Overview
The vagus nerve is the longest cranial nerve. It contains both motor and sensory fibers and,
because it passes through the neck and thorax to the abdomen, has the widest distribution in the
body. It contains somatic and visceral afferent fibers and both general and special visceral efferent
fibers.
Gross Anatomy
Exit From the Brain
The vagus nerve exits from the medulla oblongata in the groove between the olive and the inferior
cerebellar peduncle. It leaves the skull through the middle compartment of the jugular foramen,
where it has upper and lower ganglionic swellings, which are the sensory ganglia of the nerve. The
superior ganglion (jugular) is less than 0.5 cm in diameter, while the inferior (nodose) ganglion is
larger (2.5 cm) and lies 1 cm distal to the superior ganglion (see the image below). The vagus nerve
is joined by the cranial root of the accessory nerve (cranial nerve XI) just below the inferior
ganglion.[1, 2, 3, 4, 5]
Connections of the vagus to the glossopharyngeal and accessory
nerves.
For a summary of the types of fibers and pathways, see Table 1 in the section Other
Considerations.
Course of the Vagus Nerve
The vagus nerve descends vertically within the carotid sheath posterolateral to the internal and
common carotid arteries and medial to the internal jugular vein (IJV) at the root of the neck.
The right vagus crosses in front of the first part of the subclavian artery then travels into the fat
behind the innominate vessels. It then reaches the thorax on the right side of the trachea, which
separates it from the right pleura. It then inclines behind the hilum of the right lung and courses
medially toward the esophagus to form the esophageal plexus with the left vagus nerve.
The left vagus crosses in front of the left subclavian artery to enter the thorax between the left
common carotid and subclavian arteries. It descends on the left side of the aortic arch, which
separates it from the left pleura, and travels behind the phrenic nerve. It courses behind the root
of the left lung then deviates medially and downwards to reach the esophagus and form the
esophageal plexus by joining the opposite (right) vagus nerve.
The anterior and posterior gastric nerves are then formed from the esophageal plexus. The
anterior gastric is formed mainly from the left vagus but contains fibers from the right vagus.
The posterior gastric nerve is formed mainly from the right vagus but contains fibers from the left
vagus nerve. The gastric nerves supply all abdominal organs and the gastrointestinal tract ending
just before the left colonic (splenic) flexure (see the images below).
Course of the vagus nerve.
recurrent laryngeal nerve to the ligament of Berry.
Relation of the
Branches of the Vagus Nerve
Branches in the jugular foramen

Meningeal branch: This branch arises at the superior ganglion and re-enters the cranium
through the jugular foramen to supply the posterior fossa dura.

Auricular branch: This branch supplies sensations to the posterior aspect of the external
ear (pinna) and the posterior part of the external auditory canal. It arises also from the
superior ganglion and enters the mastoid canaliculus in the lateral part of the jugular
foramen. It exits again through the tympanomastoid suture of the temporal bone to reach
the skin. It communicates with branches of the seventh (facial) and ninth
(glossopharyngeal) cranial nerves.
Branches in the neck

Pharyngeal branches: These branches arise from the inferior ganglion and contain sensory
and motor fibers. The motor fibers are contributed by cranial nerve XI. They reach the
middle constrictor muscle after crossing between the external and internal carotid
arteries. They reach the pharyngeal plexus formed by cranial nerve IX and the sympathetic
chain. Branches of the pharyngeal plexus supply the pharyngeal muscles and mucous
membrane and palate except for the tensor palatini muscle. The intercarotid plexus, at the
carotid bifurcation, is also formed by vagal fibers from the pharyngeal plexus joined by
glossopharyngeal and sympathetic fibers. These vagal fibers and visceral afferents mediate
impulses set up by the chemoreceptors in the carotid body.


