Download The accessory nerve XI

Cranial Nerves Lesion and Blood Supply
29/04/2017
The Accessory Nerve XI
It's a purely motor nerve and it has 2 motor roots: spinal and
cranial roots, which they unite together in the posterior cranial
fossa to exit from jugular foramen.
The Cranial root :
Originate from the lower part of the nucleus ambiguous in the
medulla and its axons emerge between the olive and the inferior
cerebellar peduncle.
! The nucleus ambiguous is seen at the level of the medulla, level
of the olive, and gives also the motor roots for the
glossopharyngeal VII and Vagus X nerves.
The Spinal root :
As the name indicates it originates from the spinal cord,
specifically from the spinal nucleus in the anterior horn of the
gray mater which is located in the upper 5 cervical segments, then
the axons of the spinal nucleus enter through foramen magnum till
they reach the posterior cranial fossa to unite with the cranial root.
Then, the 2 roots unite and exist from the jugular foramen but after
a short distance, the spinal root separates from the cranial root.
The cranial root joins the Vagus nerve and is distributed in its
pharyngeal and recurrent laryngeal branches to the muscles of the
pharynx and the larynx.
The spinal root descend downward to supply both
sternoclediomastoid and trapezius muscle.
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The Hypoglossal Nerve XII
It's a purely motor nerve, supplies the intrinsic and the extrinsic
muscles of the tongue except the palatoglussal muscle. The
hypoglossal nucleus is seen the most medially to the midline at the
level of the olive in the medulla then the axons of the nucleus
emerge between the pyramids and the olive.
! The fibers of the hypoglossal nerve considered as General
somatic efferent fibers (GSE) that innervate skeletal muscles of
tongue except the palatoglussal muscle that is supplied by the
pharyngeal plexus.
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The lesion of the Cranial Nerves
Trigeminal nerve
The Trigeminal nerve has both sensory and motor root. We test the
motor function by asking the patient to clench his teeth, then the
masseter and the temporalis muscles are felt harden as they
contract; that is the normal state since these muscle are supplied
by branches from the mandibular motor division of the trigeminal.
We test the sensory function by using a pin over the areas that are
supplied by the sensory divisions of the trigeminal nerve.
Trigeminal Neurogelia
It's a disease affecting the sensory part of trigeminal nerve
characterized by a stapping pain which is felt over the skin areas
that are innervated by the maxillary and the mandibular divisions
of the V, rarely the pain is felt in the area supplied by the
opthalmic. This pain occurs with no reason or suddenly by simple
contraction of the masticatory muscles when chewing or shaving,
treated by an anticonvulsant or antidepressants. It's a serious
disease because the pain symptom last from second to several
minutes, 3 minutes to be precise, and occurs for hundred of times
during the day especially after touching specific areas in the face.
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The Facial Nerve
We know that the facial nerve has motor, sensory and
parasympathetic nuclei. The motor nucleus of the facial nerve give
arise to the fibers that supply the muscles of the facial expressions,
and the part of the motor nucleus - that supplies the muscles of the
upper part of the face - receives corticonuclear fibers from both
cerebral hemispheres, also the part of the motor nucleus - that
supplies the muscles of the lower part of the face- receives only
corticonuclear fibers from the opposite cerebral hemisphere.
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2
1- In upper motor neuron injury ( injury to the corticonuclear
fibers or the cerebral cortex ) :
The lower part of the face is the only part that is affected on the
opposite side to the injured area. Its sign is deviation of the
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angle of the mouth downwardly on the opposite side to the
injured area, the muscles of the forehead are not affected and
we will find normally working orbicularis oculi.
! Explanation
The part of the motor nucleus that controls the muscles of the
upper part of the face is not affected, because this part of the motor
nucleus receives corticonuclear fibers from both hemispheres, so
any injury to one bundle of the corticonuclear fibers won't affect
this part, since it's also under the control of the other bundle from
the other hemisphere, and as a result, it won't affect the upper part
of the face, but the injury affects hugely the part of the motor
nucleus that control the lower part of the face, since it receives the
corticonuclear fibers only from the contralateral hemisphere ,that
means, there is only one relay of the corticonuclear on this part of
the motor nucleus contralaterally, hence affecting the lower part
of the face markedly.
