editor:
Drs. Di Filippo and Calabresi found highly selective hippocampal MR signal changes and restricted diffusion in a patient with transient global amnesia (TGA).1 The authors suggest that these imaging changes, and particularly the resolution of abnormalities on the diffusion scan with persistence of signal change on fluid-attenuated inversion recovery (FLAIR), support a vascular etiology for TGA.
Given the absence of conventional vascular risk factors and imaging evidence of prior cerebral ischemic events in this case, and ongoing debate as to whether TGA occurs on a vascular basis, other mechanisms should perhaps be considered.
The selective and symmetric hippocampal signal changes in this case are similar to those seen in limbic encephalitis, and particularly in cases associated with voltage gated potassium channel (VGKC) antibodies.2,3 In VGKC antibody-associated limbic encephalitis, hippocampal signal change is accompanied by striking anterograde and particularly retrograde memory deficits. As in this case, signal change on FLAIR MRI can persist for many months.2,3 Furthermore, limbic encephalitis can be associated with restricted diffusion on MRI.4
While the majority of cases of VGKC antibody-associated limbic encephalitis have persistently high titers of antibodies and required immunosuppression to stop ongoing inflammation and atrophy of …
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