Hypoglossal nerve

Hypoglossal nucleus & its central connections 1) Its nucleus receive Corticonuclear fibers from both cerebral hemispheres, but the cel...

Hypoglossal nucleus & its central connections

1) Its nucleus receive Corticonuclear fibers from both cerebral hemispheres, but the cells supplying the genioglossus muscle receives corticonuclear fibers only from the opposite cerebral hemisphere
2) It supplies

1. All the intrinsic muscles of the tongue
2. Styloglossus
3. Hyoglossus
4. Genioglossus
5. Doesn’t supply Palatoglossus – Supplied by the vagus

3) Function is to control the movement of the tongue
4) In the upper part, the Hypoglossal nerve is supplied by the C₁ fibers

Examination of the hypoglossal muscle
1) Ask the patient to open the mouth & inspect the tongue
2) Look for evidence of:

1. Atrophy (Increased folds, wasting)
2. Fibrillations

3) Ask the patient to protrude the tongue : Note any deviation or difficulty (Protrude tongue deviates towards the side of weakness)

The summary of cranial nerves

Nerve	Component	Function	Opening in skull
1.Olfactory	Sensory	Smell	Openings of the cribriform plate of the ethmoid
2.Optic	Sensory	Vision	Optic canal
3.Occulomotor	Motor	Raises upper eye lid Turns eye balls upwards, downwards, medially Constrict pupils Accommodate eyes	Superior orbital fissure
4. Trochlear	Motor	Turn the eye ball downward & lateral	Superior orbital fissure
5. Trigeminal
Ophthalmic division	Sensory	Cornea, skin of forehead, scalp, eyelids, nose mucus membranes of paranasal sinuses & nasal cavity	Superior orbital fissure
Maxillary division	Sensory	Skin of face over maxilla, Teeth of upper jaw, mucus membrane of nose, maxillary sinus & palate	Foramen rotundum
Mandibular division	Motor	Muscles of mastication, Mylohyoid, anterior belly of Digastric, tensor veli palatini, tensor tympani	Foramen ovale
	Sensory	Skin of cheek, skin of mandible & side of head, teeth of lower jaw & TMJ, mucus membrane of mouth & anterior part of the tongue
6. Abducent	Motor	Turns eye balls laterally	Superior orbital fissure
7. Facial	Motor	Muscles of face & scalp, Stapedius, posterior belly of Digastric, Stylohyoid muscles	Internal acoustic meatus, facial canal, stylomastoid foramen
	Sensory	Taste from anterior 2/3 of the tongue, from floor of the mouth & palate
	Secretomotor (PS)	Sub mandibular & sub lingual salivary glands, Lacrimal glands
8. Vestibular cochlear
Vestibular	Sensory	From utricle, saccule & semi circular canals – Position & movement of head	Internal acoustic meatus
Cochlear	Sensory	Organ of Corti – Hearing
9.Glossopharyngeal	Motor	Stylopharyngeus	Jugular foramen
	Sensory	General & taste sensation from the posterior 1/3 of the tongue & pharynx, carotid sinus (Baroreceptors) and Carotid sinus (Chemoreceptor)
	Secretomotor (PS)	Parotid gland
10. Vagus	Motor	Note	Jugular foramen
	Sensory
11.Accessory
Cranial root	Motor	Supply the muscles of Soft palate (Except tensor veli palatini), Pharynx (Except stylopharyngeus), Larynx (Except cricothyroid)	Jugular foramen
Spinal root	Motor	SCM & trapezius
12. Hypoglossal	Motor	Muscles of the tongue except palatoglossus	Hypoglossal canal