The Asterion-to-Transverse Process of the Atlas Line as a Surgical Landmark

Abstract

Introduction Proposed landmarks to predict the anatomical location and trajectory of the sigmoid sinus have varying degrees of reliability. Even with neuronavigation technology, landmarks are crucial in planning and performing complex approaches to the posterolateral skull base. By combining two major dependable structures—the asterion (A) and transverse process of the atlas (TPC1)—we investigate the A-TPC1 line in relation to the sigmoid sinus and in partitioning surgical approaches to the region.

Methods We dissected six cadaveric heads (12 sides) to expose the posterolateral skull base, including the mastoid and suboccipital bone, TPC1 and suboccipital triangle, distal jugular vein and internal carotid artery, and lower cranial nerves in the distal cervical region. We inspected the A-TPC1 line before and after drilling the mastoid and occipital bones and studied the relationship of the sigmoid sinus trajectory and major muscular elements related to the line. We retrospectively reviewed 31 head and neck computed tomography (CT) angiograms (62 total sides), excluding posterior fossa or cervical pathologies. Bone and vessels were reconstructed using three-dimensional segmentation software. We measured the distance between the A-TPC1 line and sigmoid sinus at different levels: posterior digastric point (DP), and maximal distances above and below the digastric notch.

Results A-TPC1 length averaged 65 mm and was posterior to the sigmoid sinus in all cadaver specimens, coming closest at the level of the DP. Using the transverse-asterion line as a rostrocaudal division and skull base as a horizontal plane, we divided the major surgical approaches into four quadrants: distal cervical/extreme lateral and jugular foramen (anteroinferior), presigmoid/petrosal (anterosuperior), retrosigmoid/suboccipital (posterosuperior), and far lateral/foramen magnum regions (posteroinferior). Radiographically, the A-TPC1 line was also posterior to the sigmoid sinus in all sides and came closest to the sinus at the level of DP (mean, 7 mm posterior; range, 0–18.7 mm). The maximal distance above the DP had a mean of 10.1 mm (range, 3.6–19.5 mm) and below the DP 5.2 mm (range, 0–20.7 mm).

Conclusion The A-TPC1 line is a helpful landmark reliably found posterior to the sigmoid sinus in cadaveric specimens and radiographic CT scans. It can corroborate the accuracy of neuronavigation, assist in minimizing the risk of sigmoid sinus injury, and is a useful tool in planning surgical approaches to the posterolateral skull base, both preoperatively and intraoperatively.

Keywords

posterolateral skull base - retrosigmoid - far lateral - jugular foramen - asterion - transverse process of the atlas - sigmoid sinus

