Magnetic resonance imaging of tissues compatible with supernumerary extraocular muscles

Numerical Aberrations of the Extraocular Muscles and the Levator Palpebrae Superioris: An Anatomical and Clinical Insight

PURPOSE

To comprehensively review the literature about numerical aberrations of the orbital muscles of ocular motility (here referred to as extraocular muscles [EOMs]) and the levator palpebrae superioris (LPS).

METHODS

The authors summarize the embryologic bases and the possible etiopathogenetic causes of numerical aberrations of the EOMs and the LPS and organize these lesions into several broad categories. The clinical and radiologic diagnostic challenges are discussed.

RESULTS

Numerical aberrations of the EOMs include: 1) the complete absence of EOMs, 2) duplication of an entire EOM, 3) the presence of muscle bands that connect 2 EOMs, and 4) minor morphological variations such as bifid muscles (partial splitting of the muscle). Some cases may defy categorization into any of the above or may resemble atavistic remnants of the retractor bulbi muscle. Broadly speaking, numerical aberrations of the LPS generally fall into the same categories although the LPS has several peculiar numerical anomalies of its own.

CONCLUSIONS

Although numerical EOM and LPS variations are relatively rare and of little clinical significance, raising awareness about their presence is a fundamental clinical keystone not just for the strabismus surgeon but for the orbital surgeon as well. During orbital surgery, this may spare the surgeon from pursuing an orbital witch hunt for these benign innocuous accessory orbital structures that were accidentally discovered by the radiologist and misinterpreted as sinister etiologies. For the strabismus surgeon, the failure to identify them may result in an unfavorable surgical outcome if these structures are missed because of a lack of awareness despite being responsible for generating complex strabismus patterns or having a restrictive potential of their own.

Challenges in management of congenital enophthalmos due to anomalous accessory orbital extraocular muscle bands

INTRODUCTION

Congenital enophthalmos is a rare condition characterized by posterior displacement of the globe, often associated with bony orbital anomalies or whole globe development defects. The purpose of this report is to present two unrelated cases of congenital enophthalmos secondary to anomalous accessory orbital bands and to describe characteristics of orbital imaging that differentiate this condition from the other causes.

METHODS

The case records of two patients who presented with congenital enophthalmos and were discovered to have anomalous accessory orbital extraocular muscle bands were reviewed. The clinical features, initial diagnosis, high resolution magnetic resonance imaging (MRI) findings, and surgical outcomes were noted. A 3-dimensional reconstruction model was used to understand the approach and surgical management in one of the cases.

RESULTS

Both patients presented with unilateral severe enophthalmos, globe retraction, and restricted ocular motility in all directions since birth. High-resolution MRI of the orbits revealed a short anomalous band, isointense to the muscle, arising from a rectus muscle belly and attaching to the posteroinferior part of the globe adjacent to the optic nerve. The caliber of the extraocular muscles and ocular motor nerves was normal. In one patient, surgery was not pursued due to the extreme posterior location of the band with proximity to the optic nerve. In the other patient, the deviation did not improve, despite successfully severing the accessory band, due to extensive scarring.

CONCLUSION

Anomalous accessory orbital extraocular muscle bands are a rare and often overlooked cause of congenital enophthalmos when associated with limited ocular motility. Imaging the orbit can aid in diagnosis and help differentiate it from other causes. Safe surgical approaches to address the problem are limited, and available approaches may not be effective. These two cases highlight that the management of accessory extraocular muscle bands causing enophthalmos can be extremely challenging and difficult to improve even with intensive surgical intervention.

Lateral rectus pulley concerning the orbital wall. Area of a stereotyped bony insertion

Purpose

To examine the lateral rectus muscle pulley and its bony insertion concerning the orbital rim and periorbita.

Design

Prospective. An observational anatomic study.

