High-resolution magnetic resonance imaging demonstrates varied anatomic abnormalities in Brown syndrome

Masquerading Superior Oblique Palsy

PURPOSE

We evaluated patients with hypertropia compatible with a diagnosis of superior oblique (SO) palsy to ascertain whether the 3-step test (3ST) can distinguish SO atrophy characteristic of trochlear nerve pathology from masquerading conditions.

DESIGN

Prospective cross-sectional study.

METHODS

In an academic practice, we performed quasi-coronal plane, surface coil magnetic resonance imaging in 83 patients clinically diagnosed with SO palsy. We evaluated alignment, SO cross-sectional area, SO contractility, and rectus muscle pulley positions.

RESULTS

A total of 57 patients with mean age 39 years (SD = 21 years) had unilateral SO palsy manifested by SO atrophy (22 congenital and 35 acquired). There was normal SO size in 26 patients with an average age of 39 years (SD =16 years) considered masquerades (8 congenital and 18 acquired). Maximum palsied SO cross-section averaged 9.5 ± 3.8 mm2, less than 18.4 ± 3.9 mm2 contralaterally (P < 10-24). In masquerades, maximum hypertropic SO cross-section was 20.7 ± 3.1 mm2, which was not different from the hypotropic SO or the contralesional muscle in SO palsy. Head tilt testing in masquerades was indistinguishable from SO palsy. In SO palsy, central hypertropia averaged 13.2 ± 9.4Δ, increasing to 21.1 ± 14.0Δ in ipsilateral tilt, and decreasing to 4.3 ± 5.3Δ in contralateral tilt. In masquerades, central hypertropia averaged 13.1 ± 8.7Δ, and was 17.7 ± 11.1Δ in ipsilateral and decreasing to 4.9 ± 5.1Δ in contralateral tilt. Upright hypertropia was larger at 17.7 ± 9.9Δ in congenital than 12.0 ± 8.4Δ in acquired SO palsy (P = 0025) but was indistinguishable from congenital masquerades. Contractile change in SO cross-section was bilaterally similar in masquerades. Relevant coordinates of rectus pulleys were similar bilaterally in masquerades.

CONCLUSIONS

The 3ST pattern characteristic of unilateral SO palsy may be mimicked in all respects by masquerades.

Can Binocular Alignment Distinguish Hypertropia in Sagging Eye Syndrome From Superior Oblique Palsy?

Purpose

Although the three-step test (3ST) is typically used to diagnose superior oblique palsy (SOP), sagging eye syndrome (SES) has clinical similarities. We sought to determine if alignment measurements can distinguish unilateral SOP from hypertropia in SES.

Methods

We studied hypertropic subjects who underwent surface-coil magnetic resonance imaging (MRI) demonstrating either SO cross-section reduction indicative of congenital or acquired palsy (SOP group) or lateral rectus muscle sag (SES group). Alignment was measured by Hess screen and prism-cover testing. Multiple supervised machine learning methods were employed to evaluate diagnostic accuracy. Rectus pulley coordinates were determined in SES cases fulfilling the 3ST.

Results

Twenty-three subjects had unilateral SOP manifested by SO atrophy. Eighteen others had normal SO size but MRI findings of SES. Maximum cross-section of the palsied SO was much smaller than contralaterally and in SES (P < 2 × 10-5). Inferior oblique cross-sections were similar in SOP and SES. In both SOP and SES, hypertropia increased in contralateral and decreased in ipsilateral gaze and was greater in ipsilateral than contralateral head tilt. In SES, nine subjects (50%) fulfilled the 3ST and had greater infraplacement of the lateral than medial rectus pulleys in the hypotropic orbit. Supervised machine learning of alignment data distinguished the diagnoses with areas under the receiver operating curves up to 0.93, representing excellent yet imperfect differential diagnosis.

Conclusions

Because the 3ST is often positive in SES, clinical alignment patterns may confound SES with unilateral SOP, particularly acquired SOP. Machine learning substantially but imperfectly improves classification accuracy.

