Case Report: Value of MR relaxometry and spectroscopy in multimodal imaging characterization of limbic encephalitis...

Central nervous system involvement is uncommon in systemic sclerosis, and inflammatory temporomesial syndromes in this context are rarely reported. We present a 58-year-old man with systemic sclerosis who developed subacute cognitive impairment and dialeptic seizures arising from the right temporal lobe. Video electroencephalography confirmed a right temporal seizure onset zone. Brain magnetic resonance imaging demonstrated enlargement and subtle T2 hyperintensity of the right hippocampus and amygdala, while fluorodeoxyglucose-positron emission tomography/computed tomography images showed focal hypermetabolism of the enlarged right amygdala. Proton magnetic resonance spectroscopy demonstrated bilateral reduction of total N-acetylaspartate compared with an age-matched healthy reference subject, with a more pronounced difference on the right, a pattern compatible with bilateral, right-accentuated neuronal dysfunction or injury. MR relaxometry demonstrated significant bilateral T2 prolongation in the amygdalae and hippocampal heads, whereas T1 abnormalities were more region-dependent, involving the right amygdala and both hippocampal heads. Serum testing detected anti-pyruvate dehydrogenase antibodies, whereas routine clinical neural antibody testing was negative. The patient became seizure-free under antiseizure medication and immunosuppressive therapy with cyclophosphamide. Notably, although the unilateral conventional imaging findings did not meet the bilateral mesial temporal criterion required by current consensus criteria for definite autoimmune limbic encephalitis, MR relaxometry revealed bilateral temporomesial abnormalities. This finding is consistent with available neuropathological and experimental evidence and suggests that routine imaging may underestimate disease extent. This case highlights a rare presentation of antibody-atypical limbic encephalitis in the setting of systemic sclerosis and illustrates how multimodal imaging can support diagnosis and tissue characterization when routine antibody testing is unrevealing.