Diagnosing children presenting with asymmetric pendular nystagmus.

Horizontal asymmetric nystagmus usually occurs in one of three situations: secondary to an intracranial lesion, with monocular visual loss, or as part of the triad that constitutes the diagnosis of spasmus nutans (asymmetric nystagmus, abnormal head posture, head shake). Clinical records of 277 children, presenting with congenital nystagmus over an 8-year period were reviewed. Nystagmus was asymmetric in 24 of 277 cases. Seven of these patients were diagnosed with spasmus nutans. This is a rare condition that is only diagnosed retrospectively based on the absence of any abnormal neuroimaging or electrophysiological findings. Twelve of 24 patients had intracranial pathology and all had abnormal visual evoked potentials (VEPs). Five patients were diagnosed with congenital sensory defect nystagmus including one with albinism, three with congenital cone dysfunction, and one with cone-rod dystrophy. This paper stresses that although neuroimaging is necessary in all patients presenting with asymmetric nystagmus, such nystagmus can also occur with retinal disease or albinism and indicates the importance of non-invasive VEP/ERG testing in all forms of nystagmus.