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| | == Synonyms == |
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| <h2>Location of the Hypoglossal Canal</h2>
| | * Also referred to as the canal of the twelfth cranial nerve. |
| <ol>
| |
| <li>The hypoglossal canal is a component of the skull structure.</li>
| |
| <li>It is situated in the posterior fossa in the superior border of the petrous part of the temporal bone.</li>
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| <li>It is situated above the condylar region and adjacent to the condylar canal and the stylomastoid foramen.</li>
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| </ol>
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| <ol>
| | == Detailed Anatomy and Boundaries == |
| <li>It can be accessed after removing the jugular tubercle and applying retraction at the midportion of the cerebellar hemisphere.</li>
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| <li>It should be preserved if it is not affected by any lesions.</li>
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| <li>Structures such as the styloglossus, stylopharyngeal, and stylohyoid muscles are within this canal.</li>
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| </ol>
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| <h2>Title: Comprehensive Details on the Hypoglossal Canal</h2>
| |
| <ol>
| |
| <li>The internal orifice of the canal is posterolateral to that of the posterior condylar canal.</li>
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| <li>It is situated just posterolateral to the small condylar canal.</li>
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| <li>There is no communication between the condylar canal and this canal.</li>
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| <li>The supracondylar vein and a meningeal branch of the occipital artery are found in the posterior condylar canal.</li>
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| <li>It is a canal that is supplied by meningeal branches.</li>
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| </ol>
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| <h2>Title: "Detailed Information on the Hypoglossal Canal and Nerve"</h2>
| | * The hypoglossal canal is a bilateral structure located at the base of the skull. |
| <ol>
| | * It is situated along the lateral margin of the anterior half of the foramen magnum. |
| <li>This canal is crucial for the passage of the hypoglossal nerve.</li>
| | * Anatomically, the canal is approximately 5 mm above the junction of the posterior and middle third of the occipital condyle. |
| <li>The nerve is a purely somatic efferent nerve that supplies the musculature of the tongue.</li>
| | * The canal's position is significant, as it lies near critical structures at the [[Skull Base|skull base]]. |
| <li>The rootlets pass from the preolivary sulcus to the canal.</li>
| |
| <li>The nerve arises in front of the olive in the brainstem.</li>
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| <li>The canal provides a passage for the nerve from the brain to the tongue.</li>
| | == Neighbouring Structures == |
| <li>The nerve travels through the canal.</li>
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| <li>The canal is a pathway for the nerve's rootlets.</li>
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| <li>The distance between the upper surface of the nerve and the roof of the canal is typically measured in millimeters.</li>
| | * The hypoglossal canal is close to the [[jugular foramen]] and the nerves that pass below it. |
| <li>The nerve is responsible for the movement of the tongue.</li>
| | ** The canal is located medial to the jugular foramen. |
| <li>The nerve is responsible for innervating the muscles of the tongue.</li>
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| <li>The nerve descends between the carotid artery and the jugular vein.</li>
| | * It is also near the occipital condyle and the foramen magnum, which are key landmarks in skull base anatomy. |
| <li>The nerve is located below the level of the digastric muscle.</li>
| |
| <li>One of the rootlets of the nerve loops around the origin of the pica.</li>
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| <li>The canal also contains the digastric nerve.</li>
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| <li>The nerve descends vertically in the neck after leaving the canal.</li>
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| <li>The nerve turns anteriorly across the lateral wall of the artery.</li>
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| <li>The nerve descends lateral to the vagus nerve after leaving the cranial cavity.</li>
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| <li>The nerve passes adjacent to the vagus nerve.</li>
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| <li>The right canal specifically houses the hypoglossal nerve.</li>
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| <li>The nerve reaches a level just below the angle of the mandible.</li>
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| <li>After traversing the canal, the two bundles of rootlets unite.</li>
| | == Contents of the Canal == |
| <li>The somatic efferent fibers of the nerve emerge from the medulla oblongata.</li>
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| <li>The nerve also innervates all intrinsic muscles of the tongue.</li>
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| <li>The nerve's rootlets originate ventral to the inferior olive.</li>
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| | * The hypoglossal nerve (Cranial Nerve XII) passes through this canal. |
| <li>Dysfunction of the nerve can result in difficulty with speaking and swallowing.</li>
| | ** The rootlets pass from the preolivary sulcus to the canal. |
| <li>The nerve innervates the hyoglossus, genioglossus, and styloglossus muscles.</li>
| | * The nerve is responsible for motor control of the tongue muscles. |
| </ol>
| | * Structures such as the styloglossus, stylopharyngeal, and stylohyoid muscles are within this canal. |
| <h2>Title: Anatomy and Relationships of the Hypoglossal Canal</h2>
| | |
| <ol>
| | == Clinical Significance == |
