lower cranial nerve anatomy

1. DR. AJAY KUMAR SINGH
DNB NEUROSURGERY
VPIMS

2. References…
 Rhoton Cranial Anatomy And Surgical Approaches
 DeJong's the neurologic examination
By William Wesley Campbell, Russell N. DeJong, Armin F.
Haerer
 Localization in clinical neurology
By Paul W. Brazis, Joseph C. Masdeu, José Biller
 Clinical Neuroanatomy By Richard S. Snell
 B D C Human anatomy

3. The fibres passes forwards and laterally b/w olivary
nucleus and ICP, through reticular formation of medulla.

4. MICROSURGICAL NEUROANATOMY
 The glossopharyngeal, (IX)
vagus, (X) and spinal accessory
(XI) nerves arise as a line of
rootlets that exit the brainstem
along the posterior edge of the
olive in the post-olivary sulcus.
 The IX and X nerves arise at the
level of the superior third of the
olive, rostral to the level of origin
of the XI rootlets

5.  IX nerve: one or rarely
two rootlets just caudal
to the origin of the VII
and VIII nerve.
 X nerve: a line of
tightly packed rootlets
separated by as much
as 2 mm.

6.  Rootlets pass ventral to the choroid plexus protruding from the foramen of
Luschka on its way to the jugular foramen, Ventral: motor, Dorsal: sensory.
 Several small rootlets originate ventral to the majority of the vagal rootlets.

7.  The IX N enters the JF
below the cochlear
aqueduct. The X behind IX
nerve.
 The auricular branch of the
vagus nerve (Arnold’s
nerve) arises at the level of
the superior ganglion and
passes around the anterior
wall of the jugular bulb.
 XI nerve is formed by
multiple rootlets, which
arise from the medulla and
spinal cord. The accessory
rootlets collect together to
form a bundle that blends
into the lower margin of the
X nerve at the level of JF.

8.  The XI rootlets arise
along the post.
margin of the inf 2/3
of the olive and from
the lower medulla
and the upper
segments of the
cervical spinal cord.
 The cranial rootlets
of the XI nerve arise
as a line of rootlets
caudal to the vagal
fibers

9.  The spinal
accessory fibers
pass superolateral
from their origin to
reach the jugular
foramen. Cranial
and spinal portion
of the accessory
nerve enter the
vagal meatus
together, they may
infrequently be
separated by a dural
septum.

10.  JF is b/w the T’ and O’
bones. It is directed
forward, medially, and
downward.

11.  It has a larger lateral
part, the sigmoid
part, which receives
the drainage of the
sigmoid sinus, and a
smaller medial part,
the petrosal part,
which receives the
drainage of the
inferior petrosal
sinus.

12.  The SS descends in the
sigmoid sulcus and makes a
sharp ant turn to enter the JF.
The jugular bulb extends
upward under the petrous T’
bone toward IAM.
 The IX, X, XI Nerves penetrate
the dura on the medial side of
the intrajugular process

13.  The IX, X nerves
descending b/w ICA and
IJV in the area
immediately below the
jugular foramen.
 The IX nerve descends
along the lateral side of
ICA.
 The XI nerve passes
backward across the
lateral surface of the IJV.

14.  The spinal accessory
fibers pass
superolateral from
their origin to reach
the jugular foramen.

15.  The IX nerve expands at
the site of the superior
and inferior ganglia.
 The superior ganglion of
the X nerve is located at
the level of or just below
the dural roof of the
foramen, and
 The inferior ganglion is
located below the
foramen at the level of
the atlanto-occipital
joint.

16.  The spinal part
arises from a
column of cells
(the accessory
nucleus) that
extends from the
first to the fifth
cervical cord
segments in the
dorsolateral part
of the ventral horn
of the spinal cord.

17.  The column of cells are
somatotopically arranged:
cord levels C1 and C2
innervate predominantly the
ipsilateral SCM muscle,
 And levels C3 and C4
innervate primarily the I/L
trapezius.

18.  The vertebral artery courses anterior to the nerves in the lower
neurovascular complex.

19.  The proximal part of
the PICA passes
around or between
and often stretches
or distorts the
rootlets of the nerves
in the lower complex.