Methods

Study population: Twenty postmortem orbits (10 right, 10 left) of 10 Caucasian cadavers (8 females, 2 males; age range at death, 57-100 years; median age, 79.5 years) fixed by the Thiel method.Intervention: The floor of the temporal fossa was exposed, and a bone window on the lateral wall of the orbit, posterior to the sphenozygomatic suture, was created, keeping the periorbita intact. The lateral canthus and lateral palpebral ligament were isolated and opened, and the eyelids were folded back. The frontozygomatic suture was identified, and the orbital septum opened adjacent to the orbital rim. The conjunctiva was opened at the limbus, and the lateral rectus insertion was isolated. The bone pillar containing the frontozygomatic suture and the insertion of the periorbita and the pulley was isolated and removed en bloc. The lateral rectus muscle was isolated and excised.Main outcome measures: Position of the pulley ring on the lateral rectus muscle belly and its bony attachment area in the lateral wall of the orbit.

Results

The pulley bony attachment was roughly quadrilateral with an approximate area of 90 mm2, 3 mm (mean, range 1-5 mm) posteroinferior to the frontozygomatic suture and 1 mm posterior to the orbital rim. The anterior margin of the pulley sleeve was found at 21.0 mm (median, p25-75 20.0-22.8) from the scleral insertion.

Conclusions

The lateral rectus pulley is stereotyped in its position in the muscle belly and its bony insertion, coinciding with the point of greatest adhesion of the periorbita to the anterior part of the lateral wall of the orbit.

Two cases of Duane retraction syndrome with abnormal orbital structures

Duane retraction syndrome (DRS) is a rare congenital nonprogressive restrictive strabismus. The absence/hypoplasia of the abducens nerve and the aberrant innervation of the lateral rectus muscle by the oculomotor nerve have been hypothesized as causes of DRS, although the phenomenon of globe retraction can also occur in the setting of mechanical factors, such as congenital abnormal orbital structures or orbital trauma. We present the cases of 2 DRS patients with absent abducens nerve and abnormal muscular bands connecting the superior rectus and inferior rectus muscles on the temporal side of the optic nerve.

Double-bellied inferior rectus muscles with aplasia of medial rectus muscles

This report describes a rare occurrence of double-bellied inferior rectus muscle with aplasia of the medial rectus muscle in both eyes of a young woman seeking cosmetic correction for her strabismus. The patient presented with a large-angle exotropia and a -4 limitation of adduction in each eye. On attempted adduction, there was minimal downshoot and upper eyelid retraction. Magnetic resonance imaging of the orbit revealed hypoplastic medial rectus muscles; however, intraoperatively the muscle was not found at the insertion or when traced back as far as possible. The inferior rectus muscles were noted to have double bellies converging close to each other at the insertion. The patient underwent a bilateral lateral rectus recession with nasal transposition of the inferior rectus muscles and was cosmetically well aligned, with a residual exotropia of 4Δ at 3 months' follow-up. This unusual anatomical variation may be the result of deviation of muscle paths.

Clinical Insight Into a Rare Anatomical Variation: An Autobiographical Case Report of a Supernumerary Extraocular Muscle (SEOM) in a Patient With Hyperthyroidism

In this case report, we present the rare occurrence of supernumerary extraocular muscles (SEOM) in a 35-year-old male with hyperthyroidism. SEOMs are unusual anatomical variations involving extraocular muscles that deviate from the typical muscle arrangement in the eye. While SEOMs are rare, they can have diverse clinical manifestations, including restrictive strabismus and lid abnormalities. In this case, the patient displayed right-sided lid retraction and an asymmetrical palpebral aperture, which raised concerns about a potential association with thyroid eye disease. However, imaging revealed that the SEOM was anatomically connected to the superior rectus muscle, possibly contributing to the observed lid retraction. Understanding the complexities of SEOM and its potential interactions with conditions like thyroid ophthalmopathy is crucial for accurate diagnosis and management. Further research is needed to fully comprehend the development and clinical impact of SEOMs due to their rarity and limited knowledge in the medical literature.

A rare variation of superior rectus muscle

The extraocular muscles are responsible for all eye movements required to track and fix objects. Superior rectus muscle is located in the superior level of the orbital cavity, below musculus levator palpebrae superioris, tilted slightly to the lateral part of the orbit. In a routine dissection, we found a left, unilateral variation of the superior rectus muscle with no variation in other structures, such as nerves and vessels. The abnormal muscle presented in two parts - medial and lateral ones. The medial part bifurcated into two heads with different insertion points. It is a case of a rare variation of the extraocular muscles, which, to our knowledge, has not yet been reported.

