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Chapter 5: Diagnostic Categories and Classifications of Strabismus -  

Superior oblique palsy

Lecture 5 of 5  NEXT»

Superior oblique palsy is the most commonly occurring isolated cranial nerve palsy seen by the strabismologist. However, I do not know of any reliable figures comparing the relative occurrence of fourth and sixth nerve palsies. Certainly, third nerve palsy is rarer than either fourth or sixth nerve palsy. In some practices, particularly those of the neuro-ophthalmologist, sixth nerve palsy may be the most common.

Superior oblique palsy can occur from trauma, congenital causes, a microvascular accident, and from a mass lesion. These etiologies are differentiated primarily on the basis of history with additional information obtained from physical and imaging findings.

The fourth nerve nucleus is in the rostral part of the brain stem in the tectum. The nerve fibers emerge from the nucleus dorsally and decussate. The fibers then pass through the tentorium as delicate fibrils. They course into the orbit through the superior orbital fissure where they have as their sole purpose the innervation of the superior oblique muscle. These delicate fibrils are vulnerable to violent to-and-fro motion of the brain, such as occurs with a sudden deceleration in an automobile accident or similar head trauma.


Patient presentation

History. The patient or parents of the patient frequently either describe an acute event (such as a motor vehicle accident) that is likely to be the cause of a traumatic fourth nerve palsy or report a history of diplopia, asthenopia, or anomalous head posture, often present for many years or for life. Occasionally, old pictures demonstrating a head tilt and chin depression are useful in supporting the diagnosis of congenital superior oblique palsy.

Head posture. The usual head posture in superior oblique palsy is the head tilted to the opposite side with the chin depressed. Actually, the head moves where the eye cannot be moved by the paretic superior oblique. This is the rule when fusion potential is present in a person with incomitant strabismus. With the head in this posture, the eyes look upward and to the opposite side, completely out of (opposite) the field of action of the paretic muscle. In a very small percentage of patients, the head posture may be in the opposite direction, presumably to maximize the separation of diplopia and make it easier to suppress.

Torticollis. Neck contracture can occur in very young children with superior oblique palsy. However, neck contracture from superior oblique palsy does not occur before the child sits up and/or walks. The head tilt from superior oblique palsy does not occur with the child supine or prone but only when the child is vertically oriented, sitting, standing up or walking.

Motility. Versions are an extremely important part of the diagnosis of superior oblique palsy. The most tell-tale finding is inferior oblique overaction, and to a lesser extent superior oblique underaction, which occurs to varying degrees. Sometimes the superior oblique underaction is slight or undetectable.

Diplopia. Vertical diplopia is a common complaint in adult patients but rare in children. Asthenopia is also common in adults. This may take the form of neck ache while reading.

Chin depression. In the presence of a V pattern the chin is often down. This occurs with bilateral superior oblique palsy.

Cyclodiplopia. Spontaneous complaint of cyclodiplopia is a common sign of acquired bilateral superior oblique palsy. It also occurs in iatrogenic Brown syndrome after superior oblique strengthening.

Double Maddox rod torsion. Seeing a tilted line on testing with double Maddox rod is very supportive of the diagnosis of superior oblique palsy. This usually means that the superior oblique palsy is acquired.

Overaction of the contralateral superior oblique. Underaction of the ipsilateral inferior rectus (so-called fixation duress because it is working against a contracted antagonist) and overaction of the contralateral superior oblique, its yoke, occurs in longstanding superior oblique palsy with contracture of the ipsilateral superior rectus.

Double Maddox rod torsion greater than 15 degrees. This is a strong indication of bilateral superior oblique palsy.

Bielschowsky head tilt test. This test is considered positive for superior oblique palsy when the vertical deviation increases with the head tilted toward the higher eye. If the Bielschowsky head tilt test reverses, then a bilateral superior oblique palsy is suspected. If the Bielschowsky head tilt test does not reverse but is reduced to no or very little hypertropia in the same direction on tilt to the side opposite the paretic superior oblique, a masked bilateral superior oblique palsy may be suspected.

Fundus torsion. Torsion may be noted during examination with the indirect ophthalmoscope. If the macula is rotated downward or clockwise in the left eye and counterclockwise in the right eye, so that the macula is below a line drawn parallel to the orbit floor and temporal from the lower disc margin, torsion can be inferred. This is confirmed if the macula is also shown to be roughly equidistant between the temporal arcades while in its lower position.

Inhibitional palsy of the contralateral antagonist. When the eye with the paretic superior oblique is used for fixation the yoke inferior rectus in the contralateral eye receives extra innervation. Its antagonist, the superior rectus and also the levator palpebri on that side are inhibited resulting in hypotropia and more importantly, pseudoptosis. When the normal eye takes up fixation, the ptosis disappears.

