Absence of the abducens nerve in Duane syndrome verified by magnetic resonance imaging

MRI evaluation of cranial nerve abnormalities and extraocular muscle fibrosis in duane retraction syndrome and congenital extraocular muscle fibrosis

PURPOSE

To investigate the alterations in extraocular muscles (EOMs) by magnetic resonance imaging (MRI) among patients diagnosed with Duane retraction yndrome (DRS) and congenital fibrosis of the extraocular muscles (CFEOM), who present with various cranial nerve anomalies in an attempt to enhance the clinical diagnostic process.

METHODS

A case-control study was conducted to evaluate 27 patients with DRS and 14 patients with CFEOM. All patients underwent MRI scans of the brainstem and orbital examination. Neurodevelopmental assessments were conducted through MRI, and maximum cross-sectional area and volumes of EOMs were obtained. Three types of models were constructed using machine learning decision tree algorithms based on EOMs to predict disease diagnosis, cranial nerve abnormalities, and clinical subtypes.

RESULTS

Patients with bilateral CN VI abnormalities had smaller volumes of LR, MR, and IR muscles compared to those with unilateral involvement (P < 0.05). Similarly, patients with CFEOM and unilateral third cranial nerve abnormalities had a smaller maximum cross-section of the affected eye's SR compared to the contralateral eye (P < 0.05). In patients with both CN III and CN VI abnormalities, the volume of SR was smaller than in patients with CN III abnormalities alone (P < 0.05). The prediction model using EOMs volume showed a diagnostic precision of 82.5% for clinical cases and 60.1% for predicting cranial nerve abnormalities. Nonetheless, the precision for identifying clinical subtypes was relatively modest, at only 41.7%.

CONCLUSION

The distinctive volumetric alterations in EOMs among individuals exhibiting distinct cranial nerve anomalies associated with DRS or CFEOM provide valuable diagnostic insights into to Congenital Cranial Neurodevelopmental Disorders (CCDDs). MRI analysis of EOMs should thus be regarded as a crucial diagnostic modality.

Refractive features and amblyopia in Duane's Retraction Syndrome: A review of the 582 patients

PURPOSE

To report the visual and refractive characteristics and the prevalence of amblyopia in patients with different types of Duane's Retraction Syndrome (DRS).

METHOD

This retrospective study was performed on hospital records of 582 DRS patients at Farabi Hospital, Iran, from 2012 to March 2022.

RESULTS

The mean age of patients was 19.4 ± 11.9 (range, 3-70) years [335 (57.6 %) females and 247 (42.4 %) males (P < .001)]. DRS type I, II, III, and IV were presented in 347 (59.6 %), 148 (25.4 %), 82 (14.1 %), and 5 (0.9 %) patients, respectively. There were 530 (91.1 %) patients with unilateral and 52 (8.9 %) with bilateral involvement. In the unilateral patients, the DRS eyes' corrected distance visual acuity (CDVA) and astigmatism were significantly worse than the Non-DRS Eyes (P < .001). The mean amount of all refractive and visual parameters in bilateral patients' right or left eyes was significantly lower than in unilateral patients' non-DRS eyes (all P < .05). Anisometropia was observed in 75(12.9 %) of the patients. Amblyopia was observed in 18.5 % (98 patients) and 36.5 % (19 patients) of unilateral and bilateral DRS patients, respectively (P < .001). In unilateral patients, amblyopia was found in 57 (16.4 %) patients with Type I, 22 (14.9 %) patients with Type II, 16 (19.5 %) patients with Type III, and 3 (60 %) patients with Type IV. Forty-four (37.6 %) of patients with amblyopia had anisometropia.

CONCLUSION

This large-scale study indicates that DRS types differ in terms of refractive error, visual acuity, and the prevalence of amblyopia and anisometropia. Clinicians should be aware of the clinical features associated with different types of DRS.

Magnetic Resonance Imaging Findings in Patients With Duane Retraction Syndrome

BACKGROUND

Duane retraction syndrome (DRS) is known to relate to the absence of the abducens nucleus, with abnormal innervation of the lateral rectus (LR) muscle by branchesof the oculomotor nerve (CN III). The purposes of this study were to investigate the morphological characteristics of the oculomotor nerve (CN III), the abducens nerve (CN VI), and the extraocular muscles in patients with clinically diagnosed Duane retraction syndrome (DRS) using MRI. In addition, we assessed the association between ocular motility, horizontal rectus muscle volumes, and CN III/VI in patients with Duane retraction syndrome (DRS).

METHODS

The study comprised 20 orthotropic control subjects (40 eyes) and 42 patients with Duane syndrome (48 eyes), including 20 patients with DRS Type I (24 eyes), 5 patients with DRS Type II (6 eyes), and 17 patients with DRS Type III (18 eyes). Three-dimensional (3D) T1/2 images of the brainstem and orbit were obtained to visualize the cranial nerves, especially the abducens (VI) and oculomotor (III) nerves, as well as extraocular muscles.

RESULTS

Based on the clinical classification, among 42 patients, MRI showed that the abducens nerves (CN VI) on the affected side were absent in 24 of 24 eyes (100%; 20 patients) with Type I DRS and in 16 of 18 eyes (88%; 16 patients) with Type III DRS. However, CN VI was observed in 6 of 6 eyes (100%; 5 patients) with Type II DRS and in 2 of 18 eyes (11%) with Type III DRS. CN III was observed in all patients. The oculomotor nerves on the affected side were thicker than those on the nonaffected contralateral side in DRS Type I ( P < 0.05) and Type III ( P < 0.05), but not in DRS Type II. Smaller LR and larger MR volumes were shown in the affected eye than that in the nonaffected eye in DRS Types I and III. Based on the presence or absence of CN VI, there was a tendency for thicker oculomotor nerves in the affected eye than in the nonaffected eye in the absence groups ( P < 0.05). However, no significant difference was found in the present group. In the CN VI absence groups, similar results were found in the affected eyes than in the nonaffected eyes as in DRS Types I and III. In addition, the presence of CN VI was correlated with better abduction ( P = 0.008). The LR and MR volumes have positive correlations with the oculomotor nerve diameter in the affected eye. However, there was no correlation between the range of adduction/abduction and the LR/MR ratio in patients with or without an abducens nerve.

