Proprioceptive Stimuli as a Trigger for Leucine-Rich Glioma-Inactivated-1 (LGI1) IgG Associated Autoimmune Seizures, a Case Report

Leucine-rich glioma-inactivated-1 (LGI1) IgG-associated autoimmune encephalitis typically presents with faciobrachial dystonic seizures, hyponatremia, and temporal lobe MRI abnormalities. However, the clinical spectrum of LGI1 IgG-associated AE extends beyond these classical features, with reports of diverse seizure semiologies and atypical presentations challenging traditional diagnostic paradigms. This study reports a male in his late 60s presenting with recurrent episodes of right foot cramping and electric shock-like pain, progressing to generalized tonic-clonic seizures. Initial workup suggested chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), but LGI1 IgG antibodies were subsequently detected. Despite treatment with intravenous immunoglobulin (IVIG), the seizures persisted. This case highlights the heterogeneity in LGI1 encephalitis presentations. The patient's proprioceptive-induced reflex seizures represent a rare manifestation of the disease. Treatment with rituximab, a B-cell depleting therapy, resulted in significant improvement, suggesting its potential effectiveness in LGI1 encephalitis with a resistant seizure course. The case also emphasizes the intricate interplay between the mesial temporal lobe, basal ganglia, and frontal regions in LGI1 encephalitis pathophysiology.