Changhu Liang MD, PhD, Presenter: Nothing to Disclose

To obtain the normal image and sectional anatomical data of the abducent nerve and its related arteries with MRI and sectional specimen.

A total of 57 volunteers underwent 3D-CISS MR imaging, and 20 of these volunteers also underwent MR angiography in which a time-of-flight sequence was used ，the anatomical features and neurovascular relationships of the abducent nerve were observed from the successive multiplanar reconstruction (MPR) images, the sectional specimens, and 3D-CISS imaging of cranial specimens.

（1）The abducent nerve were identified with certainty in 97% obtained in the axial，sagittal planes and in 95% obtained in the coronal plane. On the contrary, we were never able to identify the abducent nerve by using the TOF sequence in 20 volunteers.（2）The nerve emerged from the pontomedullary sulcus in 103(93%) of cases, and 7 cases emerged from an area superior to the sulcus . We consistently identified only one nerve root and never detected a doubling of the nerve. The facial colliculus and Dorello's canal are the important landmarks to find the abducent nerve.（3）The AICA was the blood vessel most often identified. When the AICA was identified, it was noted to be in contact with the abducent nerve in 71（74.7%）of 95 nerves, and not in contact in 24（25.3%）of the 95 nerves.（4）MRI revealed the similar result corresponding to the slices and 3D-CISS MPR images of the specimens in displayng the abducent nerve.

The anatomical course of the abducent nerve and its relationship to the AICA can be reliably identified using a 3D-CISS MR sequence with the facial colliculus and Dorello's canal serving as landmarks.

Familiarity with neurovascular relationships are  very important for preoperative planning and for providing a more accurate decompression procedure.

Liang, C, A Comparative Study on Anatomy of the Cisternal Segment of the Abducent Nerve with MRI and Sectional Specimen.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11001322.html