CONCLUSIONS

Different types of DRS have different characteristic appearances of CN VI and CN III on MRI. Horizontal rectus muscles have morphological changes to adapt to dysinnervation of CN VI and aberrant innervation of CN III. Thus, these neuroimaging findings may provide a new diagnostic criterion for the classification of DRS, improving the comprehension of the physiopathogenics of this disease.

Superior Rectus Transposition in the Management of Duane Retraction Syndrome: Current Insights

Various surgical approaches have been described for the management of Duane retraction syndrome (DRS), a type of congenital cranial dysinnervation disorder (CCDD), the goals of which include correcting the primary position deviation and abnormal head posture (AHP), minimizing globe retraction and overshoots and improving the ocular rotations. Vertical rectus transposition (VRT) is one such technique, found more effective in improving abduction and thereby expanding the field of binocular vision, as compared to horizontal muscle surgery. VRT, however, is associated with the risk of inducing vertical deviations and also poses a risk for development of anterior segment ischemia. To overcome these concerns, transposition of only the superior rectus to the lateral rectus was proposed and evaluated to reveal improvement in alignment, AHP and motility comparable to VRT but with lesser surgical time and fewer post-operative complications. With promising results in the management of DRS, superior rectus transposition (SRT) has been extensively studied and has evolved over the last decade with several modifications to further increase the efficiency and reduce the risk of post-operative complications. This article focusses on the pre-operative considerations while planning SRT in DRS, various approaches and surgical techniques described, and the outcomes and complications of SRT in DRS. The role of SRT in the management of other CCDDs may be explored with further studies.

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.

Non-classical 1p36 deletion in a patient with Duane retraction syndrome: case report and literature review

Background

Monosomy of 1p36 is considered the most common terminal microdeletion syndrome. It is characterized by intellectual disability, growth retardation, seizures, congenital anomalies, and distinctive facial features that are absent when the deletion is proximal, beyond the 1p36.32 region. In patients with proximal deletions, little is known about the associated phenotype, since only a few cases have been reported in the literature. Ocular manifestations in patients with classical 1p36 monosomy are frequent and include strabismus, myopia, hypermetropia, and nystagmus. However, as of today only one patient with 1p36 deletion and Duane retraction syndrome (DRS) has been reported.

Case presentation

We describe a patient with intellectual disability, facial dysmorphism, and bilateral Duane retraction syndrome (DRS) type 1. Array CGH showed a 7.2 Mb de novo deletion from 1p36.31 to 1p36.21.

Discussion

Our patient displayed DRS, which is not part of the classical phenotype and is not a common clinical feature in 1p36 deletion syndrome; we hypothesized that this could be associated with the overlapping deletion between the distal and proximal 1p36 regions. DRS is one of the Congenital Cranial Dysinnervation Disorders, and a genetic basis for the syndrome has been extensively reported. The HES3 gene is located at 1p36.31 and could be associated with oculomotor alterations, including DRS, since this gene is involved in the development of the 3rd cranial nerve and the 6th cranial nerve’s nucleus. We propose that oculomotor anomalies, including DRS, could be related to proximal 1p36 deletion, warranting a detailed ophthalmologic evaluation of these patients.

Reoperation in esotropic Duane retraction syndrome: Long-term motor outcome of superior rectus transposition

AIM

The aim was to evaluate the long-term motor outcome of superior rectus transposition procedure in patients affected by unilateral esotropic Duane retraction syndrome with residual esotropia and anomalous head position.

METHODS

A retrospective analysis of medical records of patients affected by esotropic Duane retraction syndrome who underwent superior rectus transposition procedure as reoperation for residual esotropia and/or residual anomalous head position. Amount of deviation, anomalous head position, duction limitation, globe retraction, presence of upshoot/downshoot, and vertical deviation were analyzed before and after superior rectus transposition procedure.

RESULTS

Twenty patients were selected. All patients underwent unilateral medial rectus recession or bilateral medial rectus recession, for unilateral esotropic Duane retraction syndrome at least 2 years before superior rectus transposition reoperation. Mean age at surgery (superior rectus transposition) was 12 ± 6.8 years, and the follow-up period was 2.7 ± 0.6. Mean deviations at distance and near before surgery were 19.5 ± 5.7 and 15.2 ± 6.8, respectively. Two patients showed upshoot. Head turn was 11.4 ± 5.1°; abduction limitation was -2.6 ± 0.9. After superior rectus transposition, all patients showed an improvement of esotropia at distance and near (8.1 ± 5.7 and 5.1 ± 5.6, respectively; p < 0.05), anomalous head position (5.6 ± 3.9°; p < 0.05), and abduction limitation (-2.3 ± 0.8; p < 0.05). No statistically significant changes occurred in globe retraction. No adduction limitation, vertical deviation, and upshoot/downshoot were present after superior rectus transposition procedure. Results were stable during follow-up.

CONCLUSION

Superior rectus transposition procedure is an effective procedure in esotropic Duane retraction syndrome patients who previously undergone unilateral/bilateral medial rectus recession, with residual esotropia and anomalous head position. It allows improvement of esotropia, head turn, and partial recovery of abduction in a significant percentage of patients (30%) with no vertical complications.

