Abnormalities of the oculomotor nerve in congenital fibrosis of the extraocular muscles and congenital oculomotor palsy

Novel variants in TUBA1A cause congenital fibrosis of the extraocular muscles with or without malformations of cortical brain development

Variants in multiple tubulin genes have been implicated in neurodevelopmental disorders, including malformations of cortical development (MCD) and congenital fibrosis of the extraocular muscles (CFEOM). Distinct missense variants in the beta-tubulin encoding genes TUBB3 and TUBB2B cause MCD, CFEOM, or both, suggesting substitution-specific mechanisms. Variants in the alpha tubulin-encoding gene TUBA1A have been associated with MCD, but not with CFEOM. Using exome sequencing (ES) and genome sequencing (GS), we identified 3 unrelated probands with CFEOM who harbored novel heterozygous TUBA1A missense variants c.1216C>G, p.(His406Asp); c.467G>A, p.(Arg156His); and c.1193T>G, p.(Met398Arg). MRI revealed small oculomotor-innervated muscles and asymmetrical caudate heads and lateral ventricles with or without corpus callosal thinning. Two of the three probands had MCD. Mutated amino acid residues localize either to the longitudinal interface at which α and β tubulins heterodimerize (Met398, His406) or to the lateral interface at which tubulin protofilaments interact (Arg156), and His406 interacts with the motor domain of kinesin-1. This series of individuals supports TUBA1A variants as a cause of CFEOM and expands our knowledge of tubulinopathies.

Magnetic Resonance Imaging in 14 Patients with Congenital Oculomotor Nerve Palsy

PURPOSE

To elucidate the imaging findings of congenital oculomotor nerve palsy by evaluating the oculomotor nerve and extraocular muscles on magnetic resonance (MR) imaging in a relatively large series of 14 patients with congenital oculomotor nerve palsy.

METHODS

Ophthalmologic examination of 14 consecutive patients diagnosed with congenital oculomotor nerve palsy, and MR imaging of the orbit and oculomotor nerves were performed.

RESULTS

Of the 14 patients with congenital oculomotor nerve palsy, 13 patients (93%) were unilateral and 12 patients (86%) had incomplete palsy. On MR imaging, 5 patients (36%) had hypoplasia or aplasia of the oculomotor nerve with variable degrees of extraocular muscle atrophy on the affected side. Of the 14 patients, nine (64%) had normal-sized oculomotor nerves with or without muscle atrophy. The most frequently involved muscles were the inferior rectus (64%) and medial rectus (50%), followed by the superior rectus (29%) and inferior oblique muscles (14%). None of the 14 patients showed an abnormal abducens nerve.

CONCLUSION

Congenital oculomotor nerve palsy was mostly incomplete and hypoplasia or aplasia of the oculomotor nerve was apparent in one third of patients showing variable degrees of extraocular muscle atrophy, mostly of the medial rectus and inferior rectus muscles.

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.

Marshall M. Parks Memorial Lecture: Ocular Motor Misbehavior in Children: Where Neuro-Ophthalmology Meets Strabismus

Clinical diagnosis has been supplemented by neuroimaging advances, genetic discoveries, and molecular research to generate new neurobiological discoveries pertaining to early maldevelopment of ocular motor control systems. In this focused review, I examine recent paradigm shifts that have transformed our understanding of pediatric ocular motor disease at the prenuclear and infranuclear levels. The pathogenesis of complex ocular motor disorders, such as paradoxical pupillary constriction to darkness, benign tonic upgaze of infancy, congenital fibrosis syndrome, and the constellation of unique eye movements that accompany Joubert syndrome, are elucidated.

