Alphabet Patterns and Oblique Muscle
Dysfunctions
Kenneth W. Wright
I n this chapter, A- and V-pattern strabismus and oblique dysfunction are discussed, including management strategies.
Under the category of A- and V-patterns, special subtypes are described. The section on oblique dysfunction includes the fol- lowing: head tilt test, inferior oblique paresis and inferior oblique overaction, superior oblique paresis and superior oblique overaction, and Brown’s syndrome.
A- AND V-PATTERNS
A significant difference in the horizontal deviation from upgaze to downgaze is described as an A- or V-pattern. An A-pattern is described as more divergence in downgaze versus upgaze of at least 10 prism diopters (PD), whereas a V-pattern is increasing divergence in upgaze versus downgaze by 15 PD or more. A- and V-patterns are often a result of oblique muscle overaction or oblique muscle paresis. Other less common causes include nerve misdirection such as Duane’s syndrome, ectopic muscle course with ectopic muscle pulleys, and a rotated orbit associ- ated with craniofacial abnormalities.
5,6,29Examples of strabismus patterns (1 through 5) follow.
Example 1.
A-pattern V-pattern
XT A-pattern ET A-pattern XT V-pattern ET V-pattern
Upgaze XT 10 ET 30 XT 30 ET 10
Primary position XT 20 ET 20 XT 20 ET 20
Downgaze XT 30 ET 10 XT 10 ET 30
XT, exotropia; ET, esotropia.
9
284
A- and V-Pattern Subtypes
Look critically at the type of pattern: is it symmetrical or does the change in horizontal deviation occur more in upgaze or downgaze? This is important to know, as the configuration or subtype of the A- or V-pattern can indicate an identifying etiol- ogy and can influence the surgical plan. For example, a V-pattern consisting of convergence in downgaze without significant change in horizontal deviation from primary position to upgaze is highly suggestive of a bilateral superior oblique palsy. Listed below are subtypes of A- and V-patterns in which the change in horizontal deviation is asymmetrical.
V-P
ATTERNS
UBTYPESY-P
ATTERNThe Y-pattern is a V-pattern subtype with divergence occur- ring in upgaze and little change in the horizontal deviation between primary position and downgaze. This pattern is highly suggestive of bilateral inferior oblique overaction, which is often associated with infantile esotropia and may also be seen with intermittent exotropia. Y-pattern can also be seen in patients with Brown’s syndrome, Duane’s syndrome with upshoot, and rarely congenital aberrant innervation of the lateral rectus muscle with the superior rectus nerve (see Example 2).
Example 2.
ET Y-pattern XT Y-pattern
Upgaze ET 10 XT 30
Primary position ET 25 XT 15
Downgaze ET 30 XT 10
A
RROWP
ATTERNAnother V-pattern subtype is convergence that largely occurs
between primary position and downgaze. This author has
termed this pattern “arrow” pattern. The presence of an arrow
pattern and extorsion in downgaze is virtually diagnostic for
bilateral superior oblique muscle palsy. The lack of abduction
and intorsion in downgaze because of weak superior oblique
muscles allows unopposed adduction and extorsion by the
inferior recti muscles (see Example 3).
Example 3.
ET Arrow Pattern
Upgaze Ortho
Primary Position ET 5
Downgaze ET 20
A-P
ATTERNS
UBTYPEL
AMBDAP
ATTERNThe lambda pattern, an A-pattern subtype, is characterized by a divergence in downgaze without much change in the horizontal deviation from primary position to upgaze. A lambda pattern is most frequently associated with bilateral superior oblique over- action. Overrecessed or slipped inferior rectus muscles will also cause an A-pattern lambda subtype with apparent superior oblique muscle overaction. In contrast, inferior oblique muscle underaction causes an A-pattern with most of the horizontal change as convergence in upgaze (see Example 4).
Example 4.
XT lambda pattern Lambda pattern
Upgaze XT 15
Primary Position XT 20
Downgaze XT 35
X-P
ATTERNAn X-pattern occurs when there is divergence in upgaze and divergence in downgaze, which can occur without a specific cause. Patients with long-standing large-angle exotropia will fre- quently show an X-pattern, presumably caused by a tight con- tracted lateral rectus muscle. As the eye adducts against the tight lateral rectus muscle, it acts as a leash and produces lateral forces. If the eye then rotates up or down the tight lateral rectus slips above or below the eye and pulls the eye up and out, or down and out, respectively. This leash effect of the lateral rectus is also seen in Duane’s syndrome, usually type III, with both an upshoot and downshoot present on attempted adduction.
Lateral rectus recessions reduce the X-pattern associated with
exotropia, and an ipsilateral lateral rectus recession with a Y-
split works well to reduce the vertical overshoot and X-pattern
associated with Duane’s syndrome type III
29(see Example 5).
Example 5.
XT X-Pattern
Upgaze XT40
Primary position XT30
Downgaze XT40
Treatment of A- and V-Patterns
A- and V-patterns with minimal or no oblique overaction can be managed by offsetting, or transposing, the horizontal rectus muscles superiorly or inferiorly. Transpose the medial recti insertions toward the apex of the pattern (up for an A-pattern and down for a V-pattern) and the lateral recti insertions to the wide part of the pattern (down for an A-pattern and up for a V- pattern) (Fig. 9-1). An A-pattern exotropia, for example, can be treated by recessing both lateral rectus muscles and transposing them inferiorly (Fig. 9-2). Vertical transposition of horizontal muscles in the treatment of A- or V-patterns changes vector forces and muscle tension as the eyes rotate up and down. For example, when the medial recti are infraplaced for a V-pattern, they gain increased function as the eyes rotate up, thus collaps- ing the V-pattern. Conversely, when the eyes rotate down, the infraplaced medial rectus muscles slacken, resulting in diver- gence of the apex of the V-pattern. One-half-tendon-width
FIGURE 9-1. Direction to transpose the rectus muscles to correct for A- and V-patterns. Left diagram: transposition for a V-pattern, with the lateral rectus muscles moved up and medial rectus muscles moved down.
Right diagram:transposition for an A-pattern, with the medial rectus muscles moved up and the lateral rectus muscles moved down. The medial rectus is moved toward the apex of the A or V and the lateral rectus is moved away from the apex of the A or V. This transposition holds true whether the muscles are recessed or resected.
(5 mm) of vertical displacement results in approximately 15 PD of pattern correction. A full-tendon-width vertical displacement results in approximately 25 PD of correction and is reserved for extremely large A- or V-patterns. Vertical transposition of a horizontal rectus muscle by one full-tendon-width reduces the vector forces at the horizontal plane and, in this author’s opinion, often results in unpredictable horizontal alignment. For example, a full-tendon-width infra-placement of the lateral rectus muscles for an A-pattern would predispose to an over- correction (esotropia) in primary position. This author rarely performs a horizontal rectus muscle transposition more than one-half tendon-width (5 mm) except in cases of a large A- or V- pattern associated with craniofacial disorders or absent muscles.
