Published online: 2018-12-07 518 Original Article Deconstruction of the Surgical Approach to the Jugular Foramen Region: Anatomical Study Jaafar Basma1,2 L. Madison Michael II1,2,3 Jeffrey M. Sorenson1,2,3 Jon H. Robertson1,2,3 1 Department of Neurosurgery, University of Tennessee Health Address for correspondence Jaafar Basma, MD, Department of Sciences Center, Memphis, Tennessee, United States Neurosurgery, University of Tennessee Health Sciences Center, 847 2 Medical Education Research Institute, Memphis, Tennessee, United States Monroe Avenue, Suite 427, Memphis, TN 38163, United States 3 Semmes-Murphey Clinic, Memphis, Tennessee, United States (e-mail: [email protected]). J Neurol Surg B 2019;80:518–526. Abstract Introduction The jugular foramen occupies a complex and deep location between the skull base and the distal-lateral-cervical region. We propose a morphometric anato- mical model to deconstruct its surgical anatomy and offer various quantifiable target- guided exposures and angles-of-attack. Methods Six cadaveric heads (12 sides) were dissected using a combined postauri- cular infralabyrinthine and distal transcervical approach with additional anterior transstyloid and posterior far lateral exposures. We identified anatomical landmarks and combined new and previously described contiguous triangles to expose the region; we defined the jugular and deep condylar triangles. Angles-of-attack to the jugular foramen were measured after removing the digastric muscle, styloid process, rectus Keywords capitis lateralis, and occipital condyle. ► jugular foramen Results Removing the digastric muscle and styloid process allowed 86.4° laterally and ► far lateral 85.5° anteriorly, respectively. Resecting the rectus capitis lateralis and jugular process ► infralabyrinthine provided the largest angle-of-attack (108.4° posteriorly). The occipital condyle can be approach drilled in the deep condylar triangle only adding 30.4° medially. A purely lateral ► styloid process approach provided a total of 280.3°. Cutting the jugular ring and mobilizing the vein ► occipital condyle can further expand the medial exposure. ► cranial nerves Conclusion The microsurgical anatomy of the jugular foramen can be deconstructed ► distal cervical using a morphometric model, permitting a surgical approach customized to the approach pathology of interest. Introduction foramen pathologies. However, the neurosurgeon and head- Lesions involving the jugular foramen continue to be chal- and-neck surgeon should always consider surgery in complex lenging surgical targets for the modern neurosurgeon. This is lesions that are not amenable to radiation therapy alone. These mainly due to their deep location, proximity to major neu- include lesions of larger size, with malignant biological beha- This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. rovascular structures (►Fig. 1), and potential high vascular- vior, compressing the brain stem, and/or encasing important ity and invasiveness. Anatomical knowledge, coupled with neurovascular elements resulting in neurological deficits.1 meticulous microsurgical technique, is a key element in A multitude of surgical approaches and procedures has been planning and executing any surgical intervention in this area. described to access the jugular foramen, including the follow- The relatively benign natural history of many of these ing: the preauricular transinfratemporal fossa approach,2 distal – lesions, along with advancements in radiation therapy, has cervical approaches with mandibular procedures,3 5 the lateral – reduced the surgical indications in the management of jugular transtemporal infralabyrinthine approach,6 8 the juxtacondylar received © 2019 Georg Thieme Verlag KG DOI https://doi.org/ August 6, 2018 Stuttgart · New York 10.1055/s-0038-1676512. accepted after revision ISSN 2193-6331. October 25, 2018 published online December 7, 2018 Deconstruction of the Surgical Approach to the Jugular Foramen Region Basma et al. 519 Fig. 1 Anatomy of the jugular foramen. (A) The infratemporal fossa (ITF) represents the anterior aspect of the lateral external skull base, while the jugular foramen (JF) occupies its posterior part. Bony borders of the jugular foramen include the jugular process of the occipital bone posteriorly, mastoid bone (M) and digastric groovelaterally, styloid process (St) anterolaterally, and occipitalcondyle (OC) medially. Other abbreviations: A, asterion; EAC, external auditory canal; HC, hypoglossal canal; SMF, stylomastoid foramen. (B) Anatomical dissection with an inferior view to the jugular foramen region. The internal carotid artery (ICA) enters the petrous bone anterior to the jugular vein (IJV). The rectus capitis lateralis (RCL) muscle