Measurement of extracranial line parallel to intracranial AC-PC line by neuronavigation

Objective To study the correlation between extracranial reference line and intracranial AC -PC line for finding an extracranial scan basic line and using it as reference line before stereotactic intracranial neurosurgery.Methods Brain MRI images neuronavigation data of 39 patients of intracranial tumors admitted to our hospital from Nov.2005 to March 2010 were analyzed.The data were treated by GE Insta Trak 3500 navigation workstation.The AC - PC line was moved to extracranial surface parallelly in sagittal plane and axial plane.The distances from these lines to the center of external mestus were measured.Results The distance from the parallel line of AC - PC line in the same axial plane to the central of external mestus in males and females were ( 49.31 ± 6.28 ) mm and ( 46.60 ± 6.13 ) mm respectively and the general average was (47.71 ± 6.26 )mm.There was no difference between males and females.The distance from the line , being the parallel line of AC - PC line and outer canthus, to the central of external mestus in males and females were (32.23 ± 6.32 )mm and (27.41 ± 5.79)mm respectively .The results showed statistical difference.Conclusion Using neuronavigation to measure extral cranial line of AC - PC line is direct and reliable.The distances from the line , being the parallel line of AC - PC line and crossing outer canthus, to the central of external mestus in males and females are different. Key words: Stereotactic neurosurgery;  AC-PC line;  Extracranial reference line; Neuronavigation