Cranial Nerve Anatomy by. Greg McLauchlin. I (Olfactory Nerve). The olfactory nerve is unique, but not in ways that make it particularly interesting. The sensory . Lecture 6: Cranial Nerves. Objective: To understand the organization of cranial nerves with respect to their nuclei within the brain, their course through and exit. Cranial Nerves. CN 1. Olfactory Nerve. CN 2. Optic Nerve. CN 3. Oculomotor Nerve. CN 4. Trochlear Nerve. CN 5. Trigeminal Nerve. CN 6.
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Detailed Review of Cranial. Nerves. Charlie Goldberg, M.D.. Professor of Fields (Cranial Nerve 2 - Optic) . terney.info Considerations. TSHA Convention Gail L. Davie, M.A. CCC/SLP & Denise Barringer, M.S. CCC/SLP. Cranial Nerves & Their Function. CRANIAL NERVE. PDF | Advances in neuroimaging using high-resolution images from computerized tomography A wide range of disease processes can affect cranial nerves.
The cranial nerves are twelve pairs of nerves from the central nervous system. The cranial nerves are loosely based on their functions. In this summary, we discuss the nomenclature of the cranial nerves and supply some background information that might make it easier to understand the nerves and their function. Download our cranial nerves PDF summary table here. You can also check out our Cranial Nerve Anatomy Quiz here. The cranial nerve nuclei will be covered in more detail in each cranial nerve article.
For now, it is worthwhile knowing that a nucleus refers to a collection of neuronal cell bodies within the central nervous system and they give rise to one of seven major types of fibres below:. Afferent fibres carry sensory information back to the brain. Efferent fibres carry motor information away from the brain. The cranial nerves themselves can be a complex area of anatomy to learn.
We have broken the cranial nerves down to their bare essentials. The other cranial nerve articles in this series build on the information presented here.
It also carries parasympathetic fibers from the inferior salivatory nucleus; these fibers split off the glossopharyngeal nerve as the tympanic nerve; and terminate in the otic ganglion; postganglionic fibers from the otic ganglion terminate in the parotid gland. These are the highlights of this nerve and should be remembered.
More details are given in the drawings that follow. We enter the jugular foramen; we pass through the superior and inferior ganglia of CN IX without synapsing, and exit the cranium. At this point we split off CN IX, we form a small nerve, the tympanic nerve, and move superiorly back into the bone of the skull and in the middle ear; here, on the promontory we form the tympanic plexus with the sympathetic postganglionic fibers that origi- nate in the superior cervical ganglion.
Leaving the tympanic plexus, we change our name to lesser petrosal nerve. We emerge in the cranial cavity through the hiatus for the lesser petrosal nerve, we move anteriorly, we enter foramen ovale, we exit the cranial cavity once again, and synapse on the otic ganglion. We convey our information to cell bodies of the otic ganglion, postganglionic fibers of which enter the auricular branch of V3, which moves posteriorly and takes us to the parotid gland where we synapse. End of our trip.
Origins, targets, and components The tympanic nerve Note that the tympanic nerve emerges from the glossopharyngeal nerve as soon as the latter emerges from the jugular foramen. Observe the tympanic nerve moving superiorly and posteriorly and entering the bone of the skull heading to the middle ear.
We ride in the glossopharyngeal nerve, CN IX, and move posteriorly and superiorly. We enter the skull bone through the jugular foramen.
Here we observe a swelling, the inferior or petrous ganglion of the glossopharyngeal nerve, where our cell body exists. From the petrous ganglion, we observe the tympanic nerve emerging.
We move superiorly and pass through a second swelling, the superior ganglion of CN IX, which we pass and enter the cranial cavity. Next, we enter the tissue of brainstem and terminate on the solitary nucleus.
However, it also contains motor fibers from nucleus ambiguus SVE to the stylopharyngeus muscle. Clinical correlations Glossopharyngeal neuralgia is a rare syndrome in which patient experiences recurring severe pain attacks in the back of the throat, the tonsils, the back of the tongue, and the middle ear.
The cause is unknown but it is generally believed that an artery compresses the nerve. Glossopharyngeal neuralgia is related to mul- tiple sclerosis. Unilateral lesions of nucleus ambiguous result in ip- silateral atrophy and paralysis of all palatal muscles with the exception of tensor veli palatini muscle, which is innervated by CN V.
Patient presents with nasal speech, uvula deviation toward the normal side, and may complain of nasal regurgitation. Bilateral lesions of the nucleus ambiguus will result in adduction of the vocal cords and suffocation. Supranuclear lesions do not result in deficits because of bilateral innervation of nucleus ambiguus. Details are presented below.
The point of emergence in the brainstem The vagus nerve contains motor and sensory fibers, somatic, sensory, autonomic, visceral, and special sensory. A summary of the origins, tar- gets, as well as components is presented in the following schematic. Origins, targets, and components.
