Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology Current Thought and A Practical Guide_Wilson, Saunders, Trivedi_2008

15.1Syndromes Primarily Associated

15.2Syndromes Primarily Associated

15.2.3Congenital Fibrosis Syndrome  . . . . .   206

•Children with duction deficits and abnormal head posture are likely to have an identifiable ocular motility syndrome.

•Most defined motility syndromes present with a spectrum of clinical appearance and severity.

•Clinical history, along with careful evaluation of versions and ductions, will usually reveal the correct diagnosis. Ancillary testing, such as forced ductions or estimates of generated muscle force, will sometimes be required in planning treatment.

•Surgical intervention can usually improve the strabismus and eliminate the abnormal head posture, but ocular motility is rarely restored to normal.

horizontal eye movements, usually a deficiency of abduction, and some degree of globe retraction in adduction. This is most easily identified by a narrowing of the palpebral fissure, which develops or worsens in adduction. Abnormal head posture is common, as are up-shoots and down-shoots of the globe. If the fellow eye has normal ocular motility, patients will almost invariably assume a head position to allow binocular vision.

The etiology of most cases of DRS is believed to be maldevelopment of the sixth cranial nerve nucleus, fascicle and nerve, with subsequent misinnervation of the lateral rectus muscle by a branch (or branches) of the third cranial nerve [25, 42]. The underlying pathology is hypoplasia of the motor neurons in the six cranial nerve nucleus, with sparing of the internuclear neurons [42]. This finding helps explain why DRS manifests as unilateral duction abnormalities, rather than as a horizontal gaze palsy, as seen in internuclear ophthalmoplegia. Rare acquired cases suggest that a supranuclear basis is also possible [1].

DRS can be associated with other ocular and nonocular abnormalities; however, it most often presents as an isolated disorder. Rather than a single entity, DRS should be viewed as a spectrum of ocular dysmotility, with precise clinical findings determined by the degree of lateral rectus muscle paresis and patterns of dysinnervation of the lateral rectus and sometimes other extraocular muscles. Although binocular vision is frequently maintained in DRS, about one half of cases require a compensatory face turn to maintain orthotropia. Most reports demonstrate diplopia outside a relatively small field of single binocular vision [50]. Surgical treatment is most often performed to correct a strabismus in primary gaze (and associated compensatory face turn), but it is occasionally indicated to treat cosmetically objectionable globe retraction, diplopia, up-shoot and/or down-shoot, or ocular discomfort.

15.1.1.1History and Epidemiology

While first described by Heuck in 1879 [24], and later by Stilling and Turk [66, 69], Alexander Duane is usually credited for describing the characteristic constellation of impaired horizontal eye movements based on a review of 54 patients with this disorder which bears his name [14]. These findings consisted of globe retraction, narrowing of the palpebral fis-

sure, and oblique eye movements in attempted adduction. Duane retraction syndrome, or Stilling–Turk–

Duane syndrome, is now a commonly recognized abnormality of ocular motility. It is usually sporadic in occurrence, but inherited cases have been reported

[8]. Familial DRS is inherited in an autosomal-dom- inant pattern [49]. Several phenotypes have been described, with genetic loci identified on chromosomes 2, 8, and 20 [2, 3, 7]. Occasionally, associated findings in DRS include ocular anomalies, such as iris dysplasia, cataract, and other dysinnervation disorders including Marcus Gunn jaw wink and “crocodile tears” syndrome [63]. Non-ocular findings, including radial dysplasia and auricular abnormalities, occur in about 30% of cases [49]. DRS is specifically known to occur in association with Goldenhar syndrome and Klippel–Feil syndrome, and has been described following fetal exposure to thalidomide [40]. For this reason, and the high prevalence of associated systemic malformations in the DRS patient, it has been proposed that normal innervation of the extraocular muscles is susceptible to disruption between the fourth and fifth weeks of embryogenesis [11, 21].

