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Cranial nerves - esson presentation.pptx
1. Cranial Nerves
Cranial nerves are spinal nerves that originate
from the brain instead of the spinal cord and
come out of the encasement through cranial
foramina instead of intervertebral foramina
2. Cranial Nerves
Cranial nerves are spinal nerves that originate
from the brain instead of the spinal cord and
come out of the brain through cranial foramina
instead of intervertebral foramina.
They can serve either a sensory, motor or mixed
(both) functions.
7. Cranial Nerve I: Olfactory
• Arises from the olfactory epithelium
• Passes through the cribriform plate of the
ethmoid bone
• Fibers run through the olfactory bulb and
terminate in the primary olfactory cortex
• Functions solely by carrying afferent impulses
for the sense of smell
S
9. Cranial Nerve II: Optic
• Arises from the visual cortex of the cerebrum
• Optic nerves pass through the optic canals and
converge at the optic chiasm
• They continue to the thalamus where they synapse
• From there, the optic radiation fibers run to the
retina of the eye
• Functions solely by carrying afferent impulses for
vision
S
11. Cranial Nerve III: Oculomotor
• Fibers extend from the ventral midbrain, pass
through the superior orbital fissure, and go to the
extrinsic eye muscles
• Functions in raising the eyelid, directing the eyeball,
constricting the iris, and controlling lens shape
• The latter 2 functions are parasympathetically
controlled
• Parasympathetic cell bodies are in the ciliary ganglia
M
14. Cranial Nerve IV: Trochlear
• Fibers emerge from the dorsal midbrain and
enter the orbits via the superior orbital
fissures; innervate the superior oblique
muscle
• Primarily a motor nerve that directs the
eyeball
M
16. Cranial Nerve V: Trigeminal
• Composed of three divisions: ophthalmic
(V1), maxillary (V2), and mandibular (V3)
• Conveys sensory impulses from various
areas of the face (V1) and (V2), and supplies
motor fibers (V3) for mastication
• These (sensory & motor) Fibers run from
the face to the pons via the superior orbital
fissure (V1), the foramen rotundum (V2),
and the foramen ovale (V3)
B
18. Cranial Nerve VI: Abducens
• Fibers leave the inferior pons and enter the orbit
via the superior orbital fissure
• Primarily a motor nerve innervating the lateral
rectus muscle (abducts the eye; thus the name
abducens)
Figure VI from Table 13.2
M
20. Cranial Nerve VII: Facial
• Fibers leave the pons, travel through the
internal acoustic meatus, and emerge
through the stylomastoid foramen to the
lateral aspect of the face
• Motor functions include facial expression,
and the transmittal of autonomic impulses
to lacrimal and salivary glands
• Sensory function is taste from the anterior
two-thirds of the tongue
B
23. Cranial Nerve VIII: Vestibulocochlear
• Fibers arise from the hearing and equilibrium
apparatus of the inner ear, pass through the internal
acoustic meatus, and enter the brainstem at the
pons-medulla border
• Two divisions – cochlear (hearing) and vestibular
(balance)
• Functions are solely sensory – equilibrium and
hearing
S
25. Cranial Nerve IX: Glossopharyngeal
• Fibers emerge from the medulla, leave the skull via
the jugular foramen, and run to the throat
• Nerve IX is a mixed nerve with motor and sensory
functions
• Motor – innervates part of the tongue and pharynx,
and provides motor fibers to the parotid salivary
gland
• Sensory – fibers conduct taste and general sensory
impulses from the tongue and pharynx
B
27. Cranial Nerve X: Vagus
• The only cranial nerve that extends beyond the head
and neck
• Fibers emerge from the medulla via the jugular
foramen
• The vagus is a mixed nerve
• Most motor fibers are parasympathetic fibers to the
heart, lungs, and visceral organs
• Its sensory function is in taste
B
29. Cranial Nerve XI: Accessory
• Formed from a cranial root emerging from the
medulla and a spinal root arising from the
superior region of the spinal cord
• The spinal root passes upward into the
cranium via the foramen magnum
• The accessory nerve leaves the cranium via
the jugular foramen
M
30. Cranial Nerve XI: Accessory
• Primarily a motor nerve
– Supplies fibers to the larynx, pharynx, and soft
palate
– Innervates the trapezius and sternocleidomastoid,
which move the head and neck
32. Cranial Nerve XII: Hypoglossal
• Fibers arise from the medulla and exit the
skull via the hypoglossal canal
• Innervates both extrinsic and intrinsic
muscles of the tongue, which contribute to
swallowing and speech
M
34. Mnemonics
There are a variety of mnemonics that help you
remember the cranial nerves.
For number in order
“On occasion, our tiny truck acts funny, very good
vehicle anyhow”
For Function
“Some say marry money but my brother says bigger
brains matter more”
35.
36. Functions (modalities) of the Cranial nerves
Each cranial nerve can be described as being
sensory, motor or both.
They can more specifically transmit seven types of
information;
Three of these types of information are unique to
cranial nerves (SSS, SVS and SVM).
37. Sensory (afferent) Modalities:
• General somatic sensory (GSS) – general sensation
from skin.
• General visceral sensory (GVS) – general sensation
from viscera.
• Special somatic sensory (SSS) – senses derived from
ectoderm (e.g. sight, sound, balance).
• Special visceral sensory (SVS) – senses derived from
endoderm (e.g. taste, smell).
38. Motor (efferent) Modalities:
• General somatic motor (GSM) – skeletal muscles.
• General visceral motor (GVM) – smooth muscles
of gut and autonomic motor.
• Special visceral motor (SVM) – muscles derived
from pharyngeal arches.
40. Examination of Cranial Nerve Function
Each cranial nerve carries out specific functions.
Testing for a deficiency of a cranial nerves'
function can give a radiographer an idea of
where the problem is located in a person’s brain.
41. Cont…
Necessary to know the most frequent
pathologies that may involve cranial nerves and
recognize their typical characteristics of imaging.
Cranial nerve dysfunctions may be the result of
pathological processes of the cranial nerve itself
or be related to tumors, inflammation,
infectious processes, or traumatic injuries of
adjacent structures.
43. Common Cranial Nerve Conditions
Bell’s Palsy results from damage to the seventh
cranial nerve or facial nerve.
Bell's palsy is characterized by a one sided facial
droop that comes on within 72 hours
Trigeminal neuralgia is a condition involving
intense pain in the area innervated by the
Trigeminal or fifth cranial nerve.
44. Neural Imaging
-Visualization of cranial nerves in routine clinical
practice can be challenging as most are quite small
and difficult to resolve.
-Intracranially, the cisternal (as they pass from the
brain to their respective foramina) portion is most
readily appreciated as the nerves are surrounded
by CSF.
45. Neural Imaging
As the nerves exit the skull, their location can be
implied by knowledge of normal anatomy but, due
to the complicated anatomy of the base of the skull
and head and neck, actually visualizing these small
structures is challenging on all modalities.
46. Neural Imaging
MRI - considered the gold standard in the study of
the cranial nerves.
CT – only allows, usually, an indirect view of the
nerve and is useful to demonstrate the
intraosseous segments of cranial nerves
(intraforamina segment) thru which they exit skull
base and their pathologic changes.