Supernumerary Extraocular Muscle: A Rare Cause of Atypical Restrictive Strabismus

Background and objectives: Supernumerary extraocular muscle (SEOM) is extremely rare. The purpose of this paper was to review the clinical characteristics and surgical outcomes of SEOM patients with atypical restrictive strabismus. Materials and Methods: A retrospective review was conducted on the data from 12 SEOM cases. Pre- and post-operative measurements consisted of visual acuity, cycloplegic refraction, ocular alignment, ocular motility, binocular vision, and imaging. Management strategies included either conservative or surgical treatments. Results: Of the 12 cases reviewed (seven females, five males), the mean ± SD age was 14.3 ± 10.6 years (range: 4-38 years). The right eye was affected in six cases, the left in five, and both eyes in one case. The major clinical manifestations included restrictive ocular motility (12 cases), with seven cases in no less than three directions; varying degrees of horizontal or vertical strabismus; ipsilateral amblyopia (10 cases); and unequal palpebral aperture (10 cases). Imaging results revealed muscular bands originating from the annulus of Zinn and insertion into the globe or other recti, as well as anomalous muscular bands connecting two or more recti, sometimes with optic nerve involvement. Three patients received conservative treatment, while rectus recession with or without resection (seven patients) or rectus disinsertion plus globe fixation (two patients) were performed in those receiving surgical treatments. A surgical success was achieved in four cases. Conclusions: For restrictive strabismus, imaging plays an important role in the diagnosis of SEOM. When the SEOM is difficult to resect, a personalized surgical strategy may be required to achieve a good ocular alignment.

Supernumerary Medial Rectus Muscle of the Orbit

Supernumerary extraocular muscles (EOMs) are relatively rare in humans compared to other species. Therefore, few cases are reported on pediatric patients with strabismus. 

We describe a case of an incidental intraoperative finding of a right eye accessory medial rectus (MR) muscle in a child with normal ocular motility. This supernumerary muscle was found inserted underneath the original MR muscle and was of a similar size. In this article, we discuss the anomaly and its clinical relevance.

Clinical and imaging features of congenital and acquired isolated inferior rectus muscle hypofunction

BACKGROUND

Inferior rectus (IR) underaction may arise from various causes that are distinguishable through imaging. We investigated clinical and imaging characteristics of congenital and acquired causes of IR underaction.

METHODS

Cases of IR underaction were selected from data prospectively collected in a study of orbital imaging in strabismic patients.

RESULTS

Review identified 3 cases of congenital IR underaction (2 with bilateral IR aplasia and 1 with unilateral IR hypoplasia), 12 acquired cases, including 4 due to denervation (2 idiopathic, 1 after multiple strabismus surgeries, 1 after head trauma), and 8 cases of direct IR damage (5 with orbital trauma and 3 with previous surgery, including 2 sinus surgery and 1 laser blepharoplasty). Of the 23 cases, 11 adults had high-resolution magnetic resonance imaging, and 2 children had computed tomography. Imaging identified the anatomic diagnosis in congenital cases; in acquired cases, imaging helped to identify atrophy and exclude alternative orbital causes; and in direct mechanical damage, imaging clarified the mechanism of underaction, extent of IR damaged, and the degree of retained contractility. Patients with congenital IR absence or hypoplasia exhibited A pattern exotropia that was typically absent in isolated acquired denervation or direct IR damage.

CONCLUSIONS

Orbital imaging demonstrates a variety of abnormalities in patients with congenital or acquired IR hypofunction, helping to clarify the underlying mechanism and guide management.

Variant types of Duane retraction syndrome: synergistic divergences and convergences

PURPOSE

To present the clinical features of 4 patients with Duane retraction syndrome characterized by synergistic divergence or convergence, abnormal vertical movements, and accessory fibrotic bands.

METHODS

The medical records of 4 patients were reviewed retrospectively for the following clinical manifestations: visual acuity, refraction, ocular alignments, ocular motility, head position, magnetic resonance imaging, surgical techniques, and outcomes.