DRS represents approximately 1% of all strabismus cases [13]. Multiple published series of DRS have confirmed that its occurrence is greater in females (nearly 60%) and in the left eye (58–72%) [13, 50, 62,]. Approximately 20% are bilateral [13]. Curiously, there may be a male preponderance in bilateral cases [30]. As a practical matter, over one-third of all

DRS cases seen in clinical practice occur in the left eye of females. This may alert the physician to suspect the diagnosis of DRS in uncooperative children or cases where the motility findings are not perfectly clear.

15.1.1.2Clinical Findings and Classification

While the clinical manifestations of DRS may vary, reflecting the continuum of extra-ocular muscle dysinnervation, classification is still probably a worthwhile endeavor. The basic findings tend to be stereotyped, with some variability in severity of individual features, such as the horizontal duction deficit and up-shoot or down-shoot of the globe. While not intuitively obvious, most vertical phenomena can be explained by aberrant innervation of the lateral rectus muscle.

Several classification schemes have been proposed, but the one described by Huber in 1974 is still commonly used (Table 15.1) [26]. It is based on original data from medial and lateral rectus muscle electromyography in DRS patients; however, other studies have shown variability in the patterns of dysinnervation across DRS types [60]. It may therefore be equally useful for surgical planning to classify patients based on primary-gaze alignment (esotropic, exotropic, etc.), combined with the magnitude of the primary-gaze deviation and severity of associated findings, such as globe retraction [33, 34].

In addition to the three Huber types, other patterns of DRS-like motility disorders have been described, including a vertical variant that may reflect dysinnervation of the superior rectus and/or inferior oblique muscles [74]. DRS should be distinguished from other forms of extraocular muscle dysinnervation, which occasionally occur on a congenital or acquired basis but do not involve co-contraction or narrowing of the palpebral fissure in adduction.

of gaze; however, these types may blend together and the distinctions may sometimes appear arbitrary (Table 15.1). For this and other reasons, the Huber classification is not necessarily helpful with regard to planning treatment – its use is mostly limited to a convenient clinical shorthand.

Type-I DRS

Type-I DRS is the most common clinical presentation and includes approximately 85% of cases. It is characterized by limited abduction, sometimes mimicking sixth cranial nerve palsy (Fig. 15.1). Adduction is normal or only modestly reduced and associated with globe retraction and narrowing of the palpebral fissure (Fig. 15.2). Electromyography shows little or no electrical activity of the lateral rectus muscle in abduction, but paradoxical activity in adduction. This is thought to result from anomalous innervation by the third cranial nerve [4, 26].

Approximately one-half of patients with type-I DRS are orthotropic in primary-gaze position in child-

Huber described three types of DRS based on clinical findings and electromyographic data recorded from the extraocular muscles in different positions

pic. The deviation is usually less at near viewing. A compensatory face turn towards the involved eye is often present and permits sensory fusion. Amblyopia or loss of binocularity is therefore uncommon [68].

Huber II Limited adduction Co-contraction in adduction Limited abduction (variable) Upand down-shoots common

Huber III Limited abduction and adduction

Co-contraction in adduction (often severe)

Upand down-shoots common

“Splits” Same as type II, except mild co-con- traction in adduction and DRS eye abducts with lateral gaze of normal eye

Fig. 15.1  Continuum in type-I DRS. This disorder may resemble congenital sixth cranial nerve palsy when aberrant innervation is limited

Type-I DRS may need to be distinguished from both congenital sixth cranial nerve palsy and congenital esotropia. In sixth cranial nerve palsy, globe retraction and eyelid findings are absent; in congenital esotropia, abduction is normal or near normal and the deviation in primary-gaze position is generally large.

Furthermore, the deviation in type-I DRS is rarely greater than 30 prism diopters, even when the abduction deficit is severe or both eyes are affected [13, 27]. This discrepancy between primary-gaze deviation and the abduction deficit allows a virtually certain diagnosis (and obviates the need for intracranial imaging) in infants where co-contraction may not be clinically apparent. Finally, in type-I DRS, the limitation in abduction typically improves with elevation or depression (Fig. 15.3), which is not true of other “look-alike” diagnoses.

