Neurodevelopmental criteria in the classification of congenital motor nystagmus.

Congenital motor nystagmus (CMN) can be familial or non-familial. The expressivity of CMN is so variable that in one affected member of the family the oscillations are obvious, while in the others the nystagmus could be overlooked even by the patients themselves. In spontaneous cases the proof of heredity might be discovered by an ophthalmological examination or eye movement recordings of other family members. Our multidisciplinary studies of 27 children with CMN suggests that a neurodevelopmental assessment can also be valuable in establishing a diagnosis of heredity. Our studies suggest that the hereditary form of CMN is free from neurodevelopmental problems, while the non-familial form is not. Therefore, children with spontaneous CMN could be referred for neurodevelopmental evaluation in order to establish a more accurate diagnosis.