Vertical Comitance of Hypertropia in Congenital and Acquired Superior Oblique Palsy

BACKGROUND

Ivanir and Trobe have claimed that hypertropia (HT) that is greater in upgaze than downgaze, or equal to it, is characteristic of decompensated congenital superior oblique (SO) palsy and never present in ischemic, traumatic, or tumorous SO palsy. The reliability of this claim was tested in patients with SO palsy confirmed by MRI demonstration of subnormal ipsilesional SO size.

METHODS

Quasi-coronal, surface coil MRI was performed in target-controlled central gaze to identify patients with a unilateral reduction in SO cross section indicative of palsy. Nine patients gave an unequivocal history or had markedly increased vertical fusional amplitudes indicative of congenital onset (mean age 38 ± 16 years, SD). Seven patients had unequivocal acquired onset (age 47 ± 14 years and symptom duration 5.4 ± 4.8 years), including 2 with demonstrated trochlear Schwannoma and 5 with onset after severe head trauma. Fifteen patients had gradually progressive onset unequivocally not congenital yet not associated with any identifiable precipitating event (age 52 ± 20 years and symptom duration 13 ± 14 years).

RESULTS

Maximum SO cross section averaged 8.6 ± 3.9 mm2 in congenital palsy, not significantly different from 11.3 ± 3.5 mm2 in acquired palsy (P = 0.08) either unequivocally or progressively acquired, but significantly less than about 19 mm2 contralesionally in SO palsy (P < 10-4). Although mean central gaze HT was greater at 20.6 ± 8.0Δ in 9 cases of congenital than that in 22 acquired cases at 11.4 ± 6.8Δ (P = 0.002), HT was 8.4 ± 16.3Δ less in upgaze than downgaze in congenital SO palsy and 3.7 ± 11.2Δ less in acquired SO palsy. In congenital palsy, 33% of patients had HT greater in upgaze than downgaze while in 67% HT was greater in downgaze (by up to 42Δ). In acquired SO palsy, HT was greater in upgaze than downgaze or equal to it in 8 cases (36%, P = 0.87, X2). In acquired SO palsy, HT was greater in upgaze than downgaze in 37% and greater in downgaze than upgaze in 59% of cases. The HT was equal in upgaze and centralgaze in no congenital and 3 acquired cases of SO palsy. Trends were similar in unequivocal acquired and progressive acquired (noncongenital) SO palsy (P > 0.4).

CONCLUSIONS

Hypertropia is not characteristically greater in upgaze than downgaze in congenital SO palsy proven by SO atrophy on MRI. In fact, average HT is greater in downgaze than upgaze in both acquired and congenital palsy, sometimes strikingly so in the latter. The finding of HT greater in upgaze than downgaze, or equal to it, does not reliably indicate that SO palsy is congenital, nor does maximum SO cross section.

The "Eyelet Sign" as an MRI Clue for Inflammatory Brown Syndrome

BACKGROUND

Brown syndrome is characterized by a restrictive elevation deficit of the affected eye in adduction. Besides the well-known congenital form, different acquired etiologies including inflammation, trauma, and surgery may prevent the superior oblique (SO) tendon from gliding freely through the trochlea on attempted upgaze. We present MRI findings in pediatric and adult patients with inflammatory acquired Brown syndrome.

METHODS

Retrospective review of clinical and MRI findings of 6 patients (4 children: median age 8.4 years [range 6.1-8.7]; 2 adults: age 46.4 and 51.1 years). Median follow-up was 23 months (range 1-52).

RESULTS

In all 6 patients, orbital MRI demonstrated inflammatory changes of the SO tendon-trochlea complex. A striking feature was circumferential contrast enhancement of the trochlea with central sparing where the tendon passes, reminiscent of an eyelet. In all cases, the motility restriction improved either spontaneously or with systemic anti-inflammatory treatment. Although both adult patients had a history of known seronegative spondyloarthritis, there was no associated systemic condition in the children in our series.

CONCLUSIONS

Both in children and in adults, MRI can provide evidence of inflammatory changes located at the trochlea-tendon complex in acquired Brown syndrome here referred to as the "eyelet sign," which may be helpful in confirming the clinical diagnosis and guide appropriate treatment.

