Magnetic resonance imaging of the extraocular muscles and corresponding cranial nerves in patients with special forms of strabismus

Background With the technical advances, magnetic resonance imaging （MRI） is now sensitive enough to detect subtle structural abnormalities of ocular motor nerves arising from the brainstem and orbits of living subjects. This study was designed to delineate the MRI characteristics in patients with special forms of strabismus. Methods A total of 29 patients with special forms of strabismus underwent orbital and intracalvafium MRI. Imaging of the ocular motor nerves in the brainstem was performed in 0.8 mm thickness image planes using the three-dimensional fast imaging employing steady-state acquisition （3D-FIESTA） sequence. Nerves to extraocular muscles （EOMs）, EOMs and their associated connective tissues were imaged with T1 weighting in tri-planar scans by dual-phased coils within 2.0 mm thick planes. Results Patients with congenital fibrosis of the extraocular muscles exhibited hypoplasia of the oculomotor （CN3）, abducens （CN6）, trochlear （CN4） nerves, and the EOMs; hypoplasia of CN6 in the brainstem and an extra branch of the inferior division of CN3 to the lateral rectus were the most common but not the only presentation of Duane＇s retraction syndrome. Hypoplasia of CN6, facial （CN7） and hypoglossal （CN12） nerves were revealed in patients with MSbius syndrome. In a rare case of bilateral synergistic convergence and divergence, an enlarged branch of CN3 to the medial rectus and a questionable branch of CN3 to the inferior rectus bilaterally were found. Conclusion MRI can reveal subtle structures of the ocular motor nerves and their corresponding EOMs. This can provide valuable information regarding pathogenesis in some special forms of strabismus.

Magnetic resonance imaging of unilateral vertical retraction syndrome with atypical strabismus

We report two patients with unilateral vertical retraction syndrome. Magnetic resonance imaging （MRI） of the orbits of the two cases showed similar size and location of the orbital structure, but with dramatically different strabismus type. MRI sagittal reconstruction of the orbits suggested that abnormal muscle tissue arised from the inferior rectus, which might be associated with retraction and narrowing of the palpebral fissure and atypical strabismus as well.

Vertical deviation and A pattern of type Ⅲ Duane retraction syndrome

Background Researches in ocular electromyography （EMG） and Magnetic resonance imaging （MRI） of patients with Duane retraction syndrome （DRS） suggest that there may be additional abnormalities such as paradoxical innervation between horizontal rectus muscles and vertical rectus muscles, hypoplasia of vertical rectus muscle and that oblique muscles may also contribute to the heterogeneity of the clinical manifestation of DRS. This paper reports the results of superior rectus recession for vertical deviation and A pattern in DRS Type III and discusses the pathogenesis of the disease. Methods Superior and lateral rectus recession were performed in 5 cases of Huber type III DRS to treat vertical deviation and A pattern strabismus. Before operation, MRI of the brain, brainstem, cavernous sinus, and orbits were performed. Results All subjects had unilateral limitation of both abduction and adduction, with palpebral fissure narrowing and globe retraction in adduction. Three cases had A pattern of strabismus, three cases had hypertropia. The abducens nerves （CN6） were either absent or hypoplasitic in the brainstem in all patients. Two eyes had larger oculomotor foramen. Two eyes had hypoplasia of the superior rectus and the inferior rectus. There was presumably a branch of the third cranial nerve （CN3） innervating the lateral rectus （LR） in one eye. While in another eye, two branches of CN3 sent into medial rectus were revealed. After surgery, vertical deviation in the primary position was reduced in all patients and A pattern was eliminated in 3 patients. One patient developed 10A consecutive esotropia postoperatively. Conclusion The results suggest that structural abnormalities of vertical muscle and abnormal orbital innervation may be related to vertical deviation and the presence of A pattern in DRS type Ⅲ. Recession of the superior rectus muscle seems to be a safe and effective treatment for vertical deviation and A pattern strabismus in DRS Type Ⅲ.