Nightblindness-Associated Transient Tonic Downgaze (NATTD) in Infant Boys with Chin-Up Head Posture

H. J. Simonsz, R. J. Florijn, H. M. van Minderhout, A. A. B. Bergen, M. Kamermans

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Abstract

Eleven infant boys presented with chin-up head posture, tonic downgaze and, on attempted upgaze, large-amplitude upward saccades with deceleration during the slow phase downward. The gaze-evoked upward saccades disappeared at the age of 2 or 3 years. In addition, they had high-frequency, small-amplitude horizontal pendular nystagmus that remained. Among these infant boys were 2 pairs of maternally related half-brothers, 2 cousins, and 2 siblings. Visual acuity ranged from 0.1 to 0.6, ERG-amplitudes (both A- and B-wave) were reduced, and severe myopia was found in 5 cases. Eight boys had CACNA1F mutations, and 1 boy had a NYX mutation, compatible with incomplete or complete congenital stationary nightblindness (iCSNB or cCSNB), respectively. This points to a defective synapse between the rod and the ON-bipolar cell causing the motility disorder: CACNA1F is located on the rod side of this synapse, whereas NYX is located on the side of the ON-bipolar cell. The coexistence of horizontal and vertical nystagmus has been previously described in dark-reared cats
Original languageEnglish
Pages (from-to)158-164
JournalStrabismus
Volume17
Issue number4
DOIs
Publication statusPublished - 2009

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