RESULTS

All 4 cases were diagnosed as variants of Duane retraction syndrome. Two cases (cases 1 and 2) had synergistic divergence with unilateral adduction deficit, and 2 (cases 3 and 4) had synergistic convergence with bilateral abduction deficit. Case 2 manifested abnormal vertical movements of the right eye, which goes down with adduction of the left eye and goes up oppositely with abduction of left eye. Accessory fibrotic bands were detected beside the medial rectus muscle of both eyes in case 3. Synergistic convergence in case 4 occurred only after the first strabismus surgery. Weakening of the misinnervated horizontal rectus muscle improved ocular alignment and head position in cases 1, 3, and 4.

CONCLUSIONS

Synergistic divergence and convergence are extremely rare and may present with a great diversity of clinical features. A good outcome is very difficult to achieve; however, weakening of the misinnervated horizontal rectus muscle was therapeutic in these patients.

The presence of anomalous extraocular bands in Duane retraction syndrome

PURPOSE

To determine the prevalence of anomalous extraocular bands in patients who underwent surgery for Duane syndrome and to compare the clinical findings in patients with and without bands.

METHODS

Thirty-one patients with Duane syndrome who had their first surgery on rectus muscles to correct the primary deviation and abnormal head posture were included in this retrospective study. Patients were divided into two groups depending on the identification of anomalous extraocular bands intraoperatively. Baseline clinical characteristics were compared between the groups.

RESULTS

A total of 31 patients were included. Anomalous bands were found in 6 of 19 (32%) patients with esotropic Duane syndrome and 9 of 12 (75%) with exotropic Duane syndrome (P = 0.02). In esotropic Duane syndrome, the bands were localized under the medial rectus muscle in 5 patients and under the lateral rectus muscle in 1 patient. All of the bands in patients with exotropic Duane syndrome were under the lateral rectus muscle. The amount of preoperative primary deviation, globe retraction, and up- or downshoot were similar between groups. All of the bands had distinct tight insertion on the sclera, requiring a sharp dissection for disinsertion. In 7 cases, the anomalous band was a translucent structure that could be identified under the surgical microscope as scleral indentation during forced duction testing. Histological examination of 6 cases revealed only fibrous tissue in 4 and accompanying striated muscle tissue in 2 patients.

CONCLUSIONS

The present study highlights the incidence of anomalous bands in Duane syndrome. Repeating forced duction testing after disinsertion of the affected muscle and excision of the anomalous band is helpful for intraoperative identification of these structures.

Minimal invasive vertical muscle transposition for the treatment of large angle exotropia due to congenital medial rectus hypoplasia: Case Report and Literature Review

Reports of isolated anomalies of the medial rectus (MR) muscle in literature are sparse. It has been identified as a subtype of congenital cranial dysinnervation disorder that affects the normal development of brainstem motor neurons. Herein, we report a 37-year-old male presented with large-angle exotropia since the birth of right eye with palpebral fissure widening. On examination of ocular movements, there was -6 limitation of adduction. There was no limitation in other ocular movements. In the preoperative CT scan, all extraocular muscles were present. He underwent surgery in right eye. Intraoperatively in the site of medial rectus, we found an empty sheath without muscle fibers indicating medial rectus hypoplasia. The width of muscle insertion was normal. Surgery consisted of lateral rectus muscle recession 10 mm in hang-back method and vertical muscle transposition procedure, by a modification of Nishida technique, in which the vector of superior and inferior recti was transposed medially by inserting non-absorbable sutures at nasal margins of muscles secured to sclera 8 mm posterior to medial rectus site without tenotomy or splitting. The deviation was decreased to less than 10 PD exotropia in primary position. The adduction was improved from -6 to -4. The palpebral fissure asymmetry was also corrected. Here, we also reviewed clinical features of all cases of medial rectus hypoplasia/aplasia in the literature and discussed surgical approaches. For vertical rectus transposition and horizontal muscle weakening, this technique has the advantages of being simpler and less traumatic to ocular tissues and unlike the traditional transposition procedures, there is no need for tenotomy and splitting.

