Hypoglossal Canal Flashcards

Examine the hypoglossal canal's location, bony boundaries, nerve and vessel contents, anatomical relationships, and clinical significance.

Card 1 of 22Question

What is the hypoglossal canal?

A paired bony passage through the occipital bone that transmits the hypoglossal nerve.

In This Section

1. What is the hypoglossal canal?

A paired bony passage through the occipital bone that transmits the hypoglossal nerve.

2. Which bone contains the hypoglossal canal?

The occipital bone.

3. Which part of the occipital bone contains the hypoglossal canal?

The lateral part, superior to the occipital condyle.

4. Where is the intracranial opening of the hypoglossal canal located?

On the anterolateral wall of the posterior cranial fossa, immediately superior to the foramen magnum.

5. Where is the extracranial opening of the hypoglossal canal located?

On the inferior surface of the occipital bone, superior and lateral to the occipital condyle.

6. What is the general direction of the hypoglossal canal?

It courses anterolaterally through the occipital bone.

7. Which cranial nerve passes through the hypoglossal canal?

The hypoglossal nerve (cranial nerve XII).

8. From which part of the brainstem do hypoglossal nerve rootlets emerge?

The medulla oblongata, in the preolivary sulcus between the pyramid and olive.

9. How do hypoglossal nerve rootlets reach the hypoglossal canal?

They cross the subarachnoid space and converge before entering the canal.

10. What is the primary functional classification of the hypoglossal nerve?

General somatic motor.

11. Which tongue muscles receive motor innervation from the hypoglossal nerve?

All intrinsic and extrinsic tongue muscles except the palatoglossus.

12. Which meningeal arterial branch may pass through the hypoglossal canal?

The hypoglossal branch of the ascending pharyngeal artery.

13. Which venous structure accompanies the hypoglossal nerve through the canal?

A venous plexus connecting intracranial venous channels with extracranial veins.

14. Which intracranial venous plexus communicates with veins passing through the hypoglossal canal?

The basilar venous plexus.

15. Which major skull base opening lies medial and posterior to the hypoglossal canal?

The foramen magnum.

16. Which major skull base opening lies lateral to the hypoglossal canal?

The jugular foramen.

17. What is the relationship between the hypoglossal canal and the atlanto-occipital joint?

The canal passes through the occipital bone immediately superior to the occipital condyle.

18. What is a hypoglossal canal septum?

A variable bony partition that may partially or completely divide the canal into separate compartments.

19. What happens to the tongue during protrusion after a unilateral hypoglossal nerve injury?

The tongue deviates toward the affected side because of weakness of the ipsilateral genioglossus muscle.

20. What changes can develop in the tongue after a lower motor neuron lesion of the hypoglossal nerve?

Ipsilateral tongue weakness, atrophy, and fasciculations.

21. Which skull base injury can damage the hypoglossal nerve within its canal?

An occipital condyle fracture extending into or compressing the hypoglossal canal.

22. What is the clinical significance of a hypoglossal canal schwannoma?

It may enlarge the canal and compress cranial nerve XII, causing progressive ipsilateral tongue weakness.