MRI of acquired Brown syndrome: a report of two cases

Brown syndrome is characterized by upward gaze impairment while the eye is in adduction. It is caused by abnormalities involving the superior oblique tendon-trochlea complex. Imaging can help confirm the diagnosis, shed light on its etiology, and determine the best course of treatment. However, reports of magnetic resonance imaging findings of acquired Brown syndrome are scarce in the literature. Here, we describe magnetic resonance imaging features of 2 cases of acquired Brown syndrome.

Combined Brown syndrome and superior oblique palsy without a trochlear nerve: case report

Background

Congenital Brown syndrome is characterized by limited elevation particularly during adduction. The pathogenesis of congenital Brown syndrome is still controversial.

Case presentation

A 6-year-old boy had been tilting his head to the left since infancy. He showed right hypertropia (RHT) of 2 prism diopters (Δ) in the primary position. He showed RHT 6Δ in right gaze, RHT 2Δ in left gaze, RHT 12Δ in right head tilt, and orthotropia in left head tilt. The right eye showed limitation of elevation and depression on adduction, and the left eye showed overdepression on adduction. MR images showed an absent right trochlear nerve with a hypoplastic ipsilateral superior oblique muscle.

Conclusions

Congenital Brown syndrome may be associated with an absent trochlear nerve and hypoplastic superior oblique muscle suggesting an etiologic mechanism of congenital cranial dysinnervation disorder.

Size of the Oblique Extraocular Muscles and Superior Oblique Muscle Contractility in Brown Syndrome

PURPOSE

This study employed magnetic resonance imaging (MRI) to investigate possible size and contractility changes in the superior oblique (SO) muscle, and possible isometric hypertrophy in the inferior oblique (IO) muscle, resulting from abnormal mechanical loading in Brown syndrome (BrS).

METHODS

High resolution orbital MRI was obtained in 4 congenital and 11 acquired cases of BrS, and compared with 44 normal subjects. Maximal cross-section areas and posterior partial volumes (PPVs) of the SO were analyzed in central gaze, supraduction, and infraduction [corrected] for the SO, and in central gaze only for the IO.

RESULTS

In congenital BrS, mean maximum SO cross-sectional areas were 24% and 20% less than normal in affected and unaffected eyes, respectively (P = 0.0002). Mean PPV in congenital BrS was also significantly subnormal bilaterally (29% and 34% less in affected and unaffected eyes, respectively, P = 0.001). However, SO muscle size and volume were normal in acquired cases. The SO muscle did not relax in supraduction in BrS, although there was normal contractile thickening in infraduction. The IO muscle had normal size bilaterally in BrS.

CONCLUSIONS

Congenital BrS may be associated with SO hypoplasia that could reflect hypoinnervation. However, unique isometric loading of oblique extraocular muscles due to restrictive hypotropia in adduction in BrS is generally not associated with changes in muscle bulk or in SO contractility. Unlike skeletal muscles, the bulk and contractility of extraocular muscles can therefore be regarded as independent of isometric exercise history. Restriction to elevation in BrS typically arises in the trochlea-tendon complex.

Unilateral acquired Brown's syndrome in systemic scleroderma: An unusual cause for diplopia

Brown's syndrome can be congenital or acquired with multiple causes. It has been described as a ocular complication in various rheumatic and nonrheumatic diseases. We describe a case of 27-year-old female patient with 5 years old history of systemic scleroderma who developed vertical diplopia, a left head tilt, and restriction of left eye on elevation in adduction. The patient responded to systemic steroids with resolution of diplopia.

Considerations on the etiology of congenital Brown syndrome

PURPOSE OF REVIEW

Brown syndrome is an ocular motility disorder characterized by limited volitional and passive elevation of the eye in adduction. Although originally thought due to abnormalities in the trochlea or tendon sheath (limiting the free movement of the tendon through the trochlea), recent evidence suggests that some cases of congenital Brown syndrome may be related to neurodevelopmental abnormalities of the extraocular muscles (congenital cranial dysinnervation disorders, CCDD).