Anomalous orbital structure mimicking fracture of orbital floor

A 24-year-old man with a deviation of the right eye noted since childhood presented with significant enophthalmos, limitation of elevation, and globe retraction on attempted elevation. A disproportionately small right hypotropia was suggestive of a restrictive pathology, and forced-duction testing confirmed tightness of the inferior rectus muscle. Clinical features resembled those of orbital floor fracture with inferior rectus entrapment. Computed tomography disclosed no fracture but did reveal an abnormal structure arising from the orbit adjacent to the inferior rectus origin and attaching to the globe close to the optic nerve in the inferolateral aspect.

Comparison of the Superior and Inferior Rectus Muscles in Humans: An Anatomical Study with Notes on Morphology, Anatomical Variations, and Intramuscular Innervation Patterns

A comparison of the superior and inferior rectus muscles was performed to determine whether they have similar structures and innervation attributable to their participation in the same type of, although antagonistic, eye movements. The study was conducted on 70 cadaveric hemiheads, and the anatomical variations in the superior and inferior rectus muscles were assessed. Sihler's whole mount nerve staining technique was used on 20 isolated superior and 20 isolated inferior rectus muscle specimens to visualize the intramuscular distribution of the oculomotor nerve subbranches. In two cases (~2.8%), variant muscular slips were found that connected the superior and inferior rectus muscles. In 80% of cases, muscular branches arising directly from the inferior branch of the oculomotor nerve innervated the inferior rectus muscle, while in 20% of cases, the nerve to the inferior oblique muscle pierced the inferior rectus muscle and provided its innervation. In 15 of 70 specimens (21.4%), a branch to the levator palpebrae superioris muscle pierced the superior rectus muscle. The distance between the specific rectus muscle's insertion and the anterior-most terminations of the nerves' subbranches with reference to the muscle's total length ranged from 26.9% to 47.2% for the inferior rectus and from 34.8% to 46.6% for the superior rectus, respectively. The superior rectus muscle is slightly longer and its insertion is farther from the limbus of the cornea than is the inferior rectus muscle. Both muscles share a common general pattern of intramuscular nerve subbranches' arborization, with characteristic Y-shaped ramifications that form the terminal nerve plexus located near half of the muscles' length. Unexpected anatomical variations of the extraocular muscles may be relevant during orbital imaging or surgical procedures.

Double-bellied medial rectus muscle in a patient with Down syndrome and congenital esotropia

A 13-year-old male with Down syndrome, pseudophakic secondary to congenital cataract presented with esotropia. During bilateral medial rectus recession, a unilateral two-bellied right medial rectus was identified and recessed successfully with complete resolution of the deviation. Clinicians facing a two-bellied medial rectus can consider continuing with their surgical plan.

Normal Anatomy and Anomalies of the Rectus Extraocular Muscles in Human: A Review of the Recent Data and Findings

Development of modern surgical techniques is associated with the need for a thorough knowledge of surgical anatomy and, in the case of ophthalmologic surgery, also functional aspects of extraocular muscles. Thus, the leading idea of this review was to summarize the most recent findings regarding the normal anatomy and anomalies of the extraocular rectus muscles (ERMs). Particular attention was paid to the presentation of detailed and structured data on the gross anatomy of the ERMs, including their attachments, anatomical relationships, vascularization, and innervation. This issue of ERMs innervation was presented in detail, considering the research that has recently been carried out on human material using advanced anatomical techniques such as Sihler's technique of the nerves staining. The text was supplemented with a carefully selected graphic material (including anatomical specimens prepared specially for the purpose of this review) and discussion of the clinical cases and practical significance of the presented issues.

Increased restriction from an accessory lateral rectus in exotropic Duane syndrome

Supernumerary extraocular muscles can cause restrictive strabismus, unusual ocular movements, and a persistent positive forced duction test. Even among patients with clinically typical strabismus, intraoperative testing and surgical exploration may reveal the presence of supernumerary extraocular muscles. We report the case of a patient with exotropic Duane syndrome found intraoperatively to have an accessory lateral rectus muscle, with histopathologically confirmed striated fibers.