Monocular supraplacement of one rectus muscle and infraplace- ment of the partner antagonist muscle can be used to correct an A- or V-pattern in a patient with amblyopia to avoid surgery on the only good eye. Monocular A- or V-pattern horizontal muscle offsets can cause significant torsional changes and should be done only on amblyopic eyes in patients with poor binocular fusion to avoid inducing torsional diplopia. Thus, monocular horizontal offsets can be used to correct torsional diplopia.
In cases with significant inferior or superior oblique over- action and an A- or V-pattern, the appropriate oblique muscles should be weakened rather than performing a horizontal rectus muscle transposition. An exception exists for patients with
FIGURE 9-2. Drawing of a one-half-tendon-width inferior transposition of the lateral rectus muscle with recession for an A-pattern associated with an intermittent exotropia. A Insertion to limbus distance.B Recession measured from the insertion.
superior oblique overaction and binocular fusion. These patients are at risk for developing cyclovertical diplopia after superior oblique tenotomy.
23Patients with binocular fusion and mild superior oblique overaction are best treated with transposition of the horizontal recti rather than a superior oblique tenotomy.
Another surgical option for the fusing patient is a controlled tendon elongation procedure, such as the Wright superior oblique tendon expander or a split-tendon elongation. For large A- and V-patterns ( 25 PD) with 3 or more oblique overaction, consider combining oblique weakening with a half-tendon- width horizontal rectus muscle transposition.
OBLIQUE DYSFUNCTION
Clinical Evaluation of Oblique Dysfunction
When an oblique muscle overacts or underacts, all three func- tions of the muscle are involved: torsional, vertical, and hori- zontal. Clinical quantification of oblique dysfunction, however, is primarily based on the vertical hyper- or hypofunction seen on version testing. To assess oblique function, move the eye under examination into adduction and make an observation.
Then move the eye into the field of action of the muscle: adduc- tion and elevation for the inferior oblique muscle, and adduc- tion and depression for the superior oblique muscle. The amount of overaction or underaction can be graded on a scale of 1 to
4 for overaction and 1 to 4 for underaction. A measurement of 1 overaction is recorded if there is no hypertropia with hor- izontal versions, but there is slight overaction when the eye is moved into the field of action of the oblique muscle vertically.
With 2 overaction, there is a slight hypertropia in horizontal gaze, and with 3 overaction, there is obvious hypertropia on direct horizontal gaze. In 4 overaction, there is a large hyper- tropia in horizontal gaze with an abduction movement as the eye moves vertically into its field of action. Figure 5-3 in Chapter 5 shows degrees of inferior oblique overaction on version testing.
The amount of A- or V-pattern and amount of fundus torsion are additional parameters to help quantitate the amount of oblique dysfunction.
When evaluating oblique dysfunction, the abducting eye
should be fixing so the adducting eye is free to manifest oblique
dysfunction. For example, when the right inferior oblique is
being evaluated, a version movement to the left is directed, the right eye is partially covered, and the right eye is observed behind the cover for an upshoot (see Chapter 5, Fig. 5-4).
Discussion of the characteristics of individual oblique muscle dysfunctions follows.
Primary Oblique Overaction Versus Paresis
Overaction of an oblique muscle can be primary (i.e., unknown etiology) or can be secondary to a muscle paresis. Primary oblique muscle overaction is commonly found in association with A- and V-pattern horizontal strabismus. One possible eti- ology for what appears to be primary oblique muscle overaction is ectopic location of rectus muscles and their pulleys.
5,6A transient congenital oblique muscle paresis could also cause secondary overaction of its antagonist muscle. A congenital superior oblique paresis, for example, produces ipsilateral infe- rior oblique overaction. Oblique overaction can also be caused by paresis of its yoke vertical rectus muscle of the contralateral eye (Hering’s law of yoke muscles). For example, a left inferior rectus paresis causes apparent overaction of the right superior oblique muscle and is best observed when the patient fixes with the paretic left eye, down and in abduction.
In general, acquired oblique muscle paresis is associated with underaction of the agonist and with relatively mild over- action of the antagonist oblique muscle. Congenital and long- standing oblique muscle paresis are usually associated with minimal superior oblique underaction and significant overaction of the antagonist oblique muscle. The head tilt test, described below, is used to distinguish primary oblique dysfunction from oblique dysfunction secondary to a vertical or oblique muscle paresis. A positive head tilt test is a strong indication that there is a vertical rectus or oblique muscle paresis whereas a negative head tilt usually indicates a primary oblique overaction. If the vertical deviation changes by more than 5 PD on right tilt versus left tilt, then the head tilt test is said to be positive. If there is no significant difference in the deviation (5 PD or less) from right tilt to left tilt, then the head tilt test is said to be negative.
B
IELSCHOWSKYH
EADT
ILTT
ESTTilting the head stimulates the utricular reflex and invokes tor-
sional eye movements to correct and maintain the appropriate
retinal orientation. A tilt right, for example, invokes intorsion of the right eye and extorsion of the left eye. The intortors are the superior oblique and the superior rectus muscles, and the extortors are the inferior oblique and the inferior rectus muscles.
This arrangement keeps vertical forces balanced during the head tilt. If one of the torsional muscles is paretic, then there will be an imbalance of vertical forces and a vertical deviation will occur on head tilt testing. Figure 9-3 demonstrates this concept for a right superior oblique paresis. As the head tilts to the right, the right superior oblique and right superior rectus contract to intort the right eye. Because the superior oblique is paretic, the superior rectus has unopposed vertical force and elevates the eye, creating an increasing right hyperdeviation on head tilt to the right.
The head tilt test is used in patients with a vertical devia- tion to determine if either a vertical rectus or oblique muscle is paretic. When a patient presents with a vertical deviation, first perform the head tilt test to see if a paretic muscle is present. If the head tilt test is positive ( 5 PD difference in right tilt vs.
left tilt), then it is likely there is a vertical rectus or oblique muscle paresis. To determine which muscle is paretic, measure the deviation in sidegaze and use the three-step test as described next.
FIGURE 9-3. Diagram of a right superior oblique paresis with a positive head tilt in tilt right. As the head tilts to the right, the left eye extorts and the right eye intorts. The extorters of the left eye are the inferior rectus and the inferior oblique. Their vertical functions cancel each other, so there is no vertical overshoot. The intortors of the right eye are the superior rectus (SR) and superior oblique (SO) muscles. Because the right superior oblique is paretic, the elevation effect of the superior rectus is unopposed, and a right hypertropia occurs on tilt to the right.