20.  At the
posterolateral
margin of the
medulla, it passes
between the fila of
the IX, X, XI CN.
 At the anterolateral
medulla, the PICA
passes around or
between the
rootlets of the XII
CN.

21.  The PICA may be
ascending
descending, or
passing laterally or
medially, or may be
involved in a
complex loop that
stretches and
distorts these
nerves as it passes
between them.

22. GLOSSOPHARYNGIAL NERVE
IXth CRANIAL NERVE
 The IX nerve
contains motor,
sensory, and
parasympathetic
fibers.

24. Sensory fibers of CN IX
 Sensory nurons of CN IX are
located in supreior and
inferior glossophryngial
ganglion.
1. GSA fibres convey
exteroceptive sensation.
1. GVA fibres conveys
information from carotid
body and carotid sinus, as
well as visceral sensation
form pharynx.
2. SVA fibres convey taste.

25.  The GSA fibers convey
exteroceptive sensation
from the mucous
membranes of the
tympanic cavity, mastoid
air cells, and auditory
canal via the tympanic
plexus and tympanic
branch.
 Sensation from the
pharynx, tonsil, and
posterior third of the
tongue travels via the
pharyngeal, tonsilar,
and lingual branches.

26.  GVA- Carotid branch of CN
IX (carotid sinus nerve,
sinus nerve of Hering)
arises just below the jugular
foramen and descends on
the ICA to the carotid sinus
and carotid body
Terminates centrally on
cells in the middle third of
the nucleus of the
solitary tract.

27.  SVA - Taste fibers
(primarily sour and bitter)
from the circumvallate
papillae, mucous
membranes of the base
and taste buds on the
posterior third of the
tongue, glossoepiglottic
and pharyngoepiglottic
folds, and lingual surface
of the epiglottis.

28. Motor fibres of CN IX (SVE)
 UMN arises from primary motor
cortex and descend in the
coricobulbar tract and synapse in
rostral nucleus of ambiguus.
 Motor fibers from the rostral
nucleus ambiguus in the
dorsolateral medulla first head
posteriomedially toward the floor
of the fourth ventricle, and then
turn and sweep laterally and
forward and emerges out from
posterior sulcus.

29.  It innervates the
stylopharyngeus
muscle (a
pharyngeal elevator)
and (with the vagus
nerve) the
constrictor muscles
of the pharynx.

30.  Corticobulbar input to the
nucleus ambiguus is bilateral
therefore supranuclear(UMN)
lesions, if unilateral, do not
result in any neurologic
deficit.

31. (GVE) Parasympathetic fibers Inferior salivatory nucleus
(periventricular gray matter of the rostral medulla, at
superior pole of the rostral nucleus of cranial nerve
X)
Glossopharyngeal nerve(preganglionic
fibers)
Petrous ganglion (INF)
Tympanic nerve (Jacobson's
nerve)
Lesser superficial petrosal nerve
Otic ganglion (postganglionic fibers)
Joins
Auriculotemporal nerve (Br. of the
trigeminal nerve)
Parotid gland.

32. VAGUS NERVE
(Xth CRANIAL NERVE)
 The vagus (L. “wandering,”
because of its wide
distribution) is the longest
and most widely
distributed cranial nerve.
 It contains motor, sensory
and parasympathetic
fibers.

35. Motor fibres of CN X
 The cortical center regulating
vagus function lies in the lower
portion of the pre-central gyrus
 Supranuclear innervation is
bilateral but primarily crossed.
 Fibers descend in the
corticobulbar tracts to synapse
in the nucleus ambiguus.
 Branchiomotor
 Pharyngeal
 Superior laryngeal
 Recurrent laryngeal.

36.  The pharyngeal branch
runs b/w ICA and ECA
and enters the pharynx,
where it ramifies to form
the pharyngeal plexus.
 The plexus also receives
fibers from the external
laryngeal branch, CN IX,
and the sympathetic
trunk.

37.  The vagus, with a
contribution from the
bulbar portion of CN XI,
supplies all the striated
muscles of the soft palate,
pharynx, and larynx
except for the
stylopharyngeus (CN IX)
and tensor veli palatini
(CN V).