Other indicators.

  1. Diagnostic position prism and cover testing is more important for quantification of the deviation than it is for diagnosis.
  2. Facial asymmetry is seen commonly in cases of congenital superior oblique palsy. The face is always fuller on the side of the paretic muscle. The reason for this is the abnormal head posture assumed to maintain single binocular vision.
  3. Horizontal strabismus can occur in addition to the superior oblique palsy.
  4. Amblyopia in the presence of congenital superior oblique palsy may indicate an abnormal or even absent superior oblique.

When the preceding considerations have been dealt with and when full measurements have been completed, especially prism and cover testing in the diagnostic positions, double Maddox rod testing, and the head tilt test, it is possible to diagnose, classify, and establish a treatment plan for a patient with superior oblique palsy.


Acquired superior oblique palsy

Patients with acquired unilateral palsy will usually have the following characteristics:

  • A discrete history of onset
  • Complaint of intermittent vertical diplopia
  • Head tilt and chin depression with a comment, “I see better if I assume this head position”
  • Measurable torsion with the double Maddox rod, less than 15 degrees
  • A vertical deviation usually less than 20 prism diopters (deviation may be greater at near and in longstanding cases).

Bilateral acquired superior oblique palsy differs in that a ‘V’ pattern is the rule; single vision is more likely to occur in upgaze with chin down; Bielschowsky test is bilaterally positive; that is, right hyper with right tilt and left hyper with left tilt or the hyper may disappear or nearly so on head tilt to one side; and the Maddox rod frequently shows a cyclotropia of greater than 15 degrees. Unilateral superior oblique palsy from a microvascular accident is usually much smaller amplitude than unilateral superior oblique palsy from trauma. These patients usually have a vertical deviation in the neighborhood of 5 to 10 prism diopters and are older, being more often in the seventh or eighth decade, and they complain of diplopia. They may not demonstrate a head tilt. These patients deserve a medical/neurological work up for hypertension, diabetes, etc.

In the operating room, patients with acquired superior oblique palsy, either unilateral or bilateral, will usually be found to have a normal superior oblique tendon on the traction test. The tendon is very easily felt, and the traction test is usually bilaterally symmetrical in unilateral disease.


Congenital superior oblique palsy

  • There is usually no history of trauma.
  • The condition is long-standing and characterized by a large head tilt and supported by family pictures showing a head tilt.
  • In cases of absence of the superior oblique tendon, amblyopia and horizontal strabismus are common.
  • Facial asymmetry is common in all types of congenital superior oblique palsy. The face is fuller on the involved side.
  • There is frequently no torsion measured with the double Maddox rod.
  • There are fewer complaints of diplopia in congenital compared to acquired superior oblique palsy.

In the operating room, patients with congenital superior oblique palsy a frequently found to have a lax superior oblique traction test (see page 97). At exploration of a superior oblique tendon that was found to be loose or lax with the traction test, an anomalous superior oblique tendon will be noted to be either too long, inserted in the wrong place, or absent.


Superior oblique treatment classification

Treatment is based on prism cover measurement findings, torsion, and the results of superior oblique traction testing indicating the state of the tendon. Hatched areas shown in the diagrams on the following pages represent the field of greater deviation and assume left superior oblique palsy. The pattern of deviation is the examiner’s view.

The scheme described here is that proposed by Philip Knapp in 1971. It remains, with a few modifications, valid today (Figure 14).

 

fig. 14

Figure 14 Superior oblique palsy -- scheme for etiology



Class I

Knapp I--overaction of antagonist inferior oblique with deviation about 20 prism diopters or less in the field of action of the antagonist; this is a common pattern for both acquired and congenital superior oblique palsy.

Surgery. Weaken antagonist inferior oblique. This is the ‘safest’ surgical procedure for any superior oblique palsy.

graphic 1


Class II

Knapp II--underaction of the paretic superior oblique with the deviation greater in the field of action of the paretic superior oblique seen mostly in smaller angle, acquired microvascular superior oblique palsy. This is best treated with prism and time. A larger angle deviation with this pattern can occur in congenital absence of the superior oblique tendon. If a pattern like this emerges in a congenital superior oblique palsy with facial asymmetry and pronounced superior oblique underaction, superior oblique traction testing followed by exploration of the superior oblique will lead to the appropriate surgical plan which could include superior oblique tuck, inferior oblique weakening, or yoke inferior rectus weakening depending on the angle and the state of the superior oblique.

graphic 2


Class III

 

Knapp III--In this class, the deviation is approximately equal in the field of the paretic superior oblique and the antagonist inferior oblique.

