An uncommon case of horizontal Gaze Palsy with scoliosis and associated brain-stem anomaly (HGPPS)

HGPPS is a rare congenital disorder resulting from cranial nuclear maldevelopment and characterized by absence of conjugate horizontal eye movements, preservation of vertical gaze & convergence, progressive scoliosis developing in childhood and hypoplasia of dorsomedial brainstem structures associated with sagittal cleft of pons and medulla. We present a 19 years old male, with restriction of eye movements, reduced visual acuity & had clinical and imaging findings of HGPPS. The patient revealed bilateral horizontal gaze palsy with normal vertical eye movements and normal convergence. Best corrected visual acuity was 6/24 in right eye & 6/36 in left eye.PA view X-ray spine show thoraco-lumbar scoliotic deformity. MRI revealed split pons sign associated with hypoplasia of pons & medulla. Hypoplasia of the dorsomedial brainstem structures leads to defect of the abducens nucleus and MLF which leads to horizontal gaze palsy whereas scoliosis could be due to chronic muscle tone abnormalities resulting from primary brainstem anomaly.