Acute limbic encephalitis with focal hyperperfusion on single photon emission computed tomography

Psychiatric Illness or Immune Dysfunction-Brain Perfusion Imaging Providing the Answer in a Case of Anti-NMDAR Encephalitis

BACKGROUND

We investigated the potential use of SPECT quantification in addition to qualitative brain perfusion analysis for the detection of anti-NMDAR encephalitis. The question is how to normalize brain activity to be able to quantitatively detect perfusion patterns. Usually, brain activity is normalized to a structure considered unaffected by the disease.

METHODS

Brain [99mTc]-HMPAO SPECT was performed as a method to detect brain perfusion patterns. The patterns of abnormal brain perfusion cannot always be reliably and qualitatively assessed when dealing with rare diseases. Recent advances in SPECT quantification using commercial software have enabled more objective and detailed analysis of brain perfusion. The cerebellum and whole brain were used as the normalization structures and were compared with visual analysis.

RESULTS

The quantification analysis performed with whole brain normalization confirmed right parietal lobe hypoperfusion while also detecting statistically significant left-to-right perfusion differences between the temporal lobe and thalamus. Whole brain normalization further described bilateral frontal lobe hyperperfusion, predominantly of the left lobe, and was in accordance with visual analysis.

CONCLUSION

SPECT quantitative brain perfusion analysis, using the whole brain as the normalization structure rather than the cerebellum, in this case, improved confidence in the visual detection of anti-NMDAR encephalitis and provided unexpected solutions to atypical psychiatric dilemmas.

Dystonic Seizures and Intense Hyperperfusion of the Basal Ganglia in a Patient with Anti-N-Methyl-D-Aspartate Receptor Encephalitis

This report describes a rare case presenting with dystonic seizures due to anti-N-methyl-D-aspartate (NMDA) receptor encephalitis. The patient was an 18-year-old woman with repeated right-dominant dystonic seizures even under sedation. Single-photon emission computed tomography (SPECT) showed intense hyperperfusion of the caudate nuclei, putamen, globus pallidus, thalamus, and insula on the left side, suggesting encephalitis. Antibodies against NMDA receptors were detected in the sera and cerebrospinal fluids. Immune-mediated treatments were administered. Three months later, the dystonic seizures disappeared. We diagnosed her with anti-NMDA receptor encephalitis. SPECT suggested that the main region of encephalitis was the basal ganglia. Therefore, we propose that the patient's dystonic seizures may originate from the insula and be generated by intense hyperactivity of the basal ganglia.