Note: 1. The pharyngeal nerve is one of the nerves that form the pharyngeal plexus, which is formed on the walls of the pharyngeal constrictor muscles; the other nerves that contribute to the formation of the pharyngeal plexus are: the glossopharyngeal nerve, sympathetic fibers, and the laryngeal nerve.
All muscles of the pharynx and the soft palate except the tensor veli palatini, which is innervated by the trigeminal nerve are innervated by the pharyngeal plexus. The external laryngeal innervates the cricothyroid muscle, and contributes to the pharyngeal plexus.
The internal laryngeal is distributed to the mucous membranes of the larynx as far down as the vocal folds. Remember the parasympathetic nervous system is also called craniosacral. The fibers of the recurrent laryngeal SVE originate in the nucleus ambiguus in the brainstem, exit as the cranial part of the accessory, and join the vagus nerve. The superior cervical ganglion provides the postganglionic fibers for the innervation of head structures. The fibers of the recurrent laryngeal SVE originate in the nucleus am- biguus in the brainstem, exit as the cranial part of the accessory, and join the vagus nerve.
The fibers of the recurrent laryngeal nerve originate in the ambiguus nucleus and exit the brainstem with the cranial portion of the accessory nerve. The recurrent laryngeal nerve changes its name to inferior laryngeal nerve at the upper border of the cricoid cartilage. Branches of the vagus nerve In the Neck: Pharyngeal Superior laryngeal Recurrent Superior cardiac In the Thorax: Inferior cardiac Anterior bronchial Posterior bronchial Esophageal In the Abdomen: Gastric Celiac Hepatic Vagus, thoracic and abdominal parts Clinical notes Unilateral nuclear or infranuclear damage to the vagus nerve causes paralysis of the soft palate, pharynx and larynx and consequently effects changes in voice.
Bilateral lesions cause death as the vocal cords adduct and prevent respiration. Esophageal distension in swallowing of food may be the cause of swallow syncope fainting.
It is thought to be related to the vagus nerve vasovagal reflex causing cardiac inhibition. Testing for the gag reflex by touching the soft palate with a cotton swab gives indications of damage to CN IX and X. Absence of the reflex indicates damage.
The accessory nerve or spinal accessory nerve is a motor nerve. There are two distinct parts, the cranial part which originates in the nucleus am- biguus SVE , and the spinal part, which originates in the spinal cord.
The cranial part joins the vagus and eventually splits off as laryngeal nerve and innervates the larynx. The spinal part innervates the trapezius and the sternocleidomastoid muscles. The spinal accessory nerve, CN XI, has two parts, the cranial part, and the spinal part. The cranial part joins the vagus nerve, CN X, while the spinal part forms a distinct nerve. Both parts exit from the jugular foramen, as do vagus and glossopharyngeal nerves.
T he internal or cranial part of the accessory nerve originates in the nucleus ambiguus, joins vagus and eventfully emerges as the recurrent laryngeal nerve, while the external or spinal part originates in in the anterior column of the gray substance of the medulla and spinal cord as low as the fifth cervical nerve, and follows a distinct route to the trapezius and sternocleidomastoid muscles.
The recurrent nerve on the right side curves around the subclavian artery from front to back and ascends to the larynx; on the left side it follows the vagus into the thoracic cavity to the level of the aortic arch around which it curves from front to back, and then ascends to the level of the larynx between the esophagus and the trachea.
It enters the larynx between the thyroid and cricoid cartilages; it innervates all the muscles of the larynx except the cricothyroid. The cranial part of the accessory, which as we have said originates in nucleus ambiguus, is classified as special visceral efferent SVE or branchial.
There is disagreement on whether the spinal part which innervates the trapezius and sternocleidomastoid muscles is also special visceral efferent; some researchers classify it as general somatic efferent GSE. The accessory nerve, cranial portion, carries special visceral branchial efferent fibers SVE from the nucleus ambiguus to the laryngeal muscles. Patient will not be able to raise his arm above the horizontal level.
Bilateral lesions will result in difficulty to hold head in an upright position. Remember that the trigeminal and glossopharyngeal provide sensory innervation of the tongue.
RANDOM TIP Nucleus ambiguus fibers travel with cranial nerves IX, X, XI Nucleus ambiguus fibers are special visceral efferent SVE and innervate muscles derived from branchial arches striated muscles of the soft palate, pharynx, larynx, and upper part of the esophagus Nucleus ambiguus fibers are also referred to as branchial motor, or branchiomotor The location of the hypoglossal nucleus in the brainstem RANDOM TIP Trigeminal nerve: pain in the face Facial nerve: muscles of facial expression The hypoglossal nerve as it emerges from the brainstem in relation to the rest of the cranial nerves.
RANDOM TIP The autonomic nervous system is involved in heart rate, respiration rate, salivation, digestion, perspiration, pupil diameter, sexual arousal, and micturition urination The hypoglossal nerve innervates the extrinsic and intrinsic muscles of the tongue The hypoglossal nerve innervates the intrinsic and extrinsic muscles of the tongue.