P
ARKST
HREE-S
TEPT
ESTMarshall Parks in 1958 published the “Three-Step Test” for the diagnosis of cyclovertical muscle palsies.
23This test identifies which muscle is paretic in patients with a hypertropia caused by an isolated vertical rectus muscle or oblique muscle palsy.
The three steps are to determine (1) which paretic muscle might be causing the hyperdeviation in primary position, (2) where the hypertropia is greatest, in rightgaze or leftgaze, and (3) on head tilt, which side the hypertropia is greatest: tilt right or tilt left.
See Table 9-1 for results of the three-step test for both vertical and oblique muscle palsy.
The first step is to determine which paretic muscle could be causing a hyperdeviation in primary position. A right hyper- deviation, for example, might be caused by a weak depressor muscle of the right eye (i.e., right inferior rectus or right supe- rior oblique) or a weak elevator muscle of the left eye (i.e., left superior rectus or left inferior oblique).
The second step is to determine in which horizontal field of gaze the hypertropia increases. If the hypertropia increases on gaze away from the hypertropic eye, the paretic muscle is the
TABLE 9-1. Responses to the Three-Step Test for All Vertical and Oblique Muscle Palsies.
Third step: hyper increases with Second head tilt (hyper⬎ ipsilateral step: hyper tilt⫽ oblique First step: hyper increases hyper⬎ contralateral
in primary in gaze tilt⫽ vertical rectus)
RSO
RIR RIR R LIO
RHT vs. R
LSR LIO L RIR
LIO
RSO R RSO
L
LSR L LSR
RSR
RIO RSR R RSR
LHT vs. R
LSO LSO L LSO
LIR
RIO R LIR
L
LIR L RIO
ipsilateral oblique or contralateral vertical rectus. A hypertropia that increases to the side of the hypertropia is caused by a paretic vertical muscle on the side of the hypertropia or the contralat- eral vertical rectus muscle, that is, the paretic muscle is a vertical rectus muscle of the abducting eye or an oblique muscle of the adducting eye. For example, a right hyperdeviation that increases in leftgaze could only be caused by a paretic left superior rectus muscle or a paretic right superior oblique muscle.
The third step is based on the Bielschowsky head tilt test as previously described. This last step can be difficult to calcu- late, so this author uses a trick that he shamelessly calls Wright’s rule. The author states, “I am sure others have used the same trick to simplify the head tilt test, but I like the way it sounds:
Wright’s Rule.” Wright’s rule states that if the hyperdeviation increases on head tilt to the same side of the hyperdeviation, then an oblique muscle is paretic. If the hyperdeviation increases to the opposite side of the hyperdeviation, then a vertical rectus muscle is paretic. For example, if the right hyper increases on head tilt to the right (same side as the hyper), then the oblique muscle is paretic; namely, the right superior oblique (SO) or left inferior oblique (IO) muscle. If the right hyper increases on left head tilt (opposite side of the hyper), then it is the vertical rectus muscle that is weak; namely, the left superior rectus (SR) muscle or right inferior rectus (IR) muscle. Example 6 describes charac- teristics of a right superior oblique paresis.
Example 6. Right Superior Oblique Paresis
Rightgaze Leftgaze
RHT10 RHT 15 RHT 25
Head tilt test: right, RHT 15 PD; left, RHT 4 PD.
P
ARKST
HREE-S
TEPT
EST FORE
XAMPLE6 Step 1: Right hypertropia
Right IR or SO versus left SR or IO (underacting muscles, right eye vs. left eye).
Step 2: Right hypertropia increases in leftgaze
Left SR or right SO (the muscles with field of action in leftgaze).
Step 3: Right hypertropia increases in head tilt to the right
Right tilt induces intorsion of the right eye and extorsion of
left eye. Both the muscles in contention (RSO and LSR) are
intortors, but only the RSO intorts on right tilt. Therefore, the diagnosis is right superior oblique paresis.
or, by Wright’s rule:
Right hyperdeviation increases on right head tilt (same side as the hyper); therefore, it has to be an oblique muscle paresis.
As we are down to two choices from step 2, RSO and LSR, the paretic muscle is the right superior oblique.
S
HORTCUT TO THET
HREE-S
TEPT
ESTClassically, the paretic muscle is determined by the Parks three- step test as just described. In 1967, Helveston
13described com- bining steps 1 and 2 to make a two-step test.
This author prefers to start with the head tilt test and use Wright’s rule. To know which vertical rectus or oblique muscle is weak, determine in which horizontal gaze the vertical devia- tion increases, right or left. As an example, a right hypertropia that increases on head tilt to the right and increases on rightgaze has to be caused by an oblique muscle paresis because the tilt is positive to the same side as the hypertropia. Because the right hypertropia increases on rightgaze, in the field of action of the left inferior oblique muscle (not in the field of action of the right superior oblique muscle), the paretic muscle is the left inferior oblique. Using Wright’s rule alone narrows the choices to two muscles: either an oblique or a vertical rectus muscle of each eye. Determining the horizontal gaze where the hypertropia is greatest tells us which eye, the right eye or the left eye.
P
ROBLEMS WITH THEH
EADT
ILTT
ESTA positive head tilt test is not infallible when diagnosing cyclovertical muscle paresis. Patients with dissociated vertical deviations, as well as some patients with intermittent exotropia, show a positive head tilt. In addition, the head tilt test is designed to diagnose an isolated paretic muscle, and it may not be reliable when multiple muscles are paretic or if an ocular restriction is present.
Superior Oblique Paresis
A superior oblique paresis is the most common cause for an
isolated vertical deviation. The typical findings of a unilateral
superior oblique paresis include an ipsilateral hypertropia that
increases on contralateral side-gaze and a positive head tilt test
with the hyperdeviation increasing on head tilt to the ipsilateral
shoulder (see Example 6). There may be relatively little superior oblique underaction and mostly inferior oblique overaction (Fig.
9-4A,B). Mild extorsion is recorded if less than 10°. To reduce the hypertropia and fuse, patients with a unilateral superior oblique paresis adopt a compensatory head tilt to the side, oppo- site the paresis, combined with a face turn away from the side of the palsy. Long-standing unilateral superior oblique paresis with a large hypertropia may show pseudosuperior oblique over- action of the contralateral eye, as a result of contraction of the ipsilateral superior rectus muscle because of the long-standing hypertropia and Hering’s Law of yoke muscles. As the ipsil- ateral eye has restricted depression in abduction, the yoke muscle overacts (i.e., contralateral superior rectus muscle).
FIGURE 9-4A,B. Composite nine-gaze photograph of patient with a congenital right superior oblique palsy. Note the large RHT in primary position that increases in leftgaze. There is 3 right inferior oblique overaction and 2 superior oblique underaction. In straight rightgaze, it appears that the left superior oblique is overacting, but the right superior oblique is slightly tight because of secondary contracture. (B) Positive head tilt test with large RHT on tilt right.