Superior laryngeal nerve: This nerve passes between the external and internal carotid
arteries at the level of crossing of cranial nerve XII. At the tip of the hyoid, the superior
laryngeal nerve divides into the external and internal branches. The internal laryngeal
nerve pierces the thyrohyoid membrane to enter the larynx. The external nerve passes
inferiorly with the superior thyroid vessels to the inferior pharyngeal constrictor muscle.
The cricothyroid muscle is supplied by the external branch of the superior laryngeal nerve.
The internal branch of the superior laryngeal supplies most of the mucosa above the
glottis. It is divided into the following 3 divisions:
o
The first division supplies mucosa of the laryngeal surface of the epiglottis.
o
The middle division supplies the mucosa of the true and false vocal folds, as well
as the aryepiglottic fold.
o
The inferior division supplies the arytenoid mucosa, anterior wall of the
hypopharynx, upper esophageal sphincter, and part of the subglottis. The major
part of the subglottis is innervated by the ipsilateral recurrent nerve.
Recurrent laryngeal nerve: This nerve is also known as the inferior laryngeal nerve. The
right nerve branches from the vagus at the root of the neck around the right subclavian
artery. It courses superiorly in the tracheoesophageal groove to enter the larynx between
the cricopharyngeus and the esophagus.
o
The left recurrent laryngeal nerve has a similar course to the right recurrent,
except that it loops around the aortic arch distal to the ligamentum arteriosus.
o
The main trunk of the recurrent lies in a triangle bound laterally by the common
carotid artery, IJV, and the vagus nerve and medially by the trachea and
esophagus. The recurrent nerve passes under the posterior suspensory ligament
of Berry (located on either side of the trachea, extending from the cricoid cartilage
and the first 2 tracheal rings to the posteromedial aspect of the thyroid gland),
before entering the larynx (see the image below). A few variations may occur in
this area (see the Natural Variants section)
Relation of the recurrent laryngeal nerve to the ligament of Berry.

o
All the intrinsic laryngeal musculature is supplied by the ipsilateral recurrent nerve
except the cricothyroid muscle, which is supplied by the superior laryngeal nerve.
The interarytenoid muscle is the only one that receives bilateral supply (ie, from
the left and right recurrent laryngeal nerves).
o
The ramus communicans or nerve of Galen connects the superior and the
recurrent laryngeal nerves. It provides the tracheal and esophageal mucosa and
smooth muscle with visceral motor input.
Superior cardiac nerve: The superior cardiac nerve is made up of 2-3 branches. They
communicate with the sympathetic fibers.
Branches in the thorax

Inferior cardiac branch: This branch is also called ramus cardiaci inferiors. On the right
side, it arises from the trunk of the vagus as it lies besides the trachea. On the left side, it
originates from the recurrent laryngeal nerve only. They end in the deep part of the
cardiac plexus.

Anterior and posterior bronchial branches: These are distributed as 2-3 branches on the
anterior surface of the root of the lung. They form the anterior pulmonary plexus after
joining branches from the sympathetic trunk. The posterior bronchial branches are larger
than the anterior and lie on the posterior surface of the root of the lung to form the
posterior pulmonary plexus (with contributory sympathetic fibres) as well.

Esophageal branches: These are anterior and posterior branches. Together, they form the
esophageal plexus. The posterior surface of the pericardium is supplied by filaments from
this plexus.
Branches in the abdomen

Gastric branches: The rami gastrici supply the stomach. The right vagus forms the
posterior gastric plexus and the left forms the anterior gastric plexus. They lie on the
posteroinferior and the anterosuperior surfaces, respectively.

Celiac branches: The rami caeliaci are mainly derived from the right vagus nerve. They join
the celiac plexus and supply the pancreas, spleen, kidneys, adrenals, and intestine .

Hepatic branches: The hepatic branches originate from the left vagus. They join the
hepatic plexus and through it are distributed to the liver.
Microscopic Anatomy
The recurrent and external branches of the superior laryngeal nerves carry parasympathetic fibers
from the dorsal motor nucleus to the subglottis and supraglottic regions, respectively. The
superior cervical ganglion sends sympathetic innervation.[5, 6, 7]
Histological sections have revealed the presence of Meissner corpuscles, Meckel cells, and taste
buds scattered in the larynx.
The mucosal surface sensory receptors are more numerous on the laryngeal surface of the
epiglottis than on the true vocal folds. On the other hand, the chemoreceptors are limited to the
supraglottic mucosa.
Natural Variants
The position of the recurrent laryngeal nerves is very important for the thyroid surgeon.[8, 3, 9, 10]
The following are some anatomical variations (see the image below):
Schematic representation of the different vagal fibers and their
distribution.

