Title: Orbital MRI imaging in congenital cranial dysinnervation disorders

Yonghong Jiao

INTRODUCTION: In patients with congenital cranial dysinnervation disorders（CCDDs）, visualization of the motor nerves to the extraocular muscles (EOMs) in the deep orbit can provide useful information.

METHODS: A human orbit was embedded in celloidin and serially sectioned for HE stain as reference to distinguish motor nerves to the EOMs. A total of 43 patients with CCDDs underwent orbital and intracalvarium MRI. Nerves to EOMs in the orbits were imaged with FSE/T1WI oblique-coronal planes by dual-phased coils within 2.0 mm thick planes.

RESULTS: Patients with congenital fibrosis of the extraocular muscles exhibited hypoplasia of the oculomotor, abducens, trochlear nerves, and the EOMs. Hypoplasia of CN6 and an extra branch of the inferior division of oculomotor nerve to the lateral rectus were the most common but not the only presentation of Duane's retraction syndrome (DRS). Abducens nerve was present with two branches from the inferior division of oculomotor nerves to the medial rectus in two patients of inverse DRS. Hypoplasia of abducens nerve were seen in patients with Mobius syndrome.

DISCUSSION：Contiguous coronal orbital MRI plays an important role in the evaluation of the normal and pathologic ocular motor nerves.

CONCLUSION: Orbital MRI provides valuable information regarding pathogenesis in CCDDs.