Optic nerve projections in patients with primary ciliary dyskinesia
Recently, it has been suggested that misprojections of the temporal retina to the contralateral hemisphere might not be specific for patients with albinism and might also be associated with the Kartagener syndrome (i.e., with situs inversus totalis in the presence of primary ciliary dyskinesia [PCD]). The authors tested whether such projection abnormalities are associated with PCD and situs inversus. In 10 patients with PCD (five with situs inversus totalis) and in 10 age- and sex-matched controls, visual evoked potentials (VEPs) were recorded monocularly, as follows: conventional pattern-onset VEPs (cVEPs) and multifocal VEPs (mfVEPs) for 60 locations constituting a visual field of 44° diameter. cVEPs from 13 albinotic subjects were included as a reference. For each eye, interhemispheric difference potentials were calculated and correlated with each other to assess the lateralization of the responses: positive and negative correlation coefficients indicated lateralizations on same or opposite hemispheres, respectively. Misrouted optic nerves are expected to yield negative interocular correlations. For both cVEPs and mfVEPs, the distribution of the correlation coefficients in the PCD patients yielded largely positive values and did not differ from that of the controls. Consequently, neither large- nor small-scale lateralization abnormalities were observed in PCD. Further, the optic nerve projection did not depend on the presence of situs inversus. The absence of evidence for projection abnormalities in a cohort of 10 subjects with PCD, five of whom had Kartagener syndrome, underscores that misrouting of the optic nerves is not a common trait of these subjects.