RECENT FINDINGS

CCDD is a term encompassing congenital abnormalities of eye movements caused by congenital innervational abnormalities. The abnormal development of cranial nerve nuclei or abnormalities in cranial nerve axonal transport affects the development of the extraocular muscle(s). Currently, congenital fibrosis of the extraocular muscles, Duane syndrome, Moebius syndrome, Horizontal gaze palsy and progressive scoliosis, and synergistic divergence are included as CCDDs. In addition, congenial ptosis, Jaw Wink ptosis, and congenital superior oblique palsy are also included. Recently, it has been suggested that some cases of congenital Brown syndrome and congenital superior oblique paresis are related, and these entities may be part of the CCDDs spectrum.

SUMMARY

Important findings regarding the cause of congenital Brown syndrome will be reviewed.

Magnetic resonance imaging in congenital Brown syndrome

AIMS

Our aim was to elucidate the etiology of Brown syndrome by evaluating the trochlea position, morphologic characteristics of the extraocular muscles including superior oblique muscle/tendon complex, and the presence of the cranial nerves (CN) III, IV, and VI using magnetic resonance imaging (MRI) in eight patients with unilateral congenital Brown syndrome and one patient with bilateral congenital Brown syndrome.

METHODS

Nine consecutive patients diagnosed with congenital Brown syndrome had a comprehensive ocular examination and MRI for the CN III, CN VI, and the extraocular muscles. Five of the nine patients underwent additional high resolution MRI for CN IV. The distance from the annulus of Zinn to the trochlea was measured.

RESULTS

Normal sized CN III, IV, and VI, as well as all extraocular muscles, could be identified bilaterally in all patients with available MRI. The distance from the annulus of Zinn to the trochlea was the same in both eyes.

CONCLUSIONS

The findings for our patients, particularly in those who underwent additional high resolution MRI, did not provide evidence of a lack of CN IV as a cause of Brown syndrome.

The Apt Lecture. Connective tissues reflect different mechanisms of strabismus over the life span

BACKGROUND

Connective tissue pulleys determine extraocular muscle force directions and pulley heterotopy can induce strabismus. The etiology and type of pulley abnormalities vary with patient age, resulting in different but predictable types presentations of strabismus.

METHODS

Magnetic resonance imaging (MRI) was obtained in 95 patients with pulley heterotopy, of whom 56 had childhood-onset pattern strabismus, and was compared with published data on 28 patients aged 69 ± 12 years who had sagging eye syndrome. Control data were from age-matched normal controls with no strabismus.

RESULTS

Patients with childhood-onset strabismus had intact lateral rectus-superior rectus band ligaments and straight extraocular muscle paths but exhibited pulley array A pattern-associated incyclorotation or V pattern-associated excyclorotation. Rectus transposition surgery collapsed patterns. Patients with sagging eye syndrome exhibited blepharoptosis, superior sulcus defect, and inferolateral displacement of rectus pulleys with elongation of extraocular muscles that followed curved paths. Symmetrical lateral rectus pulley sag was associated with divergence paralysis esotropia; asymmetrical sag > 1 mm, with cyclovertical strabismus. Both lateral rectus resection and medial rectus recession treated divergence paralysis esotropia. Partial vertical rectus tenotomy treated cyclovertical strabismus.

CONCLUSIONS

Childhood onset pulley abnormalities are associated with A or V pattern strabismus and external anatomical features suggest that these pulley defects are probably congenital. Adult onset pulley defects commonly result from age-related tissue involution and external features such as adnexal laxity are also helpful in recognizing involution as a possible etiology of strabismus.

Possible association of congenital Brown syndrome with congenital cranial dysinnervation disorders

BACKGROUND

Congenital cranial dysinnervation disorders (CCDDs) are known to arise from abnormal development of individual and multiple cranial nerve nuclei or abnormalities in cranial nerve axonal transport. We report our findings for several patients with Brown syndrome in association with other known abnormalities characteristic of CCDDs.

METHODS

The medical records of patients presenting during a 4-year period with congenital Brown syndrome were retrospectively reviewed. Patients with Brown syndrome confirmed by forced ductions were included in the study if the Brown syndrome was associated with either an abnormal development of the superior oblique muscle or superior oblique paresis, ptosis, Duane syndrome, or other known CCDDs.