Bilateral superior oblique paresis is associated with bilat- eral superior oblique underaction, a V-pattern (arrow subtype), little or no hypertropia, and a right hypertropia in leftgaze and a left hypertropia in rightgaze (Fig. 9-5). Other signs include a bilateral extorsion (total greater than 10°), a reversing head tilt test with a right hypertropia in tilt right, and a left hypertropia in tilt left. The presence of an arrow pattern with extorsion increasing in downgaze (Example 7) is diagnostic for an acute bilateral superior oblique palsy and is often seen with traumatic superior oblique palsies. Clinical signs of unilateral versus bilateral superior oblique paresis are shown in Table 9-2.
Example 7. Bilateral Superior Oblique Paresis
Rightgaze Leftgaze
LHT10 RHT 2, ET4 RHT 10
RHT 5, ET 20 Bilateral Maddox Rod—15° Extorsion.
Bilateral extorsion on fundus exam.
Head tilt test: right, RHT 10 PD; left, LHT 10 PD.
ET on downgaze
FIGURE 9-5. Composite nine-gaze photograph of patient with bilateral traumatic superior oblique palsy. Patient has a small esotropia and extor- sion in primary position that increases in downgaze. Note the V-pattern (arrow pattern subtype) with a large esotropia in downgaze. There is also severe underaction of both superior oblique muscles associated with rel- atively mild inferior oblique overaction.
A bilateral asymmetrical superior oblique paresis can look like a unilateral superior oblique paresis; this is termed masked bilateral superior oblique paresis.
16,17Suspect a masked bilateral paresis if the hypertropia precipitously diminishes in lateral gaze toward the side of the obvious paretic superior oblique muscle and if there is even slight inferior oblique overaction of the fellow eye (see Example 8).
Example 8. Masked Bilateral Superior Oblique Paresis
Rightgaze Leftgaze
RHT5 RHT 20 RHT 30
Head tilt test: right, RHT 25 PD; left, RHT 3 PD.
The presence of a V-pattern and bilateral extorsion on fundus examination also suggest bilateral involvement in patients with a presumed unilateral paresis. In these cases of masked bilateral superior oblique paresis, if surgery is performed only for a uni- lateral superior oblique palsy, the contralateral superior oblique paresis will become evident postoperatively.
F
ALLENE
YESignificant underaction of the superior oblique muscle and fix- ation with the paretic eye will produce the classic finding called the fallen eye. When a patient with a superior oblique paresis fixes with the paretic eye and tries to look into the field of action of the paretic superior oblique muscle, the weak superior oblique muscle requires a large amount of innervation to make the eye
TABLE 9-2. Unilateral Versus Bilateral Superior Oblique Paresis.
Clinical sign Unilateral Bilateral
Superior oblique underaction Ipsilateral underaction Bilateral underaction Inferior oblique overaction Ipsilateral overaction Bilateral overaction V-pattern Less than 10 PD Greater than 10 PD with
arrow pattern (convergence in downgaze) Hypertropia Greater than 5 PD Less than 5 PD (except
asymmetrical paresis) Head tilt test Increasing hyper on Positive head tilt to both
ipsilateral head tilt sides (RHT on right tilt (Rt SOP RH tilt and LHT on left tilt) right)
Extorsion Less than 10° Greater than 10°
move down and nasally. Because of Hering’s law, the yoke muscle (contralateral inferior rectus muscle) receives an equally large amount of innervation. Because the contralateral inferior rectus muscle has normal function, this increased innervation produces a large secondary hypotropia, or the fallen eye (Fig. 9-6).
I
NHIBITIONALP
ALSY OF THEC
ONTRALATERALA
NTAGONISTChavasse, in 1939, described the term inhibitional palsy of the
contralateral antagonist. This term relates to a patient who
chronically fixates with the paretic eye, resulting in an apparent
weakness on version testing of the yoke muscle to the antago-
nist of the paretic eye. That is, the paretic eye moves easily into
the field of its antagonist with little innervation because the
agonist is weak. The yoke muscle to the antagonist of the paretic
muscle receives the same small innervation (Hering’s law), so it
FIGURE 9-6. Photograph of a traumatic right superior oblique palsy, showing the fallen eye, left eye. The right eye is fixing in the field of action of its paretic superior oblique muscle (i.e., down and in adduction), requiring a great deal of innervation. Because of Hering’s law of equal innervation of yoke muscles, the left inferior rectus muscle (yoke muscle to the paretic right superior oblique muscle) also receives a great deal of innervation. Because the left inferior rectus is at full strength, it overacts and pulls the left eye down, thus causing the appearance of a left fallen eye.will appear paretic on versions because its antagonist is inner- vated. Clinically, this is seen in association with a congenital fourth nerve palsy and ipsilateral inferior oblique overaction when the patient fixates with the paretic eye. For example, a left fourth nerve palsy with left inferior oblique overaction will produce a left hypertropia increasing in rightgaze. If the patient fixates with the left eye, the innervation required for the left eye to look up and right is minimal, as it is in the field of the over- acting left inferior oblique muscle. The yoke muscle to the left inferior oblique muscle is the right superior rectus muscle, and it too will receive little innervation. The right superior rectus will appear to underact or be paretic because its antagonist, the right inferior rectus, is normally innervated and holds the eye down. Inhibitional palsy of the contralateral antagonist is only seen on version testing when the paretic eye is fixing.
P
RIMARYI
NFERIORO
BLIQUEO
VERACTIONV
ERSUSS
UPERIORO
BLIQUEP
ALSYPrimary inferior oblique overaction can be differentiated from superior oblique palsy by the head tilt test and type of V-pattern (Table 9-3).
Traumatic Superior Oblique Paresis
Traumatic superior oblique paresis is usually associated with severe closed head trauma, loss of consciousness, and cerebral concussion; however, even very mild head trauma without loss of consciousness can cause a superior oblique paresis. Traumatic superior oblique paresis occurs when the tentorium traumatizes
TABLE 9-3. Primary Inferior Oblique Overaction Versus Superior Oblique Paresis.
Clinical sign Primary overaction Superior oblique paresis
Inferior oblique overaction Yes Yes
V-pattern Yes, Y-pattern Yes, “arrow” pattern
Head tilt test Negative Positive
Subjective torsion No Yes (except in congenital
superior oblique paresis)
Objective extorsion (fundus Yes Yes
examination) Underaction of ipsilateral
superior oblique muscle No (minimal if any) Yes
the trochlear nerves as they exit the posterior midbrain posteri- orly. Since the two trochlear nerves exit the midbrain together, only a few millimeters apart, the nerve trauma is almost always bilateral. Thus, most cases of traumatic superior oblique paresis are bilateral, although the paresis may be asymmetrical.