38.  The SLN arises distal to the
pharyngeal branch and divides
into an internal and external
branch.
 The internal branch is primarily
sensory and external branch is
motor.
 The recurrent laryngeal nerves
both descend deep into the
thorax and then loop back to
the larynx.

39. Parasympathetic fibers
 The dorsal motor
nucleus (DMNX) of
the vagus a long cell
column is situated on
the floor of the fourth
ventricle.
 Dorsolateral to the
hypoglossal nucleus
extending from the
upper pole of the
inferior olive to the
lower portion of the
medulla.

40. Parasympathetic fibers
 DMNX gives rise to preganglionic
parasympathetic fibers that
innervate the pharynx, esophagus,
trachea, bronchi, lungs, heart,
stomach, small intestine,
ascending and transverse colon,
liver, and pancreas.
 Vagal discharge causes
bradycardia, hypotension,
bronchoconstriction,
bronchorrhea, increased
peristalsis, increased gastric
secretion, and inhibition of
adrenal function.

41. Sensory fibers of CN X
 It conveys exteroceptive GSA
sensation from the pharynx,
larynx, ear, and meninges.
 GVA fibers from the larynx,
viscera of the thorax and
abdomen, and receptors in the
aorta.

42.  Sensory neurons of CN X
are located in supreior and
inferior vagus ganglion.
 The superior vagal
ganglion is located in the
upper part of the jugular
foramen.
 It communicates through
several delicate branches
with the cranial portion of
CN XI and with the
petrous ganglion of CN IX,
with CN VII, and with the
superior cervical ganglion.

43.  The inferior vagal ganglion lies
just beneath the jugular
foramen. The cranial root of the
CN XI passes through it to join
CN X. The inferior ganglion also
communicates with CN XII, the
superior cervical ganglion, and
the loop between C1 and C2.
 Both vagal ganglia are sensory,
containing unipolar neurons
that mediate GSA, SVA, and
GVA.

44.  The superior ganglion primarily
conveys somatic sensation, and
most of its communication is with
the auricular nerve.
 The inferior ganglion relays general
visceral sensation and taste.

45.  GVA from the pharynx, larynx,
vagally innervated viscera, and from
baroreceptors and chemoreceptors
in the aorta travel over the
peripheral processes of neurons in
the inferior vagal ganglion.
 The central processes terminate in
the caudal portion of the solitary
tract.

46.  SVA-Taste fibers from the region of the epiglottis and
aretynoids, which travel with the taste fibers of CN IX
to terminate in the rostral solitary tract.
 Collaterals to the reticular formation, DMNX, and other
cranial nerve nuclei mediate important visceral reflexes
and are involved in the regulation of cardiovascular,
respiratory, and gastrointestinal function.

47. Clinical Examination
 Difficult to examine because most or all of its
functions are shared by other nerves.
 It is possible to examine pain and touch sensation of
the pharynx, tonsillar region and soft palate, and the
gag reflex.
 Not possible to isolate the motor functions from those
of the vagus.
 Stylopharyngeus: The only deficit that might be
detectable is a slight lowering of the palatal arch at rest
on the involved side.
 Other palatal motor functions are subserved either by
CN X, or the two nerves working together.

48.  The gag reflex is elicited by touching the lateral
oropharynx in the region of the anterior faucial pillar
with a tongue blade, applicator stick, there are three
motor components seen:
 elevation of the soft palate to seal off the nasopharynx,
 closure of the glottis to protect the airway,
 constriction of the pharynx to prevent entry of the
substance.

49. Disorders of Function
 U/L supranuclear lesions cause no deficit bcz of B/L
corticobulbar innervation. B/L lesion may cause pseudobulbar
palsy.
 Nuclear and infranuclear pathologies that may affect CN IX
include intramedullary and extramedullary neoplasms and
other mass lesions
 Glomus jugulare tumor
 Trauma
 MND
 Syringobulbia
 Retropharyngeal abscess
 Demyelinating disease
 Surgical section or other trauma to the carotid branch may
cause transient or sustained hypertension.

