Cranial Nerves 11th & 12thNeuroanatomy block-Anatomy-Lecture

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01 List the nuclei related to accessory and hypoglossal nerves in the brain stem.

02 Describe the type and site of each nucleus.

03 Describe site of emergence and course of accessory & hypoglossal nerves.

04 Describe important relations of accessory & hypoglossal nerves in the neck.

05 List the branches of accessory and hypoglossal nerves.

06 Describe the main motor effects in case of lesion of accessory & hypoglossal nerves.

Color guide ● Only in boys slides in Green● Only in girls slides in Purple● important in Red● Notes in Grey

At the end of the lecture, students should be able to:

Objectives

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● Type: Motor.● Has two parts (roots): cranial & spinal.● Foramen of exit from skull: Jugular foramen.

There’re 4 structures that pass through the jugular foramen : Cranial nerves IX,X,XI and internal jugular vein

● The axons leave the cord via series of rootlets, emerge laterally midway between the dorsal & ventral roots of the spinal nerves.

● Courses rostrally and enter the cranial cavity through the foramen magnum, and joins the cranial root briefly.

● Separates once again as the nerve leaves the cranial cavity through the Jugular foramen.

● Supplies the: sternomastoid and trapezius muscles.

2. Spinal Partarises from motor neurons in ventral horn of

the spinal gray matter at levels C1-C5 (spinal nucleus).

❶

❷❸

Accessory nucleus in

ventral horn of spinal cord segment C1-C5

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❹

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❶

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● Emerges from lateral aspect of the medulla as a linear series of rootlets between olive and inferior cerebellar peduncle,caudal to rootlets of the vagus nerve.

● At the side of medulla it joins the spinal root briefly.

● It separates once again as the nerve leaves the cranial cavity through the Jugular foramen.

● At the level of jugular foramen these fibres join the vagus nerve and distribute with it to muscles of the: soft plate, esophagus, pharynx and larynx.

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❷

❸

❹

1. Cranial Partcarries fibres that originate in the caudal

part of nucleus ambiguus.

11th CN: Accessory Nerve

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● The nucleus ambiguus and the spinal nucleus receive bilateral corticonuclear fibers (from both cerebral hemispheres).

Functions of accessory nerve:1. Movements of the soft palate, larynx, pharynx.2. Controls the movements of neck.

Injury of spinal root of accessory nerve:

Because of the relatively superficial position of the nerve in the posterior

triangle, it may be damaged by penetrating trauma as stab wounds.

Causes:

It is considered the most commonly iatrogenically injured nerve as during

removal of malignant lymph nodes in the posterior triangle.

01.

02.

Atrophy & weakness of trapezius.

Unilateral paralysis of trapezius: is evident by inability to elevate & retract the

shoulder ,difficulty in elevating the arm & Winging of scapula.

Drooping of the shoulder.

Difficulty in swallowing and speech & Inability to turn the head.

Manifestations:

11th CN: Accessory Nerve

● The fibers emerge from the anterior surface of the medulla oblongata through the sulcus between the pyramid & the olive.

● The nerve courses downward with cervical neurovascular bundle (internal carotid artery, internal Jugular vein, vagus nerve). Then curves forward behind mandible to supply the tongue.

● During its initial course, it carries C1 fibers which leave in a branch to take part in the formation of ansa cervicalis (a loop of nerves supplying neck muscles).

12th CN: Hypoglossal Nerve

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● Type: Motor.● Origin: Hypoglossal nucleus of the medulla (in the floor of 4th ventricle).● Foramen of exit from skull: hypoglossal canal.

1. corticonuclear fibers from both cerebral hemispheres EXCEPT the region that supplies genioglossus muscle (receives contralateral supply only).

2. Afferent fibers from nucleus solitarius and trigeminal sensory nucleus.

Course:

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Hypoglossal nucleus

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The hypoglossal nucleus receives:

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03. The tongue paralyses, atrophies,

becomes shrunken and furrowed on the

affected side (LMN paralysis).

Functions of Hypoglossal nerve:1. Supplies motor innervation to all of the muscles of the tongue

Except the palatoglossus (which is supplied by the vagus nerve). ➔ So, it Controls the movements and shape of the tongue during speech & swallowing.

2. Carries proprioceptive afferents from the tongue muscles.

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12th CN: Hypoglossal Nerve

Manifestations Lesion of the nerve (LMN) :

01. Loss of tongue movements.

02. Difficulty in chewing & speech.

04. On protrusion, tongue deviates to the affected side.

05. If both nerves are damaged,person can’t protrude tongue.

Practice Q1: The Accessory Nerve exit from which foramen in the skull?

A. Foramen ovale

B) Foramen Lacerum

C) Jugular Foramen

D) Foramen Magnum

Q2: The spinal part of Accessory Nerve supplies which muscles?

A. Sternomastoid & Trapezius

B. Serratus anterior & Trapezius

C. Sternomastoid and scalene

D. Sternomastoid and omohyoid

Q3: Which of the following nerve commonly injured during removal of malignant lymph

nodes in the posterior triangle?

A.Cranial root of Accessory Nerve

B.Hypoglossal Nerve

C. Spinal root of Accessory Nerve

D. Vagus Nerve.

Q4: The function of accessory cranial nerve is ?

A.Movements of the tongue

B. Controls the movements of the neck

C. Carries proprioceptive afferents from the tongue muscle

.

Q5: The 12th cranial nerve is

A. glossopharyngeal nerve

B. vagus nerve

C. hypoglossal nerve

D. optic nerve

Q6: Lesions of the 12th cranial nerve wouldn’t affect which muscle ?

A.Palatoglossus.

B.Styloglossus.

C. Hyoglossus.

D. Tongue.

Q7: If the tongue is deviated to the left side that means?

A.Right hypoglossal nerve injury.

B. Left hypoglossal nerve injury.

C. Both A&B.

D. None of the above.

Q8 : Type of paralysis combined with 12th cranial nerve lesions is ?

A. LMN paralysis.

B. UMN paralysis.

C. Upper motor neuron lesion

Answers: Q1(C) Q2(A) Q3(C) Q4(B) Q5(c) Q6(A) Q7(B) Q8(A) 7

Girls team :

● Ajeed Al Rashoud● Taif Alotaibi● Noura Al Turki● Amirah Al-Zahrani● Alhanouf Al-haluli● Sara Al-Abdulkarem● Renad Al Haqbani● Nouf Al Humaidhi● Jude Al Khalifah● Nouf Al Hussaini● Rahaf Al Shabri● Danah Al Halees● Rema Al Mutawa● Amirah Al Dakhilallah● Maha Al Nahdi ● Razan Al zohaifi ● Ghalia Alnufaei

Boys team:

● Mohammed Al-huqbani● Salman Alagla● Ziyad Al-jofan● Ali Aldawood● Khalid Nagshabandi● Omar Alammari● Sameh nuser● Abdullah Basamh● Alwaleed Alsaleh● Mohaned Makkawi● Abdullah Alghamdi

Team leaders

● Ateen Almutairi● Abdulrahman Shadid

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