Abstract
Background/Objectives Leucine-rich glioma-inactivated 1 antibody (LGI1-IgG) encephalitis is a rare disorder classically associated with facio-brachial dystonic seizures (FBDS), but with protean clinical manifestations.
Methods This case report details an atypical presentation of LGI1-IgG encephalitis.
Results An 81-year-old female presented with six months of progressive abulia and executive dysfunction. Her primary complaint was "lip and tongue swelling". There was no history of seizure (including FBDS), sleep disturbance or neuromyotonia.
Initial neurological examination demonstrated tonic partial protrusion of the tongue secondary to lingual dystonia, higher-order gait dysfunction, adynamic aphasia, and frontal-predominant dysexecutive syndrome on Addenbrooke Cognitive Examination.
The left medial temporal lobe demonstrated asymmetric MR T2 hyperintensity and marked FDG-PET hypermetabolism consistent with limbic encephalitis.
She had euvolaemic hyponatremia. CSF was acellular with oligoclonal bands that were equally prominent in serum. EEG showed mild, intermittent slowing over the left temporal region, without epileptiform activity. LGI1-IgG was positive by cell-based assay in serum and CSF. She responded to methylprednisolone and rituximab, with modest improvement in cognition and abulia on serial examination. Whole body PET scan was not suggestive of a paraneoplastic syndrome.
Conclusion This case highlights an atypical presentation of LGI1-IgG encephalitis. Rapidly progressive cognitive impairment, especially accompanied by unexpected neurological features such as movement disorders or seizures, should prompt comprehensive neuroimmunological testing for autoimmune encephalitis. Accurate diagnosis is crucial to facilitate timely and potentially life-saving immunotherapy.
