Study On The Microscopical Anatomy Of Glabellar Keyhole Approach

Objective:To investigate the exposure area and to measure the anatomical parameters of glabellar keyhole approach(GKA) in craniotomy,to provide the evidence for clinical application.Methods:Mimetic procedure of GKA for craniotomy and topographic anatomy were studied in 12 Chinese adult formalin-fixed perfused cadaveric heads(24 sides). The incision of GKA was U-shaped at glabellar region,and extended bilaterally to the supraorbital foramen(supraorbital incisure).The muscles,arteries,veins and nerves were observed.Formed a bone window with 30mm×25mm in size,in the center of the glabellar region 10mm above the nasofrontal suture,and observed the relationship between it and the frontal sinus.Sheared the dura and the cerebral falx,and the exposure area was observed and related anatomical parameters were measured under operating microscope.The data were analyzed with SPSS 13.0 software.Results:The supraorbital nerve,supraorbital artery,supraorbital vein, supratrochlear nerve,supratrochlear artery,supratrochlear vein,nasofrontal suture and frontal sinus were observed.After drawing the longitudinal fissure and elevating the frontal lobe,GKA can reach the anterior skull base and sellar region,and expose the first,the second,the third,the forth and the fifth gap-joint.Through the bone window many structures could be seen under the operating microscope.In the exposed area there were cerebral falx,superior sagittal sinus,corpus callosum, anterior commissure,frontal pole,frontal base,cribriform plate,erista galli,olfactory sulcus,olfactory bulb,olfactory tract,sphenoidal plateau,tuberculum sellae,anterior and posterior clinoid process,diaphragma sellae,tentorium cerebelli,optic chiasm, optic nerve,optic tract,internal carotid artery,posterior communicating artery, anterior choroidal artery,anterior cerebral artery,anterior communicating artery, middle cerebral artery,temporal lobe,parahippocampal gyrus,oculomotor nerve, pituitary stalk and lamina terminalis,etc.Removed the lamina terminalis,the third ventricle could be seen.The average distance between bilateral superorbital foramen (supraorbital incisure) was(45.92±5.86)mm,average distance between bilateral supratrochlear incisure was(33.14±4.23)mm and the distance from nasofrontal suture to middle of inter-canthus line was(16.25±1.52)mm.The distance from the center of bone window to the central point of optic chiasm anterior margin was (64.30±3.20)mm,to the central point of the tuberculum sellae was(57.38±2.72)mm, to the central point ofdiaphragma sellae was(67.04±2.89)mm,to the central point of the lamina terminalis was(66.18±3.79)mm,to the anterior communicating artery was (60.64±4.61)mm,to the entrance of the left or fight optic nerve into the dura sheet was(57.78±2.25)mm or(57.64±1.46 ) mm,to the left or right anterior clinoid process was(63.34±2.82)mm or(62.36±3.69)mm,to the left or right posterior clinoid process was(66.63±3.44)mm or(66.95±2.28)mm,and to the left or fight bifurcation of the internal carotid artery was(68.02±3.43)mm or(66.24±3.71)mm.Conelusion:GKA can expose fairly the anatomical structures around the midline of anterior skull base and sellar region.It can be recommended to the resection of lesions of midline anterior skull base,such as the meningiomas in olfactory groove and sphenoidal plateau,and it can be applied to the management of lesions of midline sellar and suprasellar region.It also can be used for the clipping of the anterior communicating aneurysms.This approach can provide the same exposure as the traditional anterior interhemispheric approach.The advantages of GKA are small incision,small bone window,less injury of frontal lobe and more possibility of preserving the olfaction.But there is the risk of infection and cerebrospinal fluid fistula.It can not be used in cases suffering from brain swelling.