Altered brain activity in patients with strabismus and amblyopia detected by analysis of regional homogeneity: A resting‑state functional magnetic resonance imaging study

Previous studies have demonstrated that strabismus or amblyopia can result in marked brain function and anatomical alterations. However, differences in spontaneous brain activity in strabismus and amblyopia (SA) patients as compared with control individuals remain unclear. The present study aimed to analyze the potential brain activity changes in SA patients and their association with behavioral performance. In total, 16 patients with SA (10 women and 6 men) and 16 healthy controls (HCs; 6 men and 10 women) with matched age and sex were recruited. All subjects were examined with resting-state functional magnetic resonance imaging (rs-fMRI), and changes in the spontaneous brain activity of SA patients were evaluated by the regional homogeneity (ReHo) method. The diagnostic ability of the ReHo method was assessed using receiver operating characteristic (ROC) curve analysis. In addition, the association between the mean ReHo value in different brain regions and the behavioral performance was explored by correlation analysis. It was observed that the ReHo value was significantly increased in SA patients compared with HCs in the following brain regions: left lingual gyrus, right middle occipital gyrus/precuneus, bilateral anterior cingulate, left middle occipital gyrus and bilateral precentral gyrus. By contrast, the ReHo value of the left inferior frontal gyrus was significantly lower than that in HCs. ROC curve analysis indicated that the ReHo method has certain credibility for the diagnosis of SA patients. In addition, no similar changes were detected in other brain regions. These results revealed abnormal spontaneous brain activity in certain parts of the brain in adult patients with SA, which suggests the involvement of the neuropathological or compensatory mechanism in these patients, and may be beneficial for clinical treatment.

Binocular Function in Subjects with Orthotropic Duane Retraction Syndrome

Introduction and Purpose: The aim of this study is to evaluate binocular vision parameters such as near point of accommodation (NPA), near point of convergence (NPC), fusional vergence ranges in subjects with orthotropic Duane retraction syndrome (DRS) and to compare with normal age-matched controls Patients and Methods: A total of 24 subjects (14 Type 1, 2 Type 2, 8 Type 3 DRS) who were diagnosed to have DRS and 15 normals were included in the study. The following binocular vision parameters were assessed in all subjects: amount of the deviation (for near and distance in all gazes), NPC, NPA, positive and negative fusional vergence (PFV and NFV) reserve and stereopsis. Results: Accommodative amplitude was normal in subject with DRS (median (95% confidence interval (CI):15D (11.9-18.1)) compared to age-matched controls. However, NPC was significantly receded (median [95% CI]:17 cm [14.4-19.6]). PFV reserve and NFV reserve were reduced in subjects with DRS. Subjects with Type 3 DRS have poor PFV reserve and NFV reserve for distance when compared to Type 1 DRS (p = 0.009 and 0.006 respectively). Stereopsis was poor in the subjects with DRS (p < 0.001). Conclusion: Subjects with DRS have good accommodation, but have poor convergence and fusional vergence. Stereopsis was noted to be poor as well.

Duane retraction syndrome: causes, effects and management strategies

Duane retraction syndrome (DRS) is a congenital eye movement anomaly characterized by variable horizontal duction deficits, with narrowing of the palpebral fissure and globe retraction on attempted adduction, occasionally accompanied by upshoot or down-shoot. The etiopathogenesis of this condition can be explained by a spectrum of mechanical, innervational, neurologic and genetic abnormalities occurring independently or which influence each other giving rise to patterns of clinical presentations along with a complex set of ocular and systemic anomalies. Huber type I DRS is the most common form of DRS with an earlier presentation, while Huber type II is the least common presentation. Usually, patients with unilateral type I Duane syndrome have esotropia more frequently than exotropia, those with type II have exotropia and those with type III have esotropia and exotropia occurring equally common. Cases of bilateral DRS may have variable presentation depending upon the type of presentation in each eye. As regards its management, DRS classification based on primary position deviation as esotropic, exotropic or orthotropic is more relevant than Huber’s classification before planning surgery. Surgical approach to these patients is challenging and must be individualized based on the amount of ocular deviation, abnormal head position, associated globe retraction and overshoots.

Imaging of Cranial Nerves III, IV, VI in Congenital Cranial Dysinnervation Disorders

Congenital cranial dysinnervation disorders are a group of diseases caused by abnormal development of cranial nerve nuclei or their axonal connections, resulting in aberrant innervation of the ocular and facial musculature. Its diagnosis could be facilitated by the development of high resolution thin-section magnetic resonance imaging. The purpose of this review is to describe the method to visualize cranial nerves III, IV, and VI and to present the imaging findings of congenital cranial dysinnervation disorders including congenital oculomotor nerve palsy, congenital trochlear nerve palsy, Duane retraction syndrome, Möbius syndrome, congenital fibrosis of the extraocular muscles, synergistic divergence, and synergistic convergence.

Pearls and pitfalls in the management of Duane syndrome

Duane syndrome (DS) is a common form of congenital cranial dysinnervation disorders. The ocular motility pattern lies in a wide clinical spectrum, and the choice of treatment must be individualized depending on the severity of the clinical findings. There is no perfect method of treatment and no real “cure” in DS. In this paper, the aim is to give some guidelines to the reader for selection of the most appropriate treatment method for the patient.

Abducens Nerve in Patients with Type 3 Duane's Retraction Syndrome

Background

We have previously reported that the presence of the abducens nerve was variable in patients with type 3 Duane’s retraction syndrome (DRS), being present in 2 of 5 eyes (40%) and absent in 3 (60%) on magnetic resonance imaging (MRI). The previous study included only 5 eyes with unilateral DRS type 3.

Objectives

To supplement existing scarce pathologic information by evaluating the presence of the abducens nerve using high resolution thin-section MRI system in a larger number of patients with DRS type 3, thus to provide further insight into the pathogenesis of DRS.

Data Extraction

A retrospective review of medical records on ophthalmologic examination and high resolution thin-section MRI at the brainstem level and orbit was performed. A total of 31 patients who showed the typical signs of DRS type 3, including abduction and adduction deficit, globe retraction, narrowing of fissure on adduction and upshoot and/or downshoot, were included. The abducens nerve and any other extraocular muscle abnormalities discovered by MRI were noted.

Results

DRS was unilateral in 26 patients (84%) and bilateral in 5 patients (16%). Two out of 5 bilateral patients had DRS type 3 in the right eye and DRS type 1 in the left eye. Of the 34 affected orbits with DRS type 3 in 31 patients, the abducens nerve was absent or hypoplastic in 31 eyes (91%) and present in 3 eyes (9%). Patients with a present abducens nerve showed more limitation in adduction compared to patients with an absent abducens nerve (P = 0.030).