2- In lower motor neuron injury ( injury to the facial motor
nucleus itself, its fibers or the facial nerve ):
The upper and the lower parts of the face are affected on the
same side to the injured area. The muscles of the face on the
same side would be paralyzed and its signs: deviation is in
lateral angle of the eye and the corner of the mouth at the same
side to the injured area ,tears will flow over the lower eyelid,
and saliva will dribble from the corner of the mouth leading to
the a dry mouth. The patient will be unable to close the eye and
will be unable to expose the teeth fully on the affected side..
To test the facial nerve,
IThe patient is asked to show the teeth by separating the
lips with the teeth clenched. Normally, equal areas of the
upper and lower teeth are revealed on both sides. If a
lesion of the facial nerve is present on one side, the mouth
is distorted. A greater area of teeth is revealed on the side
of the intact nerve, since the mouth is pulled up on that
side.
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II-
We ask the patient to close both eyes firmly, then we open
the eyes gently raising the patient's upper lids, normally if
there is no lesion, we feel some resistance the patient
shows to open his eye . On the side of the lesion, the
orbicularis oculi is paralyzed so that the eyelid on that
side is easily raised.
Bell Palsy
Facial paralysis, usually temporally but in some cases it's
permanent , it's a lower motor neuron lesion that result from
compression on the facial nerve within the facial canal. It's
classified as one category ; it is usually unilateral probably due to a
viral infection or cold draft. It has the signs of lower motor neuron
lesion.
Facial Nerves and Related Cranial Nerves
i.
The facial nerve injury may affect the abducens since the
axons of the facial nuclei wind around the abducens nucleus
forming the facial colliculus on the posterior surface of the
pons.
Case I:
A patient with a problem with some muscles of the eye,
specifically the extraoclular muscles, and has Bell palsy.
In this case: Bell palsy indicates that there is a lower motor neuron
facial nerve injury, and the extraocular muscles problem that is
due to the trochlear (supplying the superior oblique), abducens
(supplying the lateral rectus) or occulomotor (supply all of the
muscles of the eye except the superior oblique and the lateral
rectus) , so if it's "some extraocular muscles" then the nerve
affected is either the IV or VII but the one that is related to the
facial nerve is the abducens at the level of the pons as mentioned
earlier, so the level of injury would be at the level of pons.
ii.
Facial nerve injury may affect the vestibulocochlear nerve at
the level of the junction between the pons and the medulla
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oblongata or when the cochlear and vesibular nerves enter
internal acoustic meatus in accompany with the facial nerve.
Case II:
A pataint with Bell palsy and has deafness or vertigo.
In this case: Since the patient has Bell palsy then he has a facial
nerve injury. Deafness or vertigo is due to an injury to the cochlear
or vestibular nerves respectively, that are located lateral to facial
nerve at the lower border of the pons. Hence the lesion is at the
level between the pons and the medulla oblongata or at the level of
internal auditory meatus.
iii.
The facial nerve exists the internal auditory meatus and
gives branches within the parotid gland, so any infection or
cancer in the parotid gland would affect the facial nerve.
The Vestibulocochlear Nerve
It consists of the vestibular and cochlear nerves. The vestibular
lesion cause vertigo, nystagmus and affects the balance state. The
cochlear nerve lesion causes deafness and tinnitus.
! Nystagmus
Rhythmic oscillation of the eyeball that is due to an injury in the
vestibular nerve since the vestibular nuclei emit efferent fibers to
the nuclei of the occulomotor, trochlear and abducens nerve – the 3
nerves control the extraocular muscles- through the medial
longitudinal fasciculus.