The pattern of strabismus is classically, minimal or no hypertropia in primary position, a left hypertropia in rightgaze, a right hypertropia in leftgaze, underaction of both superior oblique muscles, and an esotropia in downgaze (Figs. 9-5, 9-6).
There is a positive head tilt with a right hypertropia on right tilt and a left hypertropia on left tilt. Extorsion increasing in downgaze can be demonstrated by Maddox rod and indirect oph- thalmoscopy. Patients complain of horizontal or vertical tor- sional diplopia that is worse in downgaze (Fig. 9-5). In most cases, there is not much ipsilateral inferior oblique muscle over- action, usually 1 or less. Because the strabismus is acquired, patients complain of diplopia—torsional, vertical, and horizon- tal—that increases in downgaze.
The management of traumatic superior oblique paresis is discussed later in this chapter under Treatment of Superior Oblique Paresis.
Congenital Superior Oblique Paresis
The cause of congenital superior oblique paresis is usually
unknown. The paresis may be associated with a lax superior
oblique tendon or rarely an absent tendon.
12Most cases present
as a unilateral paresis or an asymmetrical masked bilateral
paresis. Typically, there is a large hypertropia in primary posi-
tion and significant inferior oblique overaction, usually with
relatively little superior oblique underaction (see Fig. 9-4). The
most common presenting sign is a head tilt opposite to the side
of the palsy. Even though the paresis is present at birth, symp-
toms often occur in late childhood or even adulthood. It is
common for patients to be diagnosed for the first time in middle
age. Normally vertical fusional amplitudes are weak and even
small acquired hyperdeviations of 3 to 5 PD cannot be fused and
result in constant diplopia. Patients with congenital superior
oblique paresis, however, develop large vertical fusional ampli-
tudes, and fuse large hypertropias up to 35 PD. The presence
of large vertical fusion amplitudes is an important clinical sign
that the hyperdeviation is long-standing, rather than acutely
acquired, and is suggestive of a congenital superior oblique palsy.
Over time, the fusional control weakens, resulting in a devia- tion that becomes manifest in later life.
In addition to large fusional vergence amplitudes, patients with congenital superior oblique paresis adopt a compensatory head tilt opposite to the palsy to minimize the deviation and establish binocular fusion. Patients with congenital superior oblique paresis typically have good stereopsis and manifest the hyperdeviation intermittently, usually when fatigued. Even though patients with congenital superior oblique paresis have high-grade stereopsis, most also have the ability to suppress when tropic so that they usually do not experience diplopia. This sensory adaptation is similar to the adaptation of patients with intermittent exotropia. Typically these patients also do not demonstrate extorsion by Maddox rod testing as they adapt to the retinal extorsion.
Facial asymmetry is seen in approximately 75% of patients with congenital superior oblique palsy, with one side of the face being hypoplastic and smaller.
26The hypoplastic side of the face is on the side of the head tilt (i.e., the dependent side of the face) (Fig. 9-7). One theory for the facial asymmetry is that gravita-
FIGURE 9-7. Photograph of patient with a compensatory right head tilt and right face turn associated with a left congenital superior oblique palsy.
Note the facial asymmetry, as the right side of the face is hypoplastic.
Hypoplasia is ipsilateral to the head tilt and contralateral to the superior oblique palsy.
tional pull on the dependent side of the face causes changes in size of facial structures. Another theory is that facial asymme- try represents a mild form of congenital plagiocephaly associ- ated with the superior oblique palsy.
In summary, signs that a superior oblique palsy is congeni- tal and not acquired include childhood photographs showing a long-standing head tilt, facial asymmetry, lack of extorsional diplopia, lack of extorsion by Maddox rod, and large vertical fusion amplitudes. In most cases, the diagnosis of congenital superior oblique muscle palsy can be made on the basis of clinical evaluation.
Other Causes of Superior Oblique Paresis
The majority of superior oblique pareses are either congenital or traumatic, but other causes include vascular disease with brain- stem lacunar infarcts, multiple sclerosis, intracranial neoplasm, herpes zoster ophthalmicus, diabetes and associated mononeu- ropathy, and iatrogenic after superior oblique tenotomy. An acquired idiopathic superior oblique paresis requires a neuro- logical workup including neuroimaging. Patients with cran- iosynostosis may have bilateral superior oblique palsies caused by absent superior oblique tendons.
Treatment of Superior Oblique Paresis
The treatment of superior oblique paresis depends on the pattern of the strabismus. Cardinal position of gaze measurements and evaluation for inferior oblique overaction and superior oblique underaction are needed to determine the pattern of strabismus and where the deviation is greatest. Subjective torsion should be assessed by double Maddox rod testing in acquired cases;
however, patients with a congenital superior oblique palsy will not have subjective torsion. Objective torsion evaluated by indi- rect ophthalmoscopy can be useful for verifying torsional abnor- malities but is usually not the major clinical sign that directs the treatment plan.
Most treatment strategies require identifying where the
hypertropia is greatest, and surgery is then designed to correct
the deviation in primary position while reducing the incomi-
tance.
15For example, a right unilateral superior oblique paresis
with a hypertropia less than 10 PD in primary position, inferior
oblique overaction, and minimal superior oblique underaction
can be treated with a simple ipsilateral inferior oblique weak- ening procedure (e.g., inferior oblique muscle graded anterior- ization). If the hypertropia in primary position is greater than 15 PD, then an isolated inferior oblique recession may not be enough to correct the hypertropia. In this case, especially if there is a significant hypertropia in downgaze, one should add a contralateral inferior rectus recession to an ipsilateral inferior oblique recession (Table 9-4). Late overcorrections have been known to occur after inferior rectus recessions. This author has changed to a nonabsorbable suture or a long lasting absorbable suture for inferior rectus muscle recessions, and this choice seems to have solved the late overcorrection problem. In cases of congenital superior oblique palsies, be conservative in regard to recessing the contralateral inferior rectus muscle. A small undercorrection is usually well tolerated, but an overcorrection and a reverse hypertropia is difficult for these patients to fuse.
Tightening the entire width of the superior oblique tendon by performing a superior oblique tuck has theoretical utility for improving superior oblique function. A superior oblique tuck, however, usually results in minimal to no improvement of supe- rior oblique function, and the tight tendon creates a restrictive leash of elevation in adduction (i.e., iatrogenic Brown’s syn- drome). The tuck has been suggested for patients with congen- ital superior oblique paresis secondary to a lax superior oblique tendon.
12,27Plager
27suggests performing exaggerated forced duction testing of the superior oblique tendon at the beginning of surgery to see if the tendon is lax or absent. Caution should
TABLE 9-4. Treatment of Unilateral Superior Oblique Paresis.