| <li>The bone of the jugular tubercle is situated above the canal.</li>
| | |
| <li>The canal is located below the jugular tubercle on the upper surface of the jugular process of the occipital bone.</li>
| | * The hypoglossal canal and nerve are crucial considerations in surgeries involving the skull base, particularly in the region of the foramen magnum. |
| <li>The canal is a part of the jugular foramen.</li>
| | * Lesions or pathologies affecting the hypoglossal canal can lead to hypoglossal nerve palsy, characterized by tongue weakness or paralysis. |
| <li>The canal is connected to the jugular process of the occipital bone.</li>
| | * The nerve's proximity to the jugular foramen makes it susceptible to involvement in jugular foramen syndromes. |
| <li>The inferior boundary of the jugular tubercle is the canal.</li>
| | * Understanding the canal's anatomy is vital for procedures like suboccipital craniectomies, where inadvertent damage to the hypoglossal nerve can have significant functional implications. |
| <li>The canal is located medial to the jugular foramen.</li>
| | |
| <li>The jugular tubercle is located just above and anterior to the canal.</li>
| | == Surgical Considerations == |
| <li>The canal is involved in the venous drainage of the jugular bulb and adjacent part of the internal jugular vein.</li>
| | |
| <li>The jugular process is a component of the wall of the jugular foramen, alongside the canal.</li>
| | * Access to the hypoglossal canal requires careful navigation to avoid damaging the hypoglossal nerve. |
| <li>The canal is located deep to the jugular vein.</li>
| | * It can be exposed extradurally for increased access to the front of the [[brainstem]], especially in complex skull base surgeries. |
| <li>The canal is involved in the removal of all or part of the jugular tubercle.</li>
| | * Surgical approaches must account for the canal's proximity to other [[cranial nerves]] and vascular structures. |
| <li>The hypoglossal nerve joins the nerves exiting the jugular foramen on the medial side of the internal jugular vein.</li>
| |
| <li>The glossopharyngeal, vagus, and accessory nerves pass through a shallow furrow on the surface of the jugular tubercle, which is located above the canal.</li>
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| <li>The jugular tubercle forms the roof of the canal.</li>
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| <li>The bone of the jugular tubercle can be removed extradurally to gain additional exposure of the canal.</li>
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| <li>The canal is closely related to the jugular foramen.</li>
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| <li>The canal is located between the internal carotid artery and internal jugular vein.</li>
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| <li>The canal is a passageway for nerves below the jugular foramen.</li>
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| <li>The canal can be reached when accessing the jugular foramen, internal acoustic meatus, and inferior surface of the tentorium.</li>
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| <li>Tumors can also spread through the canal from the jugular foramen to the cerebellopontine angle.</li>
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| <li>The jugular tubercle serves a dual role, providing structure to both the canal and the jugular foramen.</li>
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| <li>The jugular tubercle is an oval prominence found above the canal.</li>
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| <li>The canal is exposed after resecting a segment of the internal jugular vein and jugular bulb.</li>
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| <li>The canal descends with the nerves exiting the jugular foramen.</li>
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| <li>The canal shares a relationship with the internal acoustic meatus and jugular foramen.</li>
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| <li>The canal opens laterally into the interval between the jugular foramen and carotid canal.</li>
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| <li>The canal is located laterally to a large irregular jugular foramen.</li>
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| <li>The canal is usually connected to the sigmoid sinus or jugular bulb.</li>
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| <li>It is located approximately mm below the jugular tubercle.</li>
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| </ol>
| |
| <h2>Title: Anatomical Positioning and Characteristics of the Hypoglossal Canal</h2>
| |
| <ol>
| |
| <li>The intracranial end of this canal is situated inferomedial to the petrosal part of the jugular foramen.</li>
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| <li>It is positioned medial to the lower half of the intracranial end of the jugular foramen.</li>
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| <li>This canal is located above the occipital condyle.</li>
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| <li>It is one of the structures present on the intracranial surface.</li>
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| <li>It can be found at the posterior border of the intracranial end.</li>
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| <li>A sinus that crosses the intracranial surface communicates with the veins within this canal.</li>
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| <li>It is located within the skull.</li>
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| <li>It is positioned above the condyle.</li>
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| <li>This canal is found at the lateral aspect of the intracranial end.</li>
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| <li>It serves as the intracranial entrance of a structure.</li>
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| <li>It is one of the structures, along with the jugular foramen and internal acoustic meatus, that penetrate the intracranial surface.</li>
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| <li>The extracranial end of the canal is positioned medially.</li>
