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Chapter 5: Diagnostic Categories and Classifications of Strabismus -

Superior oblique palsyLecture 5 of 5 NEXT»

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

Superior oblique palsy can occur from trauma, congenital causes, a microvascularaccident, and from a mass lesion. These etiologies are differentiated primarily on thebasis 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 nervefibers emerge from the nucleus dorsally and decussate. The fibers then pass through thetentorium 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 obliquemuscle. 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 headtrauma.

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 fourthnerve palsy or report a history of diplopia, asthenopia, or anomalous head posture, oftenpresent for many years or for life. Occasionally, old pictures demonstrating a head tiltand 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 tothe opposite side with the chin depressed. Actually, the head moves where the eyecannot be moved by the paretic superior oblique. This is the rule when fusion potentialis present in a person with incomitant strabismus. With the head in this posture, theeyes 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 posturemay be in the opposite direction, presumably to maximize the separation of diplopia andmake it easier to suppress.

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

Motility. Versions are an extremely important part of the diagnosis of superior obliquepalsy. The most tell-tale finding is inferior oblique overaction, and to a lesser extentsuperior 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 whilereading.

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

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

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

Overaction of the contralateral superior oblique. Underaction of the ipsilateralinferior rectus (so-called fixation duress because it is working against a contractedantagonist) and overaction of the contralateral superior oblique, its yoke, occurs inlongstanding 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 palsywhen the vertical deviation increases with the head tilted toward the higher eye. If theBielschowsky 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 littlehypertropia 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 indirectophthalmoscope. If the macula is rotated downward or clockwise in the left eye andcounterclockwise in the right eye, so that the macula is below a line drawn parallel tothe orbit floor and temporal from the lower disc margin, torsion can be inferred. This isconfirmed if the macula is also shown to be roughly equidistant between the temporalarcades 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 superiorrectus and also the levator palpebri on that side are inhibited resulting in hypotropia andmore importantly, pseudoptosis. When the normal eye takes up fixation, the ptosisdisappears.

Other indicators.

1. Diagnostic position prism and cover testing is more important for quantificationof the deviation than it is for diagnosis.



2. Facial asymmetry is seen commonly in cases of congenital superior obliquepalsy. The face is always fuller on the side of the paretic muscle. The reason forthis 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 anabnormal or even absent superior oblique.

When the preceding considerations have been dealt with and when full measurementshave 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, andestablish 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; singlevision is more likely to occur in upgaze with chin down; Bielschowsky test is bilaterallypositive; that is, right hyper with right tilt and left hyper with left tilt or the hyper maydisappear or nearly so on head tilt to one side; and the Maddox rod frequently shows acyclotropia of greater than 15 degrees. Unilateral superior oblique palsy from amicrovascular accident is usually much smaller amplitude than unilateral superioroblique palsy from trauma. These patients usually have a vertical deviation in theneighborhood of 5 to 10 prism diopters and are older, being more often in the seventhor 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 orbilateral, will usually be found to have a normal superior oblique tendon on the tractiontest. The tendon is very easily felt, and the traction test is usually bilaterallysymmetrical 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 foundto have a lax superior oblique traction test (see page 97). At exploration of a superioroblique tendon that was found to be loose or lax with the traction test, an anomaloussuperior 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 shownin the diagrams on the following pages represent the field of greater deviation andassume 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 afew modifications, valid today (Figure 14).

Figure 14 Superior oblique palsy -- scheme for etiology



Class I

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

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

Class II

Knapp II--underaction of the paretic superioroblique with the deviationgreater in the field of action of the paretic superior oblique seen mostly insmaller angle, acquired microvascular superior oblique palsy. This is besttreated with prism and time. A larger angle deviation with this pattern canoccur in congenital absence of the superior oblique tendon. If a pattern likethis emerges in a congenital superior oblique palsy with facial asymmetry andpronounced superior oblique underaction, superior oblique traction testingfollowed by exploration of the superior oblique will lead to the appropriatesurgical plan which could include superior oblique tuck, inferior obliqueweakening, or yoke inferior rectus weakening depending on the angle and thestate of the superior oblique.

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 greaterdeviation, only the antagonist inferior oblique weakening is done. If it isgreater than 20 prism diopters and the superior oblique traction test reveals alax tendon, and congenital superior oblique palsy is diagnosed, a tuck of thesuperior oblique can be performed; if the superior oblique tendon is tight, theyoke muscle, the contralateral inferior rectus, is recessed. If the surgeonchooses not to tuck the superior oblique tendon, even though lax, recession of



the yoke can be done.