The recurrent nerve has been observed to branch into 2 nerves before entering the larynx.
The anterior (or medial) branch supplies the adductor muscles, while the posterior (or
lateral) supplies the abductors. Most of the time, the branching occurs 0.6-3.5 cm below
the cricoid cartilage. In rare instances, the recurrent nerve may have 4-6 branches. These
may be esophageal branches or supply the inferior pharyngeal constrictor. Any nerve in
the surgical field should not be sacrificed, unless it is invaded by malignancy.

In a small number of cases, the right subclavian artery is retroesophageal and arises from
the aorta distal to the ligamentum arteriosus. In these cases, the right recurrent nerve
enters the larynx without looping around the artery.

The recurrent laryngeal nerve passes under the ligament of Berry before entering the
larynx (see the image above). In 0.25% of cases, it passes over the ligament.

A branch of the inferior thyroid artery may pass deep to the ligament of Berry or along its
inferior edge. Indiscriminate clamping of this artery could jeopardize the recurrent nerve.

A small portion of the thyroid gland may exist deep to the ligament and lateral to the
recurrent nerve. This should be removed with great care, without injuring the nerve,
during thyroidectomy because it may contain carcinoma.
Other Considerations
Neurophysiological considerations
The types of fibers that constitute the vagus nerve perform different physiological roles (see the
image below, as well as Tables 1 and 2 below), as follows:[11, 12, 13, 14, 15]

The sympathetic efferent fibers (efferent general visceral or visceral motor) are distributed
to the thoracic and abdominal viscera, to the bronchial tree, inhibitory fibers to the heart,
motor fibers to the esophagus, stomach, small intestine, and as secretory fibers to the
stomach and pancreas. They arise from the dorsal motor nucleus of the vagus.

The somatic motor fibers (efferent special visceral or branchial motor) arise from the cells
of the nucleus ambiguus. Nucleus ambiguus is the motor nucleus for striated muscles of
the pharynx, larynx and palate in the middle of the upper part of the medulla. It is
adjacent to the respiratory motor neurons in the brainstem.

The sensory fibers (afferent general and special visceral) arise from the cells of the jugular
ganglion and ganglion nodosum (superior and inferior ganglia of the vagus, respectively).
When traced into the medulla, they end by arborizing around the cells of the inferior part
of a nucleus, which lies beneath the ala cinerea in the lower part of the rhomboid fossa.
These are the sympathetic afferent fibers. A few of the taste fibers of the vagus nerve
descend in the fasciculus solitarius and end around its cells.

