The rectus capitis lateralis and the condylar triangle: important landmarks in posterior and lateral approaches to the jugular foramen

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OBJECTIVE

The rectus capitis lateralis (RCL) is a small posterior cervical muscle that originates from the transverse process of C-1 and inserts onto the jugular process of the occipital bone. The authors describe the RCL and its anatomical relationships, and discuss its utility as a surgical landmark for safe exposure of the jugular foramen in extended or combined skull base approaches. In addition, the condylar triangle is defined as a landmark for localizing the vertebral artery (VA) and occipital condyle.

METHODS

Four cadaveric heads (8 sides) were used to perform far-lateral, extended far-lateral, combined transmastoid infralabyrinthine transcervical, and combined far-lateral transmastoid infralabyrinthine transcervical approaches to the jugular foramen. On each side, the RCL was dissected, and its musculoskeletal, vascular, and neural relationships were examined.

RESULTS

The RCL lies directly posterior to the internal jugular vein—only separated by the carotid sheath and in some cases cranial nerve (CN) XI. The occipital artery travels between the RCL and the posterior belly of the digastric muscle, and the VA passes medially to the RCL as it exits the C-1 foramen transversarium and courses posteriorly toward its dural entrance. CNs IX–XI exit the jugular foramen directly anterior to the RCL. To provide a landmark for identification of the occipital condyle and the extradural VA without exposure of the suboccipital triangle, the authors propose and define a condylar triangle that is formed by the RCL anteriorly, the superior oblique posteriorly, and the occipital bone superiorly.

CONCLUSIONS

The RCL is an important surgical landmark that allows for early identification of the critical neurovascular structures when approaching the jugular foramen, especially in the presence of anatomically displacing tumors. The condylar triangle is a novel and useful landmark for identifying the terminal segment of the hypoglossal canal as well as the superior aspect of the VA at its exit from the C-1 foramen transversarium, without performing a far-lateral exposure.

ABBREVIATIONS C1TP = C-1 transverse process; CN = cranial nerve; ICA = internal carotid artery; IJV = internal jugular vein; RCL = rectus capitis lateralis; VA = vertebral artery.

Article Information

Correspondence Antonio Bernardo, Weill Cornell Medical College, 525 East 68th St., Box 99, New York, NY 10065. email: anb2029@med.cornell.edu.

INCLUDE WHEN CITING Published online January 27, 2017; DOI: 10.3171/2016.9.JNS16723.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Illustration of the RCL. The RCL originates from the C1TP and inserts on the jugular process of the occipital bone. The relationships between the RCL, IJV, occipital artery, and CN VII are depicted as well as CNs IX–XI passing through the jugular foramen adjacent to the RCL. The transverse and sigmoid sinuses are depicted as they descend to form the jugular bulb just superior to the RCL. Copyright Andy Rekito. Published with permission.

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    Surgical approaches to the jugular foramen and the RCL. The RCL separates the far-lateral approach (blue) and the transcondylar and transtubercular variant (green) from the jugular foramen (purple) anteriorly. The transmastoid approach is depicted in orange.

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    The extended far-lateral approach and the condylar triangle (CT). A and B: The suboccipital triangle (ST) is formed by the superior oblique (SO) and inferior oblique (IO) muscles and the rectus capitis posterior major. The RCL is located just anterior to the SO and is observed as it originates from the C1TP and inserts on the jugular process medial to the mastoid tip. The CT is formed by the RCL, SO, and a line connecting these muscles along the occipital bone. The intramuscular segment of the occipital artery (OA) typically courses within the CT along the occipital bone. C: The CT is opened by reflecting the SO anteriorly and inferiorly to expose the posterior aspect of the occipital condyle. DM = digastric muscle; SC = splenius cervicis.

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    A combined far-lateral transmastoid infralabyrinthine transcervical approach. Before (left) and after (right) detachment and reflection of the posterior belly of the digastric muscle and the RCL, and drilling of the jugular process. This combined approach provides exposure of the condylar fossa, jugular bulb within the mastoid, and IJV in the upper cervical region, with complete access to the jugular foramen from posterior, lateral, and anterolateral perspectives. The sigmoid sinus, jugular bulb, mastoid antrum, incus, fallopian canal, and lateral and posterior semicircular canals are skeletonized, and the presigmoid dura and endolymphatic sac are exposed.

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    Stepwise anatomical dissection of the jugular foramen, part I. A: An infralabyrinthine mastoidectomy with partial intracranial exposure of CN VII and the chorda tympani and skeletonization of the sigmoid sinus. The VA is visible as it turns posteriorly after exiting the C-1 transverse foramen before coursing medially to enter the dura. The IJV and ICA are within the carotid sheath, CN IX is anterolateral to the ICA, and CN XI and the IJV are directly anterior to the RCL. B: Removal of the mastoid tip and opening of the stylomastoid foramen improve exposure of CN VII. The jugular process is now visible superior to the RCL and anterolateral to the jugular tubercle. C: The IJV is retracted anteriorly to show CNs X and XII in the carotid sheath. D: The IJV and jugular bulb are removed, and CN VII is transposed to improve exposure of the jugular foramen. SCC = semicircular canal.

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    Stepwise anatomical dissection of the jugular foramen, part II. A: The occipital condyle is removed to expose the hypoglossal canal. CN XII is visible on both sides of the RCL. B: An occipital craniectomy is performed to expose the cerebellomedullary fissure. The CNs within the jugular foramen travel anteriorly and inferiorly forming a 120° angle with the RCL, until coursing anterior to the RCL, where they turn inferiorly to exit the jugular foramen and run parallel to the RCL. PICA = posterior inferior cerebellar artery. C: The intrajugular septum is drilled to expose the course of CN IX through the jugular foramen. D: CN XII is visible as it ascends through the hypoglossal canal at a 60° angle relative to the RCL and courses above the RCL before turning inferiorly. An instrument is passed through the distal aspect of the hypoglossal canal to show the peak of CN XII's turn above the RCL as it enters the carotid sheath, medial to CNs X and XI.

  • View in gallery

    Illustration of the RCL and its anatomical relationships. Detailed depiction of the spatial relationships between the RCL, CN VII, and the lower CNs of the jugular foramen and hypoglossal canal with removal of the IJV and occipital artery. CN VII is depicted at the stylomastoid foramen several millimeters from the anterior border of the RCL at its insertion on the jugular process. From posterior to anterior, CNs XI, X, and IX can be seen descending, after exiting the jugular foramen, adjacent to the RCL. CN XII is observed as it exits the hypoglossal canal and descends medial to the other CNs with a more anterior trajectory. Copyright Andy Rekito. Published with permission.

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    The RCL in different surgical trajectories. Depiction of the RCL in relation to the far-lateral and extended far-lateral (left arrow), transmastoid (upper arrow), and transcervical (right arrow) surgical trajectories. Copyright Andy Rekito. Published with permission.

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