Extrapyramidal Involvement as a Manifestation of ROBO3 Mutation in HGPPS: A Case Report and Review of Literatures

Abstract

HGPPS (horizontal gaze palsy with progressive scoliosis) presents in early childhood ages and one of the cardinal manifestations of the syndrome, progressive scoliosis, is the main disabling feature which usually seeks for orthopedic correction surgeries in early years. Nevertheless, the presence of scoliosis has not been explained yet by the pathogenesis of the disease, the ROBO3 mutation, which is a well-known pathology for gaze palsy by failure of axonal decussation toward the pontomedullary junction. This article highlights a novel case of HGPPS with prominent extrapyramidal findings including torticollis, cervical dystonia and facial spasm along with classic clinical, imaging and genetic correlation. Aiming to investigate the prevalence of extrapyramidal signs in this syndrome, the published cases of HGPPS in the literature have been reviewed in this study. 32% of all HGPPS cases between years of 1975 to 2020 founded to have one or more extrapyramidal features and the dystonia was the most reported sign which even proceed to the presence of scoliosis. Regarding to the fact that the scoliosis could be as a consequence of axial dystonia, its relationship to ROBO3 mutation can be explained by structural and functional changes toward the brainstem and cerebellum, which are involved in this syndrome and known to contribute with the extrapyramidal system. Knowing this possibility, not only could solve the 35-year mystery of scoliosis in the syndrome, but also would be considered as a target of treatment to prevent scoliosis in the future.