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| <li>It is located inferior to Meckel's cave and the cochlea.</li>
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| <li>The canal is positioned several millimeters below the lower part of the petroclival fissure.</li>
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| <li>It is a small oval opening located at the intracranial end.</li>
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| </ol>
| |
| <h2>Title: "Anatomical Insights and Surgical Considerations of the Hypoglossal Canal"</h2>
| |
| <ol>
| |
| <li>The canal is situated above the condyle and is part of the skull near the occipital condyle and jugular tubercle.</li>
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| <li>It is located within the occipital bone.</li>
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| <li>The canal can be exposed by drilling the cancellous bone above the posterior third of the condyle.</li>
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| <li>It allows for the removal of the lateral part of the posterior two-thirds of the condyle.</li>
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| <li>It is approximately mm above the junction of the posterior and middle third of the occipital condyle.</li>
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| <li>The average distance between the posterior edge of the occipital condyle and the posterior border of the canal is within the range of mm to mm.</li>
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| <li>The crosshatched area indicates the portion of the occipital condyle that can be removed without exposing the nerve in the canal.</li>
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| <li>The supracondylar exposure can be directed above the occipital condyle to the canal.</li>
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| <li>The posterior condylar vein passes above both the occipital condyle and the canal.</li>
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| <li>The canal is overlaid by an oval jugular tubercle on the superior surface of the occipital condyle.</li>
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| <li>It extends laterally from the area above the posterior half of the occipital condyle.</li>
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| <li>Access to the canal does not require removing the posterior third of the occipital condyle.</li>
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| <li>The cancellous body of the condyle contributes to the formation of the canal.</li>
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| <li>The maximum extent that the upper portion of the occipital condyle can be drilled without exposing the canal is limited to its posterior third of the long axis.</li>
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| <li>The central third of the occipital condyle can be removed to expose the nerve.</li>
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| <li>The canal is reached by removing approximately the posterior third of the occipital condyle.</li>
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| <li>The cortical bone of the condyle and the articular surface can be preserved during the drilling process.</li>
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| <li>The canal is an important consideration when studying the relationship of the occipital condyle to the foramen magnum.</li>
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| <li>The clivus and adjacent part of the occipital and temporal bones can be removed to expose the canal.</li>
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| <li>The canal is located anterior and superior to each condyle and crosses the occipital bone.</li>
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| <li>It is on the extracranial surface behind and above each occipital condyle.</li>
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| <li>Understanding the relationship between the canal and the occipital condyle is essential for the condyle drilling technique.</li>
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| <li>The extent of occipital condyle removal is determined by examining the canal.</li>
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| <li>Further drilling of the occipital condyle can be done without entering the canal.</li>
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| <li>The canal can be accessed by drilling into the occipital condyle from a far lateral perspective.</li>
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| <li>The lateral clivus can also be exposed while drilling the occipital condyle.</li>
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| <li>Removing less than half of the occipital condyle does not pose a risk to spinal stability.</li>
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| </ol>
| |
| <h2>Title: Detailed Information on the Hypoglossal Canal and Its Surgical Approaches</h2>
| |
| <ol>
| |
| <li>The canal is located in the lower lateral part of the clivus.</li>
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| <li>It can be exposed in the far lateral approach to the skull.</li>
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| <li>The presence of the jugular tubercle can affect the far lateral approach to the canal.</li>
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| <li>Drilling in the supracondylar location above the canal accesses the jugular tubercle.</li>
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| <li>It is located in the supracondylar area.</li>
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| <li>The canal is an important aspect of the approach.</li>
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| <li>The lateral side of the clivus can be reached by going above and below the canal.</li>
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| <li>The supracondylar approach allows access to the medial side of the canal.</li>
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| <li>The canal is located in the region accessed by the supracondylar approach.</li>
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| <li>The supracondylar approach involves removing the jugular tubercle to expose the canal.</li>
