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Case of the week 27 (
January 2012
)
Right Superior Rectus Palsy
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Parents of this 16
years old boy noted that their son's eyes show
occasional different forms of deviations .They noticed
this since early childhood , insignificant history for
pregnancy and labor. No past history of head , ocular
trauma or general illness .
The boy is healthy , passing good at school , he denies
any diplopia complaint .
Examination showed good equal VA , normal fundus both
eyes . No history of previous therapy .
MRI was done , it showed normal orbits and brain .
Forced ductions for the right eye were done in the out
clinic using local anaethetic drops , they are
passive .
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An isolated paralysis of the
SR muscle is most commonly
of congenital origin. It may also be secondary to
trauma, for instance, after the
historical bridle suture during cataract
surgery , in which
instance the paralysis is
usually temporary.
In SR palsy
the primary defect is limited elevation
in abduction. Elevation is
normal in adduction. However, when superior rectus
palsy has been present for long periods, elevation
from primary position and adduction may also become
limited simulating double
elevator palsy ( pic 1 & 3 )
. The ipsilateral inferior rectus
( pic 7 ) and the
contralateral inferior oblique (
pic 1 ) muscles overact, and a small
excyclotropia usually is present. The paralyzed eye
is hypotropic in primary position
( pic 5 ) , and Bell’s phenomenon is absent
( In supranuclear DEP there is intact
Bell’s phenomenon )
Abnormal Head
Posture occurs frequently, but the position
of the head is of little diagnostic significance
in cases of SR palsy .
Even though in most patients the head is tilted
toward the sound side, the opposite may occur. In
persons with this type of muscle paralysis of recent
onset, the face is turned upward, the chin is
elevated, and the head usually is inclined toward
the sound side , the opposite may
occurs .
Superior rectus muscle paralysis
is frequently but not always associated with
weakness of the homolateral levator palpebrae muscle
( pic 5 ) , particularly
if the paralysis is congenital. A
true ptosis caused by levator weakness must be
differentiated from pseudoptosis
secondary to the hypotropic
position of the globe.
This
patient with paralysis of the right superior rectus
and minimal ptosis
of the right eye lid with
the nonparetic eye fixating. When the paralyzed eye
fixated, the ptosis disappeared and a marked
hypertropia of the nonparalyzed eye occurred
( pic Lt head tilt ) .
The differential diagnosis of a
superior rectus muscle paralysis includes mechanical
causes that limit elevation of the eye, such as
contracture, fibrosis, high myopia (heavy eye),
myositis, endocrine orbitopathy, or a blow-out
fracture of the orbital floor. Whenever elevation is
restricted mechanically the forced duction test will
be positive, and the restriction often involves the
whole entire upper field
of gaze.
For paralysis of the superior rectus muscle , a simple
resection-recession operation of the vertical rectus
muscles usually is effective. If the deviation is
limited to upward gaze , 4-mm
resection of the paretic muscle without recession of
its antagonist may sufficient . The question arises
whether surgery should be performed on the fixating
or nonfixating eye. With rare exceptions, I prefer to operate on the paretic eye regardless
of whether it is the dominant or nondominant eye.
The amount of surgery that is necessary varies, of
course, depending on whether the paretic eye
(secondary deviation) or the nonparetic eye (primary
deviation) habitually fixates.
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