Clinical Significance of MR Spectroscopy in Differentiating Autoimmune Limbic Encephalitis of the Hippocampal Region Initially Characterized as High-grade Glioma

Abstract

Background: Autoimmune limbic encephalitis (ALE) is an inflammatory brain process involving a group of diseases with antibodies against neuronal synaptic and cellular antigens. Diagnosis is based on clinical examination, neurological functional tests, cerebrospinal fluid analysis, immunological testing, and radiological findings. Objective: This case report aims to present the case of a 68-year-old patient initially hospitalized for intermittent neurological deficits in the form of cognitive disorders of consciousness, which was initially declared as dementia without physical neurological deficit. Case presentation: Initial brain MRI (SIEMENS Magnetom Avanto, 1.5 T, Erlangen, Germany) showed changes differentially diagnosed characterised as glial neoplasm of mixed-grade astrocytoma or inflammatory process of unilateral autoimmune encephalitis. Since the neurosurgical opinion suggested a higher-grade glioma with proposed surgical treatment, the patient was referred for repeated MRI with MR spectroscopy in order to exhaust all diagnostic possibilities before surgery. MRI with MR spectroscopy (SIEMENS Magnetom Lumina, 3 T, Erlangen, Germany) revealed radiologically altered findings, in the right hippocampus and parahippocampal gyrus, which primarily corresponded to changes due to unilateral autoimmune encephalitis,due to its morphology characteristics and spectroscopy profile, making the primary glial neoplasm of lower grade less likely. Since the neurological mosaic IIFT result showed a positive LGI1 antibody finding, therapy for autoimmune encephalitis was initiated, leading to significant improvement in cognitive functions and the return of short-term memory. Conclusion: Although the detection of antibodies against onconeural, cellular, and synaptic proteins represents a significant advancement in diagnosing autoimmune limbic encephalitis, the role of conventional diagnostic tools such as MRI, EEG, and cerebrospinal fluid analysis should not be overlooked, where the application of new functional imaging techniques such as MR spectroscopy can be beneficial and should be considered.