Fig. 15.2a−c  Boy with typical bilateral type-I Duane retraction syndrome (DRS). There is marked limitation of abduction in both eyes, narrowing of the palpebral fissures in adduction, and a small-angle esotropia in primary gaze position. The esotropia usually decreases at near viewing. Surgical treatment was not recommended. (From [79])

Type-II DRS

Type-II DRS is a far less common presentation, occurring in about 10% of cases. It is characterized by limited adduction with normal or slightly limited abduction. Globe retraction and palpebral fissure narrowing on attempted adduction are common, and may be severe. Upand down-shoots of the involved eye in adduction are frequently present (Fig. 15.4). This pattern is thought to arise when the lateral rectus muscle receives innervation from the sixth cranial nerve in addition to anomalous branches of the third cranial nerve. Originally thought to be characterized by an intact sixth cranial nerve, a recent imaging study showed that type-II DRS may also be associated with sixth cranial nerve hypoplasia [12].

Nearly all patients with type-II DRS are exotropic in primary position [50]. A compensatory face turn away from the DRS eye will normally permit sensory fusion. As might be expected, the exotropia is typically greater at near than distance viewing.

Type-III DRS

Type-III DRS is a rare presentation that may be viewed as a combination of the preceding two types. There is marked limitation of both abduction and adduction. It occurs in approximately 1% of cases, but the distinction from type-I DRS may be arbitrary in cases where the limitation of adduction and abduc-

tion is symmetrical and not severe. This pattern is thought to arise when there is little or no sixth cranial nerve activity, and the lateral rectus muscle is largely innervated by anomalous branches of the third cranial nerve. Since the involved eye moves poorly, these patients are usually well aligned in primary position and fuse without (or with minimal) head posture; however, globe retraction and palpebral fissure narrowing in attempted adduction are often severe and usually the reason patients seek ophthalmologic treatment.

Synergistic Divergence

there is sufficient anomalous innervation of the lateral rectus muscle to cause an abduction movement on attempted opposite gaze, resulting in a startling “wrong way” duction. For example, with left eye involvement, when the patient attempts left gaze, the left eye moves left; but when right gaze is attempted, the eye again moves left. These patients are always exotropic in primary gaze, which is their position of least strabismus.

Vertical DRS

Often colorfully termed “the splits,” this is a rare but well-recognized variant of type-II DRS, where

Occasionally, a retraction-like syndrome will occur with a reduced vertical duction and globe retraction in the opposite position of gaze. If congenital in ori-

gin, this may properly be considered a DRS variant, however rare. It is not known whether vertical DRS results from infranuclear cranial nerve misdirection, a supranuclear disorder, or even structural abnormalities within the orbit or extraocular muscles [37]. Acquired vertical (or horizontal) motility disorders due to trauma (such as blowout fracture of the orbit), which may have a similar clinical picture, are not properly considered DRS, since they are not associated with dysinnervation of the extraocular muscles.

15.1.1.3Management of DRS

The DRS rarely is associated with amblyopia [68], although clinically important anisometropia does occur in approximately one-fourth of cases [13, 31]. This should generally be treated with glasses and/or patching prior to consideration of surgical intervention. Hyperopic glasses occasionally produce enough ocular realignment to avoid surgery. Many cases of DRS cannot be improved or do not need to be treated surgically, which is generally the preferred management in young children; however, surgical intervention is warranted in cases with a chronic face turn, manifest deviation in primary-gaze position, large upor down-shoots, and painful or cosmetically unacceptable globe retraction. Forced ductions are almost always restricted, often severely so, making strabismus surgery technically challenging.

While some general principles apply, surgical treatment is always tailored to a specific patient (Tables 15.2, 15.3). The expectations of surgical correction must be tempered with the fact that DRS can never be entirely corrected, and the risk of adverse surgical outcomes is real. Rectus muscle resection in customary dosages can worsen the globe retraction. It is therefore not commonly performed in an attempt to restore primary-gaze alignment or improve ductions.

