Anti-leucine-rich glioma-inactivated 1 encephalitis revealed by a manic episode: insights from frontal lobe dysfunction in neuropsychiatry through neuropsychology and metabolic imaging. A case report

Abstract

BackgroundAnti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis is a limbic encephalitis that rarely presents as an isolated psychiatric syndrome.Case presentationA 70-year-old patient first presented with behavioral disorder including hyperactivity, euphoria, with disinhibition and accelerated speech associated with severe insomnia and cognitive disorder. A manic episode was diagnosed and he received various psychotropic medications with no improvement. Invesitgations were negative (MRI showed T2 aspecific hyperintensities with no hyperintensities in limbic regions and EEG was normal). He was transferred to a nursing home, with a diagnosis of neurodegenerative condition. Later, he was referred to our unit for further investigations. A cerebral 18F-FDG-PET revealed an association of frontal hypometabolism and temporal and striatum hypermetabolism and CSF analysis revealed slightly increased white blood cell counts. Plasmatic anti-LGI1 antibodies were detected. The patient was treated with intra-venous immunoglobulin (IvIg) but showed no improvement. Second-line treatment (a combination of rituximab and cyclophosmphamide) was then administered for a year, leading to an improvement of neuropsychiatric symptoms and normalization of metabolic impairment on 18F-FDG-PET.ConclusionIn this report, we describe a novel case of a patient withanti-LGI1 encephalitis with a predominant long-term psychiatric presentation. An atypical presentation (such as atypical psychiatric symptoms, neurocognitive disorder, and hyponatremia) should prompt further investigations such as CSF analysis, considering that MRI and EEG may be normal. FDG-PET might be of interest but few data are available in the literature. Early treatment of anti-LGI1 encephalitis is crucial for overall prognosis and may delay the development of dementia in some cases.

Anti‐LGI1 encephalitis preceded by psychiatric symptoms: A case report

“…8 Taken together, the present and the previous cases indicate diversity in the characteristics, age of onset, and the duration of isolated psychiatric symptoms. [6][7][8] In the present case, the main symptoms at the first visit to our hospital were hallucinations and delusions, and acute psychotic disorder was also a differential diagnosis. Anti-NMDA receptor encephalitis tends to develop more frequently in young women and is associated with tumors.…”

“…Furthermore, in patients with anti-LGI1 encephalitis with FBDSs, ictal changes may not be seen on EEG, 10,11 and FBDSS may even be misdiagnosed as psychogenic seizures. 11 In fact, the previous reports showed that patients developing isolated psychiatric symptoms in the initial phase were diagnosed with psychiatric disorders, [6][7][8] and there was a long interval before anti-LGI1 encephalitis was diagnosed. 6,8 The MRI findings of anti-LGI1 encephalitis are characterized by abnormal findings in the medial temporal lobes, 1 although approximately half the cases of anti-LGI1 encephalitis accompanied by FBDSs do not show abnormal findings in the medial temporal lobes.…”

“…11 In fact, the previous reports showed that patients developing isolated psychiatric symptoms in the initial phase were diagnosed with psychiatric disorders, [6][7][8] and there was a long interval before anti-LGI1 encephalitis was diagnosed. 6,8 The MRI findings of anti-LGI1 encephalitis are characterized by abnormal findings in the medial temporal lobes, 1 although approximately half the cases of anti-LGI1 encephalitis accompanied by FBDSs do not show abnormal findings in the medial temporal lobes. 11 In addition, abnormal findings in the basal ganglia on MRI are associated with the onset of FBDSs.…”

“…To date, only a few cases of anti‐LGI1 encephalitis with isolated psychiatric symptoms in the initial phase have been reported 6–8 . Porpiglia et al reported a case of a 70‐year‐old man who presented with isolated psychiatric symptoms, such as severe insomnia, hyperactivity, euphoria, and disinhibition, for 2 years and was diagnosed with mania 6 .…”

“…Approximately 70% of patients with anti‐NMDA receptor encephalitis present with psychiatric symptoms, such as agitation and psychosis, at the time of initial diagnosis, 4 and approximately 4% of patients reportedly develop isolated psychiatric symptoms in the initial phase 5 . With regard to anti‐LGI1 encephalitis, there are only a few reports of isolated psychiatric symptoms in the initial phase 6–8 …”