Isolated Horizontal Gaze Palsy With Congenital Pontine Hypoplasia

Abstract

We read with great interest the article by Connors et al. (1) published in the Journal on the “16 syndrome.” The authors described an interesting eye movement pattern characterized by bilateral limitation of horizontal eye movements and bilateral facial nerve palsies that was caused by an acquired disorder of the pontine tegmentum. We evaluated a patient with bilateral horizontal gaze palsies due to a congenital abnormality of the central nervous system. An 11-year-old boy was referred to our clinic for evaluation of eye movements. Visual acuity was 20/20 in each eye. There was no abnormal head posture and the eyes were orthophoric in primary position. Ocular movements showed a bilateral horizontal gaze palsy with normal vertical eye movements. Horizontal movements could not be elicited with the Doll's head maneuver and horizontal saccades and pursuit movements were absent. Convergence to a near target was normal (see Supplemental Digital Content, Video, https://links.lww.com/WNO/A76). Forced duction testing was negative and the remainder of the ocular examination was unremarkable. Brain magnetic resonance imaging (MRI) revealed hypoplasia of the dorsal pons with a midsagittal cleft extending ventrally from the floor of the fourth ventricle (Fig. 1). The facial colliculi were absent and there was mild atrophy of the midbrain and medulla.FIG. 1: A. T2 axial magnetic resonance imaging (MRI) demonstrates a midsagittal cleft (arrow) producing “split pons sign.” B. T1 sagittal MRI shows pontine hypoplasia with abnormal appearance of the floor of the fourth ventricle.A variety of congenital disorders of the pons have been reported with horizontal gaze palsy. These include Moebius syndrome (2), associated with synergetic convergence (3) and with scoliosis (4,5). The clinical findings of scoliosis appear to require atrophy of the medulla ("butterfly" configuration on MRI), which was not present in our case.