Autoimmune encephalitis

Case contributed by Ryan Thibodeau
Diagnosis almost certain


Confusion/altered mental status and fever. Evaluate for acute pathology.

Patient Data

Age: 50 years
Gender: Female

There are extensive areas of restricted diffusion and T2/FLAIR-hyperintensity, primarily located in the right temporal lobe, and extending posteriorly-superiorly into the parietal lobe. Part of the insula, posterior right thalamus, and in the medial right occipital lobe are also involved. The remainder of the brain has a grossly normal signal pattern.

There is slight sulcal effacement on the right, but there is no ventricular compression, midline shift, or other major mass effect.

Nonspecific T2-hyperintensity is seen in the central pons, often associated with chronic small vessel disease.

There is fluid/mucous signal in the sphenoid sinus.

Case Discussion

This is a case of a suspected autoimmune encephalitis. The main differential was an autoimmune encephalitis. Following the above imaging findings, an lumbar puncture was performed for CSF analysis, and then the patient was started on acyclovir. However, after several days of continued worsening encephalopathy (no response to acyclovir), the patient was found to be PCR negative for HSV, but showed elevated protein in the CSF. The patient was placed on IVIG and her symptoms began to improve on the same day.

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