Background: Anti-NMDA-receptor encephalitis is an immune-mediated inflammatory disorder of the central nervous system. Brain MRI is unremarkable in at least 50% of patients and highly variable in the remaining patients with signal abnormalities in different brain regions. Only scarce reports exist on other imaging modalities.
Case presentation: A 31-year-old woman sub-acutely developed psychosis, behavioural changes, amnesia, alternating states of agitation and mutism, fever and epileptic seizures. Clinically suspected diagnosis of anti-NMDA-receptor encephalitis was confirmed by the detection of anti-NMDA receptor antibodies in CSF and serum. During the acute phase, brain MRI abnormalities were found in both insular cortices and hippocampi, whereas F(18)-FDG-PET showed hypermetabolism bilaterally in insular and prefrontal cortex. After resection of the underlying ovarian teratoma and with multimodal immunotherapy the patient substantially improved reaching a modified Rankin Scale score of 2 after 3 months. At follow-up, both hippocampi were still affected on MRI, whereas insular cortex appeared normal; however, both regions showed prominent glucose hypometabolism.
Conclusions: Here, we report bi-insular cortical abnormalities on MRI and F(18)-FDG-PET in a patient with anti-NMDA-receptor encephalitis during the acute phase and after clinical improvement.
Keywords: Autoimmune encephalitis; Case report; Frontal lobe; Hippocampus; Insular cortex; MRI; Medial temporal lobe; NMDA receptor; PET.