Conclusions

The abducens nerve is absent or hypoplastic in 91% of DRS type 3. Patients with a present abducens nerve showed more prominent limitation of adduction. As DRS type 3 partly share the same pathophysiology with type 1 and 2 DRS, the classification of DRS may have to be revised according to MRI findings.

Contralateral lateral rectus muscle recession in patients with Duane retraction syndrome type 3

AIMS

The aim of this study was to evaluate the motor, sensory, functional, and head posture results of recession of the lateral rectus muscle contralateral to the involved eye in patients with exotropic Duane retraction syndrome (DRS) type 3.

METHODS

This was a retrospective, longitudinal, observational study of a consecutive clinical case series. Of the 11 patients with DRS type 3 operated on at a tertiary medical center from 1977 to 2012, 8 underwent recession of the lateral rectus muscle contralateral to the involved eye (with combined Y-splitting of ipsilateral lateral rectus muscle in 3 of them). Full ophthalmic, orthoptic, and neurological examination was performed before and after surgery. Main outcome measures included intragroup changes in motor misalignment, abnormal head turn, ocular upshoot, and stereopsis.

RESULTS

Mean patient age was 8.75±3.1 years at surgery. Mean exodeviation for distance was -17.3±3.5 prism diopters (PD) preoperatively and -4.0±6.1 PD postoperatively; corresponding values for near were -23.1±7.2 PD and -5.9±8.7 PD. Motor deviation improved by 77% for distance (P=0.017) and 74.5% for near (P=0.01). In 7/8 patients, the postoperative residual exodeviation (distance and near) was <8.0 PD. There was an 80% improvement in head turn, from 15.3±4° before surgery to 3.1±5.0° after (P=0.01). Stereopsis improved significantly in 6/8 patients. Findings remained stable during follow-up (mean duration 35.9±50.8 months, range 5-132 months).

CONCLUSIONS

Contralateral lateral rectus muscle recession appears to be a promising technique for the treatment of moderate unilateral DRS type 3, with patients showing significant motor and functional improvement and a decrease in head turn.

Fourth cranial nerve palsy and Brown syndrome: two interrelated congenital cranial dysinnervation disorders?

Based on neuroimaging data showing absence of the trochlear nerve, congenital superior oblique palsy is now classified as a congenital cranial dysinnervation disorder. A similar absence of the abducens nerve is accompanied by misinnervation to the lateral rectus muscle from a branch of oculomotor nerve in the Duane retraction syndrome. This similarity raises the question of whether some cases of Brown syndrome could arise from a similar synkinesis between the inferior and superior oblique muscles in the setting of congenital superior oblique palsy. This hypothesis has gained support from the confluence of evidence from a number of independent studies. Using Duane syndrome as a model, we critically review the accumulating evidence that some cases of Brown syndrome are ultimately attributable to dysgenesis of the trochlear nerve.

Magnetic resonance imaging findings of the abducens nerves in type 1 Duane's retraction syndrome

PURPOSE

To investigate nervus abducens and extraocular mucles in patients with Type 1 Duane's retraction syndrome using high-definition magnetic resonance imaging.

METHODS

The study included 10 patients with Type I Duane's retraction syndrome who underwent magnetic resonance imaging (MRI) of the brain and orbits.

RESULTS

Overall, 10 cases were included in the study. There were seven women and three men. The mean age was 5.2 years (1-15 years). MRI of the abducens nerve was performed in all cases. Of the cases, the left eye was involved in eight cases, whereas the right eye was involved in two cases. There was no bilateral eye involvement. Among the 10 patients clinically diagnosed as Type 1 Duane's retraction syndrome, the abducens nerve could not be visualized in eight cases, whereas the nerve was hypoplastic in one case and bilateral abducens nerves were present in one case by MRI. The extraocular muscles were normal in all cases on T2 weighted coronal MRI of the orbits.

CONCLUSION

Absence of abducens nerve and normal extraocular muscles was detected in patients with Type 1 Duane's retraction syndrome at the affected side.

Inferior oblique myectomy for upshoots mimicking inferior oblique overaction in Duane retraction syndrome

PURPOSE

To evaluate the results of inferior oblique myectomy in selected patients with Duane retraction syndrome with upshoot on adduction.

METHODS

This was a prospective, interventional study of consecutive patients with types 1, 2, or 3 Duane syndrome with isolated upshoot in adduction operated on from January 2007 to December 2011. Patients underwent inferior oblique myectomy on the side of the upshooting eye. Only patients with gradual elevation of the eye in adduction in a pattern similar to inferior oblique overaction or patients with hypertropia in the primary position were included. All patients were followed for at least 6 months. Ductions, versions, degree of upshoot, degree of fundus torsion, and pattern of strabismus were analyzed in all patients before and after surgery.

RESULTS

A total of 11 patients were included in the study. Mean patient age at time of surgery was 6.4 ± 5.2 years (range, 3-22 years). Two patients had bilateral inferior oblique myectomy and 4 had simultaneous bilateral medial rectus muscle recession to correct horizontal misalignment. Mean duration of follow-up was 8.6 months (range, 6-36 months). Of the 11 patients, 10 (91%) had complete disappearance of the upshoot at last follow-up. None of the patients developed inferior oblique underaction postoperatively. There was a statistically significant improvement of V pattern after surgery (P < 0.01). Mean vertical misalignment in primary position was 5(Δ) before surgery and 1(Δ) after (P = 0.02). Most patients had no significant fundus torsion before or after surgery.

CONCLUSIONS

Inferior oblique muscle weakening can improve upshoot in selected patients with Duane retraction syndrome without inducing inferior oblique muscle underaction.