The somatic sensory fibers (afferent general somatic) are only a few in number. From the
posterior aspect of the external auditory canal and the back of the external ear, they join
the spinal tract of the trigeminal nerve as it descends in the medulla. They have
connections with the thalamus, sensory cortex, and medullary and spinal nuclei.
Table 1. The Pathway According to the Type of Nerve Fibers of the Vagus Nerve (Open Table in a
new window)
Type
Pathway
Branchial motor Corticobulbar (bilateral) fibers descend through the internal capsule to synapse
(efferent special in the nucleus ambiguus. The axons of the lower motor neurons come out as 810 rootlets between the olive and pyramid, exiting the skull through the jugular
visceral)
foramen. They then divide into 3 main branches: the pharyngeal, superior, and
recurrent laryngeal nerves.
Visceral motor
Fibers from the dorsal motor nucleus X pass through the spinal trigeminal
(efferent general nucleus and tract, emerging from the medulla oblongata lateral surface to join
visceral)
the rest of the vagus.
Visceral sensory
(afferent general
and special
visceral)
Nerve cells are located in the inferior (nodose) ganglion of the vagus. They
receive input from the chemoreceptors of the aortic body and other visceral
structures. Axons then descend to the tractus solitarius after entering the
medulla.
General sensory The Xth cranial nerve carries visceral sensory fibers of the recurrent and the
(afferent general internal laryngeal nerves that supply sensations to the larynx. The auricular
branch supplies sensations to the posterior parts of the pinna, external auditory
somatic)
canal, and tympanic membrane. Nerve cells are located in the superior (jugular)
ganglion of the vagus.
Table 2. Summary of Central Connections, Components, Function, and Peripheral Distribution of
the Vagus Nerve (Open Table in a new window)
Components
Function
Central
connection
Cell bodies Peripheral distribution
Branchial motor
(efferent special
visceral)
Swallowing,
phonation
Nucleus
ambiguus
Nucleus
ambiguus
Visceral motor
(efferent general
visceral)
Involuntary
Dorsal motor Dorsal
muscle and gland nucleus X
motor
control
nucleus X
Cardiac, pulmonary,
esophageal, gastric, celiac
plexuses, and muscles, and
glands of the digestive tract
Visceral sensory
(afferent general
Visceral
sensibility
Cervical, thoracic, abdominal
fibers, and carotid and aortic
Nucleus
tractus
Inferior
ganglion X
Pharyngeal branches, superior
and inferior laryngeal nerves
visceral)
solitarius
bodies
Visceral sensory
(afferent special
visceral)
Taste
Nucleus
tractus
solitarius
Inferior
ganglion X
General sensory
(afferent general
somatic)
Cutaneous
sensibility
Nucleus spinal Superior
tract V
ganglion X
Branches to epiglottis and taste
buds
Auricular branch to external
ear, meatus, and tympanic
membrane
Table 1. The Pathway Pathway
According to the Type
of Nerve Fibers of the
Vagus Nerve Type
Branchial motor
(efferent special
visceral)
Corticobulbar (bilateral) fibers descend through the internal capsule to
synapse in the nucleus ambiguus. The axons of the lower motor neurons
come out as 8-10 rootlets between the olive and pyramid, exiting the skull
through the jugular foramen. They then divide into 3 main branches: the
pharyngeal, superior, and recurrent laryngeal nerves.
Visceral motor
(efferent general
visceral)
Fibers from the dorsal motor nucleus X pass through the spinal trigeminal
nucleus and tract, emerging from the medulla oblongata lateral surface to
join the rest of the vagus.
Visceral sensory
(afferent general and
special visceral)
Nerve cells are located in the inferior (nodose) ganglion of the vagus. They
receive input from the chemoreceptors of the aortic body and other
visceral structures. Axons then descend to the tractus solitarius after
entering the medulla.
General sensory
(afferent general
somatic)
The Xth cranial nerve carries visceral sensory fibers of the recurrent and
the internal laryngeal nerves that supply sensations to the larynx. The
auricular branch supplies sensations to the posterior parts of the pinna,
external auditory canal, and tympanic membrane. Nerve cells are located
in the superior (jugular) ganglion of the vagus.
Table 2. Summary of Central Function
Connections, Components,
Function, and Peripheral
Distribution of the Vagus
Central
connection
Cell bodies Peripheral distribution
Nerve Components
Branchial motor (efferent
special visceral)
Swallowing,
phonation
Nucleus
ambiguus
Nucleus
ambiguus
Pharyngeal branches,
superior and inferior
laryngeal nerves
Visceral motor (efferent
general visceral)
Involuntary
muscle and
gland control
Dorsal motor Dorsal
motor
nucleus X
nucleus X
Visceral sensory (afferent
general visceral)
Visceral
sensibility
Nucleus
tractus
solitarius
Inferior
Cervical, thoracic,
ganglion X abdominal fibers, and
carotid and aortic bodies
Visceral sensory (afferent
special visceral)
Taste
Nucleus
tractus
solitarius
Inferior
Branches to epiglottis
ganglion X and taste buds
General sensory (afferent
general somatic)
Cutaneous
sensibility
Nucleus
Superior
Auricular branch to
spinal tract V ganglion X external ear, meatus,
and tympanic membrane
Cardiac, pulmonary,
esophageal, gastric,
celiac plexuses, and
muscles, and glands of
the digestive tract