Most cases of type-I DRS with esotropia and ipsilateral face turn respond well to unilateral or bilateral medial rectus muscle recession. Generally, an esotropia of up to 15 prism diopters can be managed with a single medial rectus muscle recession of 6 mm or less. Larger recessions typically worsen the adduction deficit, often dramatically so, especially in the context of marked co-contraction. Large recessions also risk producing a consecutive exotropia, essen-

tially converting a type-I into a type-II DRS, particularly if the patient has reduced saccadic velocity in adduction [46]. Selected patients with unilateral DRS will benefit from bilateral surgery, allowing a smaller medial rectus muscle recession in the DRS eye. If there is a mild limitation to abduction, the use of a posterior fixation suture on the contralateral medial rectus muscle may help to equalize ductions [58]. Bilateral DRS should be approached with caution and the surgical dose reduced; the measured strabismus in primary gaze may actually represent a secondary deviation because of bilaterally restricted abduction. Alternating upand down-shoots in adduction are caused by lateral rectus muscle co-contraction and are treated with recession or “Y-split” of the lateral rectus muscle, depending on clinical circumstances

[52].

The preferred treatment for type-II DRS is unilateral or bilateral lateral rectus muscle recessions, sometimes accompanied by recession of the medial rectus muscle if the co-contraction is severe. Surgical dosing typically needs to be greater than in type- I DRS. The A and V patterns, if present, may result from aberrant innervation of the lateral rectus muscle and therefore are improved with lateral rectus muscle recession.

Transposition surgery has been effective in managing DRS, particularly type-I cases. Full or partial tendon transposition of the vertical rectus muscles to the lateral rectus muscle insertion, with or without augmentation with posterior fixation sutures, can improve abduction by approximately 10−15° and relieve the compensatory face turn in over half of cases

[18, 44, 70]; however, transposition procedures can be unpredictable. In particular, they can restrict adduction and worsen globe retraction, and cause postoperative vertical strabismus in up to 15% of cases

[44]. For this reason, horizontal rectus muscle recessions are generally preferred as the initial treatment (Table 15.4).

15.1.2 Moebius Syndrome

First described by Moebius in 1888 [43], Moebius syndrome, a congenital sequence, refers to the constellation of horizontal ocular motility disorders and seventh (facial) nerve palsy [41]. Most commonly,

the presentation includes bilateral sixth cranial nerve palsy; however, the spectrum of clinical presentation can include unilateral abducens nerve palsy or a horizontal gaze palsy [23]. Most cases are sporadic; however, autosomal-dominant inheritance has been reported [76]. It is commonly associated with systemic abnormalities, including other cranial nerve palsies, limb malformations, mental retardation, and orofacial defects [19, 53].

resultant corneal hypoesthesia or anesthesia. In some cases, tarsorrhapy is required to protect the cornea. The esotropia is generally responsive to large bilateral medial rectus muscle recessions, though this approach may further limit horizontal ductions. Lateral rectus muscle resection or transposition procedures may be required in some cases [64].

15.1.2.1Clinical Findings

The Moebius patient presents early in infancy with difficulty feeding, incomplete eyelid closure, and mask-like facies. Tongue hypoplasia will often secure the clinical diagnosis. In contrast to DRS, the esotropia may be large angle; however, relatively straight eyes with deficit horizontal movement is also a frequent finding. In infants with early-onset esotropia, the deviation is often 50 prism diopters or greater. Although it is important to differentiate this presentation from congenital esotropia, the associated orofacial abnormalities make the diagnosis fairly straightforward.

15.1.2.2Management of Moebius Syndrome

The management of Moebius syndrome primarily requires careful monitoring for exposure keratitis. In addition to the facial nerve palsy, these patients can also present with fifth cranial nerve dysfunction with

15.2Syndromes Primarily Associated with Vertical Duction Deficits

The evaluation and management of patients with cyclovertical strabismus presents a unique challenge for the clinician. Vertical duction deficits associated with hyperor hypotropia may be associated with a variety of unrelated conditions, including supranuclear pathology, cranial nerve palsy, extraocular muscle restriction,orperiocularscarring.Clinicalexamination, however, will almost always yield the correct diagnosis. It is usually evident when paying close attention to duction deficits, presence and degree of vertical strabismus in different positions of gaze, assessment of restriction or extraocular muscle weakness, and occasionally other ancillary findings (Table 15.5). It is critically important to distinguish abnormalities of ocular versions (e.g., inferior oblique muscle “underaction”), which are assessment of relative (binocular) eye movements, from abnormalities of ocular ductions, which are assessment of monocular eye movements. Ductions are best assessed with the fellow eye occluded.

