Horizontal Gaze Palsy, Scoliosis, and Split Pons Sign in a 6-Year-Old Girl

Photo and Video Essay Section Editors: Melissa W. Ko, MD Dean M. Cestari, MD Peter Quiros, MD Horizontal Gaze Palsy, Scoliosis, and Split Pons Sign in a 6-Year-Old Girl Bhanudeep Singanamalla, MD, Shweta Chaurasia, MS, Chirag Jain, DM, Vikas Bhatia, DM, Neeraj Sharma, MD, Priyanka Madaan, DM, Nirmal Raj Gopinathan, MS, Lokesh Saini, DM FIG. 1. Horizontal gaze palsy and scoliosis of the index child. Gaze photograph showing primary position orthotropia (A) with limited adduction and abduction both eyes in levoversion and dextroversion (B, C) and normal elevation and depression (D, E); MRI of spine showing scoliosis (F). Abstract: A 6-year-old girl presented with complaints of absent horizontal eye movements since birth. There was also associated progressive scoliosis for past 1 year. Neuroimaging revealed split pons sign, butterfly-shaped medulla, and prominent inferior olivary nuclei. The presence of congenital horizontal gaze palsy, childhood onset progressive scoliosis, and abnormal neuroimaging findings confirmed the diagnosis of horizontal gaze palsy with progressive scoliosis. This case highlights the importance of neuroimaging in a child presenting with horizontal gaze palsy and scoliosis that helped for starting early rehabilitation of the child, prevention of Pediatric Neurology Unit (BS, PM, LS), Department of Pediatrics, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India; Department of Ophthalmology (SC), Advanced Eye Centre, PGIMER, Chandigarh, India; Department of Neuroradiology (CJ, VB, NS), PGIMER, Chandigarh, India; Council of Scientific and Industrial Research (PM), CSIR Complex, Library Avenue, Pusa, New Delhi; and Department of Orthopedics (NRG), PGIMER, Chandigarh, India. The authors report no conflicts of interest. C. Jain, V. Bhatia, and N. Sharma: analyzed the radiological investigations of the study; S. Chaurasia, P. Madaan, N. R. Gopinathan, and L. Saini: critically acclaimed the draft and provided intellectual content of the study. Address correspondence to Lokesh Saini, DM, Pediatric Neurology Division, Department of Pediatrics, Advanced Pediatric Centre, Post Graduate Institute of Medical Education and Research, Chandigarh, India; E-mail: [e-mail] Singanamalla et al: J Neuro-Ophthalmol 2021; 41: e237-e238 permanent vision loss, and parental counseling for future pregnancies. Journal of Neuro-Ophthalmology 2021;41:e237–238 doi: 10.1097/WNO.0000000000001131 © 2020 by North American Neuro-Ophthalmology Society A 6-year-old girl, first born to third-degree consanguineously married couple, presented with complaints of limited horizontal eye movements since birth and vision difficulty, which was noticed by teacher 1 month back when the child started going school. There was also a history of progressive lateral bending of spine noticed by the parents for past 1 year. The vertical eye movements were preserved, and there was no history of deviation of eyes, diplopia, drooping of eyelids, and fluctuation of symptoms. There was no history of similar complaints in the family. Ophthalmological examination revealed bilateral ametropic amblyopia with a best-corrected visual acuity of 6/ 18 (with 24D cylindrical power at 180°) and normal anterior and posterior segment examination. Oculomotility examination revealed complete limitation of horizontal gaze (absent saccades) but preserved elevation, depression, and convergence. Corneal sensations were present bilaterally. The Bell phenomenon was good, and there was no lagophthalmos. Cranial nerve examination of seventh and eighth nerve was normal, and there was e237 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Photo and Video Essay FIG. 2. MRI of brain of the index child. A T2 axial image showing midline deep clefting at dorsal aspect of pons (split pons sign) (A), loss of bulging of facial colliculi at a lower level (B), butterfly configuration of medulla at medulla (C), mid T1MPRAGE sagittal MRI sequence showing atrophic changes in pons (D), placement of Region of Interest at bilateral corticospinal tract with fiber tractography showing nondecussation of bilateral CST (E), and tractography with seeds at bilateral inferior cerebellar peduncles showing atrophy of bilateral inferior cerebellar peduncles (F). CST, corticospinal tract. presence of scoliosis (Fig. 1). Neuroimaging revealed split pons sign with absent facial colliculi, butterfly-shaped medulla, and prominent inferior olivary nuclei (Fig. 2). The presence of horizontal gaze palsy, progressive scoliosis, and classical neuroimaging findings clinched the diagnosis. Horizontal gaze palsy with progressive scoliosis syndrome (HGPSS) is a rare congenital autosomal recessive disorder caused by the loss-of-function mutations in both the alleles of ROBO3 gene on chromosome 11q23-q25. This gene helps in the hindbrain axonal midline crossing of corticospinal and somatosensory tracts (1). Hence, mutations in the ROBO gene are associated with noncrossing of selected axonal paths in the brain. In addition to the horizontal palsy, these children have nystagmus, ametropia, scoliosis, and amblyopia (2). Horizontal gaze palsy is due to failure of decussation of aberrant supranuclear inputs from pontine reticular formation and median longitudinal fasciculus (1,2). Differential diagnosis of early onset bilateral horizontal gaze palsy includes Duane syndrome Type III, interruption of parapontine reticular formation, medial longitudinal fasciculus and abducens nucleus, and Moebius syndrome. Moebius syndrome has been associated with facial weakness, chest wall abnormalities (absence of pectoralis muscle), limb abnormalities (club feet), and corneal erosions. The scoliosis can be detected as early as few months of life with no underlying pathology of muscle, spinal cord, or spine detected. The mechanism of scoliosis is still unclear, not linked to ROBO3 mutations, and probably due to abnormality of cell groups that control axial posture. MRI of brain reveals anterior and posterior midline pontine clefts (split pons sign), anterior cleft at medulla with anteriorly flattened medulla (butterfly-shaped medulla), lack of protrusion of facial colliculi into fourth e238 ventricle, and prominent inferior olivary nuclei. Diffusion tensor imaging maps reveal the absence of decussating pontocerebellar fibers and superior cerebellar peduncles (3). Early diagnosis of horizontal gaze palsy with progressive scoliosis syndrome is crucial to prevent permanent vision loss and also for parent’s genetic counseling. Despite the lack of genetics, the clinicradiologic picture gives us the clue for the diagnosis. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: L. Saini, S. Chaurasia, N. Raj Gopinathan, and V. Bhatia; b. Acquisition of data: B. Singanamalla, C. Jain, N. Sharma; c. Analysis and interpretation of data: P. Madaan. Category 2: a. Drafting the manuscript: B. Singanamalla; b. Revising it for intellectual content: L. Saini. Category 3: a. Final approval of the completed manuscript: L. Saini. ACKNOWLEDGMENTS The authors thank the parents for the pictures of the child and adding to the literature. REFERENCES 1. Yang HK, Choi JY, Park KS, Kim JH, Hwang JM. Teaching Video NeuroImages: horizontal gaze palsy with progressive scoliosis. Neurology. 2019;92:e886–e887. 2. Lin CW, Lo CP, Tu MC. Horizontal gaze palsy with progressive scoliosis: a case report with magnetic resonance tractography and electrophysiological study. BMC Neurol. 2018;18:75. 3. Shalini P, Shah VM. Horizontal gaze palsy with progressive scoliosis - a case report. Indian J Radiol Imaging. 2017;27:290– 292. Singanamalla et al: J Neuro-Ophthalmol 2021; 41: e237-e238 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited.