title: Nightblindness-associated transient tonic downgaze (NATTD) in infant boys with chin-up head posture.
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.
authors.affiliation: Molecular Ophthalmogenetics, Netherlands Institute for Neuroscience, Amsterdam. simonsz@compuserve.com
authors.forename: H J
authors.initials: HJ
authors.lastname: Simonsz
authors.forename: R J
authors.initials: RJ
authors.lastname: Florijn
authors.forename: H M
authors.initials: HM
authors.lastname: van Minderhout
authors.forename: A A B
authors.initials: AA
authors.lastname: Bergen
authors.forename: M
authors.initials: M
authors.lastname: Kamermans
mesh_terms: D002648:Child; D002675:Child, Preschool; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D009755:Night Blindness / Q000151:congenital / Q000503:physiopathology*; D012438:Saccades / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*