Congenital cranial dysinnervation disorders

The European Neuromuscular Centre (ENMC) derived the term Congenital Cranial Dysinnervation Disorders in 2002 at an international workshop for a group of congenital neuromuscular diseases. CCDDs are congenital, non-progressive ophthalmoplegia with restriction of globe movement in one or more fields of gaze. This group of sporadic and familial strabismus syndromes was initially referred to as the 'congenital fibrosis syndromes' because it was assumed that the primary pathologic process starts in the muscles of eye motility. Over the last few decades, evidence has accumulated to support that the primary pathologic process of these disorders is neuropathic rather than myopathic. This is believed that for normal development of extra ocular muscles and for preservation of muscle fiber anatomy, normal intra-uterine development of the innervation to these muscles is essential. Congenital dysinnervation to these EOMs can lead to abnormal muscle structure depending upon the stage and the extent of such innervational defects. Over last few years new genes responsible for CCDD have been identified, permitting a better understanding of associated phenotypes, which can further lead to better classification of these disorders. Introduction of high-resolution MRI has led to detailed study of cranial nerves courses and muscles supplied by them. Thus, due to better understanding of pathophysiology and genetics of CCDDs, various treatment modalities can be developed to ensure good ocular alignment and better quality of life for patients suffering from the same.

Magnetic resonance imaging in congenital Brown syndrome

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Strabismus surgery in congenital fibrosis of the extraocular muscles: a paradigm

BACKGROUND

Congenital fibrosis of extraocular muscles (CFEOM) is a rare group of disorders with variable phenotypes that result from aberrant innervation to the EOMs leading to synergistic vertical and/or horizontal deviations. We report our experience with the surgical management of patients with CFEOM.

MATERIALS AND METHODS

We reviewed the clinical findings, the surgical management, and outcomes of 52 consecutive CFEOM patients operated by one surgeon at a university hospital setting between 1993 and 2014. Patients were divided into CFEOM1, 2, or 3 based on clinical and/or molecular genetic findings.

RESULTS

Thirty-seven (71.2%) cases were bilateral and 15 (28.8%) were unilateral. Six of the bilateral cases had CFEOM2, and the rest of the patients had either CFEOM1 or CFEOM3. The median age at the first surgery was 10 (1-43) years. Twenty-five were females and 27 were males. Nineteen patients had previous strabismus and/or ptosis surgeries elsewhere. The mean number of operations at our center was 1.6 ± 0.7 (1-4). A temporary stay suture was used in eight patients and permanently in seven. Of the 40 patients with abnormal head position, 18 achieved excellent, 15 good, and seven poor outcomes and ocular alignment in primary position following the latest surgery was excellent in 19, good in 18, and poor in 14 of the patients, as defined in the "Methods" section of the paper.

CONCLUSIONS

Although patients with CFEOM present significant strabismus surgical challenges because of EOM dysinnervation, fibrosis, and/or heterotopia, satisfactory alignment and improvement of the head posture can be attained in a significant proportion of patients using an individually tailored surgical approach.

Sclerosing cavernous hemangioma of the cavernous sinus mimicking congenital fibrosis of the extraocular muscles

A girl with a clinical presentation suggestive of unilateral congenital fibrosis of the extraocular muscles type 3 at 2 years of age years later developed progressive ophthalmoplegia and an afferent pupillary defect. Reimaging revealed a lesion diagnosed as a sclerosing cavernous sinus hemangioma with focal calcification. Cavernous sinus hemangioma is a rare, benign vascular malformation whose growth causes cranial nerve compression. Although frequently missed on routine neuroimaging, characteristic radiologic findings distinguish it from lesions such as meningioma.

Functional magnetic resonance imaging of horizontal rectus muscles in esotropia

PURPOSE

Monkey neurophysiology suggests that changes in neural drive rather than extraocular muscle structure underlie sensory-induced strabismus. If this is true, then extraocular muscle structure should be normal. We used magnetic resonance imaging to measure horizontal rectus muscle size and contractility to determine whether muscle structure is a factor in human concomitant esotropia.

METHODS

High-resolution, quasicoronal plane magnetic resonance imaging was performed in target-controlled central gaze, abduction, and adduction in 13 orthotropic controls (mean age, 38 ± 19 years) and 12 adults (mean age, 52 ± 16 years) who had concomitant esotropia averaging 28(Δ) ± 18(Δ) at distance. Thyroid ophthalmopathy was excluded. Horizontal rectus muscle cross sections were determined in 6 contiguous, 2-mm-thick midorbital image planes. Contractility was computed in each plane as the difference in cross section from contraction to relaxation.

RESULTS

Medial rectus muscle cross sections in multiple planes averaged up to 39% larger in esotropic patients than in controls (P < 0.005), whereas lateral rectus muscle cross sections in esotropia were up to 28% larger but only significantly larger in one plane (P < 0.02). Medial rectus contractility was increased by up to 60% in esotropic patients (P < 0.005), whereas lateral rectus contractility in esotropia was slightly but not significantly supernormal.