Pathologic Study of Supernumerary Orbital Band in Type I Duane Syndrome

Background/Aims

Accessory orbital bands are relatively rare and very few reports detail histopathology. Cases in the literature describe the composition of the bands as muscular and/or fibrous. The composition of the supernumerary band lying deep in the medial rectus muscle in a patient with type I Duane syndrome was investigated.

Methods

Histochemical stains were used in conjunction with polarized light for differentiating compressed collagen from muscle. Immunohistochemistry was used for verification of the presence of muscle.

Results

Compressed collagen appeared red using Masson trichrome staining. Collagen was positively identified by illumination with polarized light on several stains including the underutilized Sirius red dye.

Conclusions

The findings of dense collagen fibers in the fibrotic band with focal striated muscle correlated with the restrictive strabismus. In concert with other cases in the literature, it is proposed that the fibrous bands are generally associated with restrictive strabismus. Bands that are muscular may or may not be associated with strabismus. Special techniques are needed to positively identify compressed collagen.

Bilateral muscular slips between superior and inferior rectus muscles: case report with discussion on classification of accessory rectus muscles within the orbit

Accessory rectus muscles have rarely been reported as muscular ‘bands’ or ‘slips’ originating from the common tendinous ring (annulus of Zinn) and inserting in atypical location. This group of muscles is innervated by the inferior branch of the oculomotor nerve, lies on lateral side of the optic nerve and inserts in rectus muscles. Since there are only few descriptions of such unusual findings in the medical literature, the anatomical data on accessory rectus muscles is limited. Furthermore, existing reports vary in terms of studied objects (cadavers or living subjects), medical history (absence or presence of ocular movement disorders or eye movement abnormalities) and details of anatomical description. This report complements earlier publications and provides complete anatomical description of the accessory rectus muscle observed bilaterally during the dissection of a 68-year-old male cadaver with no eye movement abnormalities reported in the medical history. The accessory rectus muscle was divided into two ‘slips’ or ‘heads’—superior and inferior—running in the sagittal plane (laterally to the optic nerve and the main trunk of the ophthalmic artery) and attached to the superior and inferior rectus muscles. Noticeable thickening of both superior and inferior rectus muscles at the insertion point of the accessory muscle heads was observed only in the sagittal plane. On both sides, the inferior head of the accessory rectus muscle was innervated by one of sub-branches derived from the inferior branch of the oculomotor nerve. No sub-branches to the superior head were macroscopically observed during the dissection. The classification, embryological background and clinical relevance of this variation have been discussed.

Congenital entropion and hypotropia secondary to duplication of the inferior rectus muscle

Congenital anomalies of the extraocular muscles apart from congenital fibrosis are relatively rare. Duplication of extraocular muscles is a particularly rare congenital anomaly that has been rarely reported in the literature. We present a case of unilateral congenital entropion and hypotropia resulting from duplication of the inferior rectus muscle.

Accessory lateral rectus in a patient with normal ocular motor control

Although supernumerary extraocular muscles are common in monkeys and other species, they are relatively rare in humans and typically are noted in the context of childhood strabismus. We present a case of an incidentally found unilateral accessory lateral rectus muscle in a 51-year-old woman with normal ocular motor control. In this patient, the accessory lateral rectus was approximately 10% the size of a normally sized lateral rectus muscle. It originated from the orbital apex, traveled between the optic nerve and the lateral rectus and attached to the superolateral aspect of the globe. This unique case demonstrates that accessory lateral rectus in humans may have no impact on eye movement and ocular alignment.

Strabismus resulting from an anomalous extraocular muscle in Gorlin syndrome

Strabismus associated with anomalous extraocular muscles is rare. We present a case of strabismus caused by an anomalous orbital structure that was histopathologically consistent with an accessory extraocular muscle rather than a fibrous band, in a patient with Gorlin syndrome (nevoid basal cell carcinoma syndrome), an autosomal dominant multisystem disorder related to a mutation in the patched tumor suppressor gene (PTCH). Histopathology of an anomalous orbital structure consistent with extraocular muscle has not been previously reported.

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.

Reproducibility of horizontal extraocular muscle insertion distance in anterior segment optical coherence tomography and the effect of head position

PURPOSE

To investigate the reproducibility of horizontal extraocular muscle insertion distance measurements in anterior segment optical coherence tomography (AS-OCT) and to evaluate the effect of eye position on the measurement.

METHODS

The right eyes of 30 healthy young subjects underwent AS-OCT. Varying eye positions were used and the muscle insertion distance was measured by two independent examiners who each measured the insertion distance twice. The measurement was performed for the lateral rectus and medial rectus muscles with the eye rotated 40°, 50°, and 60° to the midline of the instrument. Reproducibility was evaluated with the intraclass correlation coefficient (ICC) and Bland-Altman plot.

RESULTS

The lateral rectus insertion distance was smallest with 50° rotation and the medial rectus insertion distance did not show a consistent pattern in regards to gaze position. The differences in insertion distance between different eye positions were not statistically significant for both muscles. The inter- and intraexaminer ICC reproducibility values were excellent for both lateral and medial rectus insertion distance measurements.

CONCLUSIONS

Inter- and intraexaminer reproducibility were excellent for lateral and medial rectus muscle insertion distance measurements using AS-OCT. The measurements tended to be smallest with the 50° position in lateral rectus measurement; however, medial rectus measurements were variable.

Unilateral lateral rectus resection for horizontal diplopia in adults with divergence insufficiency

BACKGROUND

Divergence insufficiency (DI) is an acquired comitant strabismus in aging individuals, characterized by esotropia and diplopia at distance. Treatment options include occlusion, base-out prism glasses, and a variety of surgical procedures to the horizontal rectus extraocular muscles. Here, we present a large cohort of patients with DI who underwent unilateral resection of the lateral rectus muscle. This is a simple procedure, typically performed under regional anesthesia and on the non-dominant eye.

METHODS

Clinical characteristics and complaints were collected from patients with DI who underwent unilateral lateral rectus resection over a 6.5-year period. Treatment success was evaluated in terms of post-operative symptomatic deviation and the need for prisms in order to achieve sensory fusion.

RESULTS

The cohort consisted of 57 patients (age 54-89 years). The majority sought surgical care after prism glasses were no longer tolerated, or after onset of a larger symptomatic deviation (typically 10 to 18 prism diopters). After surgery (minimum 6 weeks follow-up; median 10 weeks), 86.0 % showed successful results with no further treatment; an additional 10.5 % stayed free of diplopia with a post-operative prism (horizontal or vertical), and only two patients (3.5 %) required further surgery and were considered failures.

CONCLUSIONS

Mild DI is usually treated with a base-out prism. Treatment of pronounced DI with unilateral lateral rectus resection was generally successful, with 96.5 % not requiring further surgery. Unilateral lateral rectus resection appears to be a valid option for treatment of DI.

Signal intensity and T2 time of extraocular muscles in assessment of their physiological status in MR imaging in healthy subjects

Background:

Lack of standardised orbital MR protocols leads to a situation, when each institution/centre may arbitrarily choose sequence parameters. Therefore, the results obtained and published by the authors may not be compared freely, and what is most important may not be considered fully reliable. Signal intensity (IS) and T2 time (T2) are important parameters in estimation of inflammatory processes of extraocular muscles in the clinical practice.

The aim of this study was to determine the reference values (i.e. cut-off values) for absolute signal intensity and T2 relaxation time in healthy subjects, their relativised values to white matter (WM) and temporal muscles (TM) and to evaluate the correlation between those parameters.

Material/Methods:

The orbital examination was performed in healthy volunteers according to the protocol prepared in the Radiology-Imaging Diagnostic Department of the Medical University of Lodz for patients with suspected/diagnosed thyroid orbitopathy. Using two of the standard sequences IS and T2 time were calculated for the muscles and two relativisation tissues in realtion to WM and TM. Subsequently cut-off values for healthy volunteers were calculated.

Results:

The differences between muscles for IS, IS MAX, IS/TM, IS/WM, IS MAX/TM, IS MAX/WM and T2 MAX/WM were not statistically significant. Therefore one cut-off value of these parameters for all the rectus muscles was calculated. T2-relaxation time and T2 relativised to white matter had to be calculated separately for each muscle.

Conclusions:

No statistical correlation was found between IS and T2-time for extraocular muscles in healthy volunteers. We calculated the reference ranges (cut-off values) for absolute IS and T2-time values and relativised parameters. In the clinical practice the objectification of IS and T2-time values should be done to WM, than to IS or T2 of the temporal muscle. The T2 MAX/WM seems to have the highest clinical utility for the assessment of the pathophysiological status of extraocular muscles.

Surgical treatment of vertical ocular motility disorders of supranuclear origin

Vertical ocular motility disorders of supranuclear origin can be congenital or acquired later in life. They produce complex forms of strabismus that require specialized surgical management to restore ocular alignment, eliminate torticollis, treat diplopia, and restore normal lid position. For each condition, surgical management must be individualized to address multiple impediments to fusion. This article outlines the surgical management of three common types of supranuclear vertical strabismus.

Radiology update in neuro-ophthalmology

PURPOSE OF REVIEW

Radiologic imaging is indispensible for the diagnosis and management of many neuro-ophthalmologic conditions. Advances in the radioimaging of neuro-ophthalmologic disorders may evolve from the clinical or the radiological side, meaning there is a constant stream of new information for the clinician.

RECENT FINDINGS

Functional MRI, diffusion tensor MRI, magnetization transfer imaging, and magnetic resonance spectroscopy are examples of nonstandard radiographic techniques, which have expanded the knowledge of neuro-ophthalmologic conditions. Studies using conventional MRI have also led to advances in understanding optic neuropathies, the ocular motor system, pseudotumor cerebri, posterior reversible encephalopathy syndrome and migraine.

SUMMARY

This article discusses recent radiologic advances relevant to neuro-ophthalmology.

Evidence of an asymmetrical endophenotype in congenital fibrosis of extraocular muscles type 3 resulting from TUBB3 mutations

PURPOSE

Orbital magnetic resonance imaging (MRI) was used to investigate the structural basis of motility abnormalities in congenital fibrosis of the extraocular muscles type 3 (CFEOM3), a disorder resulting from missense mutations in TUBB3, which encodes neuron-specific beta-tubulin isotype III.

METHODS

Ophthalmic examinations in 13 volunteers from four CFEOM3 pedigrees and normal control subjects, were correlated with TUBB3 mutation and MRI findings that demonstrated extraocular muscle (EOM) size, location, contractility, and innervation.

RESULTS

Volunteers included clinically affected and clinically unaffected carriers of R262C and D417N TUBB3 amino acid substitutions and one unaffected, mutation-negative family member. Subjects with CFEOM3 frequently had asymmetrical blepharoptosis, limited vertical duction, variable ophthalmoplegia, exotropia, and paradoxical abduction in infraduction. MRI demonstrated variable, asymmetrical levator palpebrae superioris and superior rectus EOM atrophy that correlated with blepharoptosis, deficient supraduction, and small orbital motor nerves. Additional EOMs exhibited variable hypoplasia that correlated with duction deficit, but the superior oblique muscle was spared. Ophthalmoplegia occurred only when the subarachnoid width of CN3 was <1.9 mm. A-pattern exotropia was frequent, correlating with apparent lateral rectus (LR) muscle misinnervation by CN3. Optic nerve (ON) cross sections were subnormal, but rectus pulley locations were normal.

CONCLUSIONS

CFEOM3 caused by TUBB3 R262C and D417N amino acid substitutions features abnormalities of EOM innervation and function that correlate with subarachnoid CN3 hypoplasia, occasional abducens nerve hypoplasia, and subclinical ON hypoplasia that can resemble CFEOM1. Clinical and MRI findings in CFEOM3 are more variable than those in CFEOM1 and are often asymmetrical. Apparent LR innervation by the inferior rectus motor nerve is an overlapping feature of Duane retraction syndrome and CFEOM1. These findings suggest that CFEOM3 is an asymmetrical, variably penetrant, congenital cranial dysinnervation disorder leading to secondary EOM atrophy.