Close
  Indian J Med Microbiol
 

Figure 6: Comparison of endoscopic and microscopic views with three-dimensional relationships of neurovascular structures at craniovertebral junction. (a) Endoscopic view of foramen magnum and occipitocervical joint. Transverse ligament can be seen after the removal of dens in midline. Supracondylar groove is drilled exposing hypoglossal canal and jugular tubercle. (b) Close-up view of OC1 joint. Vertebral artery can be seen posteromedial to rectus capitis lateralis muscle and lower cranial nerves can be seen anterolateral to this muscle and joining internal carotid artery. (c) Bone extending from clivus, occipital condyle, lateral mass of atlas, and anterior and posterior arch of atlas has been removed. Dura has also been removed, and jugular foramen is fully dissected. IX, X, and XI cranial nerves can be seen arising from lateral medullary sulcus and entering jugular fossa where it is joined by the spinal part of IX cranial nerve. Cranial nerve XII can be seen arising as multiple rootlets, which join to form two fascicles, which in turn join to form single trunk in hypoglossal canal from where it comes out to join other lower cranial nerves. Vertebral artery can be seen entering dura and joining other side artery to form basilar artery at pontomedullary sulcus. Pharyngeal internal carotid artery is seen followed by petrous portion before coming into foramen lacerum. Lateral to internal carotid artery, mandibular branch of V cranial nerve is visible. (d) Close-up view of vertebral artery in relation to XII nerve above and C2 nerve below. C1 nerve can be seen traveling on the underside of vertebral artery. (e) Microscopic view after the removal of jugular tubercle, occipital condyle, and jugular foramen is fully dissected. IX, X, and XI nerves can be seen coming out of jugular foramen after being joined by the spinal portion of XI nerve. XII nerve can be seen coming out separately through hypoglossal canal where two fascicles join to form a single nerve. After coming out, it joins other cranial nerves in relation to internal carotid artery and internal jugular vein. This part of lower cranial nerves is anterior to rectus capitis lateralis muscle as can be seen here. (f) Full microscopic view of lower cranial nerves and vertebral artery after the removal of lateral mass of atlas and anterior and posterior arch along with rectus capitis lateralis muscle. Internal jugular vein is reflected laterally out of view. Now, IX nerve can be seen coming out of jugular foramen through separate subcanal. After coming out, it joins internal carotid artery for a short distance before passing anteriorly to supply pharyngeal sensory and muscular branches. X nerve is the thickest of lower cranial nerves and travel posterior to internal carotid artery and anterior to internal jugular vein. XI nerve is directed more posteriorly and comes out to supply sternocleidomastoid and trapezius muscles. XII nerve travels along internal carotid artery and forms ansa cervicalis and then goes medially and forward to supply the muscles of tongue. Vertebral artery can be seen in relation to these nerves and C2 nerve. VII, VIII nerve complex can be seen entering internal acoustic meatus just anterosuperior to jugular foramen. Petrous internal carotid artery is also visible in the depth. (g) Close-up view of the same dissection. C2 gang, C2 ganglion; F mag, foramen magnum; HC, hypoglossal canal; ICA, internal carotid artery; ICA ph, pharyngeal segment of internal carotid artery; ICA pt, petrous segment of internal carotid artery; IJV, internal jugular vein; JT, jugular tubercle; OC1 joint, occipitocervical joint; RCLa, rectus capitis lateralis; Sig sinus, sigmoid sinus; TL, transverse ligament; VA, vertebral artery

Figure 6: Comparison of endoscopic and microscopic views with three-dimensional relationships of neurovascular structures at craniovertebral junction. (a) Endoscopic view of foramen magnum and occipitocervical joint. Transverse ligament can be seen after the removal of dens in midline. Supracondylar groove is drilled exposing hypoglossal canal and jugular tubercle. (b) Close-up view of OC1 joint. Vertebral artery can be seen posteromedial to rectus capitis lateralis muscle and lower cranial nerves can be seen anterolateral to this muscle and joining internal carotid artery. (c) Bone extending from clivus, occipital condyle, lateral mass of atlas, and anterior and posterior arch of atlas has been removed. Dura has also been removed, and jugular foramen is fully dissected. IX, X, and XI cranial nerves can be seen arising from lateral medullary sulcus and entering jugular fossa where it is joined by the spinal part of IX cranial nerve. Cranial nerve XII can be seen arising as multiple rootlets, which join to form two fascicles, which in turn join to form single trunk in hypoglossal canal from where it comes out to join other lower cranial nerves. Vertebral artery can be seen entering dura and joining other side artery to form basilar artery at pontomedullary sulcus. Pharyngeal internal carotid artery is seen followed by petrous portion before coming into foramen lacerum. Lateral to internal carotid artery, mandibular branch of V cranial nerve is visible. (d) Close-up view of vertebral artery in relation to XII nerve above and C2 nerve below. C1 nerve can be seen traveling on the underside of vertebral artery. (e) Microscopic view after the removal of jugular tubercle, occipital condyle, and jugular foramen is fully dissected. IX, X, and XI nerves can be seen coming out of jugular foramen after being joined by the spinal portion of XI nerve. XII nerve can be seen coming out separately through hypoglossal canal where two fascicles join to form a single nerve. After coming out, it joins other cranial nerves in relation to internal carotid artery and internal jugular vein. This part of lower cranial nerves is anterior to rectus capitis lateralis muscle as can be seen here. (f) Full microscopic view of lower cranial nerves and vertebral artery after the removal of lateral mass of atlas and anterior and posterior arch along with rectus capitis lateralis muscle. Internal jugular vein is reflected laterally out of view. Now, IX nerve can be seen coming out of jugular foramen through separate subcanal. After coming out, it joins internal carotid artery for a short distance before passing anteriorly to supply pharyngeal sensory and muscular branches. X nerve is the thickest of lower cranial nerves and travel posterior to internal carotid artery and anterior to internal jugular vein. XI nerve is directed more posteriorly and comes out to supply sternocleidomastoid and trapezius muscles. XII nerve travels along internal carotid artery and forms ansa cervicalis and then goes medially and forward to supply the muscles of tongue. Vertebral artery can be seen in relation to these nerves and C2 nerve. VII, VIII nerve complex can be seen entering internal acoustic meatus just anterosuperior to jugular foramen. Petrous internal carotid artery is also visible in the depth. (g) Close-up view of the same dissection. C2 gang, C2 ganglion; F mag, foramen magnum; HC, hypoglossal canal; ICA, internal carotid artery; ICA ph, pharyngeal segment of internal carotid artery; ICA pt, petrous segment of internal carotid artery; IJV, internal jugular vein; JT, jugular tubercle; OC1 joint, occipitocervical joint; RCLa, rectus capitis lateralis; Sig sinus, sigmoid sinus; TL, transverse ligament; VA, vertebral artery