Trigeminal Nerve Involvement
Anti-IgLON5 disease (IgLON5-D) is a progressive-onset autoimmune neurologic disorder characterized by the variable association of parasomnia, sleep apnea, bulbar symptoms, gait abnormalities, cognitive decline, and chorea, combined with serum and/or CSF anti-IgLON5 autoantibodies (IgLON5-Abs). Although brain autopsy may not reveal inflammatory infiltrates, in vitro and in vivo animal experiments suggest a potentially direct pathogenicity of IgLON5-Abs, and the strong association with the human leukocyte antigen (HLA) system (DRB1*1001 and DQB1*0501) suggests an immune-mediated process. Recently, several cohorts and case series have enlarged the spectrum of IgLON5-D, helping to better recognize their various phenotypes. Among them, a bulbar-onset motor neuron disease (MND)–like phenotype, mimicking MND, has been described. The differential diagnosis with diseases, such as bulbar-onset amyotrophic lateral sclerosis (ALS), is crucial, as IgLON5-D may require prompt immunotherapy and may rely on the identification of other signs of brainstem involvement. When bulbar symptoms are prominent, clinical and paraclinical clues should thus be carefully assessed. In this article, we describe 2 cases of bulbar-onset IgLON5-D with clinical, electrophysiologic, and MRI evidence of trigeminal nerve involvement.