RESULTS

A total of 9 patients with Brown syndrome were identified. Of these, 3 also demonstrated a contralateral superior oblique palsy; 2, a contralateral Duane syndrome; 1, an ipsilateral congenital ptosis; and 3, a moderate to severely hypoplastic ipsilateral superior oblique muscle.

CONCLUSIONS

Some patients with congenital Brown syndrome are associated with and possibly in the spectrum of CCDDs. We propose that Brown syndrome may be due to abnormal development of the trochlear nerve, which results in physical changes in the superior oblique muscle-tendon-trochlea complex. This results in a tendon that is either long and lax, absent, or abnormally inserted (ie, superior oblique paresis) or a tendon that is restricted in its movements through the trochlea (Brown syndrome).

[MRI in congenital Brown's syndrome: report of 16 cases]

INTRODUCTION

Superior oblique retraction syndrome or Brown's syndrome is one of the so-called restrictive syndromes causing anatomic strabismus. It is characterized by active and passive limitation of upward gaze in adduction in the field of action of the superior oblique muscle (SO). The etiology of this congenital syndrome remains unknown. The purpose of this prospective study is to analyze brain and orbital magnetic resonance imaging (MRI) in patients with congenital Brown's syndrome.

PATIENTS AND METHODS

Sixteen children (19 months - 9 years) underwent complete ophthalmologic evaluation followed by brain/orbital MRI with attention to the superior oblique muscle. Average age at time of MRI was 4.2 years old. Among patients included were eight girls and eight boys. MRI was performed on a 1.5T (Symphony TIM, Siemens, Erlangen) to visualize the orbit and specifically the SO.

RESULTS

Of 16 eyes, 13 demonstrated radiologic abnormalities of the SO muscle; six demonstrated tendon-trochlea complex hypertrophy, four demonstrated complete SO hypertrophy (tendon-trochlea-muscle belly), one demonstrated trochlear hypertrophy, and two demonstrated abnormalities solely of the tendons, of which one was longer and one was thinner with fibrosis.

CONCLUSION

MRI shows a high frequency of SO radiologic abnormalities in congenital Brown's syndrome. MRI permits the analysis of not only the tendon, but also the trochlea and muscle belly, whereas surgery only allows visualization of the tendon. MRI proved to be an interesting tool for investigation of these patients and for a better understanding of the pathogenesis.

Absence of the fourth cranial nerve in congenital Brown syndrome

PURPOSE

To elucidate the aetiology of congenital Brown syndrome.

METHODS

Four consecutive patients diagnosed with unilateral congenital Brown syndrome had a comprehensive standardized ocular motility examination. Any compensatory head posture was measured. Brain magnetic resonance imaging (MRI) with regard for the IV cranial nerve (CN) was performed in all patients. Orbital MRI was performed in 2/4 patients, with images acquired in eight directions of gaze and superior oblique (SO) muscle areas compared.

RESULTS

CN IV could not be identified bilaterally in two patients, but was absent only on the side of the Brown syndrome in the two other patients. On the normal side, orbital MRI revealed a smaller SO muscle area in upgaze than in downgaze, demonstrating normal actions of this muscle. On the side of the Brown syndrome, the SO area remained the same in upgaze and in downgaze and approximately symmetric to the area of SO in downgaze on the normal side.

CONCLUSIONS

These cases add further anatomical support to the theory of paradoxical innervation in congenital Brown syndrome. CN IV was absent in two patients on the side of the Brown syndrome, but without muscle hypoplasia. SO muscle size did not vary in up- and downgaze, which we interpreted as a sign of constant innervation through branches of CN III.

Brown's syndrome

PURPOSE OF REVIEW

To better understand the various causes of Brown's syndrome, provide a historical account of the progression of Brown's syndrome, and to bring attention to clinical characteristics specific to Brown's syndrome.

