hypoglossal nerve
DESCRIPTION
TRANSCRIPT
Hypoglossal nerveDr / Hytham Nafady
Introduction
hypoglossal nerve has only a somatic motor component (general somatic efferent) that supplies the extrinsic and intrinsic tongue muscles.
Anatomy
Segments of the hypoglossal nerve
• Hypoglossal nucleus.
Intracranial segments:
• Medullary segment.
• Cisternal segment.
• Canalicular segment.
Extracranial segments:
• Nasopharyngeal/oropharyngeal carotid space.
• Sublingual segment.
Hypoglossal nucleus, medullary & cisternal segments
Hypoglossal nucleus
• Location:
Hypoglossal colliculus of the medulla oblongata.
Medullary segment
• The fibers of the hypoglossal nerve course anteriorly lateral to the medial leminscus & lateral to the olive.
• The hypoglossal nerve exits the medulla at the pre-olivary sulcus.
Cisternal segment
• The hypoglossal nerve course laterally through the premedullary cistern, posterolateral to the vertebral artery.
PICA
Hypoglossal nerve
Vertebral arteries
Canalicular segment (hypoglossal canal)
Hypoglossal canal axial CT
Hypoglossal canal coronal CT
Persistent primitive hypoglossal artery
Interpeduncular cistern
ICA
Sigmoid sinus
IJV
Cn 12
Cn 10
Cn 9
Suprahyoid carotid space segment
• The hypoglossal nerve lies deep to the IJV, ICA & 9 & 10 cranial nerves.
• It become superficial as it courses anteriorly.
• At the level of angle of the mandible it loops anteriorly around the root of the occipital artery and lying deep to the posterior belly of digastric muscle.
Sublingual segment
• The hypoglossal nerve enters the sublingual space by crossing the lingual artery at the level of hyoid bone.
• The hypoglossal nerve lies superfical to the hyoglossus muscle & deep to the myelohyoid muscle.
suprahyoid carotid space segment
platymsa
base
Intrinsicmuscles
GG
GH
Action of genioglossus in sticking out the tongue
Tongue protrusion
Pushing the tongue into the cheek against resistance
Hypoglossal palsy
Medullary glioma
Vertebrobasilar dolichoectasia with hypoglossal nerve palsy
Meningioma
Cisternal hypoglossal schwannoma with tongue atrophy
Isolated hypoglossal palsy caused by synovial cyst
Hypoglossal schwannoma
Occipital condylar fracture
Skull base metastasis
Carotid artery dissection
Extracranial hypoglossal schwannoma with tongue hemiatrophy
Submandibular hypoglossal schwannoma