CONCLUSIONS

Medial rectus muscle size is supernormal and lateral rectus muscle size is not subnormal in concomitant esotropia. This finding indicates that human concomitant esotropia is associated with peripheral muscular abnormality.

Surgical management of hypotropia in congenital fibrosis of extraocular muscles (CFEOM) presented by pseudoptosis

Purpose

To describe the demographics, characteristics, management pitfalls, and outcomes of pseudoptosis associated with congenital fibrosis of the extraocular muscles (CFEOM).

Methods

A retrospective review was performed of eight patients presenting with ptosis and hypotropia to oculoplastic service. All patients underwent full ocular evaluation and magnetic resonance imaging of brain and orbit. Five of these patients underwent stepwise correction of hypotropia by single-stage adjustable strabismus surgery (SSASS), followed by a frontalis sling if needed.

Results

Eight patients had congenital strabismus with severe ptosis and a positive forced duction test. There was a highly significant improvement from preoperative mean hypotropia angle of 30 prism diopters (PD) to 9 PD mean postoperative angle (P = 0.006). Surgery for ptosis was not needed in 80% of eyes.

Conclusion

CFEOM involving both ptosis and hypotropia could be properly managed with the correct sequence of surgical steps. Proper vertical alignment by correction of hypotropia utilizing SSASS may alleviate the need for ptosis surgery.

The fate of the oculomotor system in clinical bilateral anophthalmia

The interdependence of the development of the eye and oculomotor system during embryogenesis is currently unclear. The occurrence of clinical anophthalmia, where the globe fails to develop, permits us to study the effects this has on the development of the complex neuromuscular system controlling eye movements. In this study, we use very high-resolution T2-weighted imaging in five anophthalmic subjects to visualize the extraocular muscles and the cranial nerves that innervate them. The subjects differed in the presence or absence of the optic nerve, the abducens nerve, and the extraocular muscles, reflecting differences in the underlying disruption to the eye's morphogenetic pathway. The oculomotor nerve was present in all anophthalmic subjects and only slightly reduced in size compared to measurements in sighted controls. As might be expected, the presence of rudimentary eye-like structures in the socket appeared to correlate with development and persistence of the extraocular muscles in some cases. Our study supports in part the concept of an initial independence of muscle development, with its maintenance subject to the presence of these eye-like structures.

MR imaging of congenital or developmental neuropathic strabismus: common and uncommon findings

BACKGROUND AND PURPOSE

High-resolution MR imaging enables direct imaging of the ocular motor nerves. The aim of this study was to assess the various causes of congenital or developmental neuropathic strabismus by using high-resolution MR imaging.

MATERIALS AND METHODS

High-resolution MR imaging was performed to evaluate the ocular motor nerves (CNIII, CNIV, CNVI) in 247 consecutive patients with suspected congenital or developmental neuropathic strabismus. These MR images, along with those obtained from conventional MR imaging of the brain and the orbit, were evaluated.

RESULTS

MR imaging abnormalities were found in 112 patients: ocular motor nerve abnormalities in 98 patients (88%), orbital abnormalities in 9 patients (8%), and brain abnormalities in 5 patients (4%). Ocular motor nerve abnormalities were CNIV aplasia (63%), CNVI aplasia or hypoplasia (21%), CNIII aplasia or hypoplasia (3%), and combined CNIII aplasia and CNVI hypoplasia (1%). Orbital abnormalities were EOM hypoplasia (7%), EOM hypertrophy (1%), and fibrotic mass (1%). Brain abnormalities were periventricular leukomalacia (4%) and periventricular heterotopia (1%).

CONCLUSIONS

Various MR imaging abnormalities were associated with congenital and developmental neuropathic strabismus. The most common abnormality was CNIV aplasia.

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.

Congenital fibrosis of the extraocular muscles

Background:

Congenital fibrosis of the extraocular muscles (CFEOM) describes a group of rare congenital eye movement disorders that result from the dysfunction of all or part of the oculomotor (CN 3) and the trochlear (CN 4) nerves, and/or the muscles these nerves innervate.

Aim:

To describe the clinical and neuro-radiological findings in three patients with CFEOM and review literature with respect to clinical features, genetics and management of this condition.