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| <li>The canal is located in the supracondylar and paracondylar areas.</li>
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| <li>Accessing the lateral edge of the clivus can be achieved by drilling in a supracondylar location below the canal.</li>
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| <li>The occipital transcondylar variant is a pathway that passes through the canal.</li>
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| <li>The location of the canal can be inferred by identifying the supracondylar groove.</li>
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| <li>The transcondylar approach can be used to access the canal.</li>
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| <li>The transcondylar, retrocondylar, and supracondylar modifications of the canal are described in the chapter on the far lateral approach.</li>
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| <li>The canal is involved in the transcondylar extension of the far lateral approach.</li>
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| <li>The canal is a structure that can be exposed during the transcondylar approach.</li>
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| <li>The transcondylar approach also provides access to the jugular tubercle along with the canal.</li>
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| <li>The canal is located in the lateral medullary segments.</li>
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| <li>The occipital transcondylar variant allows access to the lower clivus and the area in front of the medulla.</li>
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| <li>Drilling can be done in a supracondylar location below the canal.</li>
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| <li>The canal is directed from medial to lateral.</li>
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| <li>The canal serves as a route for the occipital transcondylar variant to reach its destination.</li>
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| <li>The large arrow indicates the direction of the transcondylar approach.</li>
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| <li>The occipital transcondylar variant is directed above the atlantooccipital joint.</li>
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| </ol>
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| <h2>Title: Comprehensive Overview of the Hypoglossal Canal and its Associations</h2>
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| <ol>
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| <li>The dura in the posterior fossa is supplied by the meningeal branches of the occipital artery, one of which enters the skull through this canal.</li>
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| <li>The occipital artery is found in this canal.</li>
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| <li>The medullary branch of the vertebral artery can be found in this canal.</li>
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| <li>The posterior ascending artery is present in this canal.</li>
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| <li>The ascending branch of this canal anastomoses with the branches of the dorsal meningeal artery.</li>
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| <li>The petrous carotid artery is located near this canal.</li>
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| <li>A collateral artery passes rostral to the anterior arch of the atlas in this canal.</li>
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| <li>The left vertebral artery is also present in this canal.</li>
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| <li>The ascending pharyngeal artery ascends medial to the carotid artery and gives branches that pass through this canal.</li>
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| <li>This canal serves as an entry point for a branch from the ascending pharyngeal artery into the posterior cranial fossa.</li>
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| <li>The ascending pharyngeal artery, which is connected to this canal, gives rise to the inferior tympanic artery.</li>
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| <li>It is a passageway through which meningeal branches of the ascending pharyngeal artery pass.</li>
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| <li>It is located behind the vertebral artery.</li>
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| <li>It is a route through which occasional small branches of the ascending pharyngeal artery enter the skull.</li>
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| <li>It contains the key meningeal artery.</li>
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| <li>The dorsal meningeal and tentorial arteries, originating from the meningohypophysial trunk, enter the skull through this canal.</li>
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| <li>In most cases, the rootlets pass posterior to the vertebral artery.</li>
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| <li>It serves as an entrance for some branches of the ascending pharyngeal artery into the skull.</li>
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| <li>It runs downward between the carotid artery and the jugular vein.</li>
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| <li>It contains a meningeal branch of the ascending pharyngeal artery.</li>
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| <li>Carotid and vertebral arteries can be found near this canal.</li>
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| <li>The arcade above the odontoid process is formed by the anterior meningeal arteries.</li>
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| <li>Occasionally, the rootlets can pass anterior to the vertebral artery, although this is rare.</li>
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| <li>The branch passing through this canal divides into an ascending branch.</li>
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| <li>It contains precentral and postcentral arteries that supply the typical cervical vertebral body.</li>
