Congenital sixth nerve palsy or Type I Duane syndrome?

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92 Oman Journal of Ophthalmology, Vol. 4, No. 2, 2011
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Dr. Siddharth Agrawal, B/3, Kapoorthala Bagh, Kursi Road, Lucknow – 226 024, India. E-mail: agrawalsiddharth@rediffmail.com
Copyright:  2011 Agrawal S, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which
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DOI:
10.4103/0974-620X.83663
Congenital sixth nerve palsy or Type I Duane syndrome?
Siddharth Agrawal, Vinita Singh, Saurabh Agrawal1
Department of Ophthalmology, CSM Medical University (Upgraded KG’s Medical College), Lucknow – 226 003,
1Sukriti Eye Clinic, Lucknow, India
Duane Syndrome (DS) in its classic form is characterized by
congenital onset limitation of horizontal eye movements with
globe retraction and narrowing of palpebral fissure (PF) on
adduction.[1] Despite significant limitation of horizontal ocular
motility, the ocular deviation in primary position is lesser than
would occur in muscle palsies.[1] Upshoot or downshoot in
adduction is commonly associated.[1] A congenital sixth nerve
or congenital lateral rectus (LR) palsy is rare and may be related
to birth trauma.[2] The title of a Souza-Dias publication stated:
“Congenital VIth nerve is Duane’s Syndrome until disproven”, and
it also reflects the rarity of congenital sixth nerve paresis.[3,4] Here,
we present a case of an adolescent, with a congenital sixth nerve
palsy presenting as Type I DS.[5] To our knowledge, a similar case
has not been reported in literature (Medline search). Our patient
was successfully managed with a single muscle surgery.
A 13-year-old girl presented to us with convergent strabismus in
right eye (RE) since birth. Ante, peri and postnatal history were
normal. There was no history of trauma or prior treatment for
the strabismus. Old family photographs showed right esotropia
(RET). The general and systemic examinations were essentially
normal. Ocular examination revealed a visual acuity of 3/60 and
N 36 in right eye which was not improving. Visual acuity in left
eye was 6/6 and N 6. Refraction revealed +2 D of against the rule
(ATR) HM astigmatism in RE. Prism cover test revealed an RET
of 70 PD with a narrow PF RE in primary position. There was
marked limitation of abduction of RE with widening of the PF on
abduction. Adduction of RE was slightly limited with upshoot and
further narrowing of PF. The esotropia had a “V” pattern of 20 PD.
There was no compensatory head posture [Figure 1]. There were
no binocular functions on Worth Four Dot and Randot Stereo
acuity Tests. Forced duction testing revealed a tight medial rectus
RE. The patient underwent 5 mm recession of right medial rectus
(MR) by conjunctival limbal approach and standard technique.[6]
A very tight MR muscle was encountered intraoperatively with
thin blue sclera under MR muscle. The patient was followed up on
day 1, 7, 14 and 60 postoperatively. Postoperative examinations
revealed RET of 10 PD in primary position. Ocular movements
showed no change in abduction. Compared to preoperative
adduction movement, a greater decrease in RE was noted. The
abnormality in PF size in different gazes including the primary
position had reduced markedly. The residual V pattern was of 12
PD. The patient was satisfied with the cosmesis [Figures 2 and 3].
An esotropic DS is more common than a congenital sixth nerve
palsy. The findings of ET in primary position with restricted
abduction and associated narrowing of PF in adduction in our
patient are consistent with Type I DS.[1,5] Slight limitation of
adduction with upshoot is also found in DS.[1,3] However, the
primary position ET is relatively small in DS (less than 30 PD)
compared to LR pasly or paresis.[7]
Although widening of PF in abduction is typical of DS,[1,3] PF
narrowing is not a very dependable diagnostic sign of mild to
moderate DS[3] as narrowing of the PF on adduction is usually
interpreted as a passive adjustment of the lids to retracting globe.[1]
Our patient was diagnosed as a case of congenital sixth nerve palsy,
with ocular motility, PF abnormalities, and forced duction test
results mimicking Type I DS. The nature of abduction in upgaze
to downgaze of LR palsy is a V pattern, compared with the curved
outward rotation (X pattern) uniquely characteristic of DS[8]
[Figure 4]. The presence of V pattern in our patient and absence
of anomalous LR innervations in upgaze and downgaze points
toward an LR palsy rather than a DS. The alteration in PF size can
be explained by a secondary contracture of RMR muscle due to
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Oman Journal of Ophthalmology, Vol. 4, No. 2, 2011 93
Agrawal, et al.: Congenital VI nerve or duane?
Figure 2:Postoperativephotographs.Notethecorrectionofdeviationinprimaryposition,correctionof“V”pattern
Figure 4: Diagrammatic representation of ocular deviation in dextroelevation,
dextroversionanddextrodepressioninthepresenceof(a)DuaneSyndrome(b)infantile
esotropiaand(c)congenitalsixth nervepalsyintherighteye.Notethe“X”patternof
deviationin(a),astraightline(noincomitance)in(b)and“V”patternin(c).An“A”or
“V”patternmaybeseenininfantileesotropia,butitisnotapparentwhentheinvolved
eyeisinabduction
Figure 1:Preoperativephotographs.Notethepalpebralssureabnormalityand“V”patternofesodevation
Figure 3:Preoperative (on left)and postoperative (onright) photographs inprimary
position.Notethecorrectionofpalpebralssureabnormality
b
a c
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94 Oman Journal of Ophthalmology, Vol. 4, No. 2, 2011
Agrawal, et al.: Congenital VI nerve or duane?
a longstanding LR palsy.[3] The tight MR would cause retraction
of the globe on adduction with consequent narrowing of PF. It
also explains the marginally limited adduction and upshoot.[3]
MR would relax in abduction, hence the apparent PF widening.
The correction of PF abnormality and limitation of adduction
postoperatively also support the presence of a fibrotic MR muscle.
The presence of thin blue sclera under MR confirms the direction
of MR pressure indentation.[3] On the other hand, MR in children
with DS does not exhibit excessive stiffness or contracture in the
primary zone, that is, it is normal.[9]
Infantile esotropia also forms a differential diagnosis of this
presentation, but it usually has full ductions. A diagnosis of
congenital LR palsy with tight MR was made on the basis of the
above features.
The collapse of V pattern can be attributed to correction of
deviation in primary position. A V pattern of up to 15 PD (residual
V of 12 PD in our patient) is considered physiological.[10] On
further retrospection, correction of such a large esodeviation in
DS would have required a more aggressive surgery like
asymmetric MR recessions or transpositions of the SR/IR muscles
temporally.[11-14] We could have probably avoided the postoperative
adduction deficit in MR by reducing the amount of MR recession
or by putting the tight muscle on hang back sutures.
References
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12. Laby DM, Rosenbaum AL. Adjustable vertical rectus muscle transposition
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rectus muscle paths by magnetic resonance imaging. Ophthalmology
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14. Molarte AB, Rosenbaum AL. Vertical rectus muscle transposition for
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Cite this article as: Agrawal S, Singh V, Agrawal S. Congenital sixth nerve
palsy or Type I Duane syndrome?. Oman J Ophthalmol 2011;4:92-4.
Source of Support: Nil, Conict of Interest: None declared.
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