Supplementary Material for: External laryngeal tremor in adult-onset Alexander disease

Introduction. Alexander disease is caused by mutations in GFAP, the glial fibrillary acidic protein gene. External laryngeal tremor has not been reported in adult-onset Alexander disease (AOAxD). The aims of this work were to report one such case, and to review the literature on palatolaryngeal tremor and AOAxD.
Case presentation. A 43-year-old man experienced involuntary movements at the front of his neck. Continuous, rhythmic vertical movements of the laryngeal skeleton, soft palate and tongue, and lower-limb dysmetria, were observed. The pathogenic GFAP variant, c.994G>A; p.(Glu332Lys) was found. MRI demonstrated spinal cord and medulla oblongata atrophy, and hyperintensities at the cerebellum and cerebral white matter.
Conclusion. External laryngeal and palatopharyngeal tremor, and cerebellar ataxia, constituted a mild phenotype as expected from this variant, herein reported in isolation for the third time. Imaging was consistent with AOAxD, including the so-called tadpole sign. Additional studies are necessary to define this infrequent disease.