RECENT FINDINGS

The inability to elevate an eye in adduction is a common problem with a number of possible causes usually pointing to cyclovertical muscle involvement. The specific cause can usually be determined by either the three-step test or forced ductions. Because Brown's syndrome does not involve a paretic cyclovertical muscle but rather a mechanical muscle limitation, forced ductions instead of the three-step test must be used to evaluate a patient of Brown's syndrome and is crucial in the diagnosis.

SUMMARY

The recognition of true Brown's syndrome can be accomplished by clinical examination and confirming the diagnosis with a positive forced duction test.

Magnetic resonance imaging of tissues compatible with supernumerary extraocular muscles

PURPOSE

To determine by magnetic resonance imaging (MRI) the prevalence and anatomy of anomalous extraocular muscle (EOM) bands.

DESIGN

Prospective, observational case series.

METHODS

High-resolution, multipositional, surface coil orbital MRI was performed using T1 or T2 fast spin echo weighting with target fixation control under a prospective protocol in normal adult subjects and a diverse group of strabismic patients between 1996 and 2009. Images demonstrating anomalous EOM bands were analyzed digitally to evaluate their sizes and paths, correlating findings with complete ophthalmic and motility examinations.

RESULTS

Among 118 orthotropic and 453 strabismic subjects, 1 (0.8%) orthotropic and 11 (2.4%) strabismic subjects exhibited unilateral or bilateral orbital bands having MRI signal characteristics identical to EOM. Most bands occurred without other EOM dysplasia and coursed in the retrobulbar space between rectus EOMs such as the medial rectus to lateral rectus, from superior to inferior rectus, or from 1 EOM to the globe. In 2 cases, horizontal bands from the medial rectus to lateral rectus muscles immediately posterior to the globe apparently limited supraduction by collision with the optic nerve. All bands were too deep to be approached via conventional strabismus surgical approaches.

CONCLUSIONS

Approximately 2% of humans exhibit on MRI deep orbital bands consistent with supernumerary EOMs. Although band anatomy is nonoculorotary, some bands may cause restrictive strabismus.

[Superior oblique sharpening surgery in the treatment of Brown syndrome plus]

PURPOSE

To describe superior oblique sharpening in congenital Brown syndrome plus.

MATERIAL AND METHODS

A retrospective study of 17 Brown syndrome cases that were treated with oblique superior sharpening from 1997 to 2007. Vertical deviation in primary position was classified as + to +++, head tilt as: mild (< 10°), moderate (10-20°) and severe (≥ 20°); elevation in adduction from -1 to -4. A good postoperative result was considered if last elevation limitation in adduction was zero or -1, without head tilt and vertical deviation in primary position.

RESULTS

Mean age was 4.9 years. Limitation elevation in adduction which was -3 in 8 cases (47.1%) and -4 in 9 (52.9%), which improved completely after surgery in 6, -1 in 9 and -3 in 2 patients. Preoperative hypotropia in 15 cases (13 mild, 1 moderate and one severe) was resolved in 13 after surgery. Of 14 patients with torticollis (3 mild, 10 moderate and one severe) it was surgically corrected in 11. Success was achieved in 14 (82.4%), 2 were under corrected (11.8%) and one was overcorrected (5.88%). Mean follow-up was 60.71 months.

CONCLUSIONS

Oblique superior sharpening as treatment for Brown syndrome plus is an effective procedure. The incidence of secondary oblique palsies has been very low.

Acquired Brown's syndrome associated with preseptal cellulitis

We describe a patient who developed vertical diplopia, a left head tilt and restriction of right eye on elevation in adduction during preseptal cellulitis. Pathways of inflammatory preseptal conditions in association with acquired Brown's syndrome are being reviewed.

Superior oblique muscle paresis and restriction secondary to orbital mucocele

Mucoceles are chronic cystic lesions of the paranasal sinuses lined by respiratory epithelium. Their extension into the adjacent orbit may result in proptosis, ocular motility disorders, and diplopia. Brown syndrome secondary to extension of a mucocele into the orbit has been reported previously. Superior oblique (SO) muscle weakness, either isolated or in combination with an ipsilateral limitation to elevation in adduction, has not been previously reported in patients with orbital mucocele.