Hypoglossal canal

Synonyms

• Also referred to as the canal of the twelfth cranial nerve.

Detailed Anatomy and Boundaries

• The hypoglossal canal is a bilateral structure located at the base of the skull.
• It is situated along the lateral margin of the anterior half of the foramen magnum.
• Anatomically, the canal is approximately 5 mm above the junction of the posterior and middle third of the occipital condyle.
• The canal's position is significant, as it lies near critical structures at the skull base.

Neighbouring Structures

• The hypoglossal canal is close to the jugular foramen and the nerves that pass below it.
  • The canal is located medial to the jugular foramen.

• It is also near the occipital condyle and the foramen magnum, which are key landmarks in skull base anatomy.

Contents of the Canal

• The hypoglossal nerve (Cranial Nerve XII) passes through this canal.
  • The rootlets pass from the preolivary sulcus to the canal.
• The nerve is responsible for motor control of the tongue muscles.
• Structures such as the styloglossus, stylopharyngeal, and stylohyoid muscles are within this canal.

Clinical Significance

• The hypoglossal canal and nerve are crucial considerations in surgeries involving the skull base, particularly in the region of the foramen magnum.
• Lesions or pathologies affecting the hypoglossal canal can lead to hypoglossal nerve palsy, characterized by tongue weakness or paralysis.
• The nerve's proximity to the jugular foramen makes it susceptible to involvement in jugular foramen syndromes.
• Understanding the canal's anatomy is vital for procedures like suboccipital craniectomies, where inadvertent damage to the hypoglossal nerve can have significant functional implications.

Surgical Considerations

• Access to the hypoglossal canal requires careful navigation to avoid damaging the hypoglossal nerve.
• It can be exposed extradurally for increased access to the front of the brainstem, especially in complex skull base surgeries.
• Surgical approaches must account for the canal's proximity to other cranial nerves and vascular structures.