Clinical manifestation Procedure
Inferior oblique overaction: small Inferior oblique weakening (author
hypertropia prefers graded anteriorization)
Hyperdeviation in primary position (common) 15 PD; deviation is greater in upgaze
Inferior oblique overaction: large Ipsilateral inferior oblique weakening
hypertropia (author prefers graded
Hyperdeviation in primary position anteriorization), with contralateral
15 PD inferior rectus recession (common)
Lax superior oblique tendon with Small superior oblique tuck (rare) superior oblique underaction
Hyperdeviation in primary position
15 PD; minimal inferior oblique overaction; deviation is greatest in downgaze
be used when tucking the superior oblique, as iatrogenic Brown’s syndrome is a frequent complication of a superior oblique tendon tuck. Most surgeons avoid the superior oblique tuck unless there is significant superior oblique underaction and an extremely lax tendon or, in cases of bilateral superior oblique paresis, where there is severe superior oblique underaction.
Traumatic superior oblique palsies should be observed for 6 months following recovery of muscle function. Patients who have partial recovery of superior oblique muscle function will often be left with extorsional diplopia worse in downgaze, without significant oblique dysfunction, V-pattern, or hyper- tropia. In these cases, extorsion can be improved by the Harada–Ito procedure, which consists of selectively tightening the anterior one-fourth to one-third of the superior oblique tendon fibers.
11Patients with a bilateral superior oblique palsy and poor recovery of muscle function show a large esotropia in downgaze (arrow subtype V-pattern), extorsion greater in downgaze, left hypertropia in rightgaze, and a right hypertropia in leftgaze, but minimal or no hypertropia in primary position.
In these cases, consider either bilateral Harada–Ito procedures and bilateral medial rectus muscle recessions with infraplace- ment one-half-tendon-width or bilateral superior oblique tendon tucks and bilateral medial rectus muscle recessions with infraplacement one-half-tendon-width. This is a difficult stra- bismus to correct; however, surgery can often improve diplopic symptoms. The superior oblique tucks will create a bilateral iatrogenic Brown’s syndrome, but this may be an acceptable trade-off for improved single binocular vision in downgaze.
Table 9-4 lists treatment strategies for unilateral superior oblique paresis, and Table 9-5 lists treatments for bilateral supe- rior oblique paresis.
Inferior Oblique Paresis
An isolated inferior oblique paresis is extremely rare and, when
it does occur, it is usually idiopathic. Pollard
28reported on 25
patients having an isolated inferior oblique palsy, with 23 being
unilateral and 2 bilateral. All cases were idiopathic and benign
without an identifiable neurological cause. Rarely, inferior
oblique palsy has been reported after head trauma
20or attributed
to a microvascular occlusive event. Patients with isolated infe-
rior oblique paresis show ipsilateral superior oblique overaction,
but they can be distinguished from those with primary superior
oblique overaction. Unlike primary superior oblique overaction, inferior oblique paresis is associated with a positive head tilt test and a hyperdeviation that is greatest when the patient looks up and in a horizontal gaze away from the affected eye. For example, a left inferior oblique paresis results in a right hypertropia that increases in rightgaze and upgaze, and the hyperdeviation increases on head tilt to the right. Note that, on versions, infe- rior oblique paresis looks similar to Brown’s syndrome with limited elevation in adduction; however, there is an A-pattern and superior oblique overaction with an inferior oblique palsy, and forced ductions are negative (Table 9-6).
The treatment of a unilateral inferior oblique paresis is an ipsilateral superior oblique weakening procedure (e.g., Wright
TABLE 9-5. Treatment of Bilateral Superior Oblique Paresis.
Clinical manifestation Procedure
Extorsional diplopia (partially recovered Bilateral Harada–Ito traumatic SOP)
Extorsional diplopia (5°), minimal hypertropia, 8 PD, small or no V-pattern (10 PD), and minimal inferior oblique overaction and superior oblique underaction
Bilateral superior oblique underaction or Bilateral superior oblique tendon (often traumatic SOP, rarely congenital tuck with bilateral medial rectus
lax SO tendon) recessions with inferior
transposition one-half tendon width
Hypertropia 8 PD and big arrow pattern (15 PD increase in esotropia from primary to downgaze), 10° extorsion in primary position increasing in downgaze, and reversing hypertropias in sidegaze
Masked bilateral or asymmetrical bilateral Bilateral inferior oblique graded superior oblique palsy (usually anteriorization (more
congenital SOP) anteriorized on the side of the
obvious SOP) and recession of inferior rectus contralateral to the obvious SOP
Hyperdeviation in primary position or
10 PD, asymmetrical inferior oblique If associated with a large head tilt,
overaction bilateral inferior oblique graded
anteriorization (more anteriorized on the side of the obvious SOP) and Harada–Ito on the side of the obvious SOP
superior oblique tendon expander) if the hypotropia is less than 10 PD, or add a recession of the contralateral superior rectus recession if the hypotropia is greater than 10 PD.
30Superior Oblique Overaction
The cause of superior oblique overaction (SOOA) is unknown.
It may be related to an associated paresis of the contralateral inferior rectus muscle, thus producing a secondary overaction of the yoke superior oblique muscle. The author has noted several patients with superior oblique overaction who also have an underacting contralateral inferior rectus muscle.
C
LINICALF
EATURES OFS
UPERIORO
BLIQUEO
VERACTIONSuperior oblique overaction is an exaggeration of the normal function of the superior oblique muscle that includes intorsion, depression, and abduction. Patients with superior oblique over- action show a downshoot of the adducting eye in lateral gaze, abduction in downgaze causing an A-pattern, and intorsion that is seen on indirect ophthalmoscopy. The A-pattern is not sym- metrical, but shows more divergence from primary position to downgaze than from upgaze to primary position. This type of A- pattern is termed a lambda pattern (Fig. 9-8).
TABLE 9-6. Differential Diagnoses of Elevation Deficit in Adduction.
Primary superior Inferior oblique Brown’s syndrome oblique overaction paresis
Bilateral Unusual Common Unusual
involvement
Pattern “Y” (divergence Lambda (divergence “A” (convergence in upgaze) in downgaze) in upgaze)
Superior oblique No Yes Yes
overaction
Inferior oblique Yes Minimal to Yes
underaction moderate
Standard forced Positive Negative Negative
ductions
Head tilt test Negative Negative Positive
Torsion None to slight Intorsion (increasing Intorsion intorsion in in downgaze) (increasing in
upgaze upgaze)
Greatest vertical Upgaze Downgaze Upgaze
deviation
Superior oblique overaction often occurs in association with horizontal strabismus such as intermittent exotropia. Most patients with superior oblique overaction do not show subjec- tive incyclotorsion with Maddox rod testing, even though indirect ophthalmoscopy reveals intorsion, because sensory adaptation of the superior oblique overaction has been present since early infancy. Like inferior oblique overaction, superior oblique overaction is usually bilateral. Another characteristic of superior oblique overaction is limited elevation in adduction, which is secondary to a contracted tight superior oblique muscle.