Surgery. If the deviation is less than 20 prism diopters in the field of greater deviation, only the antagonist inferior oblique weakening is done. If it is greater than 20 prism diopters and the superior oblique traction test reveals a lax tendon, and congenital superior oblique palsy is diagnosed, a tuck of the superior oblique can be performed; if the superior oblique tendon is tight, the yoke muscle, the contralateral inferior rectus, is recessed. If the surgeon chooses not to tuck the superior oblique tendon, even though lax, recession of the yoke can be done.

graphhic 3


Class IV

This common pattern of hyperdeviation which is class III demonstrates a spread of hyperdeviation ‘across the bottom’ occurring because of tightness of the ipsilateral superior rectus.

Surgery. If the deviation is 20 prism diopters or less, weakening of the antagonist inferior oblique and ipsilateral superior rectus is effective. If the deviation is greater, the superior oblique tendon can be tucked if it is loose or the yoke inferior rectus can be recessed if the superior oblique tendon is normal.

graphic 4

 


Class V

A hyperdeviation ‘across the bottom’ can be the pattern in a long-standing acquired superior oblique palsy pattern.

Surgery. If the vertical deviation is around 20 prism diopters, the ipsilateral superior rectus is recessed and either the superior oblique is tucked, the yoke inferior rectus is recessed or the ipsilateral inferior oblique is weakened. The recommendation to weaken the contralateral superior oblique along with a tuck of the involved superior oblique originally recommended by Knapp is a bad idea. Only a lax tendon should be tucked and be wary of weakening the normal superior oblique in a fusing patient!

graphic 5


Class VI

Bilateral superior oblique palsy

This condition is characterized by:

  1. History of trauma
  2. Spontaneous torsional diplopia
  3. Usually >15 degrees torsion with double Maddox rod testing
  4. V pattern
  5. Reversing Bielschowsky (or nearly reversing Bielschowsky) test

Surgery.There is little agreement among experts when it comes to surgical treatment of bilateral superior oblique palsy. Bilateral weakening of the yoke inferior obliques is favored by some to treat the ‘V’ and the torsion. Others do a bilateral recession of the inferior recti. The strength of either procedure is that the weakening is done on a normal muscle, one is a yoke and the other an antagonist. Bilateral weakening of the antagonist inferior obliques likewise treats the ‘V’ and the torsion, but depends on getting more out of a paretic muscle. Antero-lateral shift of the superior oblique (Harada- Ito) treats the torsion. For the ‘V,’ downshift of the medial recti can be done. The superior oblique tendon should not be tucked.

graphic 6


Class VII

Brown syndrome with superior oblique underaction (‘canine tooth’)

This condition is characterized by:

  1. History of trauma to the trochlea with mechanical restriction in upgaze and downgaze.
  2. Trauma to the trochlea restricting upgaze and residual superior oblique palsy restricting downgaze.
  3. Can occur as an iatrogenic Brown after superior oblique tuck with residual superior oblique underaction.

This problem is difficult to treat. My ‘treatment’ suggestions are:

  1. None -- if eyes are aligned around primary
  2. Yoke inferior rectus recession -- if ipsilateral hyper
  3. Take down tuck, if caused by a ‘too tight’ tuck
  4. Free superior oblique restriction if ipsilateral hypo

    graphic 7

    Congenital superior oblique palsy on an anatomic basis

    When a congenital superior oblique palsy with an anomalous tendon is encountered first by finding a loose superior oblique traction test and then after the tendon is exposed, ‘strengthening’ of the tendon is carried out on the basis of what is found.

    In 190 cases of superior oblique palsy treated by our group, 87% of those diagnosed as congenital had an anomalous superior oblique tendon. The majority of these had a redundant tendon that is class I anatomic superior oblique palsy. These are the superior oblique palsy patients who may be treated with superior oblique tuck or resection if the tendon is sufficiently loose or lax. A legitimate question is, “When lax tendons are found in cases of ‘V’ pattern congenital esotropia is this a form of bilateral congenital superior oblique palsy?” (Figure 15). Congenital ‘anatomic’ superior oblique palsy is always associated with a lax superior oblique traction test.


    fig. 15

    Figure 15
    Description of the superior oblique tendon in ‘anatomic’ congenital superior oblique palsy.


    The patient with superior oblique palsy must be managed with a comprehensive program of diagnosis and treatment.