How to deal with diplopia

Diplopia is a frequent neuro-ophthalmologic symptom with diverse etiologies. This article describes elementary diagnostic tests and frequent causes of diplopia. Monocular diplopia persists when the other eye is closed and usually disappears when the patient looks through a pinhole. It is usually caused by errors in the optical media of the eye and has to be differentiated from spectacle-induced side effect and non-organic disorders. A sign of non-organic etiology is absence of change in image position when the head is tilted. Binocular diplopia disappears regardless of which eye is closed. Binocular diplopia occurs when the images of both eyes cannot be fused. The most frequent direct cause of diplopia is acquired strabismus. Knowledge of several specific types of strabismus enables efficient patient management. Congenital and decompensating strabismus like accommodative esotropia, pathophoria, strabismus surso- and deorsoadductorius, retraction syndrome, Brown's syndrome and esotropia in high myopia only need ophthalmologic treatment. Orbital injury, orbital tumor, ocular myositis, Graves orbitopathy and vascular disease usually require multidisciplinary management. Neurogenic paresis, superior oblique myokymia, ocular neuromyotonia, myasthenia, chronic progressive external ophthalmoplegia (CPEO), internuclear ophthalmoplegia (INO) and skew deviation require specific neurologic examination. Treatment of diplopia includes treatment of the fundamental disorder, monocular occlusion, prisms and strabismus surgery.

Recent progress in understanding congenital cranial dysinnervation disorders

BACKGROUND

In 2002, the new term congenital cranial dysinnervation disorder (CCDD) was proposed as a substitute for the traditional concept of congenital fibrosis of the extraocular muscles (CFEOM) based on mounting genetic, neuropathologic, and imaging evidence, suggesting that many, if not all, of these disorders result from a primary neurologic maldevelopment rather than from a muscle abnormality. This report provides an update 8 years after that original report.

EVIDENCE ACQUISITION

Review of pertinent articles published from January 2003 until June 2010 describing CCDD variants identified under PubMed MeSH terms congenital fibrosis of the extraocular muscles, congenital cranial dysinnervation disorders, individual phenotypes included under the term CCDD, and congenital ocular motility disorders.

RESULTS

At present, a total of 7 disease genes and 10 phenotypes fall under the CCDD umbrella. A number of additional loci and phenotypes still await gene elucidation, with the anticipation that more syndromes and genes will be identified in the future. Identification of genes and their function, along with advances in neuroimaging, have expanded our understanding of the mechanisms underlying several anomalous eye movement patterns.

CONCLUSIONS

Current evidence still supports the concept that the CCDDs are primarily due to neurogenic disturbances of brainstem or cranial nerve development. Several CCDDs are now known to have nonophthalmologic associations involving neurologic, neuroanatomic, cerebrovascular, cardiovascular, and skeletal abnormalities.

Imaging findings in congenital cranial dysinnervation disorders

In 2002, the term congenital cranial dysinnervation disorders (CCDDs) was proposed to group heterogeneous syndromes with congenital abnormalities of ocular muscle and facial innervations. The concept of neurogenic etiology has been supported by discovery of genes that are essential to the normal development of brainstem, cranial nerves, and their axonal connections. The CCDDs include Duane retraction syndrome, congenital fibrosis of the extraocular muscles, Möbius syndrome, horizontal gaze palsy with progressive scoliosis, the human homeobox-related disorders, pontine cap tegmental dysplasia, and an expanding list. The purpose of this review was to update the imaging features, as well as clinical and genetic information, regarding cases of CCDDs.

Congenital innervation dysgenesis syndrome (CID)/congenital cranial dysinnervation disorders (CCDDs)

Congenital loss of innervation to the extra-ocular muscles (EOMs) can have a profound effect on the target muscle. This has been well recognised in Duane's retraction syndrome. However, it has been less emphasised in other congenital oculo-motor disorders. Such congenital ocular motor defects have been expanded to include DRS, congenital fibrosis of EOMs, monocular elevation defect, Möbius syndrome, as well as several other non-ocular muscles supplied by cranial nerves such as facial muscles. Such loss of innervation to motor muscles can be unified as a defined clinical entity, which can be labelled as congenital innervation dysgenesis syndrome or CID for short. CID may also affect other muscles supplied by nerves other than the cranial nerves and may be sensory as well as motor.

Analysis of the SALL4 gene in patients with Duane retraction syndrome in a South Indian population

Duane retraction syndrome (DRS) is a congenital eye movement disorder characterized most typically by partial or complete failure of abduction and narrowing of palpebral fissure with globe retraction on adduction. Recently mutations of the SALL4 gene on chromosome 20 have been linked to DRS associated with radial forearm malformations (Okihiro syndrome). In this prospective, non-interventional study we screened for SALL4 mutations in 72 patients clinically diagnosed as having isolated DRS or DRS associated syndromes. All four exonic and the neighboring intronic regions of SALL4 gene were amplified by sixteen sets of primers using polymerase chain reaction and were subjected to bi-directional sequencing and BLAST analysis. No genetic variations were detected in the coding region and in the neighboring intronic regions of the SALL4 gene suggesting an alternative mechanism in the pathogenesis of these disorders in the South Indian population.

Duane retraction syndrome type I, Marcus Gunn jaw-winking and crocodile tears in the same eye

Duane retraction syndrome type I, Marcus Gunn jaw-winking and crocodile tears are all syndromes of congenital aberrant innervation. The authors describe a 17-month-old boy with Duane retraction syndrome type I, Marcus Gunn Jaw-winking, and crocodile tears in the same eye and discuss the proposed mechanisms of these conditions.

Review of the major findings about Duane retraction syndrome (DRS) leading to an updated form of classification

In view of all the reported evidence by electromyography in the 1970s, by histology in the 1980s, and by cerebral imagery since the 2000s, Duane retraction syndrome (DRS) has been described as the consequence of a congenital anomaly of the 6th cranial nerve nuclei with aberrant innervations by supply from the 3rd cranial nerve. Both genetic and environmental factors are likely to play a role when the cranial nerves and ocular muscles are developing between the 4th and the 8th week of gestation. New data from eye movement recordings contributed to better understanding the binocular control of saccades. Modeling of saccades in DRS seems promising for the quantification of the innervational deficit and the mechanical properties of the eye plant. The usual clinical classification of DRS needs to be updated in order to match more accurately the underlying dysinnervation of the extra ocular muscles and to illustrate the continuum that exists between the various forms. This review aims to summarize the major findings about DRS and to guide the clinician in the surgical management of this particular form of strabismus.

