Neurophthalmologic condition associated with abnormal
ocular movement, usually not accompanied by other congenital anomalies.
Stilling Turk Duane Syndrome.
Duane retraction syndrome (DRS) is an unusual form of
congenital strabismus and accounts for 1 to 4% of children with
strabismus. It is slightly more common in females than in males (about
60:40), often is bilateral (2057%), and is significantly more frequent
in the left eye (about 3-4:1). Reported frequencies vary widely.
Approximately 56 to 90% are sporadic cases.
In the residual cases, a positive family history with autosomal dominant
transmission has been suggested, although some cases with most likely
autosomal recessive inheritance have been reported. Several gene defects can
account for hypoplastic or absent brainstem motor neurons and aberrant
innervation and therefore have been linked to DRS. Defects have been mapped
to loci 2q31, 4q27-31, 8q12.2-q21.1, and 22pter-22q11.2, to mention a few.
Innervation of the lateral rectus muscle emanates
from axons of oculomotor nuclei, which supposedly supply the medial rectus
muscle. The abducens nucleus may be hypoplastic or even absent. Attempted
adduction of the eye basically results in simultaneous contractions of the
lateral and the medial rectus muscle, with the net effect being retraction
of the globe. At the same time, the palpebral fissure narrows and horizontal
eye movement is limited (depending on the type of DRS, abduction is severely
compromised). A teratogenic event (e.g., thalidomide exposure) between days
20 and 35 of gestation has been held responsible for the genetic defect.
Severe limitation of horizontal eye movement accompanied
by narrowing of the palpebral fissure and eyeball retraction with attempted
adduction leads to the diagnosis of DRS.
Different classifications have been suggested for
DRS. The following classification is based on EMG findings:
- Type I: Abduction is more compromised than adduction, which results in globe
retraction and narrowing of the palpebral fissure, whereas abduction results
in widening of the palpebral fissure. Adduction, but not abduction, shows
EMG activity in the lateral rectus muscle. This type accounts for 70 to
90% of cases.
- Type II: Adduction is absent or limited with exotropia of the affected eye.
Attempted adduction results in globe retraction. Adduction and abduction
result in EMG activity in the lateral rectus muscle.
- Type III: Both adduction and abduction are severely limited. Attempted adduction
results in globe retraction and narrowing of the palpebral fissure. EMG
activity can be recorded for the lateral and the medial rectus muscles
during attempted abduction and abduction.
In addition to the described horizontal restrictions of eye movement,
vertical eye movement anomalies are possible.
A few other anomalies have been reported in conjunction with DRS, including
other ocular anomalies such as anisometropia, amblyopia (both in
approximately 15% of DRS patients), anisocoria, ptosis, and nystagmus.
Conductive hearing loss and sensorineural hearing loss (each in
approximately 5% of cases) have been reported. Furthermore, DRS has been