The hypoglossal nerve fibers are general somatic efferent GSE and the muscles of the tongue are somatic, not branchial. Hyoglossus: moves the tongue down and in.
Styloglossus: moves the tongue up and in. Palatoglossus: moves the tongue up. We exit the medulla in two strands roots which usually merge to form one strand, the hypoglossal nerve. We enter the hypoglossal canal, which is in the rim of the foramen magnum. We emerge from the skull and move inferiorly as far as the angle of the mandible we move anteriorly and enter the tongue from the floor of the mouth.
The cell bodies of these fibers are in a sensory ganglion located near the inner ear called the geniculate ganglion. Rather than entering the skull with the facial nerve, the chorda tympani travels separately. The chorda tympani has its own nucleus of cell bodies in the medulla, called the nucleus solitarius. Secretomotor fibers of cranial nerve VII innervate the sublingual and submaxillary glands. These fibers originate from the salivary nucleus, which is located in the pons, near the motor nucleus.
Observation and motor function. Inspect the face for droop or asymmetry. Ask the patient to look up, so that the forehead wrinkles, and observe if there is a loss of wrinkling on one side. Push down on each side of the forehead. Strength will be relatively preserved in an upper motor neuron lesion, because of bilateral innervation of the upper part of the facial musculature.
Ask patient to hold shut both eyes and compare the strength of closure on each side. Observe nasolabial folds during voluntary movement. Observe the patient frowning, showing teeth, and puffing out the cheeks. In addition, observe for facial asymmetry during spontaneous facial expression most often smiling in response to humor or good news. Muscle stretch reflexes involving the facial nerve can be elicited, but tend to be more prominent in neurologic disease. They are not useful in localizing lesions or assessing facial nerve function.
If the lesion is at the stylomastoid foramen termination of facial canal, where the facial nerve leaves skull , all muscles of facial expression are paralyzed.
The corner of mouth droops.
Creases and skin folds are effaced. The forehead is unfurrowed on the side of the lesion. The palpebral fissure is widened. The eyelids will not close.
The lower lid sags. Tears spill over onto the cheek. However, taste is intact because the chorda tympani nerve taste enters the skull in a different place than the rest of the facial nerve.
If there is hyperacusis increased auditory volume in an affected ear , this is due the stapedius muscle in the middle ear being affected. The stapedius muscle functions to dampen ossicle movements, which normally decreases volume.
If there is cranial nerve VII nerve damage, this muscle is paralyzed. Nevertheless, it is still a lower motor neuron lesion, because the lesion is not affecting the corticbulbar tract. The motor nucleus of cranial nerve VII is in the pons, lateral to the abducens nerve cranial nerve VI. The fibers of the motor division mostly cross at some level in the central nervous system, and so injuries to either the cerebral cortex or upper brainstem both of which affect the corticobulbar tract result in paresis of the lower part of the face opposite to the side of the central nervous system lesion.
However, since both cerebral hemispheres innervate the superior part of the face, central nervous system lesions spare the forehead muscle. The motor or facial nuclei also receive projections the extrapyramidal system and from the frontal lobe, which control emotional expression.
This dual innervation of the facial nucleus of cranial nerve VII may explain the phenomenon of paresis of voluntary facial expression when there still is involuntary movement associated with emotional states. National Center for Biotechnology Information , U. Journal List Psychiatry Edgmont v. Psychiatry Edgmont. Richard D. Sanders , MD. Sanders Dr. Monitoring Editor: Author information Copyright and License information Disclaimer. Sanders, Dr. Corresponding author. There was no funding for the development and writing of this article.
The authors have no conflicts of interest relevant to the content of this article.
Edwin C. Moses Blvd. Copyright notice. This article has been cited by other articles in PMC. Abstract There are close functional and anatomical relationships between cranial nerves V and VII in both their sensory and motor divisions.
Cranial Nerve V: The Trigeminal Nerve Findings in psychiatric conditions. Anatomical Relationships of the Trigeminal Nerve The trigeminal nerve V is the largest cranial nerve, and it has both a sensory and a motor division.
The Brainstem Spinal sensory trigeminal tract. Clinical Examination of the Trigeminal Nerve Observation. Cranial Nerve VII: The Facial Nerve Findings in psychiatric conditions. Sensory and Secretomotor Divisions of Cranial Nerve VII The sensory fibers of the facial nerve, called the chorda tympani nerve, respond to taste input from the taste buds of the tongue.
Localizing a Lower Motor Neuron Cranial Nerve VII Lesion If the lesion is at the stylomastoid foramen termination of facial canal, where the facial nerve leaves skull , all muscles of facial expression are paralyzed. Summary There are close functional and anatomical relationships between cranial nerves V and VII in both their sensory and motor divisions.
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