The Challenge of Axonal Path-Finding

Congenital syndromes of altered nervous system connectivity are reviewed along with recent findings on axonal growth: achiasma, congenital nystagmus, congenital horizontal gaze palsy, mirror movements and the syndromes of Kallmann, Wildervanck, Duane and Marcus Gunn. Identical guidance molecules are most likely involved in making axonal connections after injury and during development. Thus, investigations into variants of connectivity may help develop strategies to treat disconnections of axons in the adult.

Visualization of the oculomotor cranial nerves by magnetic resonance imaging

MRI is the imaging method of choice in patients with cranial nerve palsies. However, the nerves are often not seen on MR images and smaller lesions may not be diagnosed on routine brain MRI. The purpose of this study is to show that the oculomotor cranial nerves can be visualized by standard MR sequences and to present an update on clinical applications of cranial nerve imaging. In MR images of normal subjects, it is demonstrated that the oculomotor nerve, the trochlear nerve and the abducens nerve can be identified not only in the subarachnoid space and cavernous sinus, but also in the orbit. However, a precondition is the use of appropriate imaging sequences and planes (e.g., subarachnoid cisterns: T2-weighted fast spin-echo or T2*-weighted three-dimensional sequences in oblique-axial and sagittal planes; cavernous sinus: contrast-enhanced T1-weighted coronal images; orbit: T1-weighted images without contrast agent in the coronal plane obtained using surface coils). The capability of imaging cranial nerves is clinically important not only for diagnostic purposes in eye muscle palsies but also for planning surgical procedures at the cranio-orbital junction.

Clinical features associated with an I126M alpha2-chimaerin mutation in a family with autosomal-dominant Duane retraction syndrome

PURPOSE

We describe the clinical phenotype of a Mexican family segregating Duane syndrome as an autosomal-dominant trait linked to chromosome 2q31 (DURS2) and previously reported to harbor a heterozygous alpha2-chimaerin missense mutation.

METHODS

A 5-generation Mexican family was analyzed. Ten affected subjects were available for clinical examination. Participating subjects were tested for visual acuity, ocular alignment by prism cover testing, ocular ductions and versions, and globe retraction. In children, alignment was measured with the Krimsky test in cardinal positions of gaze.

RESULTS

Ten cases were included, 6 female and 4 male subjects. Five cases presented with bilateral and 5 with unilateral Duane syndrome. The right side was the most commonly affected side on unilateral cases. Five cases exhibited exotropia, 4 esotropia, and 1 hypotropia. Seven patients had severe limitation of abduction and two had moderate limitation. Four patients had mild adduction limitation and 4 had moderate limitation. No additional anomalies such as fourth (trochlear) nerve palsy, blepharoptosis, or dense amblyopia, which have been reported in previous families with Duane syndrome, were observed. All 3 cases that exhibited vertical dysfunction had upgaze limitation. One instance of nonpenetrance was recorded.

CONCLUSIONS

Considerable intrafamilial clinical variability was observed in this Duane syndrome pedigree that carried a alpha2-chimaerin mutation. The presence of bilateral involvement and associated vertical movements, which commonly are observed in this and other DURS2 families, could suggest the occurrence of CHN1 mutations as the source of the disease in isolated or familial DURS cases.

Rectus muscle posterior tenon fixation as an inactivation procedure

PURPOSE

To report a surgical technique and the results of rectus muscle posterior Tenon fixation as an inactivation procedure for treatment of Duane syndrome, restrictive strabismus, and long-standing paralytic strabismus, which conventionally require large rectus muscle recession.

DESIGN

Prospective, interventional case series.

METHODS

Three eyes in three Duane syndrome patients, one eye in one myopic strabismus fixus patient, one eye in one complete third nerve palsy patient, and one eye in complete sixth nerve palsy patient underwent rectus muscle inactivation by disinsertion and posterior Tenon fixation of its insertion. The main outcome measures were the postoperative eye position in all patients, the presence of upshoot or downshoot on adduction, and, in Duane syndrome patients only, the height of the palpebral fissure.

RESULTS

In Duane syndrome patients, the upshoot and the downshoot were improved markedly, and the height of the palpebral fissure was increased on adduction after the operation as compared with before the operation; the other patients had improved ocular alignment after surgery.

CONCLUSIONS

We believe that rectus muscle inactivation by fixation of its insertion to posterior Tenon is an effective and less invasive technique for achieving profound weakening of a rectus muscle compared with periosteal fixation of the rectus muscle.

Duane retraction syndrome: Type II with severe abducens nerve hypoplasia on magnetic resonance imaging

Duane retraction syndrome is a congenital oculomotor disorder characterized by horizontal eye movement limitations with palpebral fissure narrowing and globe retraction on attempted adduction. Recent reports showed the absence of the subarachnoid part of the abducens nerve on magnetic resonance imaging (MRI) in types I and III. We present a case of Duane syndrome type II, in which severe hypoplasia of the abducens nerve was revealed on high-resolution MRI.

Magnetic resonance imaging of innervational and extraocular muscle abnormalities in Duane-radial ray syndrome

PURPOSE

The authors used magnetic resonance imaging (MRI) to study extraocular muscles (EOMs) and nerves in Duane-radial ray (Okihiro) syndrome (DRRS) caused by mutations in the transcription factor SALL4.

METHODS

The authors examined four male and two female affected members of a pedigree previously reported to cosegregate DRRS and a heterozygous SALL4 mutation. Coronal T1-weighted magnetic resonance images of the orbits and heavily T2-weighted images in the plane of the cranial nerves were obtained in four subjects. MRI findings were correlated with motility examinations and published norms obtained using identical technique.

