Strabismus Vertical Deviation Flashcards
علل SO palsy اکتسابی؟
closed head trauma vascular problems of the CNS Dm brain tumor Direct trauma to the tendon or the trochlear area
آیا بیماران با congenital SO palsy می توانند اعصاب نرمال و bulk عضلانی نرمال داشته باشند؟
بله
ولی اغلب بیماران :
1)had absent ipsilateral trochlear nerves
2)varying degrees of SO muscle hypoplasia
پاتوفیزیولوژی congenital SO palsy؟
1) absent ipsilateral trochlear nerves ➡️ SO muscle hypoplasia
2) congenitally lax, attenuated, or even absent SO tendon 3)unusual course of the muscle
4) functional consequences of malpositioned orbital pulleys—although strictly speaking, these are not paralytic entities
علل SOUA؟
craniofacial abnormalities
differentiate congenital from acquired superior oblique muscle palsy
indicate chronicity(congenital) 1)childhood photographs 2)Facial asymmetry from long-standing head tilting 3)large vertical fusional amplitudes افتراق علل اکتسابی از این نظر اهمیت دارد که so palsy تازه تشخیص داده شده که به دلیل تروما نباشد می تواند نشانه intracranial lesion باشد
مریض عصبانی👹
Chin down
bilateral SO palsy
differentiate bilateral from unilateral superior
oblique muscle palsy?
Unilateral cases:
1)little if any V pattern
2)less than 10° of extorsion in downgaze. Subjective incyclodiplopia is uncommon, unless the palsy is severe. 3)The 3-step test yields positive results for the involved side only. Abnormal head positions—usually a tilt
toward the shoulder opposite the side of the
weakness—are common.
4)Finally, the oblique muscle dysfunction is confined to the involved eye.
Bielschowsky head-tilt test
right head tilt reveals a right hypertropia
left head tilt a left hypertropia
=bilateral SO palsy
Markedly asymmetric bilateral SO palsies that initially appear to be unilateral are called “masked bilateral palsies”
Signs of masked bilateral palsy:
1) bilateral objective fundus extorsion
2) esotropia in downgaze
3) even the mildest degree of oblique muscle dysfunction on the presumedly uninvolved side.
🎈Masked bilateral palsies are more common in
patients with closed head trauma.
🎈They must be distinguished from situations in which the initial palsy is overcorrected, leading to a postoperative oblique muscle abnormality in the fellow eye
اندیکاسیون های جراحی در so palsy
1) Abnormal head position
2) significant vertical deviation
3) diplopia
3) asthenopia
SO palsy-incomitant
1)weaken the antagonist IO muscle if
the hyperdeviation is worse in contralateral upgaze
2)strengthen the weak superior oblique muscle if
the hyperdeviation is worse in contralateral downgaze.
3)If the superior oblique muscle is lax, as in
some cases of congenital SO palsy, the tendon should be tightened; the most common procedure choice is tendon tucking. Laxity can be confirmed at surgery by a FDT in
which the globe is pushed (translated) posteriorly into the orbit while it is simultaneously extorted,
thus tensing the superior oblique tendon. The presence of cyclodiplopia or significant extorsion also
indicates that a superior oblique tendon strengthening procedure should be considered for inclusion in
the surgical plan; options include tendon tucking and the various forms of the Harada-Ito procedure
If the deviation is no greater than 15Δ in primary position, one of these options alone may be
effective. When the inferior oblique muscle is weakened, the amount of deviation in primary position
that is corrected by any weakening technique is proportional to the degree of preoperative overaction
of the muscle. This procedure is not performed in skew deviation because inferior oblique muscle
weakening would aggravate the intorsion of the higher eye.
If the hyperdeviation is incomitant and measures greater than 15Δ in primary position, it usually is
also large in the ipsilateral (secondary) gaze field. In this situation, recession of the ipsilateral
superior rectus muscle or the contralateral (yoke) inferior rectus muscle should be added to the
oblique muscle surgery. The choice depends on whether the hyperdeviation is worse in downgaze or
upgaze, as well as the tightness of these muscles on forced-duction testing. Either muscle can be
recessed with an adjustable suture.
SO palsy-comitant
If the deviation has become comitant,” vertical rectus” muscle surgery is generally preferred.
🎈For deviations of less than 15Δ–20Δ, recession of 1 vertical rectus muscle should suffice; for larger
hyperdeviations, both may have to be weakened.
🎈In the unusually severe case with a vertical deviation greater than 35Δ in primary position, 3-
muscle surgery is usually required. In this situation, most surgeons favor recession of the overacting
antagonist IO muscle, plus either the ipsilateral superior rectus or contralateral inferior
rectus muscle or both, as dictated by FDT results.
🎈Ipsilateral SO tendon tucking may have to be included if the tendon is lax.
اپروچ درمانی so palsy هر چه که باشد یک نکته را همواره مد نظر داشته باشید؟
avoid overcorrection of a long-standing unilateral
SO muscle palsy in adult patients.
🎈Overcorrection can worsen with time and can cause disabling diplopia.
Bilat so palsy-Tx
🎈If the palsies are symmetric and both IO muscles are significantly overacting➡️bilat IO weakening ( may not be completely effective on its own)
🎈If the SO muscles are lax or weak and cyclodiplopia or sizable extorsion is present, these muscles should be strengthened, using either tendon tucking or one of the variations of the Harada-Ito procedure.
🎈If the paralysis is asymmetric, a hyperdeviation is usually present in primary position and the
hyperdeviations on right and left gaze differ 1)symmetric oblique muscle surgery with a unilateral vertical rectus recession 2)asymmetric oblique muscle surgery tailored to correct more oblique muscle function in the eye with
the worse palsy.
🎈There are other, less common approaches to treating bilateral superior oblique palsy➡️ bilateral IR recessions, which serve to add extra innervational drive on downgaze to help overcome the SO deficits
تمام این اپروچ ها می توانند V-P را اصلاح کنند
قانون هرینگ مربوط به عضلات yoke است(۲چشم)
قانون شرینگتون مربوط به عضلات آنتاگونیست است(در ۱ چشم)
RSO palsy(R hyper in L gaze)➡️هرینگ➡️LIR underaction➡️
On version testing, Hering’s law may cause the SO muscle to overact in the normal
eye. If the surgeon is misled and performs superior oblique tenotomy on the normal eye, thereby
converting a unilateral superior oblique palsy to a bilateral one, disabling torsional diplopia can
result.