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| <li>During surgery, the carotid arteries need to be avoided laterally as well as the canals inferiorly.</li>
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| <li>This ascending branch passes upward in the dura covering the clivus.</li>
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| </ol>
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| <h2>Title: Comprehensive Information about the Hypoglossal Canal</h2>
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| <ol>
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| <li>It is located in the lateral view of the skull.</li>
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| <li>It is one of the foramina of the skull, located at the level of the foramen magnum.</li>
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| <li>It exists as an opening in the skull and is one of the boundaries of the exposed area.</li>
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| <li>It plays a crucial role in the movement of the tongue.</li>
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| <li>It is part of the anatomical features of the occipital bone and is found on the squamous part of the same bone.</li>
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| <li>The apical arcade of the odontoid process is located within it.</li>
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| <li>It serves as a landmark to identify the jugular process during dissection.</li>
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| <li>It contains meningeal branches that supply the associated dura mater and adjoining bone.</li>
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| <li>It is responsible for the passage of nerves in the enlargement view and is not located in the orbit.</li>
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| <li>It is situated at the base of the skull and just superior to the scaphoid fossa at the root of the medial plate of the pterygoid process.</li>
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| <li>It provides access to the front of the medulla and the pontomedullary junction.</li>
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| <li>It is traversed by the posterior condylar vein and is located in the floor of the middle fossa.</li>
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| <li>It is found on both sides of the skull and is located close to the foramen magnum.</li>
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| <li>It contains meningeal branches that pass through the foramen lacerum to distribute to the dura lining the middle fossa.</li>
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| <li>It is essential for the proper functioning of the tongue and other associated muscles.</li>
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| <li>It is a passageway through which the rootlets enter and is a part of the backsection with vertebral veins, occipital and sigmoid sinuses.</li>
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| <li>It is directed from posterior to anterior and passes forward from near the anterior margin of the foramen lacerum.</li>
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| <li>It is involved in motor control of the tongue muscles and is directed anteriorly and laterally.</li>
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| <li>It marks the transition from cancellous to cortical bone and is a landmark that is examined during the extradural dissection stage.</li>
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| <li>It is a pathway for transmitting an emissary vein when present and is located extracranially.</li>
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| <li>It is a key landmark for inferring the location before starting the inferior clivectomy.</li>
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| <li>In some cases, it is divided by a bony septum and its development is a significant marker for age determination during the subadult years.</li>
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| <li>It is where the glossopharyngeal, vagus, and accessory nerves join and also receives blood from the verse medullary veins.</li>
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| <li>It is an additional feature for reliable age determination throughout the subadult years.</li>
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| <li>It is measured in millimeters and is surrounded by various muscles, such as the sternocleidomastoid and splenius capitis.</li>
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| <li>At each level, it contains radicular prelaminar and meningeal branches, and abnormalities or damage to it can lead to various neurological disorders.</li>
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| <li>It completes development by year and its completion at a certain age is a valuable tool for age estimation.</li>
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| <li>It also has a descending branch and follows an anterolateral trajectory.</li>
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| <li>It is used to design a customized craniectomy and is a concern for avoidance during surgery with intraoperative imaging guidance.</li>
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| <li>The nerve then continues its path towards the tongue and these bundles perforate the dura mater separately.</li>
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| </ol>
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| <h2>Title: "Understanding the Hypoglossal Canal and Its Functions"</h2>
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| <ol>
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| <li>The jugular foramen or hypoglossal canal serves as a route for the meningeal branches to supply the surrounding dura of the posterior cranial fossa.</li>
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| <li>It is located at the angle and the intracranial aspect of the cranial nerves entering the jugular foramen.</li>
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| <li>This canal is situated in the posterior cranial fossa of the neck.</li>
