Periodic alternating gaze deviation associated with schizencephaly and optic nerve hypoplasia

Abstract

A 3-year-old girl presented with alternating horizontal gaze deviations lasting 20 to 30 seconds interspersed with brief 5- to 10-second periods of normal ocular motility. She had schizencephaly and optic nerve hypoplasia. This is the first case description of the entity of periodic alternating gaze deviation with these disorders. CASE REPORT A 3-year-old girl was referred for visual evaluation because of trouble following objects. Her mother stated that she could not remember ever taking a picture of her daughter when her eyes were aligned in the primary position. She noted that they were consistently directed in either right gaze or left gaze. She was diagnosed with schizencephaly by prenatal ultrasound and postnatal magnetic resonance imaging. She was severely delayed physically and cognitively and she could not walk without assistance. She was the product of an uncomplicated Cesarean delivery. Medications included polyethylene glycol for constipation and levothyroxine for hypothyroidism. Family history was unremarkable. There was no history of seizures. The examination showed difficulty fixating and following especially when the eyes were deviated in eccentric gaze. She blinked to threat only from her left visual field and mostly when her eyes were moving between either eccentric positions of gaze. Extraocular motility showed full conjugate eye movements without strabismus. Her eyes appeared forced into either extreme right or left gaze and this would last 20 to 30 seconds before they would drift to primary position for 5 to 10 seconds and then move into the opposite eccentric horizontal eye position. The eyes never deviated up or down. During the periods of eccentric gaze, she would turn her head in a contraversive manner to maintain fixation at objects in front of her. In the interictal period, she would manifest some nystagmus that beat either to the left or to the right, whichever direction that the eyes were pointing. This appeared similar to end-gaze nystagmus. During these interictal periods, she would have normal optokinetic and vestibular responses, but not during the gaze deviations when there were no responses. Eyelids were normal and face was symmetric with good eyelid closure. There was no proptosis present clinically. Pupils were equal and briskly reactive, but there was a left afferent pupillary defect. Ocular media were clear OU. Funduscopy revealed bilaterally hypoplastic nerves without pallor (Figure 1). She was alert and had minimal speech output, and muscle tone was normal throughout. Orthotics were in place on her lower extremities. Her MRI scan demonstrated a large left lateral ventricle that communicated with a subarachnoid space through the posterior parietal lobe (Figure 2). There was ectopic gray matter lining the ventricle.