D
IFFERENTIALD
IAGNOSIS OFS
UPERIORO
BLIQUEO
VERACTIONThe differential diagnosis of limited elevation in adduction includes superior oblique overaction, Brown’s syndrome, and inferior oblique paresis (Table 9-6). Brown’s syndrome is caused by a tight superior oblique muscle–tendon complex. In Brown’s syndrome, there is no superior oblique overaction, and forced ductions are positive to elevation in adduction. In addition, the syndrome is often associated with an exodeviation when the eyes move from primary position to upgaze (Y-pattern), whereas superior oblique overaction is associated with a lambda A- pattern.
FIGURE 9-8. Composite nine-gaze photograph of a patient with inter- mittent exotropia and bilateral superior oblique overaction (3 OU) with typical A-pattern (lambda subtype) with increasing divergence in downgaze.
T
REATMENT OFS
UPERIORO
BLIQUEO
VERACTIONThe ideal superior oblique weakening procedure produces a measured slackening of the muscle–tendon complex without disrupting the functional mechanics of the insertion. Many surgical approaches to weaken the superior oblique have been tried.
3,31Presently, the two procedures most commonly used are the superior oblique tenotomy and the Wright silicone tendon expander.
38,41The tenotomy technique involves cutting the tendon in two, while the silicone tendon expander consists of inserting a segment of a 240 retinal silicone band (4–6 mm) between the cut ends of a nasal tenotomy to elongate the tendon.
42Other superior oblique weakening procedures include tenec- tomy, recession, and posterior tenotomy.
3,31In a comparative study, this author found the silicone tendon expander procedure to be superior to a tenotomy, especially in patients with preop- erative fusion.
40Performing a superior oblique tenotomy on patients with high-grade stereopsis and fusion carries a signifi- cant risk for creating a secondary superior oblique paresis and causing postoperative diplopia.
25In these cases, the silicone tendon expander is preferred. Another situation where superior oblique weakening procedures can cause problems is in patients with preexisting dissociated vertical deviation (DVD); weaken- ing the superior obliques will exacerbate DVD. In these cases, options are to treat the A-pattern with horizontal rectus muscle transpositions rather than weakening the superior obliques, or to plan an undercorrection of the superior oblique overaction with the silicone tendon expander. The advantage of the supe- rior oblique silicone tendon expander is that it lengthens the superior oblique tendon in a controlled manner and holds the cut tendon ends apart at a fixed distance. This technique reduces postoperative superior oblique paresis, allows for controlled weakening, and makes it possible to find cut tendon ends if a reoperation is necessary.
Inferior Oblique Overaction
Primary inferior oblique overaction is most commonly associ- ated with a horizontal strabismus such as congenital esotropia or intermittent exotropia. Isolated primary inferior oblique over- action can also occur without associated horizontal strabismus.
Although primary inferior oblique overaction is bilateral, in
most cases it can be quite asymmetrical, with the lesser overacting inferior oblique muscle difficult to detect.
24When inferior oblique overaction is identified, it is important to differentiate primary inferior oblique overaction from a second- ary inferior oblique overaction (i.e., superior oblique paresis). It can be difficult to differentiate primary inferior oblique overac- tion from secondary overaction, as patients with marked infe- rior oblique overaction may have significant superior oblique underaction secondary to the tight inferior oblique muscle. On the other hand, patients with a superior oblique paresis often have inferior oblique overaction. In addition, indirect ophthalmoscopy will show significant objective extorsion in both primary and secondary inferior oblique overaction.
The key to distinguishing primary from secondary inferior oblique overaction is the head tilt test. The head tilt test is neg- ative in primary inferior oblique overaction and is positive with secondary inferior oblique overaction. In both groups, there is the typical upshoot of the adducting eye, and both types usually manifest a significant V-pattern, especially if there is bilateral inferior oblique overaction. The type of V-pattern, however, can help differentiate primary versus secondary inferior oblique overaction. Patients with primary inferior oblique overaction have a Y-pattern with a significant exotropia shift occurring from primary position to upgaze but relatively little change between primary position and downgaze (Fig. 9-9). The Y-pattern
FIGURE 9-9. Composite nine-gaze photograph of patient with bilateral primary inferior oblique overaction. There is a large V-pattern (Y-subtype) with divergence in upgaze. The inferior oblique overaction is 3 OU with no significant superior oblique underaction.
occurs because the inferior oblique muscles act as abductors in upgaze. In contradistinction, a V-pattern associated with supe- rior oblique paresis (especially bilateral) shows an arrow pattern with an esotropic shift that occurs when moving from primary position to downgaze. Because the inferior oblique muscle is an extortor, elevator, and abductor, these elements are exaggerated in direct proportion to the overaction. When quantitating infe- rior oblique overaction, look at the entire function of the muscle, including the upshoot, amount of V-pattern, and fundus extorsion.
10,37See Table 9-3 for a comparison of the clinical signs of primary inferior oblique overaction with secondary inferior oblique overaction caused by superior oblique paresis.
M
IMICKERS OFI
NFERIORO
BLIQUEO
VERACTIONInferior oblique overaction is the most common cause of an ocular upshoot in adduction. Dissociated vertical deviation (DVD) can look just like inferior oblique overaction, because DVD will become manifest in sidegaze as the adducted eye is occluded by the nasal bridge (see Chapter 10); this results in a hyperdeviation in sidegaze that mimics inferior oblique overac- tion. DVD can be differentiated from inferior oblique overaction by occluding the affected eye in abduction as well as adduction and evaluating for a change in the vertical deviation. If the ele- vation is the same in adduction and abduction, then this is DVD, whereas an increasing hyperdeviation in adduction suggests inferior oblique overaction. Because DVD commonly coexists with inferior oblique overaction in patients with infantile esotropia, the distinction can be extremely difficult to see.
Distinguishing clinical features such as the presence of a V- pattern (Y-subtype), a true hyperdeviation in lateral gaze with a hypotropia of the contralateral eye, and objective extorsion on indirect ophthalmoscopy will help to identify inferior oblique overaction rather than DVD.
An upshoot in adduction can be caused by a tight lateral
rectus muscle. As the eye adducts and slightly elevates, the
tight lateral rectus pulls the eye up, causing pseudo-overaction
of the inferior oblique. Aberrant innervation of the inferior
oblique and superior rectus muscles has been documented as
causing an upshoot associated with Duane’s syndrome (see
Chapter 10).