50.  Glossopharyngeal neuralgia or “tic douloureux of the
ninth nerve.” attacks of severe lancinating pain
originating in one side of the throat or tonsillar region
and radiating along the course of the eustachian tube to
TM, EAM, behind the angle of the jaw and adjacent
portion of the ear.
 Talking, eating, swallowing, or coughing.
 It can lead to syncope, convulsions, and rarely to
cardiac arrest because of stimulation of the carotid
sinus reflex.

51.  Jacobson's neuralgia, in which the pain is limited to
the ear and eustachian tube.
 Carotid sinus hypersensitivity: inadvertent
activation of the baroreceptors in the carotid sinus
causing bradycardia and hypotension
 constriction around the neck (e.g., tight collar) or a
mass in the neck impinging on the sinus.

52. IX and X cranial nerves
 Methods of examination
 Initial observation
 The pitch and quality of voice, spontaneous cough and the
ability to swallow. Regurgitation of fluids is sought by
history.
 A high-pitched hoarse voice suggests vocal cord paralysis,
whereas
 a nasal tone that increases with forward flexion is
characteristic of palate weakness.
 If the patient chokes on saliva while speaking this is
characteristic of both palatal and pharyngeal weakness.

53. Motor function
 Mouth wide open, inspects the uvula and the tongue,
The patient is asked to say “Ah” while exhaling and
“Ugh” while inhaling. The palate should elevate and
move backwards, the uvula remains in the midline
while the posterior pharyngeal muscles contract. A
deep breath alone elevates the palate and is easy
 for the patient to perform.

54. Sensory functions
Touch sensation
 A throat swab is used to stimulate the back of the throat while
the tongue is gently depressed, gag reflex is elicited from.
Taste sensation
 Testing taste in the posterior tongue is now primarily carried out
in taste
 and smell centers. It is rarely necessary as pathology never affects
this component
 of the nerve alone (possible exception is Hencken’s syndrome
type II).

55.  On phonation
 LMN weakness of the X CN, the palate elevates and moves
to the normal side.
 Bilateral absence of movement of the palate and pharynx is
accompanied by dysphagia, nasal regurgitation and nasal
speech. (b/l medullary lesions) or a bilateral upper motor
lesion from pseudobulbar palsy.
 Pseudobulbar palsy is accompanied by a hyperactive gag
reflex, bilateral spasticity and Babinski’s sign in association
with an abnormal affect (inappropriate crying or laughter).
 Repeated phonation causes fatiguability in myasthenia
gravis.

56.  Sensory loss
 Unilateral absence of the gag reflex is seen with isolated
lesions of the IX nerve.
 The normal side will trigger a full reflex.
 Phonation and direct inspection of the pharynx
demonstrates unilateral muscle weakness as a cause of
unilateral decrease of a gag reflex.
 A combination of IX and X CN lesions causes the palate
and posterior pharynx to pull to the normal side when
stimulated.
 An UMN lesion from vascular disease causes inability to
elevate the palate and constrict the pharynx on the side
contralateral to the lesion (the pharynx pulls and the
palate elevates to the normal side).

57. ACCESSORY NERVE
(XIth CRNIAL NERVE)

58. ACCESSORY NERVE
(XIth CRNIAL NERVE)
 The cranial root arises from cells situated in the caudal part
of the nucleus ambiguus of the medulla.
 The cranial rootlets of the accessory nerve are more
properly regarded as inferior vagal rootlets, since they arise
from vagal nuclei and distributed along with It.

59.  The spinal part
arises from a
column of cells
(the accessory
nucleus) that
extends from the
first to the fifth
cervical cord
segments in the
dorsolateral part
of the ventral horn
of the spinal cord.

60.  The column of cells are
somatotopically arranged:
cord levels C1 and C2
innervate predominantly the
ipsilateral SCM muscle,
 And levels C3 and C4
innervate primarily the I/L
trapezius.

61.  After passing from the jugular
foramen cranial portion branches
off as the internal ramus and joins
the vagus nerve to supply the
pharynx and larynx.
 The external ramus enters the
neck between the internal carotid
artery and the internal jugular
vein.

