Sir,

Duane's retraction syndrome (DRS) is a congenital abduction deficit of the eyeball accompanied by retraction of the globe on attempted adduction, and by upshoots or downshoots of the affected eye on adduction.1 However, these characteristic diagnostic signs of DRS may not be manifested in some patients, particularly in children2 and thus magnetic resonance (MR) imaging has been utilized for the diagnosis of DRS.3 Absence of the abducens nerves documented by MR imaging in familial DRS has not been reported.

Case report

A 30-year-old man (Case 1) was referred for the evaluation of horizontal limitation of eye movement since birth. He had esophoria of 12 prism dioptres in primary position. Abduction was completely absent in both eyes. He showed mild retraction of the globe, but did not show typical upshoots or downshoots of either eye on attempted adduction (Figure 1a). His corrected visual acuity was 20/20 in both eyes. He had a myopic astigmatism of −0.75 Dsph (Diopter in sphere) −1.00 Dcyl × 10 A in the right eye and −1.00 Dsph −1.00 Dcyl × 170 A in the left eye. He recognized 3 out of 10 circles (140 s of arc) of Randot stereotest (Stere Optical Co, Inc., Chicago, IL, USA). MR imaging was conducted in axial plane to visualize the cisternal segment of the abducens nerve using a thin-section gradient-echo T2-weighted imaging with a voxel size of 0.43 × 0.43 × 0.7 mm. Bilateral abducens nerves were absent (Figure 1b and c), contrary to the clearly delineated bilateral abducens nerves in a normal adult (Figure 1d and e).

Figure 1
figure 1

Duane's retraction syndrome type 1 in Cases 1–3. (a) In Case 1, ocular versions demonstrate bilateral abduction deficit and a small degree of narrowing of the lid fissure on adduction in both eyes. (b, c) In Case 1, right and left abducens nerves are not identified on the two axial magnetic resonance (MR) images obtained at the level of the pontomedullary junction. (d, e) Note normal abducens nerves in a normal adult. Two axial MR images show the path of the right and left abducens nerves (arrows), as linear dark structures emerging from the pontomedullary sulcus (d), coursing in the superior oblique direction toward the clivus (e). (f–i) In Case 2 (f, g) and Case 3 (h, i), right and left abducens nerves are not identified as in Case 1.

Full size image

A 34-month-old boy (Case 2) and a 5-month-old girl (Case 3) were referred for the evaluation of horizontal limitation of eye movement since birth. They had complete limitation of abductions in both eyes. They showed no retraction of the globe or upshoots or downshoots of either eye on attempted adduction. Abductions were completely limited in both eyes. They fixed and followed a 5-inch object near to either eye. They had orthotropia in the primary position with increasing esotropia in the right or left gaze. Cycloplegic refraction showed a hyperopic astigmatism of +1.75 Dsph −0.75 Dcyl × 90 A in the right eye and +1.25 Dsph −0.50 Dcyl × 90 A in the left eye in Case 2, and of +1.75 Dsph −0.25 Dcyl × 180 A in both eyes in Case 3. Case 2 only recognized Randot forms (250 arc sec) with Randot stereotest. On thin-section MR images, bilateral abducens nerves were absent (Figure 1f–i).

Comment

This study reports bilateral DRS of three family members. MR imaging documentation of familial DRS has not been described. The right and left abducens nerves were not identified in all three affected family members. Even though they did not show all the typical signs of DRS, however, on the basis of the MR findings of the previous reports,4, 5, 6 this family probably had a variant of DRS.

In conclusion, we describe familial DRS of three patients in whom the abducens nerves were absent bilaterally. MR imaging was useful for the differential diagnosis of abduction deficit in familial cases.