Radiological features of horizontal gaze palsy with progressive scoliosis. An 'Aunt Minnie' diagnosis?

Horizontal gaze palsy with progressive scoliosis (HGPPS) is a rare autosomal recessive disorder characterized by congenital absence of normal horizontal eye movements and progressive scoliosis through childhood and adolescence. The characteristic radiological features in HGPPS are butterfly configuration of the medulla, split pons sign, selective volume loss of dorsomedial brainstem, relatively spared cerebellum, relatively prominent inferior olivary nucleus and absent posterior prominence of the facial colliculi and gracilis and cuneate nuclei. These radiological features are reflective of ROBO3 gene mutation required for hindbrain axon midline crossing. Awareness of this diagnosis is important as the radiological features are characteristic enough to be considered as a rare 'Aunt Minnie' and a radiologist may be the first one to raise the possibility of this diagnosis as in this case.