T
REATMENT OFI
NFERIORO
BLIQUEO
VERACTIONSurgery is indicated when the inferior oblique overaction and V-pattern interfere with fusion, or if it becomes a cosmetic problem. In general, 2 or more inferior oblique overaction should be considered surgically significant whereas 1 or less overaction usually does not require treatment. There are, however, two important exceptions to this rule. The first excep- tion is in patients with bilateral asymmetrical inferior oblique overaction in which one eye shows minimal overaction. In these cases, both inferior oblique muscles should be weakened, even if one only shows trace overaction. Unilateral inferior oblique weakening surgery in an asymmetrical bilateral case unmasks the inferior oblique overaction of the nonoperated eye. Inferior oblique surgery should also be considered for bilateral overac- tion associated with a significant V-pattern (Y-subtype), even if there is minimal upshoot on sidegaze. Patients who have a sig- nificant divergence when the eyes move from primary position to upgaze should have inferior oblique weakening surgery, despite the minimal overaction observed with versions.
In most cases, inferior oblique overaction is bilateral and bilateral surgery should be performed. Patients with amblyopia of two lines or greater difference in visual acuity, however, should have monocular surgery, which should be limited to the amblyopic eye to avoid the risk (although slight) of surgical com- plications to the nonamblyopic eye. When inferior oblique over- action coexists with horizontal strabismus, both should be corrected in the same operation. Staged planning of two sepa- rate operations does not improve surgical results and requires a second round of anesthesia. When planning simultaneous hori- zontal and inferior oblique surgery, the horizontal surgical numbers are not altered. Even though the inferior oblique muscles have an abduction function, weakening the inferior oblique muscles does not significantly alter the horizontal align- ment unless there is an extremely large V-pattern and severe inferior oblique overaction.
S
URGICALT
ECHNIQUES FORW
EAKENING THEI
NFERIORO
BLIQUEM
USCLES(
SEE ALSOC
HAPTER11)
Surgical techniques for correcting inferior oblique overaction
include myectomy, recession, and anteriorization.
1,7,19Recently,
the anteriorization procedure has become popular, as results have been good even in cases of severe overaction. Anterioriza- tion works by transposing the inferior oblique insertion from its normal position posterior to the equator of the eye to a position anterior to the equator. When the inferior oblique insertion is anterior to the equator, the inferior oblique muscle no longer acts as an elevator but, instead, pulls the front of the eye down;
now, it is actually a depressor. This change is why anterioriza- tion procedures that place the inferior oblique muscle anterior to the inferior rectus insertion can cause the complication of an ipsilateral hypodeviation and limited elevation.
4,33This compli- cation can be avoided by keeping the anterior inferior oblique muscle fibers posterior to the inferior rectus insertion. Keeping the posterior fibers of the inferior oblique muscle at least 3 mm posterior to the inferior rectus insertion is especially important because of the inferior oblique neurovascular bundle.
34,35The neurovascular bundle is a relatively inelastic structure insert- ing in the posterior aspect of the inferior oblique muscle. If the posterior fibers are anteriorized to the level of the inferior rectus insertion, the neurovascular bundle will tighten and act as a tether holding the eye down. Anteriorizing the posterior fibers produces a J-deformity of the inferior oblique insertion. This author prefers avoiding the J-deformity and has developed a graded anterior transposition procedure that keeps the posterior fibers posterior to the anterior fibers. The graded anterior trans- position procedure yields excellent results, even in severe cases, without the complication of limited elevation.
9Because the full anteriorization procedure with a J-deformity causes limited ele- vation, it is rarely indicated. However, it can be considered if performed bilaterally for severe bilateral inferior oblique over- action with a large DVD.
Brown’s Syndrome
E
TIOLOGYBrown’s syndrome is a restrictive strabismus characterized by
limitation of elevation that is worse when the eye is in adduc-
tion (Fig. 9-10A). It can be congenital or acquired, with a variety
of causes for the restriction of elevation in adduction (see Table
9-7). The term congenital Brown’s syndrome or “true” Brown’s
syndrome, is used to refer to Brown’s syndrome caused by a con-
genitally inelastic superior oblique muscle–tendon complex.
36FIGURE 9-10A,B. (A) Preoperative composite nine-gaze photograph of patient with congenital Brown’s syndrome, right eye, with limited eleva- tion in adduction and minimal to no superior oblique overaction. Note Y-pattern with exodeviation in upgaze. Also note there is some limita- tion of the right eye even in abduction, but the limitation is greatest in adduction. Despite the severe limitation of elevation, there is only trace hypotropia in primary position. (B) Postoperative photograph after a Wright’s superior oblique tendon silicone expander, right eye, for Brown’s syndrome. Note the versions are almost normal with only a trace limi- tation to elevation, which is the optimal result, with a slight residual lim- itation of elevation in adduction right eye. This was the author’s first silicone expander patient, and the results have remained excellent over 11 years of follow-up.
There are nonsuperior oblique causes for congenital Brown’s syndrome, including inferior orbital mechanical restriction, superior nasal orbital mass, and inferior displaced lateral rectus muscle and pulley.
22,36C
LINICALF
EATURES OFB
ROWN’
SS
YNDROMEThe hallmark of Brown’s syndrome, regardless of the cause, is limited elevation in adduction. In congenital Brown’s syndrome,
TABLE 15-7. Classification of Brown’s Syndrome.
I. Congenital onset
A. True congenital Brown’s syndrome (superior oblique etiology) i. Unknown: probable inelastic muscle–tendon complex B. Congenital pseudo-Brown’s syndrome (nonsuperior oblique cause)
i. Anomalous inferior orbital adhesions ii. Posterior orbital bands
iii. Anomalous insertion of rectus muscle and pulley (e.g., inferior displacement of lateral rectus pulley or insertion)
II. Acquired onset
A. Superior pblique or trochlear etiology i. Peritrochlear scarring and adhesions
1. Chronic sinusitis
2. Trauma: superior temporal orbit 3. Blepharoplasty and fat removal
4. Lichen sclerosus et atrophicus and morphea ii. Tendon–trochlear inflammation and edema
1. Idiopathic inflammatory (pain and click) 2. Trochleitis with superior oblique myocytis 3. Acute sinusitis
4. Adult rheumatoid arthritis 5. Juvenile rheumatoid arthritis 6. Systemic lupus erythematous
7. Possibly distant trauma (CPR and long bone fractures) 8. Possibly hormonal changes postpartum
iii. Superior nasal orbital mass 1. Glaucoma implant 2. Neoplasm
iv. Tight or inelastic superior oblique muscle 1. Thyroid disease (inelastic muscle) 2. Peribulbar anesthesia (inelastic tendon) 3. Hurler–Scheie’s syndrome (inelastic tendon) 4. Superior oblique tuck (short tendon) v. Idiopathic
B. Nonsuperior oblique or trochlear causes i. Floor fracture
ii. Retinal band around inferior oblique muscle iii. Inferior temporal adhesions
Source:From Ref. 32, with permission.
