Duane's retraction syndrome as a cause of diplopia in adults

Diplopia in Cases With Type 1 Duane Retraction Syndrome

Objective In this study, we aimed to investigate the prevalence of diplopia in cases with type 1 Duane retraction syndrome (DRS). Materials and methods This study was a retrospective review of cases involving patients presenting diagnosed with DRS over a period of 24 years. Among these cases, 28 had type 1 DRS and fulfilled the inclusion criteria. The cases were evaluated in terms of age, gender, affected eye, concomitant ocular motility disorders, presence of amblyopia, manifest shift, abnormal head position (AHP), fusion, and stereopsis. Results Sixteen of the patients (57.1%) in the study were female, and 12 (42.8%) were male; the mean age of the patients was 18.9 years (range: 7-67 years). The right eye was affected in six of the cases (21.4%), and the left eye in 22 (78.6%) of the cases. On examination, diplopia was not observed in 21 (75%) cases, but it was detected in seven (25%). AHP was present in five of the seven cases with diplopia and not present in two, and all seven of the diplopic cases had fusion, while three had stereopsis. The level of stereopsis in all diplopic cases was 400 sn/ark. When the clinical findings of patients with diplopia and those without diplopia were compared, a statistically significant difference was observed only in terms of AHP. Conclusions Although diplopia is not one of the clinical features of DRS, it must be noted that in cases with type 1 DRS, diplopia may occur in directions in which the movement of the eyeball is limited. In the presence of this finding, which might mimic sixth nerve palsy, patient history must be diligently taken, other clinical findings of DRS must be thoroughly examined, and an MRI should be performed when necessary for an easier diagnosis.

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.

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.

Altering 5-hydroxymethylcytosine modification impacts ischemic brain injury

Epigenetic modifications such as cytosine methylation and histone modification are linked to the pathology of ischemic brain injury. Recent research has implicated 5-hydroxymethylcytosine (5hmC), a DNA base derived from 5-methylcytosine (5mC) via oxidation by ten-eleven translocation (Tet) enzymes, in DNA methylation-related plasticity. Here we show that 5hmC abundance was increased after ischemic injury, and Tet2 was responsible for this increase; furthermore, inhibiting Tet2 expression abolished the increase of 5hmC caused by ischemic injury. The decrease in 5hmC modifications from inhibiting Tet2 activity was accompanied by increased infarct volume after ischemic injury. Genome-wide profiling of 5hmC revealed differentially hydroxymethylated regions (DhMRs) associated with ischemic injury, and DhMRs were enriched among the genes involved in cell junction, neuronal morphogenesis and neurodevelopment. In particular, we found that 5hmC modifications at the promoter region of brain-derived neurotrophic factor (BDNF) increased, which was accompanied by increased BDNF mRNA, whereas the inhibition of Tet2 reduced BDNF mRNA and protein expression. Finally, we show that the abundance of 5hmC in blood samples from patients with acute ischemic stroke was also significantly increased. Together, these data suggest that 5hmC modification could serve as both a potential biomarker and a therapeutic target for the treatment of ischemic stroke.

Transient pseudo-Duane syndrome after lateral orbital trauma

Duane syndrome is a dysinnervation disorder that frequently involves secondary anomalous eye movement, in particular, ocular retraction and the narrowing of the palpebral fissure on the adduction. Pseudo-Duane syndrome is caused by a mechanical restriction that produces clinical findings similar to those of Duane syndrome. Most patients with pseudo-Duane syndrome have restrictive pathologies on the medial side of the globe, such as entrapment of the medial rectus muscle. We report the case of a 44-year-old man with pseudo-Duane syndrome in whom we identified a lateral orbital wall fracture and entrapment of the soft tissue surrounding the lateral rectus muscle by computed tomography. To the best of our knowledge, this etiology of pseudo-Duane syndrome has not been previously reported.

Infranuclear ocular motor disorders

This chapter covers the very large number of possible disorders that can affect the three ocular motor nerves, the neuromuscular junction, or the extraocular muscles. Conditions affecting the nerves are discussed under two major headings: those in which the site of damage can be anatomically localized (e.g., fascicular lesions and lesions occurring in the subarachnoid space, the cavernous sinus, the superior orbital fissure, or the orbit) and those in which the site of the lesion is either nonspecific or variable (e.g., vascular lesions, tumors, "ophthalmoplegic migraine," and congenital disorders). Specific comments on the diagnosis and management of disorders of each of the three nerves follow. Ocular motor synkineses (including Duane's retraction syndrome and aberrant regeneration) and disorders resulting in paroxysms of excess activity (e.g., neuromyotonia) are then covered, followed by myasthenia gravis and other disorders that affect the neuromuscular junction. A final section discusses disorders of the extraocular muscles themselves, including thyroid disease, orbital myositis, mitochondrial disease, and the muscular dystrophies.