    In summary, superior oblique palsy treatment consists of:

    1. Fresnel prism for acute symptomatic microvascular fourth nerve palsy
    2. Permanent prism for selected small-angle acquired small angle fourth nerve palsy
    3. Surgery according to angle and pattern for unilateral acquired fourth nerve palsy; avoid superior oblique tendon tuck; an anterior transfer may be done if torsion is the main problem
    4. In congenital superior oblique palsy with tendon anomaly surgery is concentrated on the antagonist, the yoke, and the lax superior oblique tendon.
    5. The safest surgical procedure in any superior oblique palsy is weakening of the antagonist inferior oblique
    6. In longstanding superior oblique palsy weaken a tight ipsilateral superior rectus if there is underaction of the ipsilateral inferior rectus and/or overaction of the contralateral superior oblique.
    7. Bilateral superior oblique palsy can be treated with weakening of the yoke, weakening of the antagonist, and antero-lateral shift of the superior oblique.
    8. Be aware of the possibility of masked bilateral superior oblique palsy. If the Bielschowsky head tilt reverses, or nearly does, be suspicious. Either treat this as a unilateral superior oblique palsy and expect to do a second procedure or do two muscles on the more involved side and one muscle on the masked side according to the scheme presented.

    Work-up of a patient with acquired superior oblique palsy should in most cases be kept to a minimum. The etiology is usually clear-cut trauma, well established congenital disease, or less clear presumed microvascular disease in an elderly individual. In the last instance, an evaluation by an internist for hypertension and/or diabetes is needed. Extensive imaging with CT or MRI or lumbar puncture and EEG studies rarely accomplish anything useful for the usual superior oblique palsy patient. In my opinion, extensive testing of the patient with fourth nerve palsy should be done only if indications other than the fourth nerve palsy itself are noted. By that I mean other significant neurologic signs or symptoms.

     

    ________________________________________________________
    TABLE I: PATIENT DEMOGRAPHICS AND PREOPERATIVE DATA FOR 190 CASES OF SUPERIOR OBLIQUE PALSY
    ________________________________________________________

    Sex
    Male: 105
    Female: 85

    Age
    Range: 6mo-79yr
    Mean: 28.8+/-22.2yr
    Mean for congenital group: 24.1+/-21.1yr
    Mean for acquired group: 40.9+/-20.5yr

    Refraction
    Mean: -0.49+/-3.04 diopters

    Visual Acuity
    Mean: 20/25
    Median: 20/20

    Congenital/acquired
    Congenital: 137
    Acquired: 53
    Origin: Trauma 29
    Iatrogenic 12
    Vascular 7
    Tumor 5

    Knapp Classifications
    Class I: 28
    Class II: 13
    Class III: 65
    Class IV: 53
    Class V: 5
    Class VI: 19
    Class VII: 1
    Class VIII: 6*

    Laterality
    Right: 92
    Left: 79
    Bilateral: 19

    Facial asymmetry
    Present: 56 51 congenital 5 acquired
    Absent: 69 40 congenital 29 acquired
    Unknown: 65 46 congenital 19 acquired

    Abnormal head posture:
    Right tilt: 55
    Left tilt: 70
    Others (eg, head turn, chin down): 10
    No abnormal head posture: 39
    Unknown: 16

    Forced duction tests
    Tests performed: 161
    Tendon laxity: 95 83 congenital
    12 acquired
    No tendon laxity: 66 37 congenital
    29 acquired

    ________________________________________________________

    * Type VIII = comitant vertical deviation

    Table 15
    Patient demographics and preoperative data for 190 cases of superior oblique palsy.
    From Helveston EM, et al. Surgical treatment of superior oblique palsy. Transactions of the American Ophthalmological Society, Vol. XCIV, 1996, pp. 315-334.
    Used with permission.

     

    ________________________________________________________
    TABLE II: SURGICAL PROCEDURES PERFORMED*
    ________________________________________________________

    Inferior oblique surgery: 177
    Myectomies and recessions: 175
    Anterior transpositions: 2

    Contralateral inferior rectus recession: 36

    Ipsilateral superior rectus recession: 32

    Superior oblique surgery: 50
    Superior oblique tuck: 26
    Superior oblique resection: 9
    Harada Ito procedure: 15

    Horizontal muscle surgery: 19

    Horizontal shifts of vertical recti or vertical shifts of horizontal recti: 3

    Number of surgeries: †
    Mean: 1.26+/-0.61
    Range: 1-6

    ________________________________________________________

    * When procedures were performed bilaterally, they have been noted only once.

    † Number of times the patient went to the operating room, rather than number of different strabismus procedures performed.

    Table 16
    From Helveston EM, et al. Surgical treatment of superior oblique palsy. Transactions of the American Ophthalmological Society, Vol. XCIV, 1996, pp. 315-334.
    Used with permission.

     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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