inserts on the jugular process of the occipital bone. (Reprinted from the online Rhoton Collection.) Other abbreviations: CEV, condylar emissary vein; Dig, digastric muscle; IPS, inferior petrosal sinus; SP, styloid process; VA, vertebral artery; VII, facial nerve. (C) Drawing illustrating the limits of the jugular foramen: (a) jugular vein; (b) internal carotid artery; (c) stylomastoid foramen; (d) styloid process; (e) rectus capitis lateralis muscle; (f) occipital condyle; (g) mastoid process; (h) digastric groove; (i) condylar canal; (j) rectus capitis anterior muscle. approach,9,10 the infrajugular transjugular tubercle separately and reflected anteriorly to fully expose the mas- approach,11,12 the retrolabyrinthine and translabyrinthine toid triangle, defined between the asterion, mastoid tip, and suprajugular approaches,13 the far lateral supracondylar and suprameatal crest.21 The neck was dissected using a standard paracondylar approaches,14,15 the extreme lateral approach,16 medial sternocleidomastoid approach. We explored the car- and recently the endoscopic and endonasal approaches.17 otid triangle—outlined by the omohyoid, the sternocleido- Although there is a wide variability in the involved steps, several mastoid muscle, and the digastric muscles—to expose the approaches overlap and there is a lack of a standard surgical carotid sheath and lower cranial nerves (►Figs. 2 and 3).22 language to simplify the anatomical understanding and the The vagus nerve was dissected between the internal jugular rationale behind choosing the appropriate surgical approach for vein and the internal carotid artery, and the hypoglossal individual cases.18 nerve was identified in its anterior course just below the Our approach has been to use the lateral distal cervical digastric muscle. postauricular approach to access pathologies involving the Three major bony structures were palpated as key land- jugular foramen.19,20 This approach offers a straightforward marks to deconstruct the approach: the mastoid tip, styloid corridor to the region, and its versatility allows for multiple process, and transverse process of the atlas (TP-C1). Muscular adaptations to specific lesions. Exposure can be obtained attachments to these structures defined surgical triangles, without requiring major mandibular procedures, facial nerve which were progressively unlocked (►Fig. 2). rerouting, or condylar and occipitocervical destabilization. The stylodigastric triangle was defined between the In this article, we quantify the angles-of-attack to the digastric groove, styloid process, and the intersection jugular foramen through the posterolateral perspective. Case between the digastric and stylohyoid muscles (►Fig. 3).22 examples are used to illustrate the anatomical scheme and Detaching the digastric muscle and mobilizing it inferiorly the rationale involved in customizing the approach to the exposed the TP-C1 and the surrounding deep musculature targeted pathology. (i.e., the superior oblique, inferior oblique, and rectus capitis This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. lateralis). The accessory nerve was identified as it crossed the fi Methods anteroinferior border of TP-C1. We typically identi ed the accessory nerve in that region before detaching the sterno- Six preserved cadaveric heads (12 sides) were dissected at cleidomastoid muscle to avoid its inadvertent injury. The the Medical Education and Research Institute microsurgical facial nerve was dissected between the styloid and the laboratory in Memphis, Tennessee, United States. The heads mastoid processes before it enters the parotid gland. The had no known intracranial or cervical pathology and were glossopharyngeal nerve was identified as it courses ante- fixed and injected with colored silicone rubber. All cadaver riorly and laterally to the internal carotid artery, just poster- specimens had preserved distal necks proximally at least to ior to the stylopharyngeus muscle. the level of the omohyoid muscle. Muscular triangles at the deeper level were recognized A retroauricular curvilinear C-shaped skin incision was after removing the digastric muscle, and carefully dissected. made 3 cm posterior to the pinna and continued inferiorly to These included the suboccipital triangle (found between the the neck over the anterior border of the sternocleidomastoid superior and inferior oblique muscles),23 and the condylar muscle. The cutaneous and muscular flaps were dissected triangle (found between the superior oblique and rectus Journal of Neurological Surgery—Part B Vol. 80 No. B5/2019 520 Deconstruction of the Surgical Approach to the Jugular Foramen Region Basma et al. Fig. 2 Surgical landmarks and triangular framework. (A) The mastoid