Objective: To analyze whether the presence of the abducens nerve might depend upon the type of Duane's retraction syndrome (DRS).
Design: Observational case series.
Participants: Sixteen patients with type 1 DRS, 2 patients with type 2 DRS, and 5 patients with type 3 DRS.
Methods: Ophthalmologic examination and thin-sectioned magnetic resonance imaging (MRI) at the brain stem level were performed in 23 DRS patients. To confirm the accuracy of the procedure, we compared the results obtained with those of a control group of 30 individuals using the same technique.
Main outcome measures: Examination of ductions and versions and the presence of the abducens nerve on MRI.
Results: The abducens nerve on the affected side could not be observed using MRI in 18 (100%) of 18 eyes (16 patients) with type 1 DRS and in 3 of 5 eyes with type 3 DRS. Conversely, the abducens nerve was observed in 2 of 2 eyes with type 2 DRS and 2 of 5 eyes with type 3 DRS. The abducens nerve was observed in 60 (100%) of 60 eyes screened as controls.
Conclusions: The abducens nerve on the affected side was absent in type 1 DRS patients and some type 3 DRS patients, but present in type 2 DRS patients as well as in some type 3 DRS patients. In terms of the presence or absence of the abducens nerve, type 1 and type 2 DRS were homogenous, and type 3 DRS was heterogenous.