Board Review 3 – Case 14

Neuroradiology board review. This lecture is geared towards the ABR core exam for residents, but it would be useful for review for the ABR certifying exam or certificate of added qualification (CAQ) exam for neuroradiology.

More description and the answer (spoiler!) are seen below the video.

This case shows
bilateral hippocampal and medial temporal T2/FLAIR hyperintensity with relatively little enhancement. The abnormal signal extends superiorly into the insula and subinsular white matter bilaterally.

The diagnosis is: limbic encephalitis

There is a differential diagnosis for this case which includes:

• herpes encephalitis
• other viral encephalitis
• limbic encephalitis
• infiltrative astroctyoma

Limbic encephalitis is an autoimmune condition often as part of a paraneoplastic syndrome. Patients have bilateral temporal lobe abnormalities that can be symmetric or asymmetric, and presence of enhancement is possible. Patients often have circulating antibodies, such as anti-GAD.

Herpes encephalitis usually has more enhancement and diffusion abnormality, but this is not reliable. Any patient suspected of having herpes encephalitis should be treated with antivirals (acyclovir) until herpes is ruled out to minimize the high morbidity and mortality. Other viral encephalitis can have this appearance as well, but the bilateral symmetry is highly suggestive of autoimmune limbic encephalitis.