Microsurgical Anatomy And Operative Approaches Of The Posterior Temporal Region

Part I Objective: To study the relationship of anatomical landmarks of posterior temporal cranial base to gain orientation regarding temporal base transtentorial approach.Materials and methods: Twenty dried skulls and fifteen injected adult cadaver specimens were used to study morphometric relationships on both sides of each specimen with 6 to 40 magnification. The anatomical relationships and the distance within the asterion, the anterior angle of parietomastoid sutures and the adjacent bone structures were studied with dried skulls. The anatomical relationships of the asterion and the anterior angle of parietomastoid sutures with STP were also studied with injected cadaver specimens. The distance between the superior line of the transverse sinus and the extended line of the superior rim of zygoma arch was measured. The relationships of the level of the bottom of the middle fossa with the supramastoid crest and the superior rim of zygoma arch were examined.Results: The distance between the superior line of the transverse sinus and the extended line of the superior rim of zygoma arch was (11.22 2.21) mm (8.20~14.45mm) The gaps from STP to the anterior angle of parietomastoid sutures and to the asterion were (2.11 2.61) mm (0. 12~ 9.33 mm) and (20. 44?. 03) mm (14.21~26.47mm) . The location of the asterion was above upper rim of the transverse sinus in 16. 7%, superior half of the transverse sinus in 26.7%, inferior half of the transverse sinus in 33. 3%, below lower rim of the transverse sinus in 23. 3%. The supramastoid crest and the superior rim of zygoma arch correlated with the level of the bottom of the middle fossa.Conclusion: The asterion is variable to the underlying transverse sinus and limits its usefulness as a consistently stable marker. The keyhole of temporal base transtentorial approach is located on the supramastoid crest with the posterior rim on anterior angle of parietomastoid sutures. The second hole is 30mm behind the first one with its inferior rim 15mm above the extended line of the superior rim of zygoma arch. The third hole is 40mm anterior to the first one with its inferior rim on the level of zygoma arch. And the fourth hole is above the third one, as the fifth of the second. The height is with regard to the need of operational exposure.