Skeletal system · Head and neck

Hypoglossal canal !

The hypoglossal canal is a canal above the occipital condyle at the skull base; it carries the hypoglossal nerve, which moves the tongue.

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What it is

A canal above the occipital condyle.

What it does

Carries the hypoglossal nerve (XII).

Key facts

Where

Occipital bone, above each occipital condyle

Function

Transmits the hypoglossal nerve (XII)

Relations

Contents

Hypoglossal nerve (XII), a meningeal branch of the ascending pharyngeal artery and a venous plexus joining the veins of the skull base to the internal jugular vein

Course

Runs forward and laterally through the occipital bone, from an inner opening just above the front edge of the foramen magnum to an outer opening above the front of the occipital condyle

Above

Jugular tubercle on the inner surface of the bone; above and lateral, the jugular foramen

Below

Occipital condyle, which articulates with the atlas

Medial

Medulla oblongata, from whose groove between pyramid and olive the nerve rootlets emerge; the vertebral artery climbs nearby through the foramen magnum

How to find it

It cannot be felt. On the inner skull base it opens just above the anterolateral edge of the foramen magnum; from below, it is found by looking up into the groove above the front of each occipital condyle. Coronal CT shows it with the condyle below and the jugular tubercle above.

Examination

• Tongue protrusion: the tip points toward the damaged side; wasting and fine twitching (fasciculations) of that half mark a lower motor neuron lesion, such as one in the canal
• Tongue pushed into the cheek against the examiner's finger: the push is weak into the cheek on the side opposite the lesion

On imaging

Thin-slice CT shows the bony canal and whether a tumour has widened or eroded it; MRI with contrast shows the nerve and lesions such as a hypoglossal schwannoma, a paraganglioma spreading from the jugular foramen, metastases or a dural arteriovenous fistula.

Clinical notes

• Causes of an isolated hypoglossal palsy at the skull base include metastases, chordoma, schwannoma, occipital condyle fractures and, lower in the neck, internal carotid artery dissection
• Occipital condyle fractures after high-energy trauma can injure XII in the canal, sometimes together with the other lower cranial nerves
• In far-lateral approaches to the foramen magnum the canal limits how much of the condyle can be drilled away

Anatomical variants

• A bony bridge can divide the canal in two (double hypoglossal canal), on one or both sides; texts differ on how often

Development

All the tongue muscles except palatoglossus arise from one premuscle mass, of occipital somite origin, that carries the hypoglossal nerve forward with it; this is why one nerve, leaving through this canal, supplies them.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2)

canalis hypoglossus TA2 559

Official Spanish (DeCS)

Conducto del nervio hipogloso

English (TA2)

Hypoglossal canal

Also called

anterior condylar foramen · anterior condylar canal · canalis hypoglossi

Related

• Hypoglossal nerve (XII)

Sources: Terminologia Anatomica (TA2); Anatomy, Head and Neck, Skull Foramen; Neuroanatomy, Cranial Nerve 12 (Hypoglossal); 16.3 The Cranial Nerve Exam (OpenStax (Rice University), 2022) · adapted, CC BY 4.0; Anatomy of the Human Body (20th ed.): Development of the Muscles (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.

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Representative model, for educational purposes only.