Table 15.5  Differential diagnosis of non-traumatic monocular upgaze deficiency

Dysthyroid orbitopathy Brown syndrome

Superior rectus muscle palsy

Inferior rectus muscle fibrosis

Orbital adherence syndrome

Monocular elevation deficiency (both infraand supranuclear)

Orbital space-occupying mass

15.2.1 Brown Syndrome

Originally described by Harold Brown, Brown’s “superior oblique tendon sheath syndrome” is now known to be associated with failure of normal movement of the superior oblique tendon through the trochlea [5].

Because of the tethering of the globe’s normal movement in the orbit, a characteristic constellation of findings occurs which normally makes the diagnosis straightforward. Forced ductions, which are typically performed in the operating room under general anesthesia, are unequivocally positive. The restricting superior oblique tendon causes a characteristic and usually unyielding limitation of elevation in adduction.

Brown syndrome is almost always congenital in etiology but can be inflammatory, post-traumatic, or even the presenting sign of sinus infection [6, 9, 20, 38, 54, 57, 65]. Superior oblique tendon tuck can also produce a virtually identical clinical picture, although usually not as severe and mostly self-limited [20, 22].

There is no known laterality or gender predilection, but it can occasionally be familial [48, 77]. Approximately 10% of congenital cases are bilateral [75].

Brown syndrome can be intermittent (so-called click syndrome), and approximately 10% of cases undergo spontaneous resolution [10, 73, 75].

15.2.1.1Clinical Findings

The signature clinical finding of Brown syndrome is monocular limitation of elevation, worse in adduction and better in abduction. When versions are tested, there is a straight-line descent of the involved eye as it moves from an elevated/abducted position to an adducted position (Fig. 15.5). If elevation is compromised near primary position, there will be a compensatory chin-up head posture, often with a face turn to position the involved eye in abduction (away from the restriction). Upgaze saccades will be normal outside the restricted gaze positions.

Children with congenital Brown syndrome often present for management of torticollis, and occasionally with the complaint that the fellow eye makes excessive upward movements in abduction. It is rarely associated with ocular torsion or “overaction” of the ipsilateral superior oblique muscle (i.e., the eyes are straight in all downgaze positions). This allows easy distinction of Brown syndrome from other entities, such as inferior oblique muscle palsy, adherence syndrome, or primary over action of the superior oblique muscle, which may also be associated with some elevation deficiency in adduction. A particularly useful clinical finding is the presence of globe proptosis in attempted elevation (Fig. 15.6), which tends to relax the restricting superior oblique tendon [59]. This finding is often striking, and partially accounts for the widening of the palpebral fissure seen when these patients attempt to look up. Pseudo-Brown syndrome

from inferior rectus muscle restriction, ocular adherence after multiple strabismus procedures, or blowout fracture of the orbit, will not exhibit this positional globe proptosis (Table 15.6).

the superior oblique muscle always carries the risk of producing an iatrogenic superior oblique muscle palsy, which can occur in up to one half of operated cases [17, 72]. In some cases, the iatrogenic postoperative strabismus can be more debilitating than the Brown Syndrome [56]. For this reason, patients

Patients with Brown syndrome may be candidates for surgical treatment if there are important symptoms or cosmetic issues interfering with daily life and there is little prospect for spontaneous improvement. Most often, the reason for surgery is a primary-gaze hypotropia with a compensatory chin-up head posture and/or face turn. The elevation deficit, particularly in adduction, can be cosmetically objectionable and associated with diplopia; however, weakening

tion above the horizontal meridian are best left unoperated. Prophylactic weakening of the ipsilateral inferior oblique muscle at the time of superior oblique tendon tenotomy has been proposed [17, 48], but has unpredictable results. This should be reserved as a secondary procedure if symptomatic superior oblique muscle palsy develops.

Except for rare cases of acquired inflammatory

Brown syndrome, which can be treated with locally injected steroids or systemic non-steroidal anti-in-