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| <li>It is a part of the cranial nerves.</li>
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| <li>Ascending meningeal branches of the upper cervical nerves pass through this canal to reach the dura in the posterior cranial fossa.</li>
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| <li>It also supplies much of the floor of the anterior wall of the posterior cranial fossa, possibly through pathways other than that of the hypoglossal nerve.</li>
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| <li>The stylomastoid foramen, a passage in the posterior cranial fossa, allows the facial nerve to exit the skull.</li>
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| <li>It is part of the pathway for the IXth through XIIth cranial nerves.</li>
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| <li>It is one of the cranial nerve canals.</li>
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| <li>It is one of the entry points for meningeal branches from cervical nerves into the posterior cranial fossa.</li>
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| <li>The internal acoustic meatus, located in the posterior cranial fossa, contains the facial nerve (cranial nerve VII) and the vestibulocochlear nerve (cranial nerve VIII).</li>
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| <li>Meningeal branches from the cervical nerves enter the posterior cranial fossa via this canal, among other openings like the foramen magnum and jugular foramen.</li>
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| <li>Second and third cervical nerves enter the posterior cranial fossa through this canal to provide sensory information to the dura in that region.</li>
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| <li>It can serve as a pathway for glomus jugulare tumors to extend from the jugular foramen to the posterior fossa.</li>
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| <li>It allows the first and second cervical nerves to enter the posterior cranial fossa, providing additional innervation to the dura.</li>
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| <li>It is directed forward and laterally from the posterior cranial fossa.</li>
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| <li>Schwannomas of the cranial nerves can cause imaging findings of tongue atrophy in this canal.</li>
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| <li>It is a passageway for cranial nerve XII.</li>
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| <li>It can widen due to schwannomas of the cranial nerves.</li>
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| <li>Posterior fossa tumors can impact this canal.</li>
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| <li>It is a point of reference in cranial depth.</li>
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| </ol>
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| <h2>Title: "Comprehensive Understanding of the Hypoglossal Canal's Venous Structure and Function"</h2>
| |
| <ol>
| |
| <li>The canal is linked to its own veins.</li>
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| <li>It houses the venous plexus, contributing to the drainage system.</li>
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| <li>The hypoglossal nerve and venous plexus are observable within the canal, with the latter surrounding the former.</li>
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| <li>The anterior spinal plexus is situated within the canal.</li>
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| <li>The canal's venous plexus links the sigmoid sinus and the internal jugular vein.</li>
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| <li>Drainage from the canal to the suboccipital vertebral plexus can occur via a vein.</li>
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| <li>The venous plexus is revealed by drilling the cortical bone.</li>
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| <li>The canal houses the internal jugular vein, which receives drainage from the inferior petrosal sinus and the venous plexus.</li>
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| <li>The inferior petroclival vein, vertebral venous plexus, and posterior condylar emissary vein are associated with the canal.</li>
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| <li>Both the dura and venous plexus should be respected when working near the canal.</li>
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| <li>The canal wall appears dark blue due to the presence of a venous plexus.</li>
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| <li>The canal links the basilar venous plexus with the marginal sinus.</li>
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| <li>The jugular bulb and internal jugular vein drainage is contributed to by the sigmoid and inferior petrosal sinuses, vertebral venous plexus, and posterior condylar emissary vein.</li>
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| <li>Occasionally, the canal drains to the suboccipital vertebral plexus via a vein.</li>
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| <li>The inferior petrosal sinus forms a plexiform confluens with the canal's venous plexus.</li>
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| <li>An emissary vein from the basilar plexus is transmitted by the canal.</li>
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| <li>Meningiomas can develop from arachnoid granulations in the jugular bulb or venous sinuses and potentially spread through the canal.</li>
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| <li>The venous plexus may sometimes consist of a single vein.</li>
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| <li>The canal is also linked to the basilar plexus.</li>
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| <li>Several venous emissary foramina are located within the canal.</li>
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| <li>The canal contains veins that link to the marginal sinuses.</li>
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| </ol></body>
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