hypoglossal nerve, origin course an termination of hypoglossal nerve, function of hypoglossal nerve, clinical examination of hypoglossal nerve, hypoglossal nerve palsy

1. HYPOGLOSSAL NERVE
DR SANA YASEEN
ANATOMY DEPARTMENT
KIMS

2. Is the 12th cranial nerve
It has somatic motor function, innervating all the extrinsic and
intrinsic muscles of the tongue (except the palatoglossus,
innervated by vagus nerve).
The hypoglossal nerve arises from the hypoglossal nucleus
in the medulla oblongata of the brainstem.
It comes out of mudulla oblongata between pyramids and the
olives
It crosses the dura matter and runs through the hypoglossal
canal.

4. The hypoglossal nerve arises from the hypoglossal nucleus in the
medulla oblongata of the brainstem. Located in front of nucleus
gracilis, medial to dorsal nucleus of vagus, and posterior to medial
longitudinal fasciculus
Fibers from the nuclei runs anterior through medial longitudinal
fasciculus, medial leminisci, olivary nucleus complex and comes
out between pyrimads and olives at pre-olivary sulcus.
 It then passes laterally across the posterior cranial fossa, within
the subarachnoid space. The nerve exits the cranium via the
hypoglossal canal.

6. COURSE:
◦ deeply placed to IJV, ICA,9th,10th,11th nerve.
◦ then it will run in between ICA and ECA within carotid
triangle.
◦ Then it will run deep to styloid process and deep to posterior
belly of digastric muscle.
◦ And through mylohyoid muscle. And enter the sublingual
region to supply the muscles of tongue.

9. ◦ Role of the C1/C2 Roots
◦ The C1/C2 roots that travel with the
hypoglossal nerve also have a motor
function. They branch off to innervate
the geniohyoid (elevates the hyoid
bone) and thyrohyoid (depresses the
hyoid bone) muscles.
◦ Another branch containing C1/C2
fibres descends to supply the ansa
cervicalis – a loop of nerves that is
part of the cervical plexus. From the
ansa cervicalis, nerves arise to
innervate the omohyoid, sternohyoid
and sternothyroid muscles. These
muscles all act to depress the hyoid
bone.

10. The hypoglossal nerve is responsible for motor innervation of the
vast majority of the muscles of the tongue (except for
palatoglossus). These muscles can be subdivided into two groups:
i) Extrinsic muscles
•Genioglossus (makes up the bulk of the tongue)
•Hyoglossus
•Styloglossus
•Palatoglossus (innervated by vagus nerve)
ii) Intrinsic muscles
Superior longitudinal
Inferior longitudinal
Transverse
Vertical
Together, these muscles are responsible for all movements of the
tongue.
FUNCTIONS

12. Cranial Nerve Examination
The hypoglossal nerve is examined by asking the patient to protrude their
tongue.
Other movements such as asking the patient to push their tongue against
their cheek and feeling for the pressure on the opposite side of the cheek
may also be used if damage is suspected.

13. Hypoglossal Nerve Palsy
Damage to the hypoglossal nerve is a relatively uncommon cranial nerve
palsy. Possible causes include head & neck malignancy and penetrating
traumatic injuries. If the symptoms are accompanied by acute pain, a
possible cause may be dissection of the internal carotid artery.
Patients will present with deviation of the tongue towards the damaged
side on protrusion, as well as possible muscle wasting and fasciculations
(twitching of isolated groups of muscle fibres) on the affected side.