Materials and Methods:

A retrospective chart review was performed of three Omani patients who had been diagnosed with CFEOM in our institution. All patients had undergone standardized orthoptic and ocular evaluations and magnetic resonance imaging (MRI) of the orbits and brain.

Results:

The three patients (age range nine months - 10 years) presented a history of congenital strabismus. All patients had severe bilateral ptosis and mild to moderate visual impairment secondary to the ptosis and astigmatism. Two of three patients demonstrated a positive jaw-winking phenomenon. A moderate to large angle exotropia with varying amount of hypotropia and limitations of almost all the extra ocular muscles was noted. Patient 3 was also developmentally delayed. MRI brain and orbit showed abnormalities of the extraocular muscles in two patients and brain malformation in one patient.

Conclusions:

CFEOM is a rare, congenital, and non-progressive disorder with multiple extra ocular muscle restrictions. CFEOM can be associated with neuro-radiological abnormalities; its diagnosis and classification is defined by clinical characteristics and genetics. Options for treatment are limited and difficult.

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.

KIF21A variant R954W in familial or sporadic cases of CFEOM1

PURPOSE

To demonstrate the clinical characteristics and determine mutations in the KIF21A gene, encoding a kinesin motor protein in patients with congenital fibrosis of the extraocular muscles (CFEOM) type 1.

METHODS

Patients of five families with congenital fibrosis syndrome and two simplex patients with CFEOM underwent ophthalmologic examination and mutation analysis in the KIF21A gene.

RESULTS

Clinical examination and passive motility testing prior to surgery met criteria for CFEOM. All patients had congenital restrictive ophthalmoplegia primarily affecting muscles innervated by the oculomotor nerve. Complete mutation screening in the KIF21A gene revealed the presence of the known and most common recurrent variant R954W in three families and in two simplex cases. Two families demonstrated linkage to chromosome 16.

CONCLUSIONS

The patients included in the study had marked restriction of movement bilaterally with nearly complete loss of vertical ocular motility, graded reduction of horizontal motility, ptosis, and compensatory chin elevation. The phenotype was variable in patients carrying the same mutation. In one family, all patients were diagnosed with mental retardation, indicating that this syndrome might not only affect the development of cranial nerves, but can also be responsible for general neurologic dysfunction. The screening data suggest frequent and exclusive appearance of the R454W variant in sporadic and familial cases of CFEOM1 in Germany.

Magnetic resonance imaging of the endophenotype of a novel familial Möbius-like syndrome

INTRODUCTION

Möbius syndrome typically presents as a sporadic trait with congenital facial palsy and abduction impairment. We used high-resolution magnetic resonance imaging (MRI) and genetic analysis to examine a family with features of Möbius syndrome.

METHODS

We examined 3 related family members having congenital complete opthalmoplegia with ptosis and facial diplegia. Orbits were imaged in quasi-coronal and sagittal planes of 2 mm thickness. Subarachnoid cranial nerves were imaged in planes of 1 mm thickness. Linkage and mutation analysis were performed to determine whether the pedigree harbored mutations in 4 candidate genes.

RESULTS

In affected subjects, MRI showed marked hypoplasia of extraocular muscles and intraorbital motor nerves. In the anterior orbit, rectus extraocular muscles were less hypoplastic but markedly curved toward insertion. Oblique extraocular muscles were hypoplastic and abnormally inserted. Posterior bony orbits were hypoplastic. Optic nerves were markedly straightened. Brainstems and cranial nerves III, VI, VII, and VIII were normal bilaterally. No pathogenic mutations were detected in affected individuals.

CONCLUSIONS

Previous MRI studies have demonstrated brainstem hypoplasia and cranial nerve aplasia in Möbius syndrome. The current family had normal brainstems and subarachnoid portions of motor cranial nerves innervating the orbit but marked extraocular muscle hypoplasia. These clinical and MRI findings are atypical for Möbius syndrome and other congenital cranial dysinnervation disorders. Congenital facial weakness and complete ophthalmoplegia may occur despite MRI evidence of normal brainstem anatomy. The endophenotype appears to result from a genetic defect distinct from the congenital cranial dysinnervation disorders defined thus far, rather than a global brainstem insult.

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.