Mediterr. J. Otol 2008; 4:(3)

The Variation of Temporal Bone Neurovascular Structures in Otologic-Neurotologic Surgeries: A Cadaver Dissection Study
Derya Ümit Talas, Zeliha Kurtoğlu, Aslihan Köseoğlu, Deniz Uzmansel, Hakan Özturk, Celal Bağdatoğlu
Mersin University, Medical Faculty, Department of Otolaryngology Head and Neck Surgery, Mersin, Turkey deryatalas@yahoo.com

Objective: This study aims to evaluate the variations of important structures by objective means for a safe otologic-neurotologic surgery.

Materials and Method: Twelve temporal bones of six cadavers were dissected under surgical microscope with micro drill using jugular foramen approach. The distance between the second genu of facial nerve to the joint point of the chorda tympani (A); the distance between the nearest points of the sigmoid sinus and the facial nerve (B); the distance between the dome of the jugular bulb and the superior part of the round window niche (C) were measured.

Results: The mean and the standard deviation of the measured distances of A for right and left temporal bones were 10.75 ± 2.17 mm ( min = 9.30 max = 13.70 ) and 10.88 ± 3.04 mm ( min = 7.80 max = 14.60 ), respectively. The mean values of B for right and left temporal bones were 5.71 ± 2.08 mm ( min = 3.20 max = 7.65 ) and 6.03 ±  1.74 mm ( min = 4.00 max = 8.20 ), respectively. Right and left mean values and standard deviations for C were found as 6.67 ± 2.85 mm ( min = 3.40 max = 11.40 ) and 8.10 ± 2.17 mm ( min = 4.80 max = 11.90 ), respectively. Significant statistical correlation was found between right and left values regarding both A and B. 

Conclusion: The joint point of chorda tympani to the facial nerve and the nearest distance between the facial nerve and the sigmoid sinus may be useful to make a prediction of the other side of the temporal bone. The variation among the values of each parameter consisting of the minimum and the maximum measurements might be considered as a useful tool for choosing the best surgical approach for lesions of the temporal bone, jugular foramen and the posterior fossa. The surgeon may recognize serious limitations for a specific approach and may choose another access with the diagnosis of anatomic variations, such as anteriorly located sigmoid sinus and high jugular bulb, by preoperative radiological evaluation.