Glossopharyngeal Nerve
Lesions of the glossopharyngeal nerve usually associated with
Vagus nerve lesions and rarely we find it as isolated injuries.
Since the sensory fibers of the glossopharyngeal nerve innervate
the posterior one-third of the tongue so we test it's lesion via
asking the patient to taste something on the posterior third of his
tongue.
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The Vagus Nerve
The Vagus nerve innervates the smooth muscles of many
important organs, that some of them are not obvious, so we
examine it by testing the function of the branches to the pharynx,
soft palate, and larynx.
We test the injury via:
I.
We ask the patient to say "ah" to observe the soft palate and
the uvula. Normally the soft palate rise and uvula move
backward in the midline normally, but if there a deviation in
the uvula to any side so there is a lesion in the Vagus.
II.
The pharyngeal or gag reflex may be tested by touching the
lateral wall of the pharynx with a spatula. This should
immediately cause the patient to gag; that is, the pharyngeal
muscles will contract.
! For the larynx, Hoarseness or absence of the voice may occur as a
symptom of vagal nerve injury.
!! All the muscles of the larynx are supplied by the recurrent
laryngeal branch of the Vagus, except the cricothyroid muscle,
which is supplied by the external laryngeal branch of the superior
laryngeal branch of the Vagus.
Accessory Nerve
Since the spinal root of the accessory nerve descend downwardly
to supply both trapezius and sternoclediomatiod, we examine the
injury by asking the patient to rotate his head to one side against
resistance, causing the sternocleidomastoid of the opposite side to
come into action. Also we ask him to shrug his shoulders, causing
the trapezius muscles to come into action. If there is a lesion in the
XI, the shoulder will droop on that side due to the atrophy of the
trapezius muscle, and will be weakness in turning the head to the
opposite side due to atrophy in the sternocleidomastoid muscle.
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Hypoglossal Nerve
The hypoglossal nerve supplies the intrinsic and extrinsic muscles
of the tongue except the palatoglussal muscle.
! The greater part of the hypoglossal nucleus receives
corticonuclear fibers from both cerebral hemispheres but the part
of the nucleus that supplies the genioglossus receives
corticonuclear fibers only from the opposite cerebral hemisphere.
The lesion can be tested by asking the patient to put out his tongue
forward and this occurs under the action of the genioglossus
muscle.
The lesion can be:
1- lower motor neuron lesion
The tongue will be smaller on the side of the lesion, owing to
muscle atrophy, and it will deviate toward the paralyzed
side.
2- upper motor lesion ( Corticonuclear fibers lesion )
There will be no atrophy of the tongue, and on protrusion,
the tongue will deviate to the side opposite the lesion.
Blood Supply of the Spinal Cord
Arteries of the Spinal Cord
The spinal cord receives its arterial supply from 3 arteries that run
longitudinally:
1- The 2 posterior spinal arteries: supply the posterior part of
the spinal cord.
2- The anterior spinal artery: supplies the anterior part of the
spinal cord.
Other arteries originate as branches from outside the vertebral
column are called the segmental arteries. As the name indicates
they enter each segment of the spinal cord and divides into
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anterior and posterior radicular arteries, to supply the anterior
and posterior parts of the spinal cord respectively - especially the
white and the gray mater - that accompany the anterior and
posterior spinal arteries.
The posterior spinal arteries branch directly from the main trunk
of the vertebral arteries or indirectly from the posterior inferior
cerebellar arteries (the largest branch of the vertebral artery).
The anterior spinal artery is formed by the union of two arteries,
each of which arises from the vertebral artery.
Veins of the Spinal Cord
The drainage is mainly through the internal vertebral venous
plexus or epidural venous plexus.
Blood Supply of the Brain
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Arteries of the Brain
The brain is supplied by the 2 internal carotid and the 2 vertebral
arteries. The four arteries lie within the subarachnoid space, and
their branches anastomose on the inferior surface of the brain to
form the circle of Willis.
