Presentation
History of memory impairment since two weeks and right sided weakness five days ago. No history of abnormal movements or fever. No history of any constitutional symptoms.
Patient Data
An ill-defined area of abnormally high T2/FLAIR signal intensity is seen implicating the left basal ganglia region with vasogenic edema of the left frontoparietal white matter. Subtle right frontal lobe white matter edema is also noted.
In post-contrast images, multiple hyperenhancing foci are seen scattered in the left basal ganglia and deep cerebral white matter on both sides more on the left side.
Follow-up study after a week of pulse steroid therapy shows:
Regressive course of the left basal ganglia and white matter edema and regression of the size of the enhancing lesions denoting therapeutic response.
Case Discussion
The insidious onset in the absence of constitutional symptoms and signs of meningism, slowly progressive course and the laboratory investigation led to a provisional diagnosis of encephalitis versus vasculitis. The laboratory investigations yielded negative ANA, ANCA and virology tests, while it yielded positive anti-NMDA antibodies; for that the diagnosis of autoimmune encephalitis was suggested. Follow-up MRI confirmed therapeutic response to pulse steroids, keeping with the autoimmune disease diagnosis.
Possible differentials include:
ADEM: however the clinical course does not support this diagnosis.
Behcet encephalitis: this diagnosis is likely due to the involvement of the basal ganglia, however anti-NMDA receptor antibodies showed in CSF analysis favor the diagnosis of autoimmune encephalitis.
Viral Encephalitis: this diagnosis is possible based on imaging alone, however lack of fever and other signs of infectious encephalitis with negative virology tests waive out this possibility.
Paraneoplastic (limbic) encephalitis: is possible but in this particular case, a CT scan was done and no evidence of malignancy was found.
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