Duane
Syndrome in its classic form is characterized by
congenital onset limitation of eye movements
with globe retraction and narrowing of palpebral
fissure on adduction. Despite significant
limitation of horizontal ocular motility, the
ocular deviation in primary position is lesser
than would occur in muscle palsies. Upshoot or
downshoot in adduction is commonly associated. A
congenital sixth nerve palsy is rare and may be
related to birth trauma. 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.
Infantile esotropia also forms a differential
diagnosis of this presentation, but it usually
has full ductions.
Sometimes it is difficult to distinguish
Duane
from a congenital sixth nerve palsy in a very
young patient. Some clues are the
following:
1.
In Duane, the primary position esotropia is
relatively small compared to the lateral rectus
underaction.
2.
Narrowing of
the fissure of the involved eye occurs only in
Duane (may be hard to see in a child).
3.
The small head
turn in Duane results in alignment, but not so
likely in sixth nerve palsy.
4.
Congenital
sixth nerve palsy can be transient; Duane is
permanent.
5.
In a congenital setting with abduction deficit,
an esotropic Duane is far more common than
a congenital sixth nerve palsy.
6.
As a last
resort in the differential diagnosis, watch the
infant. The answer will become clear with time.
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