Characteristic MRI findings in GABA_A receptor encephalitis with thymoma: a report of two cases

This case reports aimed to clarify the characteristic MRI findings in GABA_A receptor encephalitis.

We report the cases of two encephalitis patients who had a history of thymoma surgery and in whom anti-GABA_AR antibodies and characteristic MRI findings were observed. These patients were clinically diagnosed as having thymoma-associated paraneoplastic encephalitis (TAPE) before the antibodies were identified. TAPE is often associated with antibodies to various neuronal surface antigens, including GABA_AR, AMPAR, CASPR2, LGI1, and GlyR. MRI findings of autoimmune encephalitis are extremely variable, but when multiple homogenous high-signal-intensity lesions are observed on FLAIR images, as in these cases, anti-GABA_AR antibodies are likely to be involved. We have named here this MRI finding the "cotton-wool-like appearance".

In cases of encephalitis with such characteristic radiological findings, neurologists should first investigate the presence or a history of thymoma surgery, and then promptly consider testing for anti-GABA_AR antibodies.