Class IV

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

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

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 ipsilateralsuperior rectus is recessed and either the superior oblique is tucked, the yokeinferior rectus is recessed or the ipsilateral inferior oblique is weakened. Therecommendation to weaken the contralateral superior oblique along with atuck of the involved superior oblique originally recommended by Knapp is abad idea. Only a lax tendon should be tucked and be wary of weakening thenormal superior oblique in a fusing patient!



Class VI

Bilateral superior oblique palsy

This condition is characterized by:

1. History of trauma2. 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 surgicaltreatment of bilateral superior oblique palsy. Bilateral weakening of the yokeinferior obliques is favored by some to treat the ‘V’ and the torsion. Others doa bilateral recession of the inferior recti. The strength of either procedure isthat the weakening is done on a normal muscle, one is a yoke and the otheran antagonist. Bilateral weakening of the antagonist inferior obliques likewisetreats 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 thetorsion. For the ‘V,’ downshift of the medial recti can be done. The superioroblique tendon should not be tucked.

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 upgazeand downgaze.

2. Trauma to the trochlea restricting upgaze and residual superior obliquepalsy restricting downgaze.



3. Can occur as an iatrogenic Brown after superior oblique tuck withresidual 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

Congenital superior oblique palsy on an anatomic basis

When a congenital superior oblique palsy with an anomalous tendon isencountered first by finding a loose superior oblique traction test and thenafter the tendon is exposed, ‘strengthening’ of the tendon is carried out onthe 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. Themajority of these had a redundant tendon that is class I anatomic superioroblique palsy. These are the superior oblique palsy patients who may betreated with superior oblique tuck or resection if the tendon is sufficientlyloose 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 superioroblique palsy?” (Figure 15). Congenital ‘anatomic’ superior oblique palsy isalways associated with a lax superior oblique traction test.



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

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

In summary, superior oblique palsy treatment consists of:

1. Fresnel prism for acute symptomatic microvascular fourth nerve palsy2. Permanent prism for selected small-angle acquired small angle fourth

nerve palsy

3. Surgery according to angle and pattern for unilateral acquired fourthnerve palsy; avoid superior oblique tendon tuck; an anterior transfermay be done if torsion is the main problem

4. In congenital superior oblique palsy with tendon anomaly surgery isconcentrated on the antagonist, the yoke, and the lax superior obliquetendon.

5. The safest surgical procedure in any superior oblique palsy isweakening of the antagonist inferior oblique



6. In longstanding superior oblique palsy weaken a tight ipsilateralsuperior rectus if there is underaction of the ipsilateral inferior rectusand/or overaction of the contralateral superior oblique.

7. Bilateral superior oblique palsy can be treated with weakening of theyoke, 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 doa second procedure or do two muscles on the more involved side andone muscle on the masked side according to the scheme presented.

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

________________________________________________________ TABLE I: PATIENT DEMOGRAPHICS AND PREOPERATIVE

DATA FOR 190 CASES OF SUPERIOR OBLIQUE PALSY

________________________________________________________

Sex

Male: 105

Female: 85

AgeRange: 6mo-79yr

Mean: 28.8+/-22.2yr

Mean for congenital group: 24.1+/-21.1yr Mean for acquired group: 40.9+/-20.5yr

RefractionMean: -0.49+/-3.04 diopters

Visual AcuityMean: 20/25

Median: 20/20



Congenital/acquired

Congenital: 137Acquired: 53

Origin: Trauma 29

Iatrogenic 12Vascular 7

Tumor 5

Knapp Classifications

Class I: 28Class II: 13

Class III: 65

Class IV: 53Class V: 5

Class VI: 19

Class VII: 1Class VIII: 6*

Laterality

Right: 92

Left: 79Bilateral: 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: 70Others (eg, head turn, chin down): 10

No abnormal head posture: 39

Unknown: 16

Forced duction testsTests performed: 161

Tendon laxity: 95 83 congenital12 acquired

No tendon laxity: 66 37 congenital

29 acquired

________________________________________________________



* Type VIII = comitant vertical deviation

Table 15Patient 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: 177Myectomies and recessions: 175Anterior transpositions: 2

Contralateral inferior rectus recession: 36

Ipsilateral superior rectus recession: 32

Superior oblique surgery: 50

Superior oblique tuck: 26Superior 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 notedonly once.

† Number of times the patient went to the operating room, rather than

number of different strabismus procedures performed.

Table 16From 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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