Infantile nystagmus without overt eye abnormality: Early features and neuro‐ophthalmological diagnosis.

Neurological nystagmus Of the 142 patients, 33 (23%) were included in the subgroup with neurological nystagmus; the neurological diagnoses are summarized in Figure 1. The neurological examination performed within 6 months from nystagmus onset was abnormal in all infants except two patients (patient 13 and patient 15 see Table S1), both having transient isolated pontine tegmental hyperintensity at MRI,15 and substantially normal neurological examination at 1 year and 6 years follow-up. Abbreviations IIN Idiopathic infantile nystagmus MNSN Mixed neurological and sensory nystagmus OCT Optical coherence tomography SDN Sensory defect nystagmus VEP Visual evoked potential Nystagmus was defined by the child neurologist Jean Aicardì in his seminal book of paediatric neurology as 'an involuntary, rhythmical, conjugate oscillatory movement of the eyes, due to dysfunction of the complex mechanisms that maintain ocular fixation'.1 The fixation reflex that maintains the visual target centred in the fovea requires fronto-nigral-collicular circuits and depends upon the motion detection (magnocellular) portion of the visual system.2 Early in life these anatomo-functional systems are in their crucial developmental period; as these are driven by sensory input, they are consequently vulnerable to prechiasmal visual disorders. However, in infancy the most frequent aetiology of nystagmus is eye or anterior visual pathways disorder allowing for SDN.5,6 Infantile nystagmus without major ocular signs thus create a diagnostic challenge for the child neurologist. [Extracted from the article]