• References

• 1 Rhoton Jr AL. The cerebellopontine angle and posterior fossa cranial nerves by the retrosigmoid approach. Neurosurgery 2000; 47 (3, Suppl): S93-S129
• 2 Lawton MT, Daspit CP, Spetzler RF. Presigmoid approaches to skull base lesions. Adv Tech Stand Neurosurg 1997; 23: 189-204
• 3 Heros RC. Lateral suboccipital approach for vertebral and vertebrobasilar artery lesions. J Neurosurg 1986; 64 (04) 559-562
• 4 Spetzler RF, Graham TW. The far lateral approach to the inferior clivus and the upper cervical region. Technical note. BNI Q 1990; 6: 35-38
• 5 Wen HT, Rhoton Jr AL, Katsuta T, de Oliveira E. Microsurgical anatomy of the transcondylar, supracondylar, and paracondylar extensions of the far-lateral approach. J Neurosurg 1997; 87 (04) 555-585
• 6 Sen CN, Sekhar LN. An extreme lateral approach to intradural lesions of the cervical spine and foramen magnum. Neurosurgery 1990; 27 (02) 197-204
• 7 George B, Lot G, Tran Ba Huy P. The juxtacondylar approach to the jugular foramen (without petrous bone drilling). Surg Neurol 1995; 44 (03) 279-284
• 8 Rhoton Jr AL. Jugular foramen. Neurosurgery 2000; 47 (3, Suppl): S267-S285
• 9 Ballesteros-Zebadúa P, García-Garduño OA, Galván de la Cruz OO, Arellano-Reynoso A, Lárraga-Gutiérrez JM, Celis MA. Assessment of an image-guided neurosurgery system using a head phantom. Br J Neurosurg 2016; 30 (06) 606-610
• 10 Day JD, Tschabitscher M. Anatomic position of the asterion. Neurosurgery 1998; 42 (01) 198-199
• 11 Day JD, Kellogg JX, Tschabitscher M, Fukushima T. Surface and superficial surgical anatomy of the posterolateral cranial base: significance for surgical planning and approach. Neurosurgery 1996; 38 (06) 1079-1083
• 12 Ribas GC, Rhoton Jr AL, Cruz OR, Peace D. Suboccipital burr holes and craniectomies. Neurosurg Focus 2005; 19 (02) E1
• 13 Tubbs RS, Loukas M, Shoja MM, Bellew MP, Cohen-Gadol AA. Surface landmarks for the junction between the transverse and sigmoid sinuses: application of the “strategic” burr hole for suboccipital craniotomy. Neurosurgery 2009; 65 (6, Suppl): 37-41
• 14 Avci E, Kocaogullar Y, Fossett D, Caputy A. Lateral posterior fossa venous sinus relationships to surface landmarks. Surg Neurol 2003; 59 (05) 392-397
• 15 Raso JL, Gusmão SN. A new landmark for finding the sigmoid sinus in suboccipital craniotomies. Neurosurgery 2011; 68 (1, Suppl Operative): 1-6
• 16 Matsuo S, Komune N, Kurogi R, Akagi Y, Iihara K. Relationship between the horizontal part of the sigmoid sinus and the line through the digastric point and posterior edge of the condyle: an anatomic and radiologic study. World Neurosurg 2018; 114: e597-e604
• 17 Sheen TS, Chung TT, Snyderman CH. Transverse process of the atlas(C1)--an important surgical landmark of the upper neck. Head Neck 1997; 19 (01) 37-40
• 18 Furnas DW. Transverse process of the atlas: guide to high ligation of the internal jugular vein in radical neck dissections. Ann Surg 1967; 165 (03) 473-476
• 19 Gardner G, Robertson JT, Robertson JH, Cocke EW, Clark WC. Glomus jugulare tumors: skull base surgery. In: Schmidek HH, Sweet WH. eds. Operative Neurological Techniques. 2nd edition.. Philadelphia: W.B. Saunders Co.; 1988: 739-752
• 20 Lévy D, Vacher C, Lézy JP. Relations of the accessory nerve with the internal jugular vein: surgical implications in cervical lymph node clearances. Surg Radiol Anat 2001; 23 (03) 155-157
• 21 Kawashima M, Tanriover N, Rhoton Jr AL, Ulm AJ, Matsushima T. Comparison of the far lateral and extreme lateral variants of the atlanto-occipital transarticular approach to anterior extradural lesions of the craniovertebral junction. Neurosurgery 2003; 53 (03) 662-674
• 22 Mathangasinghe Y, Samaranayake UM, Silva SS, Prematilaka HC, Perera MH, Shantha SS. Anatomical landmarks to locate the junction between transverse and sigmoid sinuses in translabyrinthine and retrosigmoid open surgical approaches. Sri Lanka J Surg 2018; 36 (02) 8-12
• 23 Abolfotoh M, Dunn IF, Al-Mefty O. Transmastoid retrosigmoid approach to the cerebellopontine angle: surgical technique. Neurosurgery 2013; 73 (01) 16-23
• 24 Basma J, Michael II LM, Sorenson JM, Robertson JH. Deconstruction of the surgical approach to the jugular foramen region: anatomical study. J Neurol Surg B Skull Base 2019; 80 (05) 518-526
• 25 Kryzanski JT, Robertson JH, Heilman CB. A minimal access far-lateral approach to foramen magnum lesions. J Neurol Surg B Skull Base 2014; 75 (04) 236-242
• 26 Safavi-Abbasi S, de Oliveira JG, Deshmukh P. et al. The craniocaudal extension of posterolateral approaches and their combination: a quantitative anatomic and clinical analysis. Oper Neurosurg (Hagerstown) 2010; 66 (Suppl. 01) 54-64