The hypoglossal nerve, the twelfth cranial nerve, arises from the medulla oblongata and controls the muscles of the tongue. It has both motor and sensory components, with connections to various brain structures and a detailed extracranial course. Clinical examination involves observing tongue movement, with lesions causing distinct deviations and paralysis indicative of their location.

1. HYPOGLOSSAL NERVE
By
DR.M.MD.MUSTAFA SHARIFF
SENIOR LECTURER
SRMDCH-21

2. HYPOGLOSSAL NERVE
INTRODUCTION :
• It is twelveth cranial nerve.
• It arises from antrolateral sulcus of medulla oblongata.
• The nerve leaves the skull through hypoglossal canal.
• It supplies the muscles of the tongue.

4. FUNCTIONAL COMPONENTS:
GENERAL SOMATIC EFFERENT COLUMN:
• The fibers arise from the hypoglossal nucleus which lies
in the medulla.
• In the floor of the fourth ventricle deep to the
hypoglossal triangle.

5. GENERAL SOMATIC AFFERENT COLUMN:
 Spinal nucleus of cranial nerve 5th.
 where proprioceptive fibers from tongue end

6. HYPOGLOSSAL NUCLEUS
 It is 2cm long
 It lies in the floor of fourth ventricle beneath
the hypoglossal triangle.
 It is divided into two parts for individual
muscles innervated.

8. HYPOGLOSSAL NUCLEUS
• Connection of the nucleus with opposite pyramidal
tract forms supranuclear pathway of the nerve.
It is also connection to
 Cerebellum
 Reticular formation of medulla
 Sensory nuclei of 5th nerve
 Nucleus of tractus solitarius

9. INTRANEURAL COURSE
Fibers pass forwards
Lateral:
 Medial longitudinal bundle
 Medial lemniscus
 Pyramidal tract
Medial:
 Reticular formation
 Olivary nucleus

10. EXTRACRANIAL COURSE
• The nerve first lies
deep to internal
jugular vein and
descends between
internal jugular vein
and internal carotid
artery.

11. It is present to deep to the
 Parotid gland
 The styloid process
 The posterior belly
of the digastric and
 Stylohyoid muscle

12.  At the lower border of posterior belly of the digastric it
curves forwards and crosses internal and external
carotid artery and anterior to loop of lingual artery.
 The nerve then continues forwards on the hyoglossus.
 And Genioglossus muscles, deep to submandibular
gland and mylohyoid muscle and enters the substance
of the tongue to supply its muscles.

14. BRANCHES AND DISTRIBUTION
Muscular branches :
• It supply Intrinsic and Extrinsic muscles of the tongue .
• Except palatoglossus which is supplied by cranial root of
accessory nerve
• Other branches containing C1 nerve through 12th nerve.
• Meningeal branch
• Ansa cervicalis
• Branches to thyrohyoid and geniohyoid.

16. CLINICAL ANATOMY
o Hypoglossal nerve is tested clinically by asking the
patient to protrude his tongue.
o Lesion of the hypoglossal nerve produce paralysis of the
tongue to the side of lesion.
o If the lesion is infra nuclear there is gradual atrophy on
the side of lesion.

17. SUPRANUCLEAR LESIONS CAUSES:
 Paralysis without wasting.
 The tongue moves sluggish
and resulting in defective
speech.
 On protrusion , the tongue
deviates to opposite side.

18. REFERENCES
 EXAM-ORINTED ANATOMY SHOUKAT N.KAZI
 HEAD & NECK AK DATTA 5TH EDITION
 GRAYS ANATOMY STUDENTS EDITION
 CLINCAL ANATOMY SNELL 8TH EDITION
 CLINICAL ANATOMY MOORE 5TH EDITION
 HEAD & NECK BD CHAURASIA’S 4TH EDITION
 HEAD & NECK DR. AS.MONI