62.  It supplies SCM muscle
and emerges near the
middle of the posterior
border of the muscle.
 The ramus then crosses
the posterior cervical
triangle to supply the
trapezius muscle.

63.  In its course the nerve receives branches from the
C2,C3,C4 cervical nerves.
 The supranuclear innervation of the trapezius and SCM
muscles probably originates in the lower precentral
gyrus.
 The corticobulbar fibers to the trapezius are crossed,
and thus one cerebral hemisphere supplies the c/l
trapezius muscle.

64.  The course of the supranuclear fibers controlling the
SCM muscle is unknown, but the fibers are thought to
terminate chiefly in the I/L nuclei.
 The corticobulbar fibers to the SCM are located in the
brainstem tegmentum, and for trapezius in the ventral
brainstem.
 Thus, a ventral pontine lesion can cause supranuclear
paresis of the trapezius with sparing of the SCM
muscle.

65. THANK YOU

66.  XII nerve emerges
from the medulla in
the sulcus b/w the
pyramid and inferior
olive along a line that
is continuous
inferiorly with the
line along which the
ventral spinal roots
arise as a series of 10
to 15 rootlets on each
side, anterior to the
rootlets of CNs IX, X,
and XI.

67.  The XII Nerve
fibers gather into
two bundles,
which perforate
the dura mater
separately, pass
through the
hypoglossal
canal, and then
unite.

68.  The XII nerve passes through the
hypoglossal canal, located below
and medial to JF, and descends
with the nerves exiting the JF
 The occipital artery gives rise to a
meningeal branch, which passes
through the jugular foramen to
supply the surrounding dura, and
to the stylomastoid artery, which
passes through the stylomastoid
foramen with the VII nerve.

69.  The XII N
rootlets usually
pass behind the
vertebral artery,
however, some
rootlets
infrequently
pass anterior to
the artery.

70. HYPOGLOSSAL NERVE
(XIIth CRANIAL NERVE)
 Hypoglossal rootlets arise in
a nucleus lacated deep to the
hypoglossal triangle in the
floor of the fourth ventricle
 It exit the medulla along the
anterior margin of the caudal
two-thirds of the olive.

71.  The hypoglossal
rootlets course
anterolateral
through the
subarachnoid
space and pass
behind the
vertebral artery to
reach the
hypoglossal canal.

72.  Before entering the
hypoglossal canal,
the rootlets collect
into two bundles,
and in some cases,
the canal is divided
by a bony septum
that separates the
two bundles.

73.  After passing through
the canal, the bundles
unite and the nerve lies
medial to the internal
jugular vein, and the
glossopharyngeal,
vagus, and accessory
nerves.
 It passes between the
artery and vein, runs
forward above the
hyoid bone, and breaks
up into a number of
fibers to supply the
various tongue

74.  The branches of the hypoglossal nerve are the meningeal,
descending, thyrohyoid, and muscular.
 The meningeal branches send filaments derived from
communicating branches with C1 and C2 to the dura of the
posterior fossa.
 The descending ramus sends a branch to the omohyoid,
and then joins a descending communicating branch from
C2 and C3 to form the ansa hypoglossi, which supplies the
omohyoid, sternohyoid, and sternothyroid muscles.
 The thyrohyoid branch supplies the thyrohyoid muscle.

75.  The descending and thyrohyoid branches carry hypoglossal
fibers but are derived mainly from the cervical plexus.
 The muscular, or lingual is the main branch, supplies the
intrinsic muscles and all of the extrinsic muscles of the
tongue except the palatoglossus supplied by vagus nerve
 The extrinsic muscles protrude and retract the tongue and
move the root up and down.
 The intrinsic muscles change the length, the width, the
curvature of the dorsal surface, and turn the nonprotuded
tip from side to side.

77.  The cerebral center regulating
tongue movements lies in the
lower portion of the precentral
gyrus near and within the
sylvian fissure.
 Supranuclear fibers run in the
corticobulbar tract through
the genu of the internal
capsule and through the
cerebral peduncle.

78.  Supranuclear control to the
genioglossus muscle is
primarily crossed.
 Supply to the other muscles is
bilateral but predominantly
crossed.