The internal carotid artery
The common carotid artery bifurcate giving arise to the internal
carotid artery where it usually has a localized dilatation, called the
carotid sinus. It ascends the neck passing through the carotid
canal. The artery then runs horizontally forward through the
cavernous sinus and emerges on the medial side of the anterior
clinoid process. It now enters the subarachnoid space. Finally, it
terminates into the small anterior and large middle cerebral
arteries.
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Branches of the Cerebral Portion
I.
II.
III.
IV.
V.
The ophthalmic artery arises as the internal carotid artery
emerges from the cavernous sinus. It enters the orbit
through the optic canal to supply the eye and other orbital
structures.
The posterior communicating artery, originates from the
internal carotid artery and runs posteriorly to join the
posterior cerebral artery, thus forming part of the circle of
Willis.
The choroidal artery.
The anterior cerebral artery is the smaller terminal branch
of the internal carotid artery and it supplies all the medial
surface of the cerebral cortex
The middle cerebral artery, the largest branch of the
internal carotid and it supplies the entire lateral surface of
the hemisphere.
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! The 2 anterior cerebral arteries are joined by the anterior
communicating artery, which is so important because it form
part of the circle of Willis.
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Vertebral Artery
The vertebral artery, a branch of the first part of the subclavian
artery, ascends the neck by passing through the foramina in the
transverse processes. It enters the skull through the foramen
magnum and pierces the dura mater and arachnoid to enter the
subarachnoid space.
Branches of the Cranial Portion
I. The meningeal branches ,supplies the dura in the posterior
cranial fossa.
II. The posterior spinal artery may arise directly from the
vertebral artery or indirectly from the posterior inferior
cerebellar artery. It descends on the posterior surface of the
spinal cord.
III. The anterior spinal artery is formed from a contributory
branch from each vertebral artery near its termination. The
single artery descends on the anterior surface of the spinal
cord.
! Both anterior and posterior spinal artery are reinforced by
radicular arteries anteriorly and posteriorly respectively
IV. The posterior inferior cerebellar artery, the largest branch of
the vertebral artery, passes between the medulla and the
cerebellum.. It supplies the medulla, both posterior and the
inferior surfaces of the cerebellum beside the nuclei in the
cerebellum.
V. The medullary arteries are very small branches that are
distributed to the medulla oblongata.
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Basilar Artery
Formed by the union of the two vertebral arteries, ascends in a
groove on the anterior surface of the pons (= basilar groove ). At
the upper border of the pons, it divides into the 2 posterior
cerebral arteries.
Branches
I.
II.
III.
IV.
V.
The pontine arteries , supplies the pons.
The labyrinthine artery, supplies the internal ear. It often
arises as a branch of the anterior inferior cerebellar artery.
The anterior inferior cerebellar artery, supplies the anterior
and inferior parts of the cerebellum.
The superior cerebellar artery , supplies the superior surface
of the cerebellum.
The posterior cerebral artery
Circle of Willis
It is formed by the anastomosis between the 2 internal carotid
arteries and the 2 vertebral arteries. The anterior communicating,
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proximal pars of the anterior cerebral, internal carotid, posterior
communicating, proximal parts of the posterior cerebral, and
basilar arteries, that all contribute to the circle.
Arteries to Specific Brain Areas
The corpus striatum and the internal capsule are supplied mainly
by the medial and lateral striate central branches of the middle
cerebral artery; the central branches of the anterior cerebral artery
supply the remainder of these structures.
The thalamus is supplied mainly by branches of the posterior
communicating, basilar, and posterior cerebral arteries.
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The midbrain is supplied by the posterior cerebral, superior
cerebellar, and basilar arteries.
The pons is supplied by the basilar and the anterior, inferior, and
superior cerebellar arteries.
The medulla oblongata is supplied by the vertebral, anterior and
posterior spinal, posterior inferior cerebellar, and basilar arteries.
The cerebellum is supplied by the superior cerebellar, anterior
inferior cerebellar, and posterior inferior cerebellar arteries.
Done By : Rawan Hamdan
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