RESULTS

Five of the six subjects with DRRS had radial ray abnormalities including thumb, radial artery, radial bone, and pectoral muscle hypoplasia. Three had bilateral and three had unilateral ocular involvement. Seven eyes had limitation of both abduction and adduction, whereas two had limitations only of abduction. Most affected eyes had lid fissure narrowing and retraction in adduction. Intraorbital and intracranial abducens nerves (CN6) were small to absent, particularly ipsilateral to abduction deficiency. All subjects undergoing MRI had normal intracranial oculomotor nerves (CN3). Optic nerve (ON) cross-section findings were similar to normal. EOMs and pulleys were structurally normal in most subjects. In some affected orbits, a branch of CN3 closely approximated and presumably innervated the LR.

CONCLUSIONS

DRRS encompasses a Duane syndrome phenotype, with a variable and asymmetric endophenotype including marked CN6 hypoplasia and probable innervation or coinnervation of the LR by CN3. This endophenotype is more limited than reported in DURS2-linked Duane syndrome (On-line Mendelian Inheritance in Man, OMIM 604356) and CFEOM1 (OMIM 135700), which are clinically similar congenital cranial dysinnervation disorders that also feature CN3 hypoplasia and more widespread EOM abnormalities.

Isolated sixth cranial nerve aplasia visualized with Fast Imaging Employing Steady-State Acquisition (FIESTA) MRI

An otherwise healthy 12-month-old girl presented for evaluation of reduced abduction of the left eye detected at 6 months of age. The remainder of the examination was unremarkable. A special MRI sequence-fast imaging employing steady-state acquisition (FIESTA)-visualized the right but not the left sixth nerve cisternal segment. This is the first reported use of the MRI FIESTA sequence to diagnose aplasia of the sixth cranial nerve.

Duane retraction syndrome: MRI features in two cases

PURPOSE

Neuroimaging findings in Duane's retraction syndrome (DRS), through magnetic resonance imaging (MRI), suggest that aplasia of the abducens nerve (VI) can be responsible for several forms of DRS.

METHODS

Brain MRI was performed in two children of 2.5 and 7 years of age with left sided DRS type II and right sided DRS type I, respectively. 3D T2 weighted images through the brainstem were acquired in order to visualize the cranial nerves especially the abducens (VI) and oculomotor (III) nerves.

RESULTS

The abducens nerve on the affected side could not be observed in these two different types of DRS with normal morphology of the third nerves.

CONCLUSION

Absence of the VI nerve has been described recently in DRS types I and III only, while DRS type II is usually associated with normal VI nerve on MRI. However our results show that aplasia of the VI nerve can also be seen in DRS type II resulting in new insight of the pathogenesis of this clinical entity.

Two pedigrees segregating Duane's retraction syndrome as a dominant trait map to the DURS2 genetic locus

PURPOSE

The genetic bases of Duane's retraction syndrome (DRS) were investigated to determine its molecular etiologies. In prior studies, the transcription factors SALL4 and HOXA1 were identified as the genes mutated in DRS with radial anomalies, and in DRS with deafness, vascular anomalies, and cognitive deficits, respectively. Less is known, however, about the genetic etiology of DRS when it occurs in isolation, and only one genetic locus for isolated DRS, the DURS2 locus on chromosome 2, has been mapped to date. Toward the goal of identifying the DURS2 gene, two pedigrees have been ascertained that segregate DRS as a dominant trait.

METHODS

Members of two large dominant DRS pedigrees were enrolled in an ongoing study of the genetic basis of the congenital cranial dysinnervation disorders, and linkage analysis was conducted to determine whether their DRS phenotype maps to the DURS2 locus.

RESULTS

By haplotype analysis, the DRS phenotype in each family cosegregates with markers spanning the DURS2 region. Linkage analysis reveals maximum lod scores >2, establishing that the DRS phenotype in these two pedigrees maps to the DURS2 locus.

CONCLUSIONS

These two pedigrees double the published pedigrees known to map to the DURS2 locus and can thus contribute toward the search for the DURS2 gene. The affected members represent a genetically defined population of DURS2-linked DRS individuals, and hence studies of their clinical and structural features can enhance understanding of the DURS2 phenotype, as described in the companion paper.

Magnetic resonance imaging evidence for widespread orbital dysinnervation in dominant Duane's retraction syndrome linked to the DURS2 locus

PURPOSE

High-resolution, multipositional magnetic resonance imaging (MRI) was used to demonstrate extraocular muscles (EOMs) and associated motor nerves in Duane retraction syndrome (DRS) linked to the DURS2 locus on chromosome 2.

METHODS

Five male and three female affected members of two autosomal dominant DURS2 pedigrees were enrolled in the study. Coronal T(1)-weighted MRI of the orbits was obtained in multiple gaze positions, as well as with heavy T(2) weighting in the plane of the cranial nerves. MRI findings were correlated with motility.

RESULTS

All subjects had unilateral or bilateral limitation of abduction, or of both abduction and adduction, with palpebral fissure narrowing and globe retraction in adduction. Orbital motor nerves were typically small, with the abducens nerve (cranial nerve [CN]6) often nondetectable. Lateral rectus (LR) muscles were structurally abnormal in seven subjects, with structural and motility evidence of oculomotor nerve (CN3) innervation from vertical rectus EOMs leading to A or V patterns of strabismus in three cases. Four cases had superior oblique, two cases superior rectus, and one case levator EOM hypoplasia. Only the medial and inferior rectus and inferior oblique EOMs were spared. Two cases had small CN3s.

CONCLUSIONS

DRS linked to the DURS2 locus is associated with bilateral abnormalities of many orbital motor nerves, and structural abnormalities of all EOMs except those innervated by the inferior division of CN3. The LR may be coinnervated by CN3 branches normally destined for any other rectus EOMs. Therefore, DURS2-linked DRS is a diffuse congenital cranial dysinnervation disorder involving but not limited to CN6.

Comparison of orbital magnetic resonance imaging in duane syndrome and abducens palsy

PURPOSE

To help resolve the clinical ambiguity between Duane syndrome with severe abduction deficit and abducens palsy, we performed orbital magnetic resonance imaging (MRI) to qualify abnormalities of the lateral rectus (LR) muscle in these entities.

DESIGN

Prospective observational case series.

METHODS

Orbital MRI was performed in 13 subjects with Duane syndrome (19 eyes), 10 subjects with chronic abducens palsy (10 eyes), and 10 orthotropic control subjects (18 eyes). High-resolution, surface coil, T(1)-weighted MRI was used to obtain contiguous, 2-mm thick quasi-coronal images of the orbits in central gaze. Digital image analysis was used to quantify cross-sectional area of the ipsilesional and contralesional LR to provide comparison with control measurements.

RESULTS

Mean maximum LR cross-sectional area in Duane syndrome was statistically similar to control (P = .454) and contralesional LR cross-sectional area (P = .227). However, in chronic abducens palsy, mean maximum ipsilesional LR cross-sectional area was markedly smaller than contralesional (P = .003) and control cross-sectional areas (P < .0001), as well as smaller than the LR in Duane syndrome (P= .0017).

CONCLUSIONS

The LR muscle in abducens palsy exhibits profound atrophy. The sparing of the LR in Duane syndrome from denervation atrophy despite absence of normal abducens innervation suggests existence of alternative LR innervation. High-resolution MRI can noninvasively demonstrate LR muscle size and distinguish Duane syndrome from chronic abducens palsy in uncertain cases.

Identification and distribution of mouse carboxypeptidase A-6

Carboxypeptidase A-6 (CPA6) was recently discovered in the human genome. To gain information regarding the potential function of this novel protein, the mouse homolog of CPA6 was identified using a combination of bioinformatics and reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, homologs in rat, chicken, and frog were identified using a bioinformatics approach. The distribution of CPA6 mRNA in mouse tissues was examined using RT-PCR and in situ hybridization. A strong RT-PCR signal is detectable in olfactory bulb, and much lower levels are present in other regions such as the cerebral cortex, hippocampus, hypothalamus, striatum, and medulla. In peripheral tissues, a moderate RT-PCR signal is present in epididymis, and low levels are detectable in colon and spleen. The high level of CPA6 in adult mouse brain olfactory bulb was confirmed by in situ hybridization. Lower levels of CPA6 mRNA were found to be present in the cingulate cortex, lateral septum, pontine nucleus, and inferior olivary nucleus of the hindbrain. Within the olfactory bulb, CPA6 mRNA is enriched in the mitral and granular layer. A lower level of CPA6 mRNA is present in the internal and external plexiform layers, and no signal is detectable in the olfactory nerve layer. The distribution was also examined in whole embryos at embryonic day 14.5 and CPA6 mRNA was found to be enriched in eye, ear, osteoblasts, stomach, skin, dorsal root ganglia, and throughout the CNS. The presence of CPA6 mRNA in the rectus muscle layer of the eye at embryonic day 14.5 is consistent with the observation that the CPA6 gene is disrupted in a patient with Duane syndrome, a congenital eye defect. Taken together, the distribution of CPA6 suggests a specific role in a limited number of tissues, and it is possible that this role involves an aspect of cell migration.

Surgical management of severe cocontraction, globe retraction, and pseudo-ptosis in Duane syndrome

BACKGROUND

Correction of severe cocontraction and pseudo-ptosis present unique surgical challenges in patients with Duane syndrome.

METHODS

We report four Duane syndrome patients with esotropia in primary position, poor abduction, and severe cocontraction causing limitation to adduction, globe retraction, and pseudo-ptosis. All were treated with partial tendon transposition of the vertical rectus muscles augmented with Foster fixation sutures and surgical weakening of the ipsilateral lateral rectus muscle. One patient had a large recession of the lateral rectus muscle, and in three patients, the lateral rectus muscle was inactivated by removing from the globe and attaching its insertion to the lateral orbital wall.

RESULTS

Postoperatively, all patients were aligned within eight prisms diopters of orthotropia, had no face turn, and improved adduction and abduction. The two patients who had restriction to abduction on intraoperative forced ductions also had residual esotropia in primary position and underwent recession of the ipsilateral medial rectus muscle as a second procedure. Postoperative binocular single visual field was enlarged by 56 to 500% in the three patients who were tested preoperatively and postoperatively. Globe retraction and cocontraction were markedly relieved. Palpebral fissure widened 1.0 and 6.0 mm in two patients who had preoperative and postoperative measurements.

CONCLUSION

In Duane syndrome patients, severe cocontraction, globe retraction, and limitation to adduction may improve if the lateral rectus muscle is maximally recessed or its insertion is inactivated from the globe. Partial transposition of the vertical rectus muscles augmented with Foster sutures improved the angle of esotropia in primary position and abduction. Medial rectus muscle recession is indicated when the passive forced duction test reveals moderate-to-severe restriction to abduction.

Development of oculomotor axon projections in the chick embryo

The pattern of innervation of the extraocular muscles is highly conserved across higher vertebrate species and mediates sophisticated visuomotor processes. Defects in oculomotor development often lead to strabismus, a misalignment of the eyes that can cause partial blindness. Although it has been intensively studied from a clinical perspective, relatively little is known about how the system develops embryonically. We have therefore mapped the development of the oculomotor nerve (OMN) in chick embryos by using confocal microscopy. We show that OMN development follows a series of stereotyped steps that are tightly regulated in space and time. The OMN initially grows past three of its targets to innervate its distal target, the ventral oblique muscle, only later forming branches to the more proximal muscles. We have also investigated spatiotemporal aspects of the unusual contralateral migration of a subpopulation of oculomotor neurons by using molecular markers and have found the semaphorin axon guidance molecules and their receptors, the neuropilins, to be expressed in discrete subnuclei during this migration. Finally, we have created an embryological model of Duane retraction syndrome (DRS), a form of strabismus in which the OMN is believed to innervate aberrantly the lateral rectus, the normal target of the abducens nerve. By ablating rhombomeres 5 and 6 and hence the abducens, we have mimicked a proposed oculomotor deficit occurring in DRS. We find that the absence of the abducens nerve is not